# Power Packs and Transformers



## lgbnut1975 (Apr 2, 2017)

First off i am not new to the hobby, but i am having a major issues with powering my trains, Recently I got rid of my MRC Control Master 20 for MRC 9950 I liked the idea of the 10 amps and volt and amp meter. I unfortunately found out that it was not a smart decision, here is what happened, all my none MTS LGB trains run just fine with the new power pack, but all my MTS equipped trains require 75% throttle just to get them started, and shut down at 50% throttle. The sounds is horrible and i am frustrated. So i am in search of the rite power pack to power all my trains in analog mode, and still get the sound effects. I have been looking at the Piko 5 Amp throttle and transformer, USA Trains RTP 10, and Bridgewerks 10amp power pack. I don't have room for lashups and the biggest train i have is a set of LGB F7 with 4 Passenger cars, no more than two motors with sound running and lights. my layout will be no larger than 10 ft x 30 ft. I prefer quality to quantity, but i am hearing some major issues with bridgewerks. I know nothing about Piko and i have had usa trains and to me the quality is shady. The other question would be, Will a 1 amp lgb power pack be enough for now? please help, i have a nephew who want to see the sound engines run aqain. 

Thanks,
Evan


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## krs (Feb 29, 2008)

Off the top of my head I would go for a 5 amp LGB power pack - that way you're sure it will work properly with MTS.

I don't really understand why the MRC 9950 is having problems - sounds as if the output is PWM, the voltage output is not linear, thus the need to crank the throttle to 75% to get an MTS loco moving and the throttle shutting down suggests there is not enough current available.
You stated that you get a shut down at 50% throttle - how does that happen if you need 75% throttle to even get the loco started????

Maybe the frst step is to see if you can borrow a power pack from a G scale friend to make sure the issue is the power pack and not something else.
I have a hard time believing that MRC would design a fairly new power pack that is supposed to be compatible with G scale and then end up with a product that is not compatible with LGB considering there are tens of thousands of LGB locos out there.

Maybe someone who has that MRC power pack can shed some light on this...

Knut


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## lgbnut1975 (Apr 2, 2017)

The funny thing is I contacted MRC and they openly admitted that it would not work, they have a fix But I would have to send it in to have an update. I want an LGB power pack but they no longer sell a 120v 5 amp power supply for the US anymore, all they have is a 1 amp transformer and throttle controller.


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## Treeman (Jan 6, 2008)

We do have 5A throttles available. The come in two parts the AC transformer and a DC throttle.


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## DennisB (Jan 2, 2008)

I have had a one amp LGB power unit and it worked well on 200 feet of level track. I moved to another city and had to use something with more power so I stepped into a 3 amp Bridgewerks. Several years later Shourt Line came out with an 8 amp power supply and I was very happy with it.
Having said all that,it would be better if you got a 5 amp LGB pack. Regards, Dennis.


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## Greg Elmassian (Jan 3, 2008)

Where do you get 10 amps? The only specification I could find is 125 watts, not even any spec on voltage. Assuming the will supply the right voltage (which I think is iffy) 24 volts gives you slightly over 5 amps for 125 watts.

Given the history of MRC, I'm not surprised it does not work well for G scale.

Greg


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## Dan Pierce (Jan 2, 2008)

You can use the LGB 5009 power amp (web info has this as MTS, IT IS NOT MTS!!!)

This unit uses up to a 2 amp variable input source like the LGB 1 amp power pack, plus it uses a second power source to supply 2 amps to give 3 amps out. My 2nd source was a free dell 19 volt laptop power pack.
THe 5009 ors 2 supplies together for up tio 2 amps each for 4 amps max output. The combo above will give 3 amps.

For a google search on this you must type LGB 5009 power amplifier

FYI numbers starting with 50 are for analog/DC.
Numbers starting with 55 are for MTS/MZS.


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## lgbnut1975 (Apr 2, 2017)

So i was wrong about the specifications on the MRC power pack, I ordered a transformer and throttle from Reindeer Pass, they dont list the one item i wanted online, you have to search for it, I hope this works. Thanks for the help!


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## Greg Elmassian (Jan 3, 2008)

You really weren't wrong about the MRC, unfortunately, they often list very few specifications and ratings in VA which tells you almost nothing about the power capabilities.

I'm pretty surprised that the MRC web site and the downloadable pdf "manual" have NO specifications of voltage, current, the separate accessory terminals, etc.

It looks cool, but I'd wager that the output voltage is way too low for G scale, and that was the reason of the too high settings on the throttle.

O scale voltages are typically like 16 volts, not the 24 that is pretty standard on G, so having a SINGLE setting for O AND G was suspicious right from the start.

The good folk at Reindeer Pass will take good care of you.

Greg


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## East Broad Top (Dec 29, 2007)

The MRC 9950 has a maximum output voltage of 18 volts for large scale, which at 125 watts total output gives you about 7 amps at that voltage. MRC's larger AG990 throttle is rated at 10 amps, with a 22 volt output. 

If the output of the MRC unit is PWM, I'd just run the output through a PWM/Linear filter. I've got one on the output of my Aristo 10-amp controller, and it works just great with DCC, MTS, and DCS-equipped locos. Alas, Precision RC (Aristo/Crest's successor) doesn't appear to have that board on their web site. I don't know of a commercially-available equivalent, at least not from model railroad manufacturers. 

Later,

K


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## Greg Elmassian (Jan 3, 2008)

Kevin, where did you find the MRC documentation on output voltage? Perhaps it is stenciled on the unit itself?

I can't find any document from MRC with anything other than 125 watts...

Also, your assumption about 7 amps may be incorrect... normally (and this is true for every MRC I have encountered) the VA or wattage is the TOTAL output of the unit, both the variable DC AND the accessory outputs... so without either actually testing this unit, or seeing a detailed spec, it's hard to tell.

But, the 18 volt output matches his experience that the throttle is awfully high to run trains..

Greg


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## East Broad Top (Dec 29, 2007)

Greg, the manual can be found *here*. It shows the G-scale voltage range of 0 - 18 volts. The power is a total output power according to the literature, but if you've nothing attached to the fixed output, then the presumption is that all the power would be available for the fixed side of the equation, so at 18 volts, you'd have right around 7 amps. 

The manual advertises "precise slow speed control," which usually means pulse-width-modulation as the variable output. It doesn't surprise me to think this would play havoc with an MTS-equipped locomotive. PWM is well-known to "freak out" DCC decoders, often resulting in erratic behavior if the decoder comes to life at all. 

Greg, it's curious that you would suggest 18 volts as being "awfully high" to run trains. Might I assume you meant to say "awfully low?" That's far more in keeping with your normal recommendations for suitable track voltage, for which you tend to gravitate towards 24 volts. 

Given the fact that Evan is looking to run an MTS-equipped F7, and the MTS decoder running in an analog environment will likely chop about 6 volts off of whatever voltage is available to power the motor itself, I'd tend to agree that the 18-volt MRC unit in this instance would not be the best option. Once the voltage is processed by the decoder, you're likely to have only around 10 volts or so to actually send to the motor. That's not going to cut it for a passenger diesel if you want to run at prototypical speeds. (Though with Evan's proposed railroad being 10' x 30', I'd suggest a "slow order" lest your train make its way around the railroad every 15 seconds.) 

Later,

K


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## Greg Elmassian (Jan 3, 2008)

Thanks Kevin, the pdf I found did not have that box in it with the voltages.... weird.. but very enlightening...

And as I guessed, 125 watts is the TOTAL, so no way you are over 6.9 amps, and less if you are running accessories. I'd be interested to see the results of an actual test.

Actually worse, the data sheet says VA not watts, and they are NOT the same. Watts normally implies at maximum volts and amps. VA means that at SOME combination volts times amps is 125... most devices rated this way, and historically specifically MRC, do NOT generate max amps at max volts, so that is also an issue when you need higher voltages but are pulling a good load.

He had to turn the THROTTLE awfully high to get the trains moving... from his post... that was his complaint....
", but all my MTS equipped trains require 75% throttle just to get them started, and shut down at 50% throttle."

I do have to correct you on your last paragraph. Completely wrong... you don't "cut off" 6 volts from the voltage available to the motor, the micro in the decoder needs 5 volts to start, so stuff does not _happen _until 6 or 7 volts, *BUT the full track voltage is available to the output transistors that run the motor, all the time, even under 6 volts all the way to 18 volts. *

Please don't make stuff up when you don't actually know.

Greg


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## East Broad Top (Dec 29, 2007)

With regard to the 75%, I see where you're coming from. At 75% throttle, the PWM signal is 75% full voltage, 25% zero. My guess is that it's only at that point that the MTS decoder can understand that it's seeing analog DC voltage as opposed to a really messed-up DCC signal, and switches into analog mode. Once in analog mode, it probably assumes analog DC until the pulses get more or less 50/50, at which point it thinks it's seeing a really messed-up DCC signal again and shuts down. As I wrote, PWM makes DCC decoders do unpredictable things. It's a crapshoot. Some play well, some not at all, most operate at various points in between. 

As to the voltage going to the motor, I'm not "making stuff up." I've seen this play out on my workbench. Put two Piko locos on the track; one with a decoder, one without. Apply DC to the track. Watch what happens. At 6 volts, the non-DCC loco is running at a fair clip, the DCC-equipped loco is still. At 18 volts, the non-DCC loco is running at full speed. The DCC-equipped loco is not running as fast, because the motor is not getting the same 18 volts as the non-DCC-equipped loco. I've seen this behavior in other locos as well, where the top speed under DCC was noticeably faster than it was under analog DC at the same track voltage. These are locos whose top speed (CV 5) has not been limited in any respect.

Having said that, I recently reviewed a TrainLine DCC-equipped loco (German 0-6-0 with a Zimo decoder) whose top speed under DCC--regardless of track voltage--was a stoic 18 scale mph. (I have two systems, 15 volts and 22 volts.) That same loco running on analog DC had a top speed of 34 scale mph at 22 volts. My gut tells me the decoder had the speed range under DCC programmed to be prototypical, but I didn't program the decoder so I can't say for certain. 

Later,

K


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## Greg Elmassian (Jan 3, 2008)

It's clear the decoder "takes" some voltage, but you are wrong in assuming it "takes" that 6 volts subtracted from the voltage applied to the motor.

I was very clear about this, and I did not say as fast or anything else. Trying to obfuscate the issue won't work. 

You made an erroneous statement, here it is:

" and the MTS decoder running in an analog environment will likely chop about 6 volts off of whatever voltage is available to power the motor itself"

WRONG.... why can't you just admit this? And then people will get the CORRECT information.

I would not make a big deal out of this, but people make certain assumptions about people who are moderators and write articles in magazines, they assume they give correct information, more than just the ordinary joe.

Don't write a big confusing paragraph about something else, just correct your statement to how I explained it, the motor ALWAYS gets rectified track voltage, ALWAYS. Any voltage "loss" is from the full wave bridge that the track power goes through, and the loss in the output transistors, which typically is 2 volts. This is correct, and has been ever since DCC decoders were invented.

Greg


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## Fred Mills (Nov 24, 2008)

Looks like the "Perts under pressure" are at it again. I'm not complaining in any way; I actually enjoy the banter, and more importantly; we all can learn a heck of a lot from these two guys, if we give them a chance.......Are we having fun, yet ?....!!


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## Greg Elmassian (Jan 3, 2008)

NO, but I hate misinformation worse.


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## East Broad Top (Dec 29, 2007)

Greg, I stand by that statement. Based on my experience with the two Piko locos and other DCC-equipped locos I've run on analog DC _whose top speeds are noticeably lower when running on analog DC versus DCC,_ it seems clear the decoder sets a "floor" for motor voltage at the point where it gets enough voltage to operate, then adds voltage to the motor in proportion to the voltage increase to the track. 

If a decoder in a locomotive needs 6 volts to "wake up," and you increase the track voltage to 7 volts, the decoder is not going to all of a sudden send 7 volts to the motor at that point. You couldn't possibly do slow-speed running in analog DC if that were the case, as each loco would lurch to a mid-range speed as soon as the decoder received enough power to turn on. Based on observing the speeds of the two Piko locos, it's evident (in that instance) that it's pretty much a 1:1 relationship between track voltage and motor voltage; the voltage going to the motor (based on observed speed) is approximately track voltage minus the voltage required for the decoder to turn on. The non-DCC equipped loco ran about the same speed at 12 volts as the DCC-equipped loco did at 18 under analog DC power. That's what I saw, that's what I measured. Don't know how else to explain it. 

Whether the MTS decoder chops "6 volts" off, I don't know. I don't have the MTS decoder in front of me to measure what it requires to wake up. However, based on my experience with the Piko decoder other decoders from other manufacturers, I'd presume that it behaves similarly, setting a "zero point" on the motor output at the point where the decoder receives sufficient voltage to operate, then increasing the voltage to the motor proportionally to voltage increases to the track as they occur.

There is no way for a DCC decoder operating in an analog DC environment to adjust a speed curve such that maximum speeds are matched between the loco operating in DC and DCC environments. The decoder would have to know what the maximum voltage is, and in an analog DC environment, there's no way for it to know that. Its "maximum" is whatever it's being fed at that point in time. 

Personally, I think you're completely misunderstanding what I'm trying to convey, because I can't for the life of me imagine you haven't seen the same behavior I describe.

Later,

K


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## Dan Pierce (Jan 2, 2008)

When programming a DCC decoder (esp Zimo) there are motor programming limits for analog operations and other program limits for digital operation.
On the Zimo decoder, CV57 limits the motor voltage in DCC, but CV 5 also limits the top speed in analog mode. Other manufacturers could have separate controls also.

I have seen sound projects use CV57 to make the top speed of a Zimo equipped loco to be prototypical. Steam engines of pre 1900 were not fast, and could be outrun by a man on a horse.


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## Greg Elmassian (Jan 3, 2008)

Sigh, the output is PWM to the motor Kevin, it ALWAYS sends full rectified track voltage to the motor. Yes it is lower, but your statement was that you subtracted 6 volts from the track voltage to the motor.

completely wrong.... 

and of course you wrote a big paragraph and tried to bring in other stuff that is NOT what I am talking about.

I see that you really do *NOT *stand by your statement, because now you are trying to change it: "
Whether the MTS decoder chops "6 volts" off, I don't know.".

When you stated previously: 

" and the MTS decoder running in an analog environment will likely chop about 6 volts off of whatever voltage is available to power the motor itself"
 
That is clearly what I took exception to, in completely clear English twice.

You could have had the honor to say, "Oh, I see, I made some assumption and I was wrong", or "I haven't the faintest clue how electronics works, and I made something up" or something like that. But no, instead of retracting it you want to fight to be right, to win, to have the last word....


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## East Broad Top (Dec 29, 2007)

Greg, you're reading far too much into what I write. My sentence about the 6 volts and the MTS decoder is because I don't know if it's _specifically_ 6 volts at which point the decoder wakes from its slumber under analog power. _I don't have one in front of me, so I can't measure it. _It's likely in that neighborhood, give or take a few volts. Most DCC decoders need between 4 and 7 volts minimum to operate in an analog DC environment. At _whatever _point it wakes up (3, 4, 5, 6, ... volts), it doesn't immediately send that full voltage to the motor right when it wakes up. When it has just enough power to wake up, the loco doesn't move (0 volts going to the motor.) When you give it a little more power (let's call it "wake up voltage plus 1") it sends that "plus 1" to the motor and the loco begins to move crawl slowly. As the voltage continues to increase (wake up voltage plus 10, 11, ...), it sends that extra voltage to the motor, and the loco's speed increases in kind. The result is that a locomotive that is equipped with a DCC decoder will tend to run slower at a given analog track voltage than an identical locomotive that is not equipped with a DCC decoder. 

I have observed this time and time again. If you want to call my observations into question, that's your thing. Again, as many DCC installations as you've done, I find it hard to believe you've not seen this same thing (which is why I still think you're reading my posts sideways and not getting what I'm trying to convey.) I write about what I've seen. The reader can draw his or her own conclusions at that point.

Later,

K


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## krs (Feb 29, 2008)

I just read through this discussion.....
the way I understand a *typical *DCC decoder works in analog mode is that input is the analog DC voltage but the output to the motor is still PWM from the decoder and not the DC track voltage like with a pure analog loco.

So, if say, the analog track voltage is 7 volts and that is just enough to start the loco moving, the 7 volt DC track voltage is fed through the diode bridge of the decoder to the decoder output MOSFETs and they provide the correct PWM duty cycle to just get the loco to start moving.
In other words there is the full track voltage less the diode bridge and MOSFET drop (about 1.5 volts) applied to the motor but because of a, say 20% PWM duty cycle, the motor only "sees" 20% of that voltage, ie 1.1 volt in my example.
The numbers I'm using are just rough values to illustrate my point.

Knut


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## Greg Elmassian (Jan 3, 2008)

Exactly Knut, that was my only point, and the incorrect statement that Kevin made about "cutting off" 6 volts and presented as a fact. I only took exception to that statement, and you can see that I have stuck to that consistently.

Kevin, you keep trying to change the point, distract, cover up, expand, move, etc.

Your techniques to do this are well known to me and do not distract me, but it is a waste of time to discuss this further with you, nor do I want to discuss it with you have again demonstrated your history of making stuff up and presenting it as fact.

I'm very disappointed in this. It's ruining a good forum, and misleading others who believe everything you say.

I would have pointed out this error to anyone who had made it, not just you, it's not personal.

Greg


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## East Broad Top (Dec 29, 2007)

Greg,

As I suspected, we're talking about the exact same thing, but from two different perspectives. Knut describes in electronic terms (bridge rectifiers, a 20% PWM duty cycle, etc.) _exactly _what I'm talking about based on observation of watching the speeds at which my locomotives run around my track. 

In my example, I make the observation that a DCC-equipped locomotive running on 7 volts analog DC will run at a speed equivalent to what a non-DCC-equipped locomotive runs at on 1 volt. In Knut's example, he explains the electronic reason_ why that happens_. A DCC-equipped locomotive getting 7 volts analog DC through the track processes that voltage, ultimately sending 1 volt to the motor after it's done processing everything it needs to process. The net result is a 6 volt drop between track voltage and motor voltage. _That's_ the 6 volts I'm referring to when I say a DCC decoder will "cut off" 6 volts. (Exact values vary based on the specific decoder. It's not always "6" volts.) 

We're. Saying. The. Same. Thing.

I knew there was no way you haven't seen what I'm talking about; you just aren't understanding the perspective from which I'm presenting it. (Not remotely the first time for that. You tend to look at things from an engineering perspective, while I tend to look at things from a more observational perspective. There's often a disconnect between the two perspectives, as anyone who's written a technical manual can attest.) I'm glad Knut offered a more technical perspective which you could latch on to. Hopefully, now, you'll better see where I'm coming from. My regret is that you tend to color these differences in perspective as me not knowing what I'm talking about ("making stuff up,") as opposed to allowing the possibility that I'm simply not presenting the material in a way which you understand. The problem with writing is that you can only control what you put on the page. You can't control how people respond to it. 

Later,

K


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## East Broad Top (Dec 29, 2007)

Okay, Greg, just to illustrate the point I'm making that you're also making that you don't think I'm making because you don't understand my perspective of how I'm making it all the while saying I'm "making stuff up..."

The Piko locos I mentioned observing in my original post have long since been returned to their rightful owners, but I figured a re-creation of my observations with empirical measurements was in order, so I went with the next best thing. 

Here's the set-up:










Massoth XXL-2 decoder
Two trucks from an LGB White Pass diesel 
14 volt power supply (Crest 10-amp throttle) via PWM/Linear filter (not shown in photo)

The truck on the right is fed directly off the power coming from the Crest throttle. The truck on the left is fed via the Massoth decoder, which is fed via the power coming from the throttle.

(Right Truck) Power Supply>Throttle>PWM/Linear Filter>Motor
(Left Truck) Power Supply>Throttle>PWM/Linear Filter>*Massoth Decoder*>Motor

Right Truck starts turning at 1.2 volts measured across track
Left Truck starts turning at 8.5 volts measured across track (1.2 volts measured across motor, consistent with Right Truck start voltage)

This is the difference to which I refer when I say DCC decoders "cut off" voltage. In this case, it's fairly extreme - 7.3 volts when the DCC-decoder-controlled motor begins to turn. I was expecting less. 

Full throttle:
Right Truck measuring 13.5 volts across motor
Left Truck reading 10.5 volts across motor

By full throttle (13.5 volts), that difference between voltage levels being sent to the motor had lessened to 3 volts. That's still a fairly significant difference in observable speed. (In other words, I could easily tell one was running faster than the other. Exactly how much faster is harder to tell. The test set-up didn't allow for running the trucks along the track to measure.)

Since the decoder is the "gatekeeper" for the voltage going to Left Truck, it doesn't surprise me to see some level of compensation and narrowing of this voltage gap as the track voltage increases, especially on a higher-end decoder like Massoth. Since the decoder controls the duty cycle of the PWM going to the motor, it's not a stretch to think it can be programmed to adjust that duty cycle proportionally to the input voltage. I suspect each decoder is different in how it handles things. The Piko locos exhibited far less observable compensation as track voltage increased. (i.e., the difference in speed as voltage increased appeared to be fairly constant.) Since I didn't measure the voltage going to the motors, I can only relate what I saw. The decoder in the Piko loco is made by Soundtraxx, and functionally is fairly basic. (Older-generation technology compared to their current line-up.) 

Being a curious sort, I switched to a 22 volt power supply and juiced things to the maximum.

Right Truck - 21.7 volts
Left Truck - 20.5 volts

Still a difference of 1.2 volts, but I suspect that's due to the internal electronics (rectifiers and MOSFETs), and that the duty cycle of the PWM signal going to the motor was much closer to 100% by this point, adjusted internally by the decoder programming.

Lacking an oscilloscope, I can't look at the voltage being sent to the motor via the decoder to see how it may be adjusting as track voltage increases. Christmas is coming, however, so if anyone is looking for gift ideas... 

Later,

K


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## Greg Elmassian (Jan 3, 2008)

Jesus help me, now you are trying to read a variable width modulated pulse signal of constant voltage with an averaging voltmeter.

I guess you will go to any lengths to be right, even mis-using measurement instruments.

Seriously, one day you will be walking down a street and will be tarred and feathered by a group of electrical engineers.

(ok just a figure of speech for the paranoid)

Greg

excuse me while my synapses recover from the stress.... I've got to get my amp meter out and measure a cup of flour


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## East Broad Top (Dec 29, 2007)

_Greg wrote: "...now you are trying to read a variable width modulated pulse signal of constant voltage with an averaging voltmeter. ... __Seriously, one day you will be walking down a street and will be tarred and feathered by a group of electrical engineers."

_Well, yes. That's all my dad ever used in his electronic endeavors. He held a Ph.D in electrical engineering, and designed everything from simple R/C throttles for model trains to super-computers for NASA. If a run-of-the-mill averaging volt meter was good enough for him and his projects, it's good enough for me. Apparently, it's also good enough for you, as you recommend everyone get one on your web site.

Besides, voltage is only part of the equation. It's how that voltage translates into speed that really matters. Here's what I was writing while you were busy denigrating the tools I used for my experiments.


******

I woke up this morning and did some more tests because I wanted to see how those motor voltages translated into actual track speeds.

Here's the hypothesis, roughly paraphrased from this discussion:

*Hypothesis:* Because a DCC decoder requires a certain amount of voltage just to power up, a DCC-equipped locomotive running on analog DC track power will always run slower than a non-DCC-equipped locomotive at a given track voltage because of that required base voltage by the DCC decoder. 

This hypothesis is based on observation DCC-equipped and non-DCC equipped locomotives running in various modes over the years. (Observations upon which my original claim in this discussion was made.)

*Methodology:* (described in the post above)

*Results as applied to measurable speed:* 

We'll accept that when the motor first starts turning (1.2 volts), the speed is effectively 0, though there is some very slow movement. 

At 8.5 volts (the point at which the DCC-equipped truck just begins to move) the non DCC equipped truck is traveling at 13" per second


At the point where the throttle is maxed out under the 14 volt supply (Left Truck 10.5 volts, Right Truck 13.5 volts)

10.5 volts = 16" / second
13.5 volts = 25" / second


At the point where the throttle is maxed out under the 22 volt supply (Left Truck 20.5 volts, Right Truck 21.7 volts)

20.5 volts = 37" / second
21.7 volts = 44" / second

Converting that to scale speeds (at 1:20)

L = Left (DCC-equipped) Truck
R = Right (straight analog DC) Truck

DCC-equipped motor start point (8.5 volts to track)
(L) 1.2 v = 0.1 mph (just beginning to move, not intended to imply sustained speed)
(R) 8.5 v = 14.7 mph

14-volt Throttle Maximum
(L) 10.5 v = 18.2 mph
(R) 13.5 v = 28.4 mph

22-volt Throttle Maximum
(L) 20.5 v = 42.0 mph
(R) 21.7 v = 50.0 mph

Throughout the voltage range, while the measured voltage gap between the DCC-equipped and non-DCC-equipped motor narrows significantly, the effective difference in speed between the motors at the various points does not narrow proportionally to voltage. When the DCC-equipped motor first begins to turn, the difference in scale speed is 14.7 mph. At full throttle (22 volts) that gap has narrowed only to a difference of 8 mph, though the gap in measured voltages shrinks from 7.3 to 1.2 volts 


*Conclusion:* Running under analog DC power, a DCC-equipped locomotive will typically travel measurably and observably slower than an identical non-DCC-equipped locomotive at any given track voltage.


A critic might say that a test of one decoder could be singled out as "cherry-picking," thus the results are not indicative of the whole. However, these results mirror observations and similar measurements of decoders from myriad other decoder manufacturers which served to support the hypothesis in the first place. Further, we must accept that DCC manufacturers by and large handle analog DC operation in similar fashion, thus these results should be taken as indicative of the class.

Later,

K


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## tomplatten (Sep 12, 2008)

I use Variacs for my trains AC and DC. I purchased my Variacs from ebay. I went to my electronics surplus store and bought three heavy transformerd the step down to 25 volts, took two output leads to my AC trains, ran to other output leads to a bridge rectifier, thru a DPDT and to my DC trains. I built a box to house all of this. I have three different layouts around my house and they are all run with Variacs. A bonus with Variacs is they have lots of windings for excellent speed control!!!!


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## Dan Pierce (Jan 2, 2008)

25 volts A/C will give most largescale locos too much voltage as the peak is 25 times 1.414 giving 35 volts minus the diode bridge drop of 1.4 max thus 33.5 volts to an engine which can destroy most DCC decoders. Even Zimo has a 30 volt limit (but more than that for a surge but not continuous).


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