# 1st decoder install



## CliffyJ (Apr 29, 2009)

Hi friends,

Yesterday I hooked up my first DCC system (NCE), and installed my first decoder, and I thought I'd share a few comments and ask a couple questions.

First off, thanks Bob B., Greg E., George S. and everyone for helping to get this far. I was all set to go hard-wired control, but thanks to you guys helping me see the light, I'll have far more freedom and less expense and greater reliability. 

Second... the darn thing worked! Woo hoo! Now, it did take a while for me to set things up, but as soon as I'd completed the programming step-by-step per NCE, bingo, that baby started moving and making sounds! That was so cool!

So now, to some specifics. 

A few weeks ago, in another thread (titled "tentative steps"), you guys helped me work it out that I'd start with a Digitrax DH465 / SFX004 combo. The instructions were clear, and installation was easy. And I gotta tell ya, it's really impressive to me how "smart" that tiny sound board is. Way cool.

Here's a pointer though, if you're going to install a board into a Hartland 4-4-0, and are as new to this kind of thing as me. All three of my DCC books, and the Digitrax & NCE lit, talked about disassembling the loco. Which I did. And though I could have tied into the conveniently-placed wire nuts behind the (removable) boiler backshell, it wouldn't have been very easy. I was curious about the wiring harness to the tender though; and once I removed the tender's body, lo and behold, a terminal block (made for the purpose) and tons of space opened up. I didn't have to disassemble the loco at all!

I know, everyone's probably getting a chuckle... and I'm sure that this kind of thing has been covered in GR articles... but there you go. That terminal block made it all simple. I suspect that it's the same with other locos that have the harness to the tender. I was wondering what it was for, so now I know!

As it turned out, that terminal block was critical. The published Hartland wire color codes have nothing to do with those normally associated with the counterpart wires in a Digitrax (and I assume all standardly-wired) decoders. I spent a lot of time coming up with the rosetta stone diagram for this loco, which was made more complicated by the fact that it's main power pickup wires (blue / gray, from the loco) were reversed in color from their diagram. I worked with a multimeter to check before I powered things up, and caught it. 

I kinda had a heart attack when I was doing two things at once: messing with CV settings for the first time, and trying to get the loco to go forward when the handheld said FWD (not REV). In the process of goofing with the latter, I tried reversing the main pickup feeds to the decoder, and then doing another CV change, and everything came to a dead stop. No action, nomatter what. Checked track voltage, forgot that you couldn't do that with a simple multimeter; un-wired the smoke unit (worked fine with it wired in, but I probably should have disconnected it anyway); opened the booster, it's output contacts read fine. NCE's on-line lit mentioned an internal fuse that I could buy "from Walmart," but I couldn't find such a thing. So I was really afraid that after all this, I'd just cooked a $400 component. About an hour went by, far more than the time required for the booster's breaker's reset... In the mean time, I read in Digitrax's lit that CV's can collide; and when all else fails, set CV08 to a value of 008. And that did the trick!! 

I've no idea which CV I messed up to cause this. Greg / all, do you have any clues? 

But now, I want to talk about what I was attempting to do.

Like I said, I'm really impressed with the SFX004. However, you can't hear it over the noise of my Hartland 4-4-0. Literally. True, I've got my test loop on an old pair of folding tables, and all mechanical noises are amplified. So... the CV list for that product has seperate volume settings for different kinds of sound. I was trying to max each one out when my problem happened. 

Even with that messing about, before everything died, I still couldn't hear much of the sounds over the loco noise. So: George S., did you ever install / test one of those amplifiers (http://store.qkits.com/moreinfo.cfm?Product_ID=2068)? I'm about to order two of their pre-assembled ones (to meet their min order), and also the voltage regulator you and Steve C. pointed out (thanks!), and a better speaker (qkits says that I should go with a 2W 8 ohm speaker for 12vdc; do you have anything to add to that spec?) 

I suppose I should start learning about how to better baffle a tender for best bass resonance and sound directing in general... does anyone have a GR issue, link or web article to direct me to on that subject?

Oh, one final comment about adjusting the output voltage on the NCE booster. Greg's advice (per his web site) is very correct: you've got to open the box to turn the pot. Reason 1: in my case, they put thick tape across the hole (same strip of tape used to secure other components), only removed by careful labor, and only if you take the cover off anyway. Reason 2: after removing the excess tape, the pot slot didn't line up with the chassis hole, and the screwdriver wouldn't turn it. Only by pushing over the outer bale or tab on the pot (not via the screwdriver slot), using a small screwdriver, could I get it to max output (per the meter; and yes, there was a definite stop when I did that).

Well, thanks for letting me share my journey on this little facet. As always, any feedback is most welcome and greatly appreciated.

===Cliff


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## CliffyJ (Apr 29, 2009)

Sorry for replying to myself ( been gettin' worse, just ask my wife







), but it's only just dawing on me the things that most of you guys know already, in regards to sound quality. 

I just read Mr. DCC's great Powerpoint presentation on "Getting the Sound Out" (http://mrdccu.com/clinics/). Great job, sir! Wish I had the audio of that talk! Anyway, it's obvious now that I shouldn't be judging the audability of my SFX004 from my current arrangement, in that my speaker's currently just flopping around on the bodiless tender chassis. Clearly, the speaker needs to be secured and have a box to resonate against. 

The last time I tried to make a speaker enclosure was over 30 years ago, but even so, I'm kicking myself for having forgotten everything it seems... So thank you, Mr. Petrarca. 

Still, I'd sure like that extra amping... George?

[later edit, about 1 hour after... sorry if I seem pushy, just excited to work things out]:

Just ordered the two amps from qkits, and four $.25 regulators (2 to cook, one to use, and one to use on the next loco) from Jameco. Also from Jameco, a whole bunch of different 8 ohm speakers, in the 2-5 watt arena. They were all cheap, so what the heck, it'll be fun experimenting. A couple of them looked like good weights for the tender!

Best regards (not to me, to you







),
===Cliffy


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## George Schreyer (Jan 16, 2009)

I have a few of those kits, I was expecting to use one in the PCC. But the SFX004 made JUST enough audio so that I didn't have to. 

As you noticed, an enclosure, even a small one, can significantly improve the sound output. 

http://www.girr.org/girr/tips/tips12/small_speaker_tips.html 

DCC doesn't care about the track polarity so unless you plan to analog convert, getting the red or black wire on the right side means nothing. Getting the orange and gray wires reversed will cause the motor to run backwards. That is fixable with programming, but if the loco is open, it is just better to swap those wires to get it going in the right direction.


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## Road Foreman (Jan 2, 2008)

Cliffy, 

Good to here it is working for you.. 

BulletBob


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## CliffyJ (Apr 29, 2009)

Posted By George Schreyer on 21 Feb 2011 05:43 PM 
I have a few of those kits, I was expecting to use one in the PCC. But the SFX004 made JUST enough audio so that I didn't have to. 

As you noticed, an enclosure, even a small one, can significantly improve the sound output. 

http://www.girr.org/girr/tips/tips12/small_speaker_tips.html 

DCC doesn't care about the track polarity so unless you plan to analog convert, getting the red or black wire on the right side means nothing. Getting the orange and gray wires reversed will cause the motor to run backwards. That is fixable with programming, but if the loco is open, it is just better to swap those wires to get it going in the right direction. Thank you George for the link to your site. I'm feeling pretty sheepish right now, because I'd not known of its existence (or wasn't paying attention). Wow, what a wealth of info there. Guys like you, Greg, and others amaze me, in that you're willing to take the time and document things for others. I'll be sure to utilize your resources.


I was amazed after seeing your video where you cup the speaker in your hand... what a diff! Gosh, I feel like such a moron for judging the system with the speaker just hanging out there in space, I should've known better! 

But a cool thing about this hobby, and this web site, is that a learner like me doesn't have to sweat it over how ignorant he might happen to be. Always someone here to lend a helping hand.

===Cliff


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## CliffyJ (Apr 29, 2009)

Posted By Road Foreman on 21 Feb 2011 05:47 PM 
Cliffy, 

Good to here it is working for you.. 

BulletBob Thanks for the reply, and thanks for the tip!


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## Greg Elmassian (Jan 3, 2008)

George's site was the first in depth reading I did, I read it 3 times cover to cover. 

It was the inspiration for my site. 

Greg


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## CliffyJ (Apr 29, 2009)

Posted By Greg Elmassian on 22 Feb 2011 05:14 PM 
George's site was the first in depth reading I did, I read it 3 times cover to cover. 

It was the inspiration for my site. 

Greg 
Good advice, and high praise well deserved I'm sure.

I'm about to check George's site out for how not to cook the lights in my stock passenger cars, when placed on track that now has 24v on it. 

Also, it's interesting to hear more on what led to what, and the interconnectedness. Thanks for the backstory Greg.

I've found Dave Bodnar's site very informative as well, and yours obviously. Any other fav's? 

Cliff


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## Greg Elmassian (Jan 3, 2008)

Bob Pero's site: http://www.liveoakrr.com/ comes to mind.


Regards, Greg


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## CliffyJ (Apr 29, 2009)

Thanks very much Greg. Yet another great resource! I just read Bob's article on speakers, it was very helpful.

For now though, before I start feeling overwhelmed yet again, I think I'll just peck away at reading George's articles (taking your advice) and yours again... I need to make a reading list for myself, based on key web sites, and discipline myself to plow thru them. And take notes. And find a way to store the notes in a strategic manner... well, I'm doing better on the last item, in creating Word docs of my plans, per topic, and citing ref's either by link or verbosely. Still, it's kinda all overwhelming! But, I asked for it! 

What a wonderful hobby. It's doing for me now what it did when I was a teenager, ~35 years ago: learning, learning, learning. And DOING. History, electronics, metallurgy, mechanics, landscaping, carpentry, increased conversation with the wife and the neighbors and the mother in law... so much here.

But I digress. I received my little 2 watt amps today (the look nice and small and well made), but am still waiting and regulators from Jameco. I'm kinda leery of messing with things electronic, but on the other hand, it will be so cool if all this works and I don't burn everything up! 

George, it would be great to confab with you on this... the instructions on the amp declare (in the main diagram) that a .25W speaker whould be hooked up, but all the other ref's declare 2W. I assume the diagram is wrong, but it shouldn't matter anyway with the 2 to 5 watt speakers I'm going to test, right? 

On a related point, if the amp's output is 2W, must I use a speaker that is rated beyond that, and not 2W? That is, if I hook up only a 2W speaker to a 2W amp, am I asking for trouble?

In the mean time, I'll be messing with enclosing and sealing the speaker I have, programming CV's (hopefully without bringing down the whole programmed set of instructions again!), and generally trying to get up to speed a little on this whole wonderful world of DCC. It's pretty mind-blowing... 

Best regards, and always an honor to get input from you DWE's (Dudes With Experience),

===Cliff


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## George Schreyer (Jan 16, 2009)

The power rating of a speaker needs only be larger than that of the amp. If you use a big amp and a small speaker, you'll probably damage the speaker when it hits the stops hard. The racket will sound so bad that you'll probably be able to turn it off before it actually burns up. The speaker may still be physically damaged though from all the hard knocks.


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## CliffyJ (Apr 29, 2009)

Posted By George Schreyer on 25 Feb 2011 05:06 PM 
The power rating of a speaker needs only be larger than that of the amp. If you use a big amp and a small speaker, you'll probably damage the speaker when it hits the stops hard. The racket will sound so bad that you'll probably be able to turn it off before it actually burns up. The speaker may still be physically damaged though from all the hard knocks. 
Thanks George.

But what about when I use a 2W speaker with the 2W amp? 

The reason I ask is that I bought the same amp that you did (from Qkits), and ordered a few speakers from Jameco, rated at 2W or more. If a 2W speaker seems to work, I don't want to "seal" it to the tender if there's a chance that it will blow out over time, if I should have used a speaker rated for more than 2W.

Put differently, what speaker would you use with the Qkits (specifically: FK602) 2W amp?

Best regards George, and I apologise for not having visited your site before and knowing just who I was conversing with,

===Cliff


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## George Schreyer (Jan 16, 2009)

A 2 watt speaker will be fine for a 2 watt amp. If you hear distortion when turned up loud, don't do that... 

The tender does not have to be perfectly sealed. Just assemble it like it was. Make sure that the speaker edge itself is sealed with hot glue or some other goop. Some folks insist that ANY leak is a disaster, not so. A small leak may cause a little loss of volume but it won't be serious. If the tender rattles or wheezes, then you need to do something about it.


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## CliffyJ (Apr 29, 2009)

Posted By George Schreyer on 25 Feb 2011 06:20 PM 
A 2 watt speaker will be fine for a 2 watt amp. If you hear distortion when turned up loud, don't do that... 

The tender does not have to be perfectly sealed. Just assemble it like it was. Make sure that the speaker edge itself is sealed with hot glue or some other goop. Some folks insist that ANY leak is a disaster, not so. A small leak may cause a little loss of volume but it won't be serious. If the tender rattles or wheezes, then you need to do something about it. Thank you Sir, will do!

Been reading thru your articles on LED lights and smoke units; very interesting and exhaustive, I really applaud you. 

I'm working with an HLW American loco for my first DCC conversion, which doesn't have any chuff cam switch output that I can find. Could you point me to an article on how to add such a thing?

Also, could you point me to where I can learn how to modify passenger car lights for DCC ops? 

BTW, experimenting with speaker mounting / enclosing did, of course, have a great effect. However, I'll be getting my speakers and regulator tomorrow, and already have the 2W amps, so I'm looking forward to applying a number of things. 

Thanks very much for all your help,

===Cliff


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## George Schreyer (Jan 16, 2009)

depending on your sound system, you may be able to synchronize the chuff well enough with decoder CVs based on speed. 

for lighting, see 

http://www.girr.org/girr/tips/tips3/streamliner_tips.html 
http://www.girr.org/girr/tips/tips2/hw_tips.html


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## CliffyJ (Apr 29, 2009)

Posted By George Schreyer on 26 Feb 2011 07:48 PM 
depending on your sound system, you may be able to synchronize the chuff well enough with decoder CVs based on speed. 

for lighting, see 

http://www.girr.org/girr/tips/tips3/streamliner_tips.html 
http://www.girr.org/girr/tips/tips2/hw_tips.html Excellent, thanks very much.


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## CliffyJ (Apr 29, 2009)

George, 

While I'm waiting for the speakers to come, I started messing with a passenger car. I was reading your articles (they're great!), but didn't see how mine could be modified in that fashion. 

Specifically, I've got 6 Aristo "Sierra" cars, with little (I think E5) screw base bulbs in (6) decorative wall fixtures mounted to the interior walls. These look pretty tough to rewire: the circuit board is permanently sandwiched between undercarraige and interior floor castings, and the wiring to each fixture is buried between walls & benches. 

So... 

I was thinking about just replacing the bulbs. I found some E5's rated at 28v / .04 amp (http://www.bulbtown.com/399_MINIATURE_BULB_MIDGET_FLANGE_BASE_p/399.htm). Kinda pricey (at a buck each, and ~36 bulbs). If I did that, would I have to do anything else? 

Probably can't use the stock LED marker lights though... or the smoke units. Right? 

Or, maybe you'd just install a voltage regulator for the hole car, and hide it somehow beneath the undercarriage? 

I emailed Aristo, to see if their (buried) circuit board can tolerate 22-24v input, but I'm not real hopeful. We'll see. 

Thanks again, 

===Cliff


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## CliffyJ (Apr 29, 2009)

Posted By Greg Elmassian on 22 Feb 2011 05:14 PM 
George's site was the first in depth reading I did, I read it 3 times cover to cover. 

It was the inspiration for my site. 

Greg 
Greg, I'm curious, what do you do with passenger car lighting?
(dang, you probably have an article on that, I'll go and check... but I'm leaving this here in case you don't).
Hope you're having a great weekend,
===Cliff


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## blueregal (Jan 3, 2008)

He has everyting over der!! And he gets upset ifin ya's don't read it firs den ask but if you ask first befer readin his site!! Regal


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## CliffyJ (Apr 29, 2009)

Posted By blueregal on 27 Feb 2011 03:40 PM 
He has everyting over der!! And he gets upset ifin ya's don't read it firs den ask but if you ask first befer readin his site!! Regal Hence, the "dang." You'll notice that it was strategically positioned in the sentence, as sort of a backup apology, if needed.

However, I still can't find where Greg addresses this, so I think I'm ok even without the "dang." 

So ifin he gets upset whar I didn read hiz stuff caus it twernt thar, he'll owe me a gosh, I figgur. *pht* (< sound of spittoon being utilized)










===Cliff


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## Greg Elmassian (Jan 3, 2008)

Since I use DCC, I have a constant voltage on the rails of about 23 volts. 

I string a number of LEDs in series, and use a CL2 regulator (2 terminal device that gives you a constant 20 milliamps)... so this really cuts the current down. For white leds, you might be able to string 5 or 6 in series, so 6 leds at a total of 20 ma really cuts the current down. (I put a full wave bridge ahead of the circuit) 

It's what I do to minimize current draw on trains with a lot of passenger cars... seems silly to have the cars draw more current than the locos. 

Greg


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## George Schreyer (Jan 16, 2009)

I don't have an Sierra cars, but I suspect that they are similar to the Classic RailBus. I haven't rewired those because it looked difficult. I run 18 volts there and the lights are indeed too bright. If you try to put them on 24 V DCC, they will get dim in a hurry. 

I would try the 28 volt bulbs before trying anything else. Running a bulb at 20% lower voltage dims them a lot and materially improves their life. 

- gws


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## CliffyJ (Apr 29, 2009)

Posted By George Schreyer on 27 Feb 2011 09:15 PM 
I don't have an Sierra cars, but I suspect that they are similar to the Classic RailBus. I haven't rewired those because it looked difficult. I run 18 volts there and the lights are indeed too bright. If you try to put them on 24 V DCC, they will get dim in a hurry. 

I would try the 28 volt bulbs before trying anything else. Running a bulb at 20% lower voltage dims them a lot and materially improves their life. 

- gws Thanks George. Will do. I appreciate the confirmation.


Unless I get feedback that I don't need to do otherwise from Aristo, I'll also disable the smoke units (probably a huge power draw anyway, but I was only going to switch them on for a photo here or there) and the marker lights on the observation car. Hope the buried circuit board can tolerate 22v though!

All the best,
Cliff


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## Greg Elmassian (Jan 3, 2008)

The smoke units are really not a huge draw, and use a switching supply, so with higher input voltage, they use less current. George has the details on his site. They won't fail any sooner on DCC voltages, and they actually work better (because the microprocessor resets under a certain voltage, so they like a constant voltage). 

Greg


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## CliffyJ (Apr 29, 2009)

Posted By Greg Elmassian on 28 Feb 2011 04:39 PM 
The smoke units are really not a huge draw, and use a switching supply, so with higher input voltage, they use less current. George has the details on his site. They won't fail any sooner on DCC voltages, and they actually work better (because the microprocessor resets under a certain voltage, so they like a constant voltage). 

Greg Oh! Well, there ya go! Thanks for that tidbit Greg, I'll leave them wired, but generally switched off. And I'll re-read George's article on smoke generators: I see now why you had to read his stuff three times!

As for the LED marker lights on the observation car, can you opine on whether they will tolerate the 22v as well? If not, what the heck; if they burn out, they burn out. It would be a shame not to have at least the bodies hanging there. 

Thanks!

===Cliff


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## George Schreyer (Jan 16, 2009)

3 times? Is it not clear or just too dense to absorb in one pass?


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## Greg Elmassian (Jan 3, 2008)

My 3 times reading was kind of like watching a movie 3 times, you get the big picture the first time, the second time, you pick up nuances and other things you miss. I read the site the 3rd time because I'm anal and did not want to miss anything ha ha! 

Greg


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## CliffyJ (Apr 29, 2009)

Posted By George Schreyer on 28 Feb 2011 07:01 PM 
3 times? Is it not clear or just too dense to absorb in one pass? Sorry George, all I meant was that your articles are so in depth that a cursory glance simply isn't enough. To use myself for an example, I go fishing for a particular answer to a particular question. E.g., quick fixes for passenger car lighting on DCC. But not only did I find the two articles you referenced have much helpful info in themselves, I also saw your article on LED's... WOW! So much to learn!

So when Greg said what he did about Aristo's plug-in smoke units, I immediately recalled my brief scan of your quite exhaustive article on smoke units (covering the Aristo ones as well), and knew that I'd have to go back and fully read the thing... at least 2 more times I figure: once to comprehend, once again to retain.

Which equals three. If not four, for me. 










===Cliffy


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## CliffyJ (Apr 29, 2009)

Just to keep the thread updated, I'm interested in emplying the chuff input to the decoder. But since my (Hartland) 4-4-0 doesn't have easy opportunity to add such a switch to the loco's drivers, I emailed them for ideas. 

Well, Phil Jensen himself responded -- what an honor! 

He responded thusly: 


Hi, Cliff: 
I don't know of anyone installing "Chuff" switches on our engines. 

However, I have had good luck installing them on one of the tender axles. It's a simple procedure. The circumference of a tender wheel is about half of a loco drive wheel. Install one magnet on a tender wheel instead of 2 on a loco drive wheel. 

This seems to work well enough to satisfy all but the most rabid critics.

All makes sense. 

Has anyone here done this, and is there a simple kit available? 

===Cliff


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## George Schreyer (Jan 16, 2009)

You need a reed switch and some small high energy magnets. 

You can buy reed switches and magnets from All Electronics, Hosfelt, DigiKey, Mouser, and many others.


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## Greg Elmassian (Jan 3, 2008)

don't give up on a reed switch underneath and 2 or 4 small rare earth magnets glued to the backside of one driver. 

This will give you nice synchronized chuffs with the position of the piston. The tender wheels will be an approximation of the right rate but will never synchronize with the piston position. 

Greg


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## TonyWalsham (Jan 2, 2008)

Agreed Greg, but the chuffs will only synchronise with the pistons if the magnets are in the correct position.
What I do is make a circular paper template that fits around the drive wheel axle. I then make sure one piston rod is at the correct stroke position and then rotate the template until one of the marks is directly opposite the reed switch. The magnets are then glued? in the four places as indicated by the template.

Like this one I made for an Accucraft K-36 loco:











Paper template removed after mounting magnets. A good quality Super Glue holds them just nicely.


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## Greg Elmassian (Jan 3, 2008)

Yes, I thought it was sort of a "duh" that the magnets need to be in the right places... but you are correct. 

Your explanation is complete and clear, as usual! 

Greg


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## TonyWalsham (Jan 2, 2008)

It is "duh" for those that know. For those that don't know I think it deserves a full explanation.


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## Gary Armitstead (Jan 2, 2008)

Great idea using the paper template to locate the magnets.


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## CliffyJ (Apr 29, 2009)

Great info, everyone! 
I can only find the small, tubular reed switches; but Tony, your pic seems to show something more robust. What is it?


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## CliffyJ (Apr 29, 2009)

Well, I was going to go to Radio Shack for a reed switch and magnets, but now I"m back to square one, because I fried my Soundbug. 

Here's the details. 
I wired the speaker output to that little 2watt amplifier (the one we've discussed, George). 
Followed all the instructions I could get my hands on for wiring the LM7812 for powering the amp. 
Removed the engine (everything's in the tender). 
Checked to make sure no bare leads were touching anything they shouldn't be. 
Was very cautious with everything...
Fired up the system... 
And *POOF*! Two nice, G-scale plumes of smoke arose from the Soundbug... with little corresponding black craters in the heat shrink... 

After restoring things, the decoder still works fine, but the SB is officially pushing up daisies. 

I've written to Digitrax, to see if their (quite generous) warrantee covers this form of "customer accident" (as they put it). 

Regardless, it would be nice to know where I went wrong. George / all, any thoughts? I sure don't want to smoke the next one... 










Cliff


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## George Schreyer (Jan 16, 2009)

without seeing a diagram of your wiring, I can't hazard a guess


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## TonyWalsham (Jan 2, 2008)

Cliff. 
I used to use small security system reed switches, They were mounted in rectangular stick on plastic holders. 
I can't get them any more so I make my own from left over tiny (and fragile) Sierra glass tube reed switches which I glue inside square rectangular styrene tubing with silicone roof and gutter sealant. They work just fine pointing at the magnets, instead of being mounted side on.


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## CliffyJ (Apr 29, 2009)

Posted By George Schreyer on 05 Mar 2011 12:44 PM 
without seeing a diagram of your wiring, I can't hazard a guess 
OK, thanks George.

I'll work on that. 

In the mean time, could you answer me this. I'm working with a simple Hartland loco, with a jack in the harness between the tender and engine. Disconneting the jack, removing the engine, and letting the tender (with the decoder) receive the track power alone couldn't have caused this problem, right? 

I don't think so.

The ONLY input to the Soundbug otherwise would have been via it's speaker/output wires, back-fed from the amp... but I know I wired that correctly... 

Oh well, still working on it. 

Maybe it was a problem with my wiring of the voltage regulator? I wired #1 leg to a rail pickup, #2 (ground) to the other, #3 (output) to the (12v input) amp. 

OK, I need to do a diagram...

===Cliffy


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## CliffyJ (Apr 29, 2009)

Posted By TonyWalsham on 05 Mar 2011 03:15 PM 
Cliff. 
I used to use small security system reed switches, They were mounted in rectangular stick on plastic holders. 
I can't get them any more so I make my own from left over tiny (and fragile) Sierra glass tube reed switches which I glue inside square rectangular styrene tubing with silicone roof and gutter sealant. They work just fine pointing at the magnets, instead of being mounted side on. Ah! Well, that explains why I couldn't find your switch in any of the major electronics manufacturer's catalogs!

But thanks Tony, that helps me understand what I should be looking for, and planning for.

===Cliffy


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## Axel Tillmann (Jan 10, 2008)

Posted By TonyWalsham on 05 Mar 2011 03:15 PM 
Cliff. 
I used to use small security system reed switches, They were mounted in rectangular stick on plastic holders. 
I can't get them any more so I make my own from left over tiny (and fragile) Sierra glass tube reed switches which I glue inside square rectangular styrene tubing with silicone roof and gutter sealant. They work just fine pointing at the magnets, instead of being mounted side on. 
How many do you want? They (the stick-on encased reeds) are still available. In some instacnes we prefer the plastic cylinder enclosed reed wehre we can drill a howl in the chassis and adjust the height before we secure them into the final position. The stick on ones not always have the right distance to some track magnets (espcially the LGB ones).


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## TonyWalsham (Jan 2, 2008)

Thanks anyway Axel. 
I have got used to making them myself now. 
It only takes a couple of minutes and I get what I want with the glass reed as close as possible to the end of the tube.


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## Axel Tillmann (Jan 10, 2008)

I just thought, the glas ones are really fragile, just don't look at them in the wrong angle


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## TonyWalsham (Jan 2, 2008)

The tine Sierra glass reed switches are very fragile. 
That is why I insert them into round or square styrene tubing with silicone sealant to hold them in place.


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## CliffyJ (Apr 29, 2009)

Posted By George Schreyer on 05 Mar 2011 12:44 PM 
without seeing a diagram of your wiring, I can't hazard a guess Here it is George... 










Lay it on me, Brutha... I'm sure I did something mega-dumb, right?
Cliff


----------



## Greg Elmassian (Jan 3, 2008)

typically you have a couple of caps on the regulator to make sure it's not oscillating, but you smoked the sound board, right? 

weird.. 

Greg


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## Hans Larsson (Apr 19, 2009)

Posted By CliffyJ on 06 Mar 2011 09:45 AM 
Posted By George Schreyer on 05 Mar 2011 12:44 PM 
without seeing a diagram of your wiring, I can't hazard a guess Here it is George... 










Lay it on me, Brutha... I'm sure I did something mega-dumb, right?
Cliff


I see a problem...
The input to the 7812 will furiously switch between +22V and -22 V.
During the -22V time, one can never be sure what the combination of the 7812 and the sound board will do to the other inputs to the board. It might short-circuit the sound board input.
I think a diode bridge between the rail and the 7812 would help a lot.
And I would also add the input and output capacitors around the regulator, that Greg talked about.


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## krs (Feb 29, 2008)

Posted By CliffyJ on 06 Mar 2011 09:45 AM 
Posted By George Schreyer on 05 Mar 2011 12:44 PM 
without seeing a diagram of your wiring, I can't hazard a guess Here it is George... 










Lay it on me, Brutha... I'm sure I did something mega-dumb, right?
Cliff

My 2 cents..............

The diagram states "22 VDC in (from rail)..........

Is that really true?
The Decoder needs DCC but the voltage regulator needs DC, so you need a diode bridge somewhere in the path to the regulator.


As to the SFX004 blowing up........
Did you orient it correctly when it was plugged into the Decoder? I don't have one but just looking at whatever pictures I could find, it doesn't look as if the SFX004 connector is polarized.
The SFX004 is also rated at 20 volts maximum, your voltage is 10% above that, and
The DH465 decoder is sold as an H0 and 0 decoder, Digitrax doesn't specify the maximum voltage it can handle, but since this decoder is not specified for G Scale or Large Scale, I would check into that as well to make sure it can handle the 22 VDCC.


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## CliffyJ (Apr 29, 2009)

Thanks KRS and Hans, you're touching on the thing I was wondering about, and should have ask for advice on before I started lighting things up. Specifically, it seems that the amp & regulator need sure polarity, but the DCC power isn't like that... What is it? Is the DCC power actually AC, after it comes out of the booster? I'm confused. 

Anyway, as you suggest KRS, would a bridge rectifier solve this? If so, maybe 4 cheap diodes from Radio Shack would suffice? I don't mind spending the $ on a proper rectifier, it's the shipping costs for thing or the other that are killing me!









Before this experiment, everything was working just great -- sound card as well. Like I said, the decoder is still working great, even after the barbecue.

No one is saying anything like "you shouldn't have disconnected the engine", so at least I can eliminate that as a cause, I suppose. 

Greg and Hans, I believe you about the capacitors, but I'm brain-dead as to what value, and where they would go... 

...I don't suppose anyone is in the mood to improve on the diagram, and cite some part numbers? 

George, I don't suppose you're going to attempt this amplifying in the near future?

Again, thanks guys for your input, and the time you put into researching this, KRS. 

Best regards, 

===Cliff


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## Greg Elmassian (Jan 3, 2008)

I assumed he was running from DC... you can run the decoder in DC mode... 

Yes, DCC is a form of Alternating Current, where the polarity changes... it's actually a modulated square wave, but a full wave bridge will turn it back into DC.. 

Get a full wave bridge rectifier. Also, you should make sure you have a heat sink on your regulator, and you should have some idea of what current the amp draws. 

Still find it hard to believe the sound card is bad... the amp, yes... the regulator, yes... 

There should have been a circuit with the regulator, right on the back of the card, but just look it up, they will recommend a filter cap, maybe 100-470 mfd after the FW bridge, and also probably a .1 disc cap too. Both will be across the 12 volt output of the regulator. the filter cap will have plus and minus, the disc cap is nonpolarized, either lead is fine. 


Greg


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## krs (Feb 29, 2008)

Posted By CliffyJ on 06 Mar 2011 01:38 PM 
Thanks KRS and Hans, you're touching on the thing I was wondering about, and should have ask for advice on before I started lighting things up. Specifically, it seems that the amp & regulator need sure polarity, but the DCC power isn't like that... What is it? Is the DCC power actually AC, after it comes out of the booster? I'm confused. 

Anyway, as you suggest KRS, would a bridge rectifier solve this? If so, maybe 4 cheap diodes from Radio Shack would suffice? I don't mind spending the $ on a proper rectifier, it's the shipping costs for thing or the other that are killing me!









Before this experiment, everything was working just great -- sound card as well. Like I said, the decoder is still working great, even after the barbecue.

No one is saying anything like "you shouldn't have disconnected the engine", so at least I can eliminate that as a cause, I suppose. 

Greg and Hans, I believe you about the capacitors, but I'm brain-dead as to what value, and where they would go... 

...I don't suppose anyone is in the mood to improve on the diagram, and cite some part numbers? 

George, I don't suppose you're going to attempt this amplifying in the near future?

Again, thanks guys for your input, and the time you put into researching this, KRS. 

Best regards, 

===Cliff


Cliff -

To get the information which bypass capacitors are recommended (if any) for a device, the best thing to do is to download the datasheet from the manufacturer and follow that.

For the LM 7812T, the National datasheet shows this:











The information may be slightly different for the same device from another manufacturer, so it's best to get the datasheet of the manufacturer whose device you are using.

Adding these capacitors won't hurt but I don't think they are necessary in your application.

As to the bridge rectifier, you can certainly use four diodes instead, just make sure they are rectifier diodes with a 1 amp or better rating, not low current signal diodes.

But Radio Shack also sells small integrated rectifier diode bridges, makes for less wiring and a neater final product.

Oh, DCC is a "bi-polar" square wave:










so after you pass it through a diode bridge you end up with the DC value less the diode drop of the bridge.

However, none of what I just posted above would rxplain why the sound module blew up other than the input voltage being too high.

But even if that wasn't the cause - Digitrax (or anyone else) won't warrant anything if the device is not used within its specified design parameters.


Can you lower the DCC voltage to 20 volts or below or does that create other issues?

Regards,

knut


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## CliffyJ (Apr 29, 2009)

Posted By Greg Elmassian on 06 Mar 2011 02:15 PM 
I assumed he was running from DC... you can run the decoder in DC mode... 

Yes, DCC is a form of Alternating Current, where the polarity changes... it's actually a modulated square wave, but a full wave bridge will turn it back into DC.. 

Get a full wave bridge rectifier. Also, you should make sure you have a heat sink on your regulator, and you should have some idea of what current the amp draws. 

Still find it hard to believe the sound card is bad... the amp, yes... the regulator, yes... 

There should have been a circuit with the regulator, right on the back of the card, but just look it up, they will recommend a filter cap, maybe 100-470 mfd after the FW bridge, and also probably a .1 disc cap too. Both will be across the 12 volt output of the regulator. the filter cap will have plus and minus, the disc cap is nonpolarized, either lead is fine. 


Greg Thanks Greg, I'll do the rectifier, and test the output, before I do anything else. 


And thanks Knut for that diagram, I very much appreciate it. It helps me picture what Greg is describing. Also for the tip on RS's rectifier.

Greg, the amp is 2W, that's all I know... but thanks for the tip on heat sinking.

Maybe I should doctor the diagram per all this advice, and push it back up here, for comment...

===Cliff


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## CliffyJ (Apr 29, 2009)

Guys, here's the diagram with rectifier and cap's.












But what value for the caps? Greg, you mentioned 100-470 mfd, but Knut, your article mentions .1mfd....

No data sheets came with the rectifiers, but I did hunt up such from three sources. Unfortunately, all their diagrams are examples that cover a range of regulator product and application, so I'm not confident in making that call. So... averaging your numbers (and maybe I'm misunderstanding them?), would a 100mfd cap suffice? Also, should I put one on both input and output legs of the regulator?

Thanks so much for your advice, Greg and Knut, I sure appreciate it. Maybe this effort, whether I have to buy a new Soundbug or not, will have some purpose in speaker amplifying, for others...?

But only if it ends up working!









One thing I didn't admit to you is that when I first applied the track power, and just before Mount Pinatubo erupted, there was a very distinct scream from the Soundbug. No speakers were attached; the sound came from the tiny board itself. It was sad... I was SO happy with it... and I killed it... I can still hear that piercing cry for help, but I wasn't quick enough to pull the plug... I'm trying to get over it... *sniff*...









But ****, you can bet I'm going to be extra-industrial-strength-anal on attempting the next install!









===Cliffy


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## krs (Feb 29, 2008)

Posted By CliffyJ on 06 Mar 2011 03:38 PM 
Guys, here's the diagram with rectifier and cap's.












But what value for the caps? Greg, you mentioned 100-470 mfd, but Knut, your article mentions .1mfd....

No data sheets came with the rectifiers, but I did hunt up such from three sources. Unfortunately, all their diagrams are examples that cover a range of regulator product and application, so I'm not confident in making that call. So... averaging your numbers (and maybe I'm misunderstanding them?), would a 100mfd cap suffice? Also, should I put one on both input and output legs of the regulator?

Thanks so much for your advice, Greg and Knut, I sure appreciate it. Maybe this effort, whether I have to buy a new Soundbug or not, will have some purpose in speaker amplifying, for others...?

But only if it ends up working!









One thing I didn't admit to you is that when I first applied the track power, and just before Mount Pinatubo erupted, there was a very distinct scream from the Soundbug. No speakers were attached; the sound came from the tiny board itself. It was sad... I was SO happy with it... and I killed it... I can still hear that piercing cry for help, but I wasn't quick enough to pull the plug... I'm trying to get over it... *sniff*...









But ****, you can bet I'm going to be extra-industrial-strength-anal on attempting the next install!









===Cliffy



Cliff,

The capacitor Gregg and I suggested are for different purposes.
The diagram I posted was straight out of the National datasheet. Those two small capacitors are required for certain designs to preven this voltage regulator from oscillating. However, in this particular design, neither of the criteria mentioned on the datasheet apply so you shouldn't need either one of them.

The 100 to 470 uf capacitor Greg mentioned is a filter capacitor and is usually required to reduce ripple when the input to the bridge rectifier is regular 60 Hz AC. With the DCC waveform being a square wave, there is essentially no ripple and a small capacitor will get rid of what little ripple there is.

However, when one runs a sound module with the DCC power there is potentially another problem. If the loco pick-ups loose power, even for just an instant, some sound modules then switch back into the start up sounds.

Don't know if that is a problem here. In those situations, adding a larger capacitor like the one Greg suggested, would bridge the loss of momentary power to the sound module and prevent that potential problem.
However, I would wire the 470 uf capacitor after the bridge and before the regulator. That way it can charge up to the full DCC voltage and the bridging effect is longer..........

This actually brings up a question, where is the power for the sound module coming from? Is that supplied by the DCC signal rectified on the decoder or sound module?
Then what I just wrote applies to the sound module power.
I guess I need to read up on that Digitrax unit a bit more.

I think before you apply power to another soundbug we should try to figure out why it blew the first time. 


Edit:
Ok, just looked at the soundbug.
It comes with a 330uf capacitor. That will do the bridging over momentary power losses. So the capacitor suggested by Greg will only keep the amplifier operational when power pick up is lost momentarily.
Still a good thing to include.


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## Greg Elmassian (Jan 3, 2008)

2 watts output at 12 volts input would be 0.167 amps (assuming 100% efficiency of the amplifier)... so I believe you are well within the rating of the regulator, although it will get warm because you have to "drop"10 volts or so (from the DCC track voltage). 

Knut is right, rectifying the DCC signal (ignore the stretched 0 part) gives you DC that will require very little filtering. Still I would put some there because of noise, and that the DCC waveform is not perfect on the rails. I'd still use 100 mfd, but that's just me, and I'd put a .1 in the input and output too. Remember you should use a 35v minimum electrolytic cap if you use one. The .1 disc caps will probably be available in 50v or above, they are cheap and small. 

All I can guess is that the DCC signal got through your regulator, and into the power amp, but that seems far fetched. Have you tested the power amp to see if it is undamaged? 

Greg


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## CliffyJ (Apr 29, 2009)

Thanks KRS. Not sure what to do, but thanks for your education on these matters. 
Perhaps Greg or George will swing in with some additional clues. 
Do you work for Digitrax? 
===Cliff


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## CliffyJ (Apr 29, 2009)

Thanks Greg, 
I'm trying to abosorb what you said, but my wife is calling me to the table, and I'll have to engage tomorrow...
It would be nice if we could have a discussion on screw threads or welding or kinematics sometime, then I wouldn't look so stupid...








===Cliffy


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## krs (Feb 29, 2008)

No Cliff,

I don't work for Digitrax........

I used to design commercial electronic circuits in the telecommunication and data industry until I moved into Product Management.

However, back to the problem at hand.
The amplifier module that you are using is described as having a common ground. So I assume the circuit looks something like this:










I wonder if one side of the soundbug output connected to ground could have caused it to blow - the output of that device was designed to normally be connected to a 32 ohm speaker with no external ground applied.


Has anyone else ever used this amplifier module with this soundbug?


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## George Schreyer (Jan 16, 2009)

The bridge is wired incorrectly 

Also, the SFX004 outputs cannot be connect to the amp that way. I has an H bridge output and NEITHER output can be connected to the ground input of the amp. You'll need to use an isolation transformer.


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## Greg Elmassian (Jan 3, 2008)

Bada BING! 

There's the answer! 

Greg


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## CliffyJ (Apr 29, 2009)

Thanks George... I think you said you've not taken on this project, correct? Or happened to have a diagram handy, to show how it's supposed to be done? 

Knut, this idea began in this thread (second page, first post): 

http://www.mylargescale.com/Community/Forums/tabid/56/aff/34/aft/118599/afv/topic/Default.aspx 

Dave Bodnar was quoted there, so I suppose he's figured it out. I'll ping him.  

[edit, about 1 minute later: Greg just confirmed your thoughts George, not that I didn't believe them Sir, it's just that this is Greek to me in many ways]

===Cliff


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## CliffyJ (Apr 29, 2009)

Posted By Greg Elmassian on 07 Mar 2011 03:16 PM 
Bada BING! 

There's the answer! 

Greg Awesome!!

I'ts clear now that I messed this whole subject up by assuming erroneous things about the DCC power. 


Can anyone help a bruther out with a diagram and component specs?

Here's the bennies (per that other thread I just cited): a $40 soundbug, which has the "slimmest watt that I've ever heard" (quoting you, George) has the potential of being made to be "heard across a very large outdoor layout! " (quoting Dave B.) with this amp kit. See: http://www.trainelectronics.com/art...AVoice.htm

If we could get the total cost for this project under $60, that would still put it ahead of the alternatives, correct? So if you guys are game, I'll keep diagramming (with your feedback) and posting until this sucker works. OR, one of you might cut to the chase, and put up a diagram of your own?









Oh, great news on my end: after I'd spilled the beans to Digitrax on how the 'bug got fried, and with my assuming the same as you Knut, their response today was this: 

_It is difficult to say why is _[sic] _smoked. If you purchased it less than one year ago it is under warranty no matter what happened. Send it to us for warrranty replacement. _ 

All I can say is, Wow! These guys really stand behind their product!! 

Oooh, I also got in the mail today my E5 (Edison 'Liliput Base', the smallest ones that ol' Tom ever planned for) 28v bulbs for the passenger cars -- only .39 cents apiece, from PlanetBulb.com! 

Thanks guys,

===Cliffy


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## Greg Elmassian (Jan 3, 2008)

Buy that isolation transformer... 

I found one in Radio shack, but it's 300 to 5,000 Hz, not good, and the impedance is too high. 

Search for 1:1 audio isolation transformer... the electronics supply places will have it. 

Greg


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## CliffyJ (Apr 29, 2009)

Well, now that I've gone back onto that subject, I couldn't help but shere this.

The new 28v bulbs went in perfectly. Here's a shot of the original AC car and bulbs, on DCC:











And here it is with the new bulbs:











Be nice if there were 50v versions of these babies; but at least these'll last for more than a couple of evening runs, and not blind me!

Thanks again for the confirmation George, you and Thomas Edison just made my day!! 

===Cliffy


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## Greg Elmassian (Jan 3, 2008)

You can add one diode to the string of lights, that will cut your DCC in about half... 

Greg


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## CliffyJ (Apr 29, 2009)

Posted By Greg Elmassian on 07 Mar 2011 03:58 PM 
Buy that isolation transformer... 

I found one in Radio shack, but it's 300 to 5,000 Hz, not good, and the impedance is too high. 

Search for 1:1 audio isolation transformer... the electronics supply places will have it. 

Greg 
Thanks for taking the time in looking that up Greg. 

I hate to admit it though, that I don't understand what the main specs mean. E.g., I did as you suggested, but I only vaguely understand Hz, but not really Ohms, let alone RMS.... do I get points for knowing that it means root mean squared? And it probably doesn't, does it?

What you've saved me another Soundbug on is that you've made it clear that an audio isolation transformer is what's called for, not a simple transformer. But even then, I don't understand the why. We're trying to get the power cooperating with the regulator with the amp, right? We haven't even started with the audio side of the circuit, right?

===Cliff


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## CliffyJ (Apr 29, 2009)

Posted By Greg Elmassian on 07 Mar 2011 04:26 PM 
You can add one diode to the string of lights, that will cut your DCC in about half... 

Greg Oh! Like, in the undercarriage, right after one or other of the pickup wires? Can't get to the circuit board, but that fix would be easy! Thank you Sir! 

===Cliffy


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## CliffyJ (Apr 29, 2009)

Back to the sound card, I was re-reading Dave B's article, and saw this: 

"It is important that you not connect the speaker output from the sound board directly to the input of the amplifier. The transistor must be bypassed." 

Don't mean to muddy the waters here, because we're speaking of DCC power, and I think his article was based on 12vdc battery or rail power. But might this warning be applicable here as well? 

===Cliff


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## CliffyJ (Apr 29, 2009)

Dave B. just PM'd me back, with this reply: 

................... 
Cliff - I would go along with putting a bridge rectifier before the 7812 along with an electrolytic capacitor (say 1000 or more mfd at 35 volts) on the input to the 7805 and a 4.7 mfd / 16 volt tantalum cap on the output. That would clean up the power that is getting to the amplifier. I don't quite understand how the sound unit got fried as it is after the decoder. Are you showing all of the wiring that is done? Is it possible that the sound unit is wired in parallel with the decoder to the track power pickups? 
.................. 


(I think I've got to cool it with PM's, but sometimes I get anxious for a dude to respond... 

Also, no Dave, the Soundbug is a piggyback board on the decoder (which still works fine, *phew* and PTL), so it couldn't have been wired as you describe. Yes, all the wiring I did is as shown on my diagram, at least to the best of my knowledge.

So... Greg and George, would the input rectifier solve the main issue? I was understanding all that, at least... or must I completely isolate things with the audio amp? That's something I don't understand. If the latter, could someone help me pick one out? 

Thanks again everyone, and thanks for putting up with me Dave, I'll behave in the future...  

===Cliffy


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## krs (Feb 29, 2008)

Posted By George Schreyer on 07 Mar 2011 03:10 PM 
The bridge is wired incorrectly 

Also, the SFX004 outputs cannot be connect to the amp that way. I has an H bridge output and NEITHER output can be connected to the ground input of the amp. You'll need to use an isolation transformer.


Re - "The bridge is wired incorrectly"

If Cliff bought a diode bridge at Radio Shack as I suggested, like this one for instance:











the wiring is fine the way the + and - connections are shown in the drawing

it's just that the diodes within the bridge are oriented incorrectly.


However, if individual diodes are used, yes then the wiring shown is wrong 

the two diodes the red arrows point to need to be reversed.












As to the SFX004 output, if it is an H-Bridge that would explain why device was destroyed when connected to the amp this way.


Using an isolation transformer is the proper way to address this issue but for the hobbyist the right ones are hard to find.


I would try to either use two non-polarized coupling capacitors or get an amplifier with a floating input.


Brings up the question - why is an amplifier even needed?
The soundbug is supposed to put out 1 watt (rms I assume), that should be enough to drive a high efficiency high impedance speaker to a reasonable volume.


The amp used is only a 2 watt amp, doubling the output power only increases the volume marginally.


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## CliffyJ (Apr 29, 2009)

Yep, I drafted the dang bridge incorrectly... 

Thanks Knut... sorry for the red herring everybody... 

I couldn't hear much of the output from the Soundbug's speaker, over the noise of the loco. As George said, "it's the slimmest watt that I've heard," and I agree, even after attempting several acoustic treatments that George describes. I'd like this sucker to be audible "on the other side of the layout" (as Dave B. describes), or at least from 10 feet away. 

Keep in mind that this sound card is intended for HO and O gauge trains. But the PNP decoder is good for G gauge. So I'm trying to amp it up. 

===Cliffy


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## krs (Feb 29, 2008)

Posted By CliffyJ on 07 Mar 2011 05:40 PM 



So... Greg and George, would the input rectifier solve the main issue? I was understanding all that, at least... or must I completely isolate things with the audio amp? That's something I don't understand. If the latter, could someone help me pick one out? 

Thanks again everyone, and thanks for putting up with me Dave, I'll behave in the future...  

===Cliffy 



On Dave's website just at the end it states:

".........The amplifier will have two pins for input. One is connected to ground (- lead on the battery) and the other goes into the amplifier circuitry. Since we already have a ground connection through the battery we only need to connect the other wire to the base (center lead) of the amplifier transistor on the sound board. It is important that you not connect the speaker output from the sound board directly to the input of the amplifier. The transistor must be bypassed."

I don't quite understand what he is trying to say....bypass which transistor?

In any case, he just seems to be connecting ONE lead from the soundbug to the input of the amplifier (the centre lead) that goes to the base of the amplifier transistor.

That would eliminate connecting ground to the output of the soundbug which is what destroyed it in the first place.

But then I don't understand Dave's next sentence: 

"It is important that you not connect the speaker output from the sound board directly to the input of the amplifier."

So how does one conncet it, via what???
And back to the other question - what transistor?

I think Dave needs to clarify things on his webpage a bit more.

knut


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## krs (Feb 29, 2008)

Posted By CliffyJ on 07 Mar 2011 05:54 PM 
Yep, I drafted the dang bridge incorrectly... 

Thanks Knut... sorry for the red herring everybody... 

I couldn't hear much of the output from the Soundbug's speaker, over the noise of the loco. As George said, "it's the slimmest watt that I've heard," and I agree, even after attempting several acoustic treatments that George describes. I'd like this sucker to be audible "on the other side of the layout" (as Dave B. describes), or at least from 10 feet away. 

Keep in mind that this sound card is intended for HO and O gauge trains. But the PNP decoder is good for G gauge. So I'm trying to amp it up. 

===Cliffy 
It's just that the audible difference between a 1 watt audio signal and a 2 watt audio signal is barely noticeable - the sound doesn't get twice as loud as many people think.


The biggest improvement using the separate amplifier is that you can now drive an 8 ohm speaker, with the soundbug I think you get a 32 ohm speaker as part of the package.
If you use an 8 ohm speaker with the soundbug you can't get any volume because the soundbug can't drive enough current through the 8 ohm speaker.


Could of course also be that the 1 watt rating of the soundbug is wishful thinking - don't know, never used one.

If you try the approach of just connecting one speaker lead to the input of the amp, I would still use a coupling capacitor to be on the safe side unless you can determine that the amp includes an input coupling capacitor on the board.

The schematic of the amp I posted doesn't show a capacitor but that schematic is just representative of a typical circuit using that amplifier chip in a grounded in/out configuration.

Have you done any googling to see if anyone has used this soundbug successfully with a high efficiency and most important, high impedance speaker?
A bit of a long shot that this would be loud enough. I really doubt the 1 watt rating, maybe it's a "peak music power" which would make the equivalent rms rating only a few milliwatts.


Knut


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## George Schreyer (Jan 16, 2009)

There is no chance that the SoundBug can make a watt. 200 mW... maybe 

you can use a small audio transformer of the kind that used to be used in transistor radios. Put the 500 or so ohm winding on the SoundBug, and the 8 ohm winding on the amp. Don't worry about the stepdown, the SoundBug will still have plenty of output voltage to drive the amp even with the step down. 

I did a similar thing with a DSX which has about the same audio power output. 

See http://www.girr.org/girr/tips/tips8/dsx_tips.html 

I found an old transformer in a junk box but it looks like this one would work

http://www.radioshack.com/product/index.jsp?productId=2103254 


And Digitrax will indeed replace it. It's called a goof proof warranty and they mean it.


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## CliffyJ (Apr 29, 2009)

Posted By George Schreyer on 07 Mar 2011 08:05 PM 
There is no chance that the SoundBug can make a watt. 200 mW... maybe 

you can use a small audio transformer of the kind that used to be used in transistor radios. Put the 500 or so ohm winding on the SoundBug, and the 8 ohm winding on the amp. Don't worry about the stepdown, the SoundBug will still have plenty of output voltage to drive the amp even with the step down. 

I did a similar thing with a DSX which has about the same audio power output. 

See http://www.girr.org/girr/tips/tips8/dsx_tips.html 

I found an old transformer in a junk box but it looks like this one would work

http://www.radioshack.com/product/index.jsp?productId=2103254 


And Digitrax will indeed replace it. It's called a goof proof warranty and they mean it. 


Thanks George!

Now I understand (after looking at your article/s diagram); I'd thought you were describing a transformer instead of the rectifier. 

I'll compose a diagram based on yours, but tries to use the Qkits amp, and see if I'm getting closer.

===Cliffy


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## CliffyJ (Apr 29, 2009)

Here's the diagram. Is this getting closer? 
The capacitors are a shot in the dark. 
George, I hope you don't mind, but I included your diagram for easier reference.


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## Greg Elmassian (Jan 3, 2008)

I'd change the cap on the regulator output to .1 mfd 
I'd have a 470 mfd or so in the input side of the regulator, in parallel with your .33 mfd... 

The .1 on the output helps transient response, the .33 on the input helps prevent oscillations, the 470 would be a filter and a little "storage time" if the power is interrupted briefly. 

Greg


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## CliffyJ (Apr 29, 2009)

Posted By Greg Elmassian on 08 Mar 2011 03:48 PM 
I'd change the cap on the regulator output to .1 mfd 
I'd have a 470 mfd or so in the input side of the regulator, in parallel with your .33 mfd... 

The .1 on the output helps transient response, the .33 on the input helps prevent oscillations, the 470 would be a filter and a little "storage time" if the power is interrupted briefly. 

Greg Like this Greg?









Also Greg, do you have any issues with the impedence of this R'shack xformer? I think this one that George recommends is different perhaps than what you referred to earlier, but I couldn't quit tell.

Thanks Greg, George, Knut, and everyone else, I apprieciate the patience you guys are exercising with me!









===Cliffy


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## krs (Feb 29, 2008)

Posted By CliffyJ on 08 Mar 2011 04:11 PM 
Posted By Greg Elmassian on 08 Mar 2011 03:48 PM 
I'd change the cap on the regulator output to .1 mfd 
I'd have a 470 mfd or so in the input side of the regulator, in parallel with your .33 mfd... 

The .1 on the output helps transient response, the .33 on the input helps prevent oscillations, the 470 would be a filter and a little "storage time" if the power is interrupted briefly. 

Greg Like this Greg?









Also Greg, do you have any issues with the impedence of this R'shack xformer? I think this one that George recommends is different perhaps than what you referred to earlier, but I couldn't quit tell.

Thanks Greg, George, Knut, and everyone else, I apprieciate the patience you guys are exercising with me!









===Cliffy



Cliffy -

Now you have the bottom two diodes in the bridge backwards.

The 0.33uf capacitor shows in your diagram as a 33uf capacitor, I don't see a decimal point.
I always use 0.xx rather than .xx in schematics, part of Bell Labs standards.
Same for the .1uf cap, I would show it as 0.1uf
On the 470uf electrolytic you need to show the polarity with a + sign or use the polarized capacitor symbol. You also need to show the voltage rating.


I think the Radio Shack transformer will work but you should show the winding impedance and the fact one side has a center tap.

Knut


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## Greg Elmassian (Jan 3, 2008)




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## CliffyJ (Apr 29, 2009)

Thanks guys.
Here's another attempt:









Questions: 
Should all the cap's be polarized electrolytics? Or do some need to be disc type?
Does 30v sound about right? Or do I need to look for caps that are good for 22v or more?
Knut, is the center tap on the xformer wired to anything?
Did I bound the amp properly (vs. George's schematic)?
Am I missing any other components? George has a couple more resistors, and a cap upstream of the speaker... 
Maybe I should also get a little breadboard to sire this stuff on (but I've never tried that).

Other than that, is anyone willing to say things like, 'that out to work' and 'you don't need anything else'?









Thanks again.

===Cliff


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## Greg Elmassian (Jan 3, 2008)

It's difficult to make non polarized capacitors in large values. at 0.1 mfd, a non polarized capacitor is cheap 

When you are at 100 mfd, then a non polarized is much bigger and more expensive, so most people use polarized (electrolytic) caps. 

Looking good, hook it up.. the revelation by George that the sound bug had an H bridge output was the key, that's why you need to isolate the output of the sound bug from the amp, and that's undoubtedly why it fried. 

Greg


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## CliffyJ (Apr 29, 2009)

Posted By Greg Elmassian on 09 Mar 2011 03:46 PM 
It's difficult to make non polarized capacitors in large values. at 0.1 mfd, a non polarized capacitor is cheap 

When you are at 100 mfd, then a non polarized is much bigger and more expensive, so most people use polarized (electrolytic) caps. 

Looking good, hook it up.. the revelation by George that the sound bug had an H bridge output was the key, that's why you need to isolate the output of the sound bug from the amp, and that's undoubtedly why it fried. 

Greg 

Thanks for explaining that Greg, I thought it was a matter of capacitor functionality!

And thanks for the green light. I'll go ahead and get the stuff, and be ready when the replacement 'bug comes in the mail. 

In my explanation to Digitrax as to how the problem happened, I promised that I was engaging expert opinion via the forums on MLS, and it wouldn't happen again. So I'm very glad that George hit on the cause, and that you so profoundly affirmed it. 

Of course, it's embarrasing that I'd not done what we talked about before, i.e., reading everything on George's site three times...







I'd not even seen yet the article he posted







. Oh well, water under the bridge; but evidence once more on the patience you folks employ here, and I'm very grateful.

===Cliffy


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## krs (Feb 29, 2008)

Cliffy -

You're pretty much good to go.

Re
Questions: 
Should all the cap's be polarized electrolytics? Or do some need to be disc type?
- As Greg explained, the 470uf is an electrilytic basically to keep the size and cost down. Must have a voltage rating of 30 volts or better and must be wired with the correct polarity.
If in doubt about the polarity post a picture of the one you have and ask!

The 0.1uf must be a ceramic disk to perform its intended function, voltage rating would automatically be 50 volts or better. These are not polarized, wire them either way.
Same for the 0.33uf one although that is probably a different type.
For the specific application you have, I don't think you really *need* either the 0.33 or 0.1uf cap but they can't do any harm.


Does 30v sound about right? Or do I need to look for caps that are good for 22v or more?
- You typically want to pick a capacitor with a voltage rating of 50% or more than the maximum voltage you expect to be applied to the capacitor.

Here with the voltage drop through the bridge, you end up with about 20 volts at the capacitor, so 30 volts or better is good.

Knut, is the center tap on the xformer wired to anything?
- The Radio Shack transformer actually has a 1000 ohm winding with a center tap. So you will be using one side and the center tap of the transformer if you want the 500 ohm impedance.

You can also try to just connect the two outer leads to get the 1000 ohm winding and connct nothing to the center tap and see what the difference in volume is.

Did I bound the amp properly (vs. George's schematic)?
- Forget George's schematic. He bought all the components and built his own amp.
In his circuit he had to add all the compensation components and the coupling capacitors separately.
You have a finished amplifier board which already includes all these required components.

Am I missing any other components? George has a couple more resistors, and a cap upstream of the speaker... 
-No, see above.

The capacitor "upstream" from the speaker in George's schematic is already on your amplifier board.
The schematic of your ready made amplifier board looks something like the drawing I posted earlier:








The board will include all of the required components except the speaker.


On this particular schematic there is already a 0.1uf capacitor across the power supply rail, so in this case you wouldn't need the one shown on your drawing.


Did you get a schematic with the amplifier you bought?
Might be a good idea to post that schematic here.


Knut


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## George Schreyer (Jan 16, 2009)

The parts on my schematic are related to issues with the particular IC that I used. Your amp is self contained and doesn't need any of that. 

You can try to use the whole primary, if you don't get enough volume, then use half of the primary (center tap to one end). The SFX004 MIGHT want to see a more resistive load so you might consider shunting the primary with a resistor, maybe 33 ohms, the rating of the speaker that originally came with the unit. It might work fine without a load resistor. 

Basically, with the audio output of the SFX004 turned all the way up, you want to drive the amp to about full power. Since the amp kit has a volume control, first turn it down, then turn it up slowly until you hear some distortion and back it off until any distortion goes away. This will give you the best signal to noise ratio through the whole system. After that, you can turn down the SFX004 output with CV57 to get the actual volume that you need.


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## CliffyJ (Apr 29, 2009)

Thanks Knut and thanks George for the further background and instruction. I sure appreciate it. 

What with one thing or the other, the shopping list got kinda long, so I just completed my mail order to Radio Shack. Maybe not the cheapest place, but at least the parts are (thanks to all you guys) defined and on the way. 

I'll be sure to post when things are working, or if I light my house on fire, which ever comes first.  

Seriously, thanks so much for all your help. 

As an aside, perhaps all this is helping my inner child get over those Heathkits I fried when I was a kid....









===Cliffy


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## CliffyJ (Apr 29, 2009)

A minor update: 

Got the power regulation board built today, and it tested out fine when hooked up to rail power (giving 12vdc output). 

But... when I installed my (replaced) Soundbug on the mother board, it didn't work at all. Apparently I toasted some elements of the decoder's circuits that feed the Soundbug, when I fried that a few weeks ago. So, it seems that I'll have to rely once more on Digitrax's generous replacement policy, but now for the decoder. 

It's nice to see a company that honors their products so well, even to the point of covering a customer's stupid mistakes. I'm sure a big fan of theirs!! 

===Cliff


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## CliffyJ (Apr 29, 2009)

Greetings Gents, 

Well, I got everything hooked up finally, and it worked! And when you crank up the volume, this baby is LOUD! 

The problem now is that there is a lot of noise coming over the (new) speaker, a steady hum (a combination of low and high pitch) that's quite loud. It changes with the volume pot setting. 

I wired things up as we discussed, with the following experiments to take this hum out: 
-- Tried putting the sound input to the audio transformer on the outer wires, then one outer with the center tap (as Knut mentioned), and it didn't make much diff.
-- Tried putting a 33mf cap across the speaker terminals (as George mentioned), no diff.
-- Disconnected from the audio transformer entirely (just speaker, 2w amplifier, and power conditioner board we designed together), still no diff. 
-- Checked the output from the power conditioner board, all is fine... which seems to leave the 2w amplifier as the culprit

Any ideas on what else this might be? If not, and if I just let it hum, does it seem like something is getting damaged? 

Other than that, no smokin' boards, and it seems to be getting close!! 

Thanks again, 

===Cliffy


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## krs (Feb 29, 2008)

Cliffy - 

On the hum............. 

Try to figure out where it comes from. 
Since the hum changes with the setting of the volume control I assume it is NOT generated by the amplifier. 
You can verify that by disconnecting the wires going from the transformer output to the amplifier input and then shorting the amplifier input. 
Always do any of this with the power OFF. 

Then, with the amplifier input shortewd, turn up the volume to see how much hum/noise is generated by the amp. Hopefully nothing or very little. 

Next step is to do the same thing but with the connection from sound bug to transformer input. 
Connect the transformer output back to the amp input and disconnect the sound bug from the transformer and shortthe input leads of the transformer to see if there is an increase of hum/noise with the transformer in the circuit. 
If that is still OK, then the hum comes from the sound bug or is picked up by the wiring. 
Unlikely that it's picked up by wiring, I assume all your wires - soundbug to transformer - to amplifier are short. 

Can't help you with the CAM input 

Knut


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## CliffyJ (Apr 29, 2009)

Oops, I was editing while you were posting Knut, sorry about that. I'll read yours carefully, and get right back. 
Thanks!


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## CliffyJ (Apr 29, 2009)

Knut, 

Here's what I've done / learned since you posted. 

Per your instruction, I disconnected the transformer from the amplifier, etc. No hum at all with the amp's audio input shorted. For grins, I tested it with the input not shorted, and the hum was about 2x as loud. 

As for the soundbug input, I see that I made a mistake in my original & edited post. It was disconnecting the soundbug's input to the audio transformer that didn't make any difference in the hum. Sorry for confusing things further. 

Since I'm still in a breadboard stage, my wires are ~18" long, with most of the gear in a trailing car. Might that be the cause? 

Thank you Sir, 

Cliff


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## Greg Elmassian (Jan 3, 2008)

Those wires will make great "hum" antennas.... 

Greg


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## CliffyJ (Apr 29, 2009)

About that Soundbug cam input... 

Digitrax's wiring instructions for the cam input are sparse. Specifically: 

"connect the white CAM lead to the cam output connection". 

We've gone over the magnet & reed switch stuff earlier, and I have all the bits. But before I blow up something else by miswiring, please confirm (or deny) the following. Sounds like I only need to feed one rail power wire to the reed switch, than to the Soundbug's (single) input wire. Does that sound right? If so, does it matter which rail side (fireman's or engineer's) the trigger power comes from? 

Thanks very much, 

===Cliffy


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## CliffyJ (Apr 29, 2009)

Posted By Greg Elmassian on 09 Apr 2011 10:53 AM 
Those wires will make great "hum" antennas.... 

Greg Oh!


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## krs (Feb 29, 2008)

Cliffy - 

Can you take your breadboard and mode it around, change the orientation and listen to the hum to see if it changes at all. 
If it does, that would give you an indication that the unitv picks up hum externally. 

Does the sound bug have a volume control on it? 
Turn that up as much as possible, just to the level before you get distortion and use the amplifier to just give it that little extra boost. 
If you do pick up hum at the input of the amp, and it sure souds as if you do, you want to amplify that as little as possible. 

You can also try twisting the longer leads, that will reduce the hum if it's picked up externally. 

Knut


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## CliffyJ (Apr 29, 2009)

So, I shortened all the wires, put elec tape on everything, and made this nice little hamster nest:











Above the speaker, on the left is the power conditioning board; on the right is the audio amp. Next is the terminal block that came with the tender. To the left of the TB is the unused smoke unit switch; above it is the Digitrax decoder with Soundbug; to its right is the audio transformer. Somewhere buried in there is the still-connected Soundbug speaker with cap.

So after this wire shortening, the low-frequency part of the hum is about 1/3 what it was -- awesome! 

There's still a high-freq squeal though, which doesn't sound electronically healthy, or due to antenna-like issues. I can live with it, but if anything comes to mind, please let me know.

I'm so pleased to finally get this far! After long discussions here, I ordered the decoder / soundbug back in December. Almost four months later, and after much appreciated input from you guys here, I'm finally hitting pay dirt, and it's very cool. So, credit where credit is due:

-- Thanks Dave, for suggesting this amplifier idea
-- Thanks George for originally recommending the Soundbug, affirming Dave B's idea of the amplifier, and helping me work thru the product choices, and everything else.
-- Thanks Greg, for encouraging this effort, and all your specific insights.
-- And thanks Knut, for going into the trenches with me on all the details, and helping this wrench-turner out .

Not trying to be gushy; but what the ****, thanks brutha's! This rat's nest, messy as it is, really works! Even without the tighter wiring and speaker sealing and sound-box making, is LOUD! No exaggeration, my dog (upstairs in the kitchen, I'm in the basement) starts barking when I let off the Soundbug whistle! Before, with the virgin 'Bug, you could barely here it over the noise of the engine's motor. True, I hadn't given the speaker proper treatment, but wow, this is truly night and day. As someone opined earlier (I think you, Dave), this would indeed be heard across the layout.

Next things to work on are:
-- elimination of that high-freq squeal
-- how to neatly / permanently mount all this stuff

I'd surely appreciate any thoughts on those issues.

Best regards all, and thanks again,

===Cliffy


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## krs (Feb 29, 2008)

Cliffy - 

Can you draw an accurate schematic (wiring diagram) and post it here, Include all the component values and for capacitors the type you used. 
Can you guess at the frequency of the squeal? 
There must be sites on the net where one can play different tones back through the computer -that way you could compare the squeal frequency to one of those to get an idea what the frequency is. 
Again, try to isolate where the squeal comes from. 

For the final design I would try to mount everything on a Vero-board and only use wiring where absoluteky necessary - do whatever connections you can using the traces of the board. 

Knut


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## CliffyJ (Apr 29, 2009)

Hi Knut, 

I followed the schematic posted last, incl. all component values. Nothing changed from what we've worked out together in this thread.

As to your prior question, the audio amp has a volume pot on it, but the Soundbug doesn't. I'll try to do as I percieve that you advised earlier, in cranking up the Soundbug volume (this will be via CV settings), and back off on the amp setting (via the volume pot). 

Thanks for your wiring / mounting thoughts, I'll have to look up Vero board.

===Cliffy


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## krs (Feb 29, 2008)

Do you get the high pitched sound when you disconnect the leads between the transformer and apmlifier input and short the amp input leads? 

I'm wondering if it comes from the regulator because it's oscillation - unlikely, but if it does it's easy to fix. 

Knut


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## CliffyJ (Apr 29, 2009)

I'll guess ~1kHz, with an ongoing sound like "aaaaack", without the 'ck'.


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## CliffyJ (Apr 29, 2009)

Posted By krs on 09 Apr 2011 01:05 PM 
Do you get the high pitched sound when you disconnect the leads between the transformer and apmlifier input and short the amp input leads? 

I'm wondering if it comes from the regulator because it's oscillation - unlikely, but if it does it's easy to fix. 

Knut 

Per your question, I just disconnected the transformer from the lead wires to the amp's input. When doing so, the buzz got quite louder. When I walked away from the dangling leads to the amp, it got softer. When I put my hand near the ends of the dangling leads, it got louder. But when I touched the ends of the leads together, and shorted the input, the noise went absolutely silent.


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## krs (Feb 29, 2008)

Posted By CliffyJ on 09 Apr 2011 01:17 PM 

Per your question, I just disconnected the transformer from the lead wires to the amp's input. When doing so, the buzz got quite louder. When I walked away from the dangling leads to the amp, it got softer. When I put my hand near the ends of the dangling leads, it got louder. But when I touched the ends of the leads together, and shorted the input, the noise went absolutely silent.




Yeah, that's the hum pick up Greg was talking about.
That's normal with a high gain amplifier.
But since there is no hum/noise with the input leads of the amp shorted, there is no self-oscillations of either the regulator or the amplifier.

I wonder if the higher frequency sound is actually coming from the sound bug itself - can you hear anything if you connect a speaker to the soundbug directly? ...disconnecting the leads from the soundbug to the transformer of course when you test that.

The other possibility maybe the high primary impedance of the audio transformer.
The soundbug I assume would like to see a typical speaker impedance of 8 or 16 ohms - with this circuit it will see 500 ohms or even 1000 ohms depending on which transformer tap you use.

Knut


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## CliffyJ (Apr 29, 2009)

The soundbug has it's own speaker, but I can't tell if the buzz is coming out of it (it's to low in volume). When disconnected, the buzz is still there. 

But I did crank up the CV for its max volume, and backed off on the amp pot, and the buzz is semi-tolerable, at least for my present state of thinking. I wouldn't like it though, if five engines were in a yard, all humming away at this level of noise. 

But maybe the noise will disappear when I choose a different engine; I'll have to check. 

Also, now that the wiring is shorter, I'll have to re-experiment with moving the Soundbug output to the center tap + outer leg of transformer, vs. going with both outer legs and not center )as I have now). 

Also, George suggested a cap across the speaker terminals. I tried the 33mf, nothing; then 470mf (closer to that supplied with the Soundbug's speaker), but it just faded the audio. But again, that was before the wire shortening. So I'll try that also. 

Probably be tomorrow, because I promised to go to Mass wiith my wife, in about, say, 5 minutes... 

Thanks so much for helping diagnose this!! 

===Cliffy


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## krs (Feb 29, 2008)

But maybe the noise will disappear when I choose a different engine; I'll have to check. 

Does that mean you're running the electric motor when you do your testing? 
If so, the wiring "ratsnest" may pick up the motor noise. 

I'll have to re-experiment with moving the Soundbug output to the center tap + outer leg of transformer, vs. going with both outer legs and not center )as I have now). 

I don't think that will make much of a difference. 
What impedance is the loudspeaker that came with the soundbug? 
I'm thinking of reversing the transformer so that the soundbug "sees" an impedance close to that of a loudspeaker, however I think the level gets all messed up if you use the transformer the other way around and I sure don't want you to burn up another soundbug. 

Also, George suggested a cap across the speaker terminals. I tried the 33mf, nothing; then 470mf (closer to that supplied with the Soundbug's speaker), but it just faded the audio. But again, that was before the wire shortening. So I'll try that also. 

You really want to eliminate the buzz and noise at the source, not at the speaker. 
I just looked at a webpage on the sound bug. The capacitor in the picture is connected to the soundbug separate from the speaker - I assume it's there to bridge momentary interruption of power to the soundbug which would "confuse" the sound generation. 
Also, I see that the supplied speaker has an impedance of 32 ohms - so forget reversing the transformer, the 8 ohm load may burn out the sound bug. 
What you can try instead is to connect a resistor, about 50 to 100 ohms, whatever you have, across the input of the transformer. That will drop the volume but the key question is, does it affect the 'buzz'. 

But before that I would try the circuit without the motor of the loco running to see if that makes a difference with the buzz.


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## CliffyJ (Apr 29, 2009)

Thanks for all the ideas Knut, here's what I've found or tried this morning.

I've been generally testing with the loco stopped.
You were right, swapping to the center tap of the xfrmr didn't make a diff.
The soundbug speaker says it's 8 ohm, 1/4 watt. 
I tried a 270ohm resistor (across transformer input) for a moment (the only one I had handy), didn't make a diff for the buzz.
I swapped out the amplifier (I'd bought 2), same exact buzz.
I swapped out the speaker, no diff.


I think I mentioned this, but after backing down the volume on the amp, and cranking it on the Soundbug (via CV's), the buzz isn't noticable over the produced audio; it's only when the audio is stopped (no bells / whistles / etc.) that it's obvious. 

Maybe that's normal for a "high gain amplifier" like you pointed out earlier?

Also, you had asked: "Do you get the high pitched sound when you disconnect the leads between the transformer and apmlifier input and short the amp input leads?", and said "I'm wondering if it comes from the regulator because it's oscillation - unlikely, but if it does it's easy to fix." The buzz did go away; but is there an experiment I can do, in case it's the regulator? 

If not, perhaps I should start the final packaging, with shortest wires possible, and just hope for the best?

Thanks again for all your help,

===Cliffy


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## krs (Feb 29, 2008)

Cliffy, 

 There is always some residual noise level that any amplifier generates but it's normally below the threshold of hearing. 

And if you don't hear any noise/buzz with this amplifier with the input shorted, that means the noise generated by the amplifier internally or possibly fed through on the power leads from the regulator is below that threshold. 
So you can eliminate the amplifier or regulator as a source of the buzz. 

Did you ever short the 500 ohm side of the transformer (disconnecting it from the soundbug) to see if the buzz volume changes? 

Maybe the buzz is inherent in the output of the soundbug.


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## CliffyJ (Apr 29, 2009)

I just re-checked, and yes, if the amp's input is shorted, silence. 

Disconnecting the soundbug from the transformer cut the buzz to about 1/4 of what it was. Shorting the transformer's input leads didn't reduce it further. 

I notice if I thought the + input to the amp, the buzz gets really loud. Might there be a ground issue? Also, would using shielded cable help?


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## krs (Feb 29, 2008)

Disconnecting the soundbug from the transformer cut the buzz to about 1/4 of what it was. Shorting the transformer's input leads didn't reduce it further. 

OK - now we're getting somewhere. 

To me this means that the transformer and the wiring from transformer to amp input contributes a little bit to the buzz but that most of the buzz actually comes directly from the soundbug (since disconnecting the soundbug drops the buzz level by quite a bit. 

I notice if I thought the + input to the amp, the buzz gets really loud. Might there be a ground issue? Also, would using shielded cable help? 

I assume you mean "touch" rather than "thought" 
Again - I would say that's normal - you act as a large antenna. I don't think there is a grounding issue with either the regulator or the amplifier - if there was you would hear the buzz with the amps input shorted. 
But what about the decoder and sound bug? The wiring schematic doesn't show how these are hooked up - are there really only two leads in and two leads out, no other connections that need to be made? 

Knut


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## CliffyJ (Apr 29, 2009)

Yes, I meant 'touch', ha ha!

What you're saying all makes sense Knut. 

The main decoder wiring is pretty basic:
'a' & 'b' track power in (those shown in the schematic)
+ & - out to loco motor
+ & - out to headlight
another + to rear light

I didn't add the output wires to the schematic, since I was only dealing with the audio end of things.

Soundbug plugs directly onto the decoder, and has:
2 speaker wires out
2 wires to the dangling capactor 
a single wire for chuff input sync.

Well, that's about it. 

Not that I know anything about it, but I asked about shielded cable because the setup reacts to where I put my "antenna'-hand, and that seems weird. 

BTW, I had been testing things with the SB's original speaker still attached. I didn't want to snip it off until I was sure I wasn't going to send it back for replacement again!







But since things have seemed stable, I clipped it off just recently. But still, no change in the buzz.

Also, all the connections between main boards, the speaker and transformer are just wires twisted together for now. Maybe things will be quieter with final / shorter wiring. 

Thanks again,

===Cliffy


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## Greg Elmassian (Jan 3, 2008)

shielded cable might help, but now what do you hook the shield to? 2 wires plus a shield would need a ground reference that was not just the negative power lead. 

have you thought of twisting the wires? if the wires are of any length, twisting them can reduce what is known as "common mode" noise... that's why telephone lines are "twisted pairs" 

Just a thought, have not been following extremely closely, but remember some mention of 18" wires... bad idea... 

Greg


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## CliffyJ (Apr 29, 2009)

Thanks Greg, good idea. 

Also guys, I was just fooling around with the DCC end of things, and here's what happened. 

-- I selected a different (non-existent) loco, thinking that the soundbug wouldn't be active. But the buzz was still there. I tried this yesterday, but I wanted to confirm the effect. 
-- Here's the new bit. When increasing the throttle to this non-existent loco, the buzz changes in tone with each step. 

So perhaps the noise is just an artifact of the DCC which sound decoders are specially designed to take out, but this hobby amplifier isn't? 

I'll try twisting the wires next... 

===Cliffy


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## CliffyJ (Apr 29, 2009)

Twisting the wires made a slight difference, but not much.


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## krs (Feb 29, 2008)

-- I selected a different (non-existent) loco, thinking that the soundbug wouldn't be active. But the buzz was still there. I tried this yesterday, but I wanted to confirm the effect. 
-- Here's the new bit. When increasing the throttle to this non-existent loco, the buzz changes in tone with each step. 

So perhaps the noise is just an artifact of the DCC which sound decoders are specially designed to take out, but this hobby amplifier isn't? 

I think the amplifier you are using is fine, so is the regulator. 

Based on what you posted so far it seems that the PWM signal of the DCC decoder is somehow being coupled into the soundbug. 
A remote possibility may be that the DCC signal also causes interference, but I think that is unlikely. 
By selecting a different loco tou eliminated the motor noise being coupled back as a potential source. 

What PWM motor frequency did you select? 
You want to pick a frequency 20 KHz or higher. 

If you already use a high motor frequency then I think the buzz is an inherent problem with this decoder/soundbug combination that has become more pronounced because you use a better speaker than the one shipped with the soundbug and you also amplify the signal more. 

There is some residual noise pickup in the current wiring and maybe with the transformer - wiring everything possible using a vero-board should help and keeping any leads as short as possible, but from what I see most of the buzz is coming directly from the soundbug.


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## CliffyJ (Apr 29, 2009)

Very interesting Kunt. 

It took a bit to look up what PWM meant, and it was set to 0 on my system (NCE). I set it to 20, 21, 23, but sadly, no diff. 

While I was doing all this, the buzzing sound changed in tone quite a bit, with each change to one DCC setting or another. It got vastly quieter when I switched things to 'program track' function, but unfortunately got back up in volume when powering the track normally. 

I'll look into that Vero-board next. 

Thanks!


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## CliffyJ (Apr 29, 2009)

Just read an article on the Veroboard usage, very cool! 

http://www.societyofrobots.com/member_tutorials/node/90 

I wish I'd used that for the power conditioning board. For now, since I only have circuit boards to deal with (plus the transformer), I'll need to mechanically fasten them to a substrate, maybe styrene. And then focus on speaker sealing and chuff sync. 

Thanks again Knut, 

===Cliffy


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## krs (Feb 29, 2008)

It took a bit to look up what PWM meant, and it was set to 0 on my system (NCE). I set it to 20, 21, 23, but sadly, no diff. 

While I was doing all this, the buzzing sound changed in tone quite a bit, with each change to one DCC setting or another. It got vastly quieter when I switched things to 'program track' function, but unfortunately got back up in volume when powering the track normally. 

Cliffy- 

I was talking about the PWM frequency the decoder uses to drive the loco motor. 
Not sure what CV you are changing, I couldn't readily find the CV options for that Digitrax decoder on the net. 
If you are changing motor drive frequencies, what frequencies do the settings 0, 20, 21 22 etc correspond to? 
The sales sheet suggests the motor drive is "Supersonic" but there is no frequency specified.


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## krs (Feb 29, 2008)

Just read an article on the Veroboard usage, very cool! 

I only looked at the beginning of this article, but if you check the net you will find that there are many different types of this vero-board. 
Different sizes, different track layouts, Radio Shack used to have quite a few different types but cut back on those. 

Lay out your components in the most logical fashion (from a connection point of view) and then draw a few options to see which type of Vero-board works best for your circuit. 
You shouldn't have to cut too many printed circuit board paths if you arrange the components properly.


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## CliffyJ (Apr 29, 2009)

Um... I don't know... 

I wasn't changing a specific CV, just going thru the menu. When I got to the topic (on the handheld) for this, it said: PWM FREQ 
And I assumed it was Khz, but maybe not? 

The NCE manual says this on the subject: 

DCC decoders almost always drive the motor of the locomotive with Pulse Width 
Modulation (PWM). This is a series of full voltage pulses that vary in width from very 
narrow for low motor speed to very wide providing higher power to the motor. How often 
the pulses are sent is called the frequency. 

The frequency is adjustable on some decoders. Settings for this CV vary so consult your 
decoder manual for the proper value. If your decoder is capable of ‘silent’ operation 
usually a 0 is required. 

I'm using a Digitrax decoder for this...


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## krs (Feb 29, 2008)

The frequency is adjustable on some decoders. Settings for this CV vary so consult your 
decoder manual for the proper value. If your decoder is capable of ‘silent’ operation 
usually a 0 is required. 

That is what I'm talking about. 
Question 1 - is the frequency adjustable on the decoder you use? 
If yes, which CV controls the frequency? 
Go to that CV and set the frequency to the highest it will go. 

If the frequency is not adjustable, what is it? 

Maybe I'm barking up the wrong tree here, but from what you posted so far it seems to me that either the PWM motor frequency or the DCC signal is feeding through to the output of the Soundbug and creating most of the buzz.


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## CliffyJ (Apr 29, 2009)

My meter is an old analog one. I tested a 1.5v battery, it read fine; didn't have a new 9v. I measured the output of my older 12v powerpack, it read 13v. 

Anyway, I hooked up that 12v (13v?) input to the new power board. It started working, but yes, the regulator bagen to heat up just as badly. 

But then, a melt down happened. The sound rapidly degraded to almost no output. 

So I hooked the thing back up to track power, changed out the audio amp, tested the 12vdc output from the power board, but no joy: seems like the amp is toast now. I had another amp board, but it quit working last week... 

I checked the soundbug with its original speaker, at least that's still working. 

Do you think there's a fundamental problem with our circuit, to cause the regulator to heat up, read funny on the meter, and thus damage the 12v amps? 

===Cliffy


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## krs (Feb 29, 2008)

Cliffy, 

Send me a PM since I can't send you one. 

There is nothing wrong with the circuit the way it's drawn, but continuing here on mls the way we have been doing isn't getting us anywhere. 

Knut


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## George Schreyer (Jan 16, 2009)

Depending on the static load of the amp, the regulator might get hot. See if you can find some kind of a heat sink for a TO-220 package. This is a very common part, a piece of bent metal with some little fingers on it.


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## Dan Pierce (Jan 2, 2008)

Since the regulator drops 22 down to 12 volts, that is a 10 volt drop. Every 100ma draw gives a 1 watt heat dissipation. So 300ms gives 3 watts. This is more heat than the TO220 can handle so a heat sink is a must. I always mount these on metal, any metal will help and as George stateds there are special mounts with fins. 

If using a 7805 on 30 volts with a 1 amp draw, there is lots of heat. 25 volts at 1 amp gives 25 watts, the type of heat a small soldering iron outputs!!!!


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## krs (Feb 29, 2008)

A heat sink is definitely needed, even more so when the circuit is mounted in the enclosed space of a locomotive, but taking a look at the amplifier spec, the 7812 regulator isn't adequate in any case. 
At 12 volts with an 8 ohm speaker the amp drwas 300ma at 0.25 walls audio output, that current rises to 1.5 amp maximum at full output. 

The best regulator would be one of these integrated three-terminal switching regulators with 85 to 90% efficiency, but they are a lot more money than a 7812. 
I use the 5 volt version of those for a very simple, cool running constant voltage lighting circuit that also works with analogue operation.


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## CliffyJ (Apr 29, 2009)

Posted By George Schreyer on 16 Apr 2011 07:12 PM 
Depending on the static load of the amp, the regulator might get hot. See if you can find some kind of a heat sink for a TO-220 package. This is a very common part, a piece of bent metal with some little fingers on it. 
Is this what you had in mind, George?

http://www.jameco.com/webapp/wcs/st..._326596_-1

If so, it looks simple to add on, with the regulator in place on the board.


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## CliffyJ (Apr 29, 2009)

Posted By Dan Pierce on 17 Apr 2011 05:29 AM 
Since the regulator drops 22 down to 12 volts, that is a 10 volt drop. Every 100ma draw gives a 1 watt heat dissipation. So 300ms gives 3 watts. This is more heat than the TO220 can handle so a heat sink is a must. I always mount these on metal, any metal will help and as George stateds there are special mounts with fins. 

If using a 7805 on 30 volts with a 1 amp draw, there is lots of heat. 25 volts at 1 amp gives 25 watts, the type of heat a small soldering iron outputs!!!! Impressive, Dan... 

So, 10v drop x 1.5A load from the amplifier = 15w heat output? Is that how it works?

It wasn't soldering-iron hot, but plenty hot enough. I could touch it for about 1 second, that's all.


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## krs (Feb 29, 2008)

I would use one with a lower thermal resistance if you have room for it. 

This one for instance: 
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_42622_-1


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## CliffyJ (Apr 29, 2009)

Posted By krs on 17 Apr 2011 08:06 AM 
A heat sink is definitely needed, even more so when the circuit is mounted in the enclosed space of a locomotive, but taking a look at the amplifier spec, the 7812 regulator isn't adequate in any case. 
At 12 volts with an 8 ohm speaker the amp drwas 300ma at 0.25 walls audio output, that current rises to 1.5 amp maximum at full output. 

The best regulator would be one of these integrated three-terminal switching regulators with 85 to 90% efficiency, but they are a lot more money than a 7812. 
I use the 5 volt version of those for a very simple, cool running constant voltage lighting circuit that also works with analogue operation. 
Knut,

I couldn't find an integrated regulator/heat sink device. But I did see a 2.4A regulator in the TO-220 'package':

http://www.jameco.com/webapp/wcs/st..._838815_-1

Reading the specs on the amp chip itself, I'm puzzled that it draws 1.5A, yet the amplifier assembly says it's 2A. 

Either way, was the amp trying to "pull" too much out of the regulator, causing a malfunction? E.g., noise? 

Does any of this have to do with the amp chip getting trashed?

BTW, when everything was working, the sound output (with just a bare, unsealed speaker) was loud -- loud enough to want to turn the volume pot down.

Cliff


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## CliffyJ (Apr 29, 2009)

Posted By krs on 17 Apr 2011 11:07 AM 
I would use one with a lower thermal resistance if you have room for it. 

This one for instance: 
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_42622_-1 I think there's plenty of room, thanks Knut. 

BTW, do you recommend a special adhesive or screws to attach it? And do I need to mount the thing off of the board, or can I just leave it where I have it?


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## CliffyJ (Apr 29, 2009)

I just saw this article from Dave Bodnar, discussing regulation of DCC rail power to 5vdc: 

http://www.trainelectronics.com/artcles/voltage_regulator_article/ 

Wow, those are some pretty big heat sinks! 

To get to a higher amp capacity, he uses a transistor. But I'd rather use a different regulator (e.g., the 2.4A I mentioned), for the simple reason that I'd rather not add to the list of things I might burn up...  

Referring to what Dan said, perhaps a lot of what Dave describes (in regards to heat) is due to the increased drop of voltage (to 5v)? And if dropping only to 12v, the heat issues aren't as dramatic (?). 

===Cliffy


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## krs (Feb 29, 2008)

Posted By CliffyJ on 17 Apr 2011 11:13 AM 
Knut,

I couldn't find an integrated regulator/heat sink device. But I did see a 2.4A regulator in the TO-220 'package':

http://www.jameco.com/webapp/wcs/st..._838815_-1

Reading the specs on the amp chip itself, I'm puzzled that it draws 1.5A, yet the amplifier assembly says it's 2A. 

Either way, was the amp trying to "pull" too much out of the regulator, causing a malfunction? E.g., noise? 

Does any of this have to do with the amp chip getting trashed?

BTW, when everything was working, the sound output (with just a bare, unsealed speaker) was loud -- loud enough to want to turn the volume pot down.

Cliff

Cliff -

It's not an integrated regulator/heatsink device I'm talking about, it's an integrated three terminal *switching* regulator like this one:
http://www.dimensionengineering.com/DE-SW050.htm

Advantage is the high efficiency - I have seen others with an efficiency up to 95%.
That means these switching regulators generate much less heat than a standard *linear* regulator which generates heat the way it was described earlier, voltage drop times current.


One question came to mind this morning - why are you even using the FA602 amp which is designed for a supply voltage of 3 to 12 volts?
That's great if you run analogue and you want the amp operating at a low DC voltage.

But if you always run DCC wouldn't it make more sense to use an amp that operates with a supply voltage around 20 volts and forget using a voltage regulator completely (and the heat issues associated with a linear one)?

Knut


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## krs (Feb 29, 2008)

Either way, was the amp trying to "pull" too much out of the regulator, causing a malfunction? E.g., noise? 
Does any of this have to do with the amp chip getting trashed? 

Well, the regulator is designed to protect itself against over current and over temperature, these devices are pretty rugged - you can usually only destroy them by wiring them up wrong. 
As to the noise - when the regulator is in its "protection modes" it reduces output voltage and current to limit the heat generated and of course it no longer regulates, so yes, it running in that "protection mode" could cause noise. 

Amp chip getting trashed would usually be too high a voltage being applied, even for an instant. Maybe some of the testing done earlier with a separate power pack could have caused that issue. 
Anybody's guess at thgis time.


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## CliffyJ (Apr 29, 2009)

Cliff -

It's not an integrated regulator/heatsink device I'm talking about, it's an integrated three terminal *switching* regulator like this one:
http://www.dimensionengineering.com/DE-SW050.htm

Advantage is the high efficiency - I have seen others with an efficiency up to 95%.
That means these switching regulators generate much less heat than a standard *linear* regulator which generates heat the way it was described earlier, voltage drop times current.


One question came to mind this morning - why are you even using the FA602 amp which is designed for a supply voltage of 3 to 12 volts?
That's great if you run analogue and you want the amp operating at a low DC voltage.

But if you always run DCC wouldn't it make more sense to use an amp that operates with a supply voltage around 20 volts and forget using a voltage regulator completely (and the heat issues associated with a linear one)?

Knut 

Thanks for clarifying Knut, yeah, that regulator is getting kinda pricey... and thanks for explaining the difference from a linear one. 

As to your last question, all I can say is, "Uh... good question." Also, that this all started with the idea of running a cheap audio amp board to boost the output from the (cheap) Soundbug; and this amp was the only thing I could find that was at least alluded to and actually used... at least to some extent...

Cliff


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## krs (Feb 29, 2008)

Wow, those are some pretty big heat sinks! 
To get to a higher amp capacity, he uses a transistor. But I'd rather use a different regulator (e.g., the 2.4A I mentioned), for the simple reason that I'd rather not add to the list of things I might burn up...  
Referring to what Dan said, perhaps a lot of what Dave describes (in regards to heat) is due to the increased drop of voltage (to 5v)? And if dropping only to 12v, the heat issues aren't as dramatic (?). 

Dave's circuit is really meant for analogue DC operation, with DCC that large 4700uf capacitor will give you problems. 
But with DC, the track voltage will be much less on average than with DCC, so even though the wattage calculation is the same, voltage difference times current, it won't be as bad as with DCC. 
And as you wrote, with less of a voltage drop through the linear regulator you get less heat produced at the same current output.


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## CliffyJ (Apr 29, 2009)

I've been trying to find a cheap audio amp that can take 24vdc power, but not joy yet, at least from Qkits. 

Regarding your misgivings about the 1A 7812, what do you think about that LM340T 2.4A regulator? 

Also, if the audio chip can't tolerate anything more than 12v, and the regulator will output at just that level, would it make sense to put in a resistor to ensure 12v isn't exceded? Probably a dumb idea, but it isn't making sense to me, supplying the amp to its absolute max power input. 

Guess I should get off the 'puter and swap out that 7812 as you suggested earlier...


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## krs (Feb 29, 2008)

BTW, do you recommend a special adhesive or screws to attach it? And do I need to mount the thing off of the board, or can I just leave it where I have it? 

You can leave the regulator where you have it but you need to apply a thin layer of thermal paste between the regulator netal tab and the heat sink. 
Then you just bolt the heat sink to the regulator tab. The thermal paste makes sure that you get good heat flow from the regulator to the heat sink. 
Also remember that the regulator tab and therefore the heat sink is electrically connected to pin2 of the regulator, so you don't want the heat sink touching anything conductive in the locomotive. 

If you order more goodies, you might as well order some of the LM340's since those are probably the regulators you will end up using with that amplifier board. 

Anyone know of an amplifier board in the $10 or less range that will run with a 20 volt or so supply voltage?


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## CliffyJ (Apr 29, 2009)

Thanks Knut.


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## krs (Feb 29, 2008)

Regarding your misgivings about the 1A 7812, what do you think about that LM340T 2.4A regulator? 

Also, if the audio chip can't tolerate anything more than 12v, and the regulator will output at just that level, would it make sense to put in a resistor to ensure 12v isn't exceded? Probably a dumb idea, but it isn't making sense to me, supplying the amp to its absolute max power input. 

Guess I should get off the 'puter and swap out that 7812 as you suggested earlier... 

LM340 with an adequate heat sink should be fine. 
The chip on the audio amplifier is actually rated for 16 volts, so 12 volts is no problem. 
There are no other active devices on that board - just take a look at the electrolytics to make sure those are all rated for at least 16 volts which is one of the standard capacitor voltages for them. 

You're right - one shouldn't run anything right at the maximum voltage but from what I see without actually having the amp board, the 12 volts is a conservative rating. 

A resistor wouldn't be any good anyway since the voltage drop across it varies with current - if anything, you could use a diode or two to drop the voltage a bit - but I don't think you need it if all the components on the amp are rated at 16 volts or better.


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## CliffyJ (Apr 29, 2009)

I don't know if a pre-amp will work, but if so, here's one that can handle 30v: 

http://www.kitsusa.net/phpstore/html/VELLEMAN-K1803---UNIVERSAL-MONO-PRE-AMPLIFIER-KIT-5066.html 

Here's a Brit kit, kinda pricey: 
http://www.quasarelectronics.com/3097-2w-mono-amplifier-module-lm380.htm


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## CliffyJ (Apr 29, 2009)

Well, Knut, I swapped out the (7812) regulator with an unused one, and it also reads 10.5v output. 

The power supply board is exactly as we've diagrammed; it's hooked up to rail power, and has no load. Very puzzling.


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## krs (Feb 29, 2008)

Posted By CliffyJ on 17 Apr 2011 01:49 PM 
Well, Knut, I swapped out the (7812) regulator with an unused one, and it also reads 10.5v output. 

The power supply board is exactly as we've diagrammed; it's hooked up to rail power, and has no load. Very puzzling.



Does the regulator get hot (or even warm) with the amplifier NOT connected?


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## krs (Feb 29, 2008)

Posted By CliffyJ on 17 Apr 2011 01:22 PM 
I don't know if a pre-amp will work, but if so, here's one that can handle 30v: 

http://www.kitsusa.net/phpstore/html/VELLEMAN-K1803---UNIVERSAL-MONO-PRE-AMPLIFIER-KIT-5066.html 

Here's a Brit kit, kinda pricey: 
http://www.quasarelectronics.com/3097-2w-mono-amplifier-module-lm380.htm 





You cannot use a pre-amp.

The other amp looks OK, but there must be some one selling something like this in the US.

There are enough audio amplifier ICs that will handle 24 volts - if you want to pursue this option maybe the fastest and chaepest is to just build your own.
If you get the right vero board it's not that complicated and you can mount the diode bridge and the filter capacitors right on the same board.


Knut


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## Greg Elmassian (Jan 3, 2008)

Something is desperately wrong when the 12v regulator puts out 10.5.... I think you still need to verify that your meter reads correctly at 12 volts... With no load you should get 12 volts, and I seem to remember your were able to get 12v before. The hot regulator and 10.5 volts are fundamental problems, I would solve them first. 

Greg


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