# Just Love Those SuperCaps!



## toddalin (Jan 4, 2008)

Years ago I fitted my Sierra sound systems with supercaps replacing the gel packs. With no open houses last year, I've not run the trains in over 2 years now.


The other day I started to clean the wheels for the upcoming open house and as soon as I supplied power to the wheels, the sound systems came alive. The 6 volt gel packs would never do this, nor would they have lasted the 2 years unattended.


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## Greg Elmassian (Jan 3, 2008)

There's a new member asking, trying to find the gel cell.... what values of supercaps did you use? I don't have a Sierra here to measure the "charging current" (i.e. max voltage) it puts out, nor do I know the capacity in Farads vs. how long they last when power is interrupted.

Thanks, Greg


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## toddalin (Jan 4, 2008)

Use three 2.7V 6-10F wired in series. You can add a 1 ohm resistor, but I found it unnecessary and it takes just that much longer to charge before activation. With three 6F, I get over 30 seconds of idle using the lighting feature. The lighting lasts longer than the sound and the duration is very dependant on the volume.

If you want to get slick, what I also did was to put a "cut-out" relay on the cap so it would "disengage" at about 3 volts. It shortens the idle time on shut-down, and you may even loose something like the air pump because it shuts off before this feature would occur.

But, when the power comes back on, it doesn't not have to start the charge cycle from scratch, so it alleviates the motorboating both on start-up and shut-down for those periods where the cap doesn't have enough juice to sustain the board and motorboats.

I use a 5 volt relay and put a resistor in series to get it to shut off at a lower voltage. Don't worry about the amperage so much but instead look for the lowest current draw you can find. But then the relay needs a small cap across its terminal as a jump start it to get it to fire and hysteresis takes care of the rest.


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## Greg Elmassian (Jan 3, 2008)

Thanks Todd. So theoretically 8.1 volts "tolerance". Very helpful.

Cool idea on the low voltage cutout...

Greg


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## toddalin (Jan 4, 2008)




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## Nick Jr (Jan 2, 2008)

toddling, found this product. AKTUDY XH-M609, your thoughts please?


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## toddalin (Jan 4, 2008)

Lowest operating voltage is 7 volts and that's too much. Needs to be down around ~3 volts.


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## Nick Jr (Jan 2, 2008)

Reading further down to Input voltage: 3V-15V so thought the cut off was at 3. I'll keep looking. thank you.


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## toddalin (Jan 4, 2008)

Any sort of a "cut-out" is going to have a parasitic loss and you want to minimize this to maximize the available power for the idle time. I can't imagine that any sort of a cut-out is going to have less draw than the one little 80 mA relay I used, though you may be able to improve on this with a different relay (i.e., < amperage draw) slightly.

You don't need the cut-out if you just wire the three supercaps in series and replace the battery with that. If you don't idle the engine for more than about a minute at a time, you will not incur the motorboating except at the very first start-up and last idle of the day. One of my GP-9s is wired like this and it stops for ~30 seconds to "refuel" every lap and it is just not an issue. I just time the stop so it falls a short of the cap going into motorboating.


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## Nick Jr (Jan 2, 2008)

toddling, I thought you mentioned that in an earlier post, thank you for clearing that up. Going to meet with a friend who runs a Batteries Plus location. He was an engineer for a battery company before striking out and he may help me finding a low draw low voltage cut out assembly. I ordered enough super caps to try on 2 locos. If I don't send them up in smoke will do the others as I don't run my electrics often enough to keep the batteries charged. I used to have a schedule to charge the batteries, but age and hard drive crash wiped that out also. Thank you for all your help.


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## Nick Jr (Jan 2, 2008)

toddling: can do the basics of electronics, enough to be dangerous. Just a couple of ?? please. The potentiometer connections: looking at it's face, tabs on the bottom: the two to the right are the connections made in the circuit?? The designations of Sierra +, goes to where the positive side of the battery goes? and the two designated Sierra - go to where the negative side of the battery goes?? How will the on/off switch for the board effect this? Any help you can give will be appreciated.


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## toddalin (Jan 4, 2008)

Nick Jr said:


> toddling: can do the basics of electronics, enough to be dangerous. Just a couple of ?? please. The potentiometer connections: looking at it's face, tabs on the bottom: the two to the right are the connections made in the circuit?? The designations of Sierra +, goes to where the positive side of the battery goes? and the two designated Sierra - go to where the negative side of the battery goes?? How will the on/off switch for the board effect this? Any help you can give will be appreciated.


We are using the potentiometer as a variable resistor. The "wiper" leg is attached to either of the two resistance legs with the difference being the direction you turn the pot to increase/decrease the resistance. I usually just use a fixed resistor here (more consistent over time) once I determine the "pert near" value from testing with the pot. The value, will actually change a bit with the volume you intend to run at.

Yes, and yes.

The on/off switch should work as it always did. The cap is now just a "replacement battery" with no other changes to the circuit except that you will never need the charger (though you can precharge the cap with it), and you never need to turn it off. It will just die away (motorboating) after about a minute of not receiving any power. And, next time it receives power, it will come to life, initially motorboating for a moment.


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## Nick Jr (Jan 2, 2008)

Toddalin, had to capitalize first letter, spell check kept changing it. I sincerely appreciate you answering my questions. The board in one actually has the sound of the loco cranking up, and it doesn't catch right away, really like that added touch and hoping to keep it. Now to continue my parts search. Again thank you.


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## toddalin (Jan 4, 2008)

Nick Jr said:


> Toddalin, had to capitalize first letter, spell check kept changing it. I sincerely appreciate you answering my questions. The board in one actually has the sound of the loco cranking up, and it doesn't catch right away, really like that added touch and hoping to keep it. Now to continue my parts search. Again thank you.


Do you mean like the Phoenix board where if you give it ~2.3 volts, the guy opens and closes the door then cranks the engine a few times before it starts? If so, that is not a Sierra board.


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## Nick Jr (Jan 2, 2008)

toddling: I am aware of that one. Unless my memory is faulty (at my age a definite possibility) I was thinking of the one in my FA unit. That will be my first conversion. When I open it up will connect a 6V battery to make the sound. If it is the one, I'll let you know the board number, if you are interested. If I've erred, I'll let you know that also.


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## toddalin (Jan 4, 2008)

Cool.

The reason I note this is because the Phoenix 2K2 board only uses a few volts from its NiMH battery. It is not the same as the Sierra battery and my Phoenix batteries have not failed on me to date, even after not being used for long periods (years).


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## Nick Jr (Jan 2, 2008)

toddalin, agree. I occasionall the Hudson on an electrified track to charge. Haven't done in a while, you reminded me, will do it now, thank you.


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## Nick Jr (Jan 2, 2008)

Video is only way I figured I could record the sound.
toddalin, I stand corrected. Neurons are still firing but the aim is off. Both have Sierra boards. The FA only has engine sounds. The Rail Bus doesn't have doors slamming, but has the brief sound of a starter motor which is trampled by the 'stuttering' at start of the board without battery. Want to build at least one, 'just because' . Thank You Again for all your help.


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## toddalin (Jan 4, 2008)

I don't know if you will get the starter with the supercaps with the relay cut-out. It could be dependant on the actual cut-out voltage selected.

If the caps are starting from "dead" without the relay (e.g., first run of the session), I doubt that you will get the starter motor.

If the caps still have charge on them because you've only shut it down for a few moments, you may well get the starter.

I guess we'll find out.

I had never even heard the Sierra for the railbus before this, only the Phoenix systems.


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## Nick Jr (Jan 2, 2008)

toddalin, I like the Phoenix for the Steam locomotives. Even got the programming disk and interface to 'massage' things like the rod clank etc. Not being that familiar with diesel's I went with the less expensive Sierra, but like them just as well. Last time I am going to impose on your generosity once more if I may. Hoping to order all parts from one site, Newark Electronics, found the closest relay they offer is RTE 24006, your thoughts on that one?? Supercaps I got elsewhere and they should arrive any day now.


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## toddalin (Jan 4, 2008)

Not a good choice as it draws too many amps. The Aromat has a coil resistance of 450 ohms (80 ma). The RTE is 90 ohms so draws five times as much current to operate (400 ma). This is current that could be going to the sound system and its loss will just reduce you idle time before the system kicks out.

It doesn't have to be the Aromat, but you want as low of a current (high of a coil resistance) as possible.


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## Nick Jr (Jan 2, 2008)

toddlin, thank you very much. The TG2E-6V seems to be discintuned, will keep looking for relay with similar values.


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## Nick Jr (Jan 2, 2008)

Received the Super Caps and couldn't wait to play.
Base Test: Sierra switch ON, no battery, no caps, system stuttered and came alive @ 12V.
First Test: Sierra switch ON, caps in place of battery, ran it for 45 sec, (I was slow to react on the video) removed track power and the sound continued for 60 sec before the caps were fully discharged just as I attempted to add track power.
Second Test: Switch ON, ran for 60 sec, removed track power. Sound system idled for 45 sec, restored track power and sound ramped up.
Third Test: Ran for 30 sec and disconnected the caps. When the caps were reconnected the system started up with no stuttering. I published the First test, have the videos of the other two and if requested will upload them also.


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## toddalin (Jan 4, 2008)

I'm glad they are working out for you. I've done several and never had a problem. The president of our club said he tried it and for whatever reason, had no success. I'm thinking he did something wrong (maybe one cap in backward?)

I also got an e-mail from a local who was also asking about them, tried them with success, and is now able to use his Sierra again.


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## Nick Jr (Jan 2, 2008)

I am very happy with the results using just the 3 supercars. Today I received the last of the parts I needed to assemble the low voltage cut off. Want to do at least 1, just because.


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## Stan Cedarleaf (Jan 2, 2008)

Hi Nick... So glad you were able get connected to the guys who REALLY could help...

It's been so many years since I've "messed" with the Sierra systems, that knowledge just went out of the memory... 🤪🤪🤪🤪


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## toddalin (Jan 4, 2008)

OK, an ALERT!!!

The other day I was running my USA 44-tonner with a Sierra and Supercaps with the relay cut-out. I was running fairly slowly and noted smoke coming from the engine. I immediately turned it off.

Today I opened it up and could see no shorts. I disconnected the Sierra and started it up and it ran fine on the stand. I connected the Sierra and it was the source of the smoke on the board. (Sheet!) Looks like possibly a voltage regulator, and now the input reads 2.5 ohms.

I had run this engine like this many times in the past without problem. After I opened it, I noted that the negative battery wire to the relay had come off the relay, but don't know if this happened en-route or on the work bench, probably the latter.

Ther are other possible culprets including the lighting voltage regulator which is not being used, but could have fallen onto the board as it was unsecured, tangled in wires, and sitting right above the Sierra board.

And, it could have been due to running too slow where the cap continually charges/discharges to near nothing making the board run hot over time. As I said, until there is some charge on the cap, the Sierra sees it as a momentary short. But the boards are fairly robust and seem to handle this on a usual basis.

This is the only one I've had fail and I've done several. If one wanted to take care of this possiblilty, you can put a 1 or 2 ohm resistor is series with the supercaps. Then the board will never see the temporary "short circuit." It will take a moment longer before the sound becomes fully active because you are now charging the caps through a resistor.


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## Nick Jr (Jan 2, 2008)

Stan, I know exactly what you mean about 'leaving memory'. to quote Al Bundy, "brain can only hold so much, when something goes in, something has to come out".
toddlin, smoke is never a good sign. Will make a note of adding the resistor, thank you for sharing. I found the exact relays you recommended. There are no contact markings. Didn't want to ASSUME anything, and tossing and turning wasn't solving it. Using what I have found on other DPDT devices confirmed the connections. Tired old eyes were strained, but I am now secure in the connections and go back to bed. Good Night All


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## Dan Pierce (Jan 2, 2008)

For DCC operations with the supercaps I use a resistor for charging the caps and a diode for the discharge. This limits the inrush current esp when you start up the command station with many engines on the track!! Should work for DC operations also.


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## Nick Jr (Jan 2, 2008)

TODDALIN, (darn spell check). I have received the relays from two different places. Exact same Aromat part number. Seems to have been at least two runs of them. The one in the upper pics has 8 connection pins, 2 for winding and the other 6 for the relay contacts. Ones I received yesterday have 10 connector pins. Data sheet shows 2 for winding and 6 for relay, the last two on the opposite end from the relay have no internal connection. Just to make life more interesting. But will still do the test as above just to be sure.
EDIT: just ordered the 1 ohm resistors for the safety factor.


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## toddalin (Jan 4, 2008)

Once I've determined the "pert near" value using the pot on the relay, I replace it with a fixed resistor. Seems to be less variable.


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## Nick Jr (Jan 2, 2008)

TODDALIN, this may sound stupid, changing the resistance of the pot, what exactly am I adjusting? And how would I know I found the sweet spot? Thank You
EDIT: Found a posting of yours from 2015, Sputter-Instant Recovery , answered my questions. Thank You Again.


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## toddalin (Jan 4, 2008)

Also, the capacitance (10 mfd shown) of the small cap may be a bit different (but maybe not as you are using the same relays). You want to keep the value low, but if it is too low the relay will go into "chatter."

What is happening is that when the relay begins to trigger, it lifts its contact and this stops the current from flowing to the relay so it goes back into its "relaxed" state where it again picks up power and begins to trigger and lifts its contact...

With the 10 mfd capacitor in place, the capacitor charges instantly as the relay is triggered and when the relay lifts its contact, the capacitor provides the necessary current to complete the "cycle" so that the relay armature actually reaches its other contact where it will stay.


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## Nick Jr (Jan 2, 2008)

toddalin, (it worked this time). In my attempt to make the circuit look as professional and neat as possible I am building it on a real circuit board with solder holes. First I put the super caps together to make sure I had them right, and they are. All wired up, and NOT. The sound board acted as though the caps weren't even there. I suspected the relay wasn't operating, so I trouble shot backward from there. I found I soldered the wire one hole off on the board, for the relay contact, so the circuit was always OPEN. Old eyes, bright light, many shiny spots on the board all added up. As soon as I joined the two contact areas I could hear the board clicking so I knew I was on the right track. Ran it for a few minutes to allow everything to charge up, turned it off for about an hour and it came right back as though it had a battery. SO I wanted to be slick, make a video of it after being idle with a meter across the caps. NOT, the meter took enough away from the circuit so the caps were now below the lowest amount for the board to start up again. Took the meter back off, charged the circuit again, it functions perfectly. THANK YOU VERY MUCH. Now lets see if I can make a few more.


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## toddalin (Jan 4, 2008)

I just use "dead bug" architecture. Glad it is working for you.


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## Nick Jr (Jan 2, 2008)

toddalin: had to look up 'dead bug' architecture. It is exactly as the name says, components mounted like on pins, Think I have an issue with the pot, more later. Still havin' fun.


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## Nick Jr (Jan 2, 2008)

toddalin, you have PM.


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## toddalin (Jan 4, 2008)

Let's ask Greg, and anyone else who may be able to provide an answer.

If a Sierra Soundtraxx sound board is run continually with its charging circuit running into an open load (infinite resistance), can this burn out it's voltage regulator or other parts?

I've run several Sierras on the supercaps without problem. Some have a relay cutout but I typically run them above the minimal voltage so they "see" the caps.

Recently one burned out what appears to be a voltage regulator. With the engine open, I can still watch it smoke, but there is very little bit of magic smoke left in it to release.

The train was running slow, testing the track, so the Sierra was primarily seeing an open circuit. Of course a dead Sierra battery also produces an open circuit as I've confirmed on an old battery. 

So, _*theoretically*_, can running the charging circuit into an open load over time harm the board?


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## toddalin (Jan 4, 2008)

After further thought, the Sierra never does try to charge an "open circuit" because it always sees at least 450 ohms for the relay coil, even when the caps kick out.


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## Nick Jr (Jan 2, 2008)

toddalin, I seem be experiencing a problem when my track voltage is below 10. The sound system seems to revert back to stuttering or just suddenly stops. I am adjusting the pot to see if that has anything to do with it. Any suggestions?? thank you


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## toddalin (Jan 4, 2008)

The Sierra charges at ~7.2-7.5 volts so needs to see at least 8.5-9 volts (or more) to its reach charge voltage. Under the charge voltage, many regulators fail to put out much of anything rather than just a somewhat lessor value. This seems to be the case here.

With the battery, the amount of charge that could be stored was far greater than with the caps, so even when running under the charge voltage and not receiving much of anything, there was a large supply held in reserve to draw from..., assuming you rememberd to precharge the battery, or ran the engine long enough at a high enough speed to charge the battery for a while. Our reserve is now severly reduced at the sake of convenience and availablilty.

More farads would better simulate the battery, but the inrush and its strain on the board is greater. Perhaps more farads could be used, but using an inrush suppressor rather than a resistor would probably be a better way to go.

Adjusting the pot _may_ give you a slightly lower start/drop out voltage. By "studdering" I assume you mean "motorboating" though the speaker (not clicking of the relay) like when you try to run with a dead battery. If this is the case you would want the sound to drop out at a higher voltage so it just goes dead rather than motorboating, and would add resistance to make teh relay drop out a bit sooner. If it is the relay clicking, you would need to increase the value of the 10 mfd cap a bit because the relay is not making it to the other pole to latch and needs a bit more "boost."


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## Nick Jr (Jan 2, 2008)

I ran the locomotive 7 minutes at a track voltage of 14, as you said you run your trains at, before lowering the track voltage. Lowering the track voltage to 10 or below, the train is at moderate speed. If that is done for more than 60 seconds the stuttering starts or suddenly cuts off. The sound is coming from the speaker of the sound system. I doubt I would be able to hear the mini relay bouncing. I've also heard a whine coming from the caps when the system is off, don't know what that indicates, not concerned about that. On the next start up the system starts by stuttering before it comes on again, which leads me to think the caps were discharged while running at the lower voltage. I'll play with it some more, but those results I mentioned were constant. I'm sure his system is fine for some, but I don't always run at those high speeds constantly. The time it takes me to slow down and come to a stop takes more than one minute at a time. I did have fun research finding the parts and building the circuit as you described, even adding the 1 ohm resistor. All is not a loss, I have enough spare parts so if while fooling around with it I produce smoke, can replace and continue.


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## Greg Elmassian (Jan 3, 2008)

What you might need is to run the sound card from a DC to DC boost converter, they are inexpensive. Then you can basically have almost constant power to the board. Look around carefully to have one whose minimum input voltage is just a couple of volts.

Greg


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## Nick Jr (Jan 2, 2008)

In the interest of continuing the project, allowing those of us that operate at lower track voltages, (not to mention the fun) that is exactly what I did. Ordered local so no extended shipping date. Will post when I have more to add.


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## Greg Elmassian (Jan 3, 2008)

There are some nuances to the power connection, but it should be wired exactly as battery powered (yeah this statement sounds dumb I know). 

I think this will do the trick for you.

Greg


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## toddalin (Jan 4, 2008)

Actually, I do have a Sierra that I would like to run slower and am wondering if the Phoenix "Big Boost" could be used. I have two of the Big Boosts that I purchased long ago with this intent, but have never tried to use them.

Based on the literature, the Big Boost puts out either 8.2 or 7.12 volts. These are not high enough to boost the incoming voltage to >10 volts, but _*perhaps*_ the 7.12 volt tap could be used between the Sierra and the Supercaps. This is about the same voltage that the Sierra puts out to the cap/battery when receiving adequate power to operate. I guess it would depend on what the Sierra is putting out to the cap at lessor voltages, and what the Big Boost actually puts out when receiving the ~7.2-7.5 volts from the Sierra when running at speed. Also, would the Big Boost "tax" the Sierra charging system by demanding too much current when the voltage is low? I assume that the Big Boost must be "trading" current for voltage. OTOH, it looks like it draws this current from the input to the board, and not the board itself.



http://www.phoenixsound.com/pdf/Boost.pdf



I guess they've really gone up in price when you can find them. 









Phoenix 7200-97 Big Boost Battery Charger for Model 96/97 | eBay


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## Greg Elmassian (Jan 3, 2008)

Not many good reviews on the Big Boost unit. It drew a lot of current in several cases, and was not super efficient. The fact you can get adjustable boost/buck inverters *really *cheaply would make me not pursue that direction.


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## toddalin (Jan 4, 2008)

Actually the Big Boost is an early boost/buck inverter. The interesting thing here is that the Big Boost feeds the battery directly from the input bypassing the Phoenix board. 

I would have thought to put boost/buck inverter from the Sierra to the supercaps boosting the voltage to these while leaving the input voltage alone so that the proper speed sound comes out of the speakers. But I can see that this could draw too much current though the Sierra when the voltage is low (as I said, trade current for voltage), and the better option may be to just boost the incoming voltage to the minimum that will reliably power the board. But you would not get the engine and assorted sounds associated with activities under 10-12 volts

But just setting the input voltage to the desired "charge" voltage and using that to both power the cap (or battery) and keep the sound board backup supply operating at full charge sounds like the better way to go.

Using this approach, would you suggest a set of diodes to keep the Sierra from "back-feeding" into the boost/buck and could this do potential damage?


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## Greg Elmassian (Jan 3, 2008)

Not a lot of data on the Big Boost.... was not aware it was anything more than boost, not aware it is buck also. 

Looking at the board, it is very simplistic, it has 2 output voltages, settable by the jumper, and it should reach full output voltage at 3.5 volts input.

I think it is boost only. Manual on the Phoenix site.

Greg


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## toddalin (Jan 4, 2008)

Nick Jr said:


> I ran the locomotive 7 minutes at a track voltage of 14, as you said you run your trains at, before lowering the track voltage. Lowering the track voltage to 10 or below, the train is at moderate speed. If that is done for more than 60 seconds the stuttering starts or suddenly cuts off. The sound is coming from the speaker of the sound system. I doubt I would be able to hear the mini relay bouncing. I've also heard a whine coming from the caps when the system is off, don't know what that indicates, not concerned about that. On the next start up the system starts by stuttering before it comes on again, which leads me to think the caps were discharged while running at the lower voltage. I'll play with it some more, but those results I mentioned were constant. I'm sure his system is fine for some, but I don't always run at those high speeds constantly. The time it takes me to slow down and come to a stop takes more than one minute at a time. I did have fun research finding the parts and building the circuit as you described, even adding the 1 ohm resistor. All is not a loss, I have enough spare parts so if while fooling around with it I produce smoke, can replace and continue.


I had a thought on this.

I run the trains at 12-14 volts. They do a lap then park for a half a minute, the sound goes to idle for half a minute then the engine again receives full power, restarts, and everything works fine. Alternatively, the train is parked and after the the relay kicks out, it just goes silent.

You are running the train at a lower voltage than will charge the cap and the relay most likely does switch the cap out of the system. But, the system is still receiving enough voltage (the train is not parked) that it wants to be "on" and make sound and run off the "reserve" provided by a battery.

But because the cap is switched out of the circuit, the system sees the open circuit as a dead battery and motorboats or like my Shay would do, keep trying to "restart" itself. Rather than motorboating, the Shay would go "whoop, whoop, whoop" as if it was trying to start when the battery was out of charge.


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## Nick Jr (Jan 2, 2008)

Here's my latest thought: Obviously can't wire it directly to track power cause the board adjusts it's speed sound by voltage. A battery and the super cap circuit allow voltage to flow either in to to store and then out to function. Will this boost circuit allow power to flow in both directions?? I have a sinking feeling NOT because there is a designated IN and OUT. May have to massage the circuit design. Just my idle mind playing with me. Will find out when they get here. I did order in the event I smoke one, or two.


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## Greg Elmassian (Jan 3, 2008)

Maybe I am missing something here.

Use the boost unit to power the sierra, from the normal battery terminals (put supercaps there too)

use the track inputs to sense the speed.

you might have to optoisolate, i'm kind of busy to go look at the schematic right now.

Is it more complex than this?

Greg


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## toddalin (Jan 4, 2008)

Greg Elmassian said:


> Maybe I am missing something here.
> 
> Use the boost unit to power the sierra, from the normal battery terminals (put supercaps there too)
> 
> ...


Maybe.

When the Sierra receives ~11 volts and "wants" to charge, where does this charge go if the booster is also providing charge? Does the cap just "see" the higher of the two voltages and everything plays together nicely (which is what I assume happens when using the intended Phoenix sound board and Big Boost), or if it "mingles" with the voltage from the booster, will this create problems for the regulator on the Sierra board?

Could a diode be used to ensure that current from the Sierra board does not "back-up" into the booster, and would this be necessary?


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## Nick Jr (Jan 2, 2008)

I still have (???) a couple of the optoisolate circuit kits Used for the R/C's on battery operated steam locos that get the chuff signal through contacts, separate from the input voltage as the diesel board does. This is getting VERY interesting, and may prove to be far more technical that I am trained for.


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## toddalin (Jan 4, 2008)

I guess I need to dig out the Sierra manual and see how they do battery power. But IIRC, that may have used the optoisolator.


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## toddalin (Jan 4, 2008)

I went through the Sierra manual and there is absolutely no information on connecting it other than to simple track power with the back-up battery. There is no info on running the unit from battery power, though you certainly could just put it across the motor leads, or how one would adapt this to the back-up battery.


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## Greg Elmassian (Jan 3, 2008)

Todd, there are tons of documents from SoundTraxx on using the sierra with batteries... I guess you don't have the full repertoire of documentation.

In fact they provided separate documentation for:

battery power with Reeds R/C
battery power with Aristo R/C
battery power with Locolinc R/C
battery power with RCS R/C
plus both revisions of technical bulletin 6, and bulletin 6r are for battery power.

There's more documentation on using the Sierra on battery than on track power.

Greg


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## Nick Jr (Jan 2, 2008)

Think the doc's came with the opt isolator kit of parts, I'll look for them. I try to keep all printed information knowing the mind can only hold so much, and lately I've sprung a leak.


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## toddalin (Jan 4, 2008)

OK, I found the documentation (Technical Note #7) and ...

Shown circuits use an LM317 regulator to _*reduce*_ the incoming voltage to "feed" the board. I assume a simple R/C with battery would be similar. None boost a low voltage.

Be that as it may, most circuits also use a diode to keep the board from backfeeding to the regulator (though some don't) and I am wondering if I could/should do the same with the Big Boost, or one would do this using a boost/buck inverter.

SOUNDTRAXX SIERRA TECHNICAL NOTE Pdf Download | ManualsLib


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## Nick Jr (Jan 2, 2008)

Bottom of each page states for DCC not straight DC, or is there a portion of it you are referring to? Beginning not to trust my eyes any more.


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## Nick Jr (Jan 2, 2008)

*Images for Sierra Optoisolator circuit*






  








  








  








  











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## Nick Jr (Jan 2, 2008)

*Images for Sierra Optoisolator circuit*
Sorry it took 2 posts to paste the prints and comment.
I don't know how that will help the circuit any?? 












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## Greg Elmassian (Jan 3, 2008)

The opto circuit solves different issues.

Todd: a diode is cheap insurance, why not, right? What, 10 cents?

The Sierra can draw a lot of current, and can have reliability issues at higher voltages.

I spent some time getting good data on this, from several people who did professional installs for years. perhaps this page will help some: (read under the NOTES section)






Soundtraxx Sierra


Greg Elmassian web site on large scale trains and garden railroads, cigars, and computers




elmassian.com





Greg


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## Nick Jr (Jan 2, 2008)

Beginning to feel we are just 'grasping at straws' here, JMHO.


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## toddalin (Jan 4, 2008)

I recognize that. The difference would be in that if the power source were straight dc, you wouldn't need the bridge rectifier because you would alway be taking off of the + and - from the battery and these don't change like the wheel current can/does.

Also, DCC would probably need bigger caps (C3) to smooth out the incoming voltage to straight dc for use by the board. The bridge rectifer, C2, and C3 become unnecessary with batterys or a dc charge that does not change polarity.

Greg, you can correct me on any of this if I'm wrong.


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## toddalin (Jan 4, 2008)

I've read your notes before. When you discuss max voltage, you don't note whether this is on terminals 7 & 8 or 2 & 4. An oversight?

BTW, the Sierra in my 44-tonner is still in the process of releasing its magic smoke. The piece that is smoking is just to the left of the LM chip and in your picture is the rectangle closest to and between pins 4 and 5. Looks like it was a voltage regulator. 

Sierra offer repairs. I wonder if they could fix this.


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## toddalin (Jan 4, 2008)

Nick Jr said:


> Beginning to feel we are just 'grasping at straws' here, JMHO.


Educated guess.


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## Greg Elmassian (Jan 3, 2008)

max voltage on the normal battery terminals 4 and 2, but a good question to be specific, I believe the track pickup inputs are ok at or below the battery voltage.

I'll get the final word. The overvoltage one is interesting, those data came from SoundTraxx after a number of years asking what the real limits were.

Which picture is the one you refer to with the smoking component? The actual picture of the board?

They do not repair Sierra boards any more I am told.

Greg


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## toddalin (Jan 4, 2008)

It is the component just above the left edge of the left switch, and above and to the right of what looks to be the bridge. You see what looks like a white line along its bottom edge.


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## toddalin (Jan 4, 2008)

BTW, though extremely doubful, it is possible that my smoking board may still work. It was working when I first saw it smoking. If this is the regulator that powers the battery, it may be possible that a buck/boost applied to the battery terminals may still work the board. There would just be no battery charging capabilities.

I can only hope.


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## toddalin (Jan 4, 2008)

Nick Jr said:


> Bottom of each page states for DCC not straight DC, or is there a portion of it you are referring to? Beginning not to trust my eyes any more.


Notice that none of the dcc operations include a battery back-up for when the engine stops receiving power. When you cut power to the track, the sound goes dead.

But a dcc engine would always receive power, even when not moving unless you shut down the entire system.


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## Greg Elmassian (Jan 3, 2008)

Looks to be a 4 terminal part, my guess is a full wave bridge... no chance to read the part number?

If not I can find out.

There is no need for battery backup when running from a fixed input voltage, either DCC from the rails, or constant DC like some people use for R/C or from battery operation.

Greg


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## toddalin (Jan 4, 2008)

Looks like three to me (two on one side and one on the other) and is the same as the one further over. I'm thinking regulator. The bridge, with four terminals, is below to the left.


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## toddalin (Jan 4, 2008)

OK, check this out. This is a Buck/boost that will handle from 3.8 - 32 volts with a selectable output from 1.25 - 35 volts. It can handle a max of 3 amps.

A single piece is $4.99. But five pieces are only $10.89 and they go down to ~$1.20 in larger quantities.

Geekcreit® DC-DC Boost Buck Adjustable Step Up Step Down Automatic Converter XL6009 Module Suitable For Solar Panel

They are also available with fixed outputs with inputs from 3 to 15 volts. Go to Banggoods and search buck/boost.

To do this, we would need to add a bridge rectifier and cap to provide the correct polarity to the buck/boost board so the minimum voltage would increase by ~1.5 volts and you are looking at runing trains with the cap charging down to ~5.5 volts on the track.

Using one of the "fixed" voltage units (assuming you find a workable voltage), you could charge down to ~4.5 volts on the track but maximum track voltage could not exceed ~16.5 volts. Based on G-scale power parameters, this is not a lot of margin for error.


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## toddalin (Jan 4, 2008)

OK, This is how I envision it could be done.

Greg, please check my logic and numbers.


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## Nick Jr (Jan 2, 2008)

toddalin, your board seems to be different than mine. The manual I copied it from is : SoundTraxx Sierra Diesel Owners Manual. 2004 Rev. B Throttle UP! Corp. This is the one I have in my loco's. Terminals 7 & 8 are basically the the same, if you exclude the switch and charging jack, but the rest don't seem to follow. Were there different versions?


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## toddalin (Jan 4, 2008)

Nick Jr said:


> toddalin, your board seems to be different than mine. The manual I copied it from is : SoundTraxx Sierra Diesel Owners Manual. 2004 Rev. B Throttle UP! Corp. This is the one I have in my loco's. Terminals 7 & 8 are basically the the same, if you exclude the switch and charging jack, but the rest don't seem to follow. Were there different versions?
> View attachment 62008


My board is the same. Pins 2 and 4 are directly linked to the two battery terminals and either can be used to get power into the board. Greg confirms this on his site.


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## Nick Jr (Jan 2, 2008)

toddalin: the print I posted is in the manual I received with each sound board. It shows pin 2 being a ground contact point for raising or lowering the volume on an external momentary contact switch. Pin 4 is a common ground for the lighting as also shown on Figure 10. The battery in that print is no where near that part of the circuit. Having never been on Greg's site I don't know where he got that from, do you?
EDIT: testing showed that below 14V of track power there was no indication across those two terminals, above 14V showed a constant 7V. Now that is voltage coming out of those terminals, don't know how that circuit would react having power applied in reverse. And how would that effect the volume and lighting circuits?


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## toddalin (Jan 4, 2008)

Nick Jr said:


> toddalin: the print I posted is in the manual I received with each sound board. It shows pin 2 being a ground contact point for raising or lowering the volume on an external momentary contact switch. Pin 4 is a common ground for the lighting as also shown on Figure 10. The battery in that print is no where near that part of the circuit. Having never been on Greg's site I don't know where he got that from, do you?
> EDIT: testing showed that below 14V of track power there was no indication across those two terminals, above 14V showed a constant 7V. Now that is voltage coming out of those terminals, don't know how that circuit would react having power applied in reverse. And how would that effect the volume and lighting circuits?


Take a meter and check for continuity between pin 2 and the - battery plug terminal, and pin 4 and the + battery plug terminal to confirm they are in fact the same. I remember doing this years ago, but didn't remember which pins. Greg's site discusses this and it is often easier to use the pins rather than dealing with the battery plug, which often breaks when the plug is removed.

As I said before, some regulators put out nothing until they see a certain voltage, but it seemed a bit lower (~12-13 volts).

The diode between the caps and Sierra in the latest sketch keeps the 7V produced by the Sierra board from feeding into the caps. The diode between the caps and buck/boost keep the caps from possibly backfeeding into the Buck/boost and taking this charge from the Sierra's idle time after shut-down. (BTW, we can still use the relay to conserve the voltage in the caps after shut-down.) I think that the Sierra will simply "see" which ever voltage is higher, so long as they are of the same polarity. It will not see the sum of the two voltages.

You can confirm this by running a train between two blocks on different dc power packs, where one block has a higher voltage, and when the train crosses blocks and sees both power packs simultaneously, it defers to the speed of the higher voltage, and not the sum of the voltages.

Again, Greg should be able to confirm this, or at least set us straight.


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## Nick Jr (Jan 2, 2008)

toddalin: It is a multi layered circuit board so visual inspection shows nothing. Did the meter tests you described. With a wire wound meter (Simpson) wasn't able to see any resistance between the points you mentioned, but with a digital I got bouncing results as if something was attempting to activate. Taking into consideration that an inactive solid state circuit may not show anything I did one more test. Attached a 6V battery (same technology) to the Battery input plug (6.42V) and read the same 6.42V between pins 2 & 4. Also consider that I am not using the lamp feature and did not activate the volume feature. I am willing to take the plunge and assemble the circuit as you describe with one difference, instead of using points 2 & 4 am going to use the battery inputs as Sierra designed. Just as a cautionary measure incase something else is involved that I couldn't see with the meters. Don't want to smoke the board as they are not supported any longer. Your thoughts?


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## Greg Elmassian (Jan 3, 2008)

Let me post the schematic for battery operation from Sierra, this might help avoid confusion, or at least give the starting point. Adding the diode, I agree with Todd's assessment and idea of protection.










Todd and many others who have installed these are correct about the alternate pins for the battery plug in the connection and why you would use them. Many of these connectors get broken, use it as you please, you have a backup that is more reliable and robust.

Greg


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## toddalin (Jan 4, 2008)

Will be anxious to see the results. 

BTW, I revised the schematic. I think I had the diodes in backwards. Wouldn't have hurt anything, just wouldn't have worked.

Greg, you were supposed to catch that.


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## Nick Jr (Jan 2, 2008)

toddalin: if you are reasonable sure of the above, I will order parts and join in on the fun. And looking at the schematic from Sierra my suspicions were confirmed, I was 'seeing' something, just didn't know what.


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## toddalin (Jan 4, 2008)

I'm good with it. Lets see if Greg will "buy off."

At the price for the BB modules through Bangoods, it pays to get 3 or 5 for the price difference. As versatile as they are, I'm sure you could find some use for them.


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## Nick Jr (Jan 2, 2008)

toddalin: I already have a use for them. The A-1-A shark I built I used diodes to drop the voltage to the motors so the fans and lights would come on before it moved. This seriously limited the top end. Would like to remove them, add the boosters for the lighting and fans, then add the limiter so not to over rev or burn the LED's. That will allow the loco to start at a lower track voltage and reach a more scale speed as it is somewhat limited at this time.


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## Nick Jr (Jan 2, 2008)

toddalin: did some testing of the boosters I wrote to you about. All tests done at the setting on the unit as received. I added a lamp and voltage limiter at the end which also acted as a load for the booster.
Track Voltage-----Booster Out
4.0----- 5.8 
6.0----- 9.1
10.0---- 13.0
12.0---- 13.1
15.0---- 15.2
20.0---- 20.0
At this setting the unit seems to level out at about 15V, which I don't see a problem with. I took video's of the tests showing each meter, but doubt anyone is that interested. As a last note, the limiter held at 3.0 - 3.1, but need more testing before I convert the Shark.
EDIT: adjustments: found if you adjusted for more boost at a certain threshold the unit starts fluctuating short circuits, adjusting for less boost can bring the threshold higher before it starts fluctuating, it also levels out sooner.


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## toddalin (Jan 4, 2008)

You are treading on new ground here.


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## Greg Elmassian (Jan 3, 2008)

OK, confused again... what is the goal here? I thought the issue was to try to basically get the sound system to run all the time and eliminate the battery?

Would you mind explaining what we are trying to do?

Normally the units I was talking about have a set output... the post above seems to not have the voltage limited, and makes no sense in terms of eliminating the backup battery and lowering the voltage that the sound can continue with.

Confused... please clarify...

Greg


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## toddalin (Jan 4, 2008)

One wants to be able to run the engine at a much slower speed than the ~12 volts now necessary to keep the Sierra system operational and provide a reserve for the power down/idle sequence sounds after track voltage is removed.

My thought is that that buck/boost should maintain 7-8 volts running from track power with track voltage ranging from ~5.5 volts to max throttle and the cap provides a reserve when the power is cut. This is apparently what the Phoenix Big Boost does except that it allows down to ~3 volts input from the rails to operate so is more "sensitive" on the "bottom end."

If we can get the Sierra to operate and the cap to charge down to <6 volts on the rails (rather than the ~12 volts now required) which is pretty slow, I think we've achieved to goal.

But based on the data, if 6 volts input is only getting 9.1 volts output, that's not going to get us there and we are probably looking at ~9 volts to get the system running/charging falling short of the goal. 

Also, as the voltage goes above this ~9 volts input, we need it to stay at 7-8 volts so it doesn't burn out the board. Perhaps there are settings on the buck/boost that Nick needs to explore to get to where we need to be.


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## Greg Elmassian (Jan 3, 2008)

So what you are using is not a regulated output boost inverter, but some kind of boost circuit with an unregulated output?

Seems that is adding problems, not removing them... then your supercaps will have to have overvoltage protection, I would think... and that will probably eat into the margin you are working so hard to maintain.

Greg


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## toddalin (Jan 4, 2008)

Greg Elmassian said:


> So what you are using is not a regulated output boost inverter, but some kind of boost circuit with an unregulated output?
> 
> Seems that is adding problems, not removing them... then your supercaps will have to have overvoltage protection, I would think... and that will probably eat into the margin you are working so hard to maintain.
> 
> Greg


Right, the voltage to the Supercaps cannot exceed 8 volts. I figured that if the BB module was set to produce 8 volts, ~0.7 volt is lost though the diode and the cap should be safe.

At 7 volts, the caps see about 6.3 volts and that should be plenty to run the Sierra reliably as the battery had a 6 volt rating.


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## Greg Elmassian (Jan 3, 2008)

Pray tell, can the mystery boost board be identified please?


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## Nick Jr (Jan 2, 2008)

Prayers not necessary, and I gave all that info to toddalin yesterday, and you over looked #85 & #86 posts mentioning the LIMITERS. Allelectronics, call it Step Up Voltage Converter, part #UDC-2. They also offer a UDC-3, but that one started at a higher voltage.
First let me say I don't have the thoreitical knowledge to deslgn a circuit, just the practical experience and training (telecommunications) to see what happens in a simple operating circuit. 5V to track, B1 is going to cost at least 1V, train barely moving if at all, the booster is receiving 4V and putting out close to 6. I suggest removing R1 and the first diode (and possibly the second) as the limiter will act as the load and protection. The sound is starting and the caps are charging. As the track voltage increases the booster levels out (out put is equal to input) at about 14 and then stays same as the track voltage, I tested to 24V to make sure it would be strong enough to with stand full track power. To limit the voltage install a limiter after the booster, like I am doing for the LEDs and fans on the Shark. My limiter for that application is set for 3, for this battery circuit set the limit to 7 or 8. as the latest print shows. Since there are the same number of Supercaps as on the other, if the track v drops to 0 they will feed the sound board for about 60 seconds before depleting but if the track voltage is held at 4 the system will still see 6 and keep the sound board going. I tried to cover the whole process. If anyone has a different board in mind please say so.
As I said previously, have the videos showing the meter readings at the different points I described. Think I have enough left over parts from other projects to assemble something later today. Hope to post something showing forward progress, or disappointment. 
EDIT: Guess I should have posted the video, show it better than I could say in words.


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## toddalin (Jan 4, 2008)

So you are doing a boost/buck, but using two boards rather than a single combined board.

As long as it works and you have the space, it should really be no different and maybe better as you have a wider selection of boost boards available, some of which will use a lower voltage, as you found.


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## Nick Jr (Jan 2, 2008)

toddalin: I'm not crazy about devices all rolled into one. Example: stereo system, amp, turn table, tuner, CD player all in one enclosure, one feature goes the whole item has to be replaced, not designed to be fixed. Also in this case gives me access to the power coming out of the booster for other uses. And you are right, this booster had the lowest starting voltage I could easily get. The diesel locomotives I have are from the end of the steam era so there is more than enough room inside for anything. Frankly I am diesel stupid, can't tell the newer ones apart. Yesterday was such a nice day I spent outside, today rain is predicted so hope to get some more testing done. I'll keep you posted.


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## Nick Jr (Jan 2, 2008)

toddalin: some encouraging progress: Referring to your print: took my voltage readings after B1, so 1.25V less than track power. I used a diode between the limiter and + side of the supercars, possible protection for the limiter, which is now set to 7.5. Advanced the super caps directly to the actual battery input leads which are before the on/off switch and charging jack. The caps started to charge and the sound system stuttered at 4.5V (after B1), left it alone to allow the booster power to climb, which it did to over 9V. I let it run for couple of minutes. I slowly lowered the feed voltage till it got to 4, and the limiter was still reading 5.9 and the sound system was still functioning. Thinking of removing the one diode, but want to see what it is costing the circuit before doing so, if only .5 going to keep it in. The locomotive wheels started to turn at about 4V of track power, so if I wanted to I could install diodes in line with the motors to keep the loco still till the track voltage climbs, like it did with the Shark. With the booster on the sound system I would only need a couple and the loco will still reach close to scale speed. Your thoughts please??


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## toddalin (Jan 4, 2008)

Sounds like you've found a viable solution. When you are sure that everything is working and no smoke is released, you should do up an article. There is no reason that you shouldn't be credited with this and there certainly are a lot of Sierra boards that could use it.

When complete, this would be great for the _GR Newsletter_, but you would first need to submit the article though a Club. If you don't belong to a Club, we could work it out. For example, I could put it in our newsletter under your name and it could go in that way.


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## Nick Jr (Jan 2, 2008)

toddalin, you designed the circuit, I just assembled parts to play, it is for everyone to see and do, hobbies are for fun


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## Nick Jr (Jan 2, 2008)

toddalin: have you received your boards from Bangoods and started your testing yet?? Been just too nice outside to play inside last few days. Next time at the bench intend to replace the limiter with one that doesn't have a V meter and make the installation permanent. Will also add a couple of diodes to lower the power to the trucks.


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## toddalin (Jan 4, 2008)

I had not ordered the boards. I have two of the original Phoenix Big Boost Boost/Buck limiters that I will eventually try when time allows.


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## Nick Jr (Jan 2, 2008)

Wired the components on a board to make the final installation have a neat look. Starting cold slowly bringing up track voltage, the lower the track voltage the longer it takes the boost board to reach its peak setting, no drawback there as once the caps charge and the sound sees 5.5V it starts. Made my own rectifier using diodes I had on hand, 1A. Your estimate of using a 3A is more like it. If the track voltage isn't raised very slowly, they are heating and causing very quick and sharp shorts. By using the battery input leads, keeping the I/O switch in the loop, you can turn it off and the caps will hold the charge until next time turned back on. My next bench play I'll replaced the under powered rectifier I assembled with ones on the way. Would also like to wire a relay (the 6V from the other print) coil with the limiter output. Then use the contacts in place of the switch. The relay is after the limiter so it should recover next time the circuit sees 6V. Any thoughts??
EDIT: forgot to mention I substituted the limiter with one that doesn't have a V meter built in.


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## toddalin (Jan 4, 2008)

Sounds like you have it nailed.


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## Nick Jr (Jan 2, 2008)

toddalin, testing showed the way I described wiring the I/O switch is not such a good idea. When left as built when track power is lowered to 4V the unit will continually operate. When track power is removed the unit will continue to produce sound for 75 seconds then the board times out. The caps actually produce a very low crying sound as they slowly discharge, and I can hear it. If the switch is turned off at that time the caps will hold the charge and start right up when turned back on. When I wire it as I described above, the relay coil wired to the limiter output, and the I/O wired through a contact in the really as soon as track power is dropped so does the relay, contact opens and the sound stops immediately, not what we want. Next test is to wire the relay coil to the caps and the contacts still wired as the switch. As the caps 'cry' down to below 6V the the relay would open, turning off the switch. Resuming power to the cap circuit should close the relay turning the switch back on??? Sounds good on paper, real test will be next time at the bench. Open to all thoughts and suggestions.
EDIT: that will not work either, the relay coil will ultimately drain down the caps, unless the cap circuit is opened as well?????????? Still scheming.


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## toddalin (Jan 4, 2008)

Nick Jr said:


> Next test is to wire the relay coil to the caps and the contacts still wired as the switch. As the caps 'cry' down to below 6V the the relay would open, turning off the switch. Resuming power to the cap circuit should close the relay turning the switch back on??? Sounds good on paper, real test will be next time at the bench. Open to all thoughts and suggestions.
> EDIT: that will not work either, the relay coil will ultimately drain down the caps, unless the cap circuit is opened as well?????????? Still scheming.


Yes, this is the way I had intended. The cap holds the relay open while it powers the board until both the board and relay drain the cap enough for it to cut out. This is why we use such a low draw relay. No, don't expect 75 seconds.., more like 30+ seconds of idle time because current is lost to the relay as well as the board.

This is also why I put the diode between the cap and the B/B so that the caps' available current doesn't also backfeed and drain through that B/B board. I don't know that it would, but this is insurance that may not be necessary and actually is detremental in that it lowers the available voltage charge to the cap a bit. But..., you can always turn up the B/B by ~0.7 volt to compensate for the loss through the diode.


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## Nick Jr (Jan 2, 2008)

toddalin, The board actually times out and turns itself off after 75 seconds of 0 track power, can actually hear the 'engine' winding down. The caps still shows over 6V, if I were to shut off the switch the caps stay charged and the system starts right back up when turned back on.
Second Thought: while I'd like more, 30 seconds may be long enough. And just applying power will turn it back on. Back to the bench, still scheming.


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## Nick Jr (Jan 2, 2008)

While I should be satisfied with the operation of the existing circuit, and turn the unit off with the switch, I would like to take it one step further. Using the output of the limiter, which immediately drops to 0 when loosing track power, I would like to add a timer circuit, that is isolated from the caps that are feeding the sound board to prevent back feed. Would like to use one of the 6V relays I have, and I read where I could use the caps in parallel with the coil windings to slow relay from releasing, but have had no success so far. If I could get that to work would use the contacts in that relay to turn the board off AFTER about 60 seconds so the caps would still have some charge for the next time. Your thoughts please?? As a side note I found in the Sierra manual that there is an option for the board to turn off at 60 seconds OR only throught the switch. The option is already set for the 60 second setting, but is really 75, give or take.


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## toddalin (Jan 4, 2008)

Yes, a cap will hold the relay open for a duration. I think the problem you are having is that the way the circuit is set up, the cap is acting to allow the armature to complete its motion and this is happening before the caps can take a full charge.

Did you try changing the 10 mfd cap for a larger value (e.g., 100 mfd)? A larger cap should take longer to the relay to pull in the armature, but should hold it there longer. But it could also be that the cap that is holding the relay open is also going to the Sierra so you are loosing charge there. If that's the case/in any case, I have another idea that would use a second relay.


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## Nick Jr (Jan 2, 2008)

The circuits I attempted were totally separate from the Sierra battery replacement (post #82) circuit board. I tried using the 10UF and just didn't hold the relay up once the power was dropped, although I'm sure there should have been more to it than just the relay and cap. Don't have any 100UF, but may order some to test. (wish Radio Shack still had stores). Also noticed the relays come up at 3V, which isn't so bad either. Would like to see any ideas you have, thank you.


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## toddalin (Jan 4, 2008)

I've been working (semi-retired consultant). Give me a little time to come up with something. It may be a matter of just using a diode to keep the relay cap from loosing its charge to the board with the Supercap.


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## Nick Jr (Jan 2, 2008)

toddalin, I am hoping it to be a separate part not necessarily having interface with the battery replacement portion. This part will just be to replace the ON/OFF switch of the Sierra system. Just battery to the relay, possibly coming from the regulator but also isolated some how, with a cap as you described and a pot to be able to adjust the fall rate of the relay. Hope that makes the design much easier. I do appreciate your attention to this as I am enjoying what I call 'playing' with it. When we do get it working, I would hope you would publish the findings as you described in a previous posting. I'm just in it for the adventure, and I do thank you for your time and sharing your expertise. BTW, I did replace the 4 diodes I made the rectifier out of with a commercially made full wave rectifier. Trying to keep the power loss low went with one rated at 2A. After several hours of testing, attached a heat sink to the unit, so coming to the conclusion that a 3A unit would have been better as your original print suggested. As soon as you post I will order the parts needed.


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## Nick Jr (Jan 2, 2008)

Catch Up: I did remove the resistor and diode between BB1 and the caps and as previously mentioned used separate boards for Boost and Limiter. Two days ago I energized the board with the locomotive on rollers and ran it successfully for several minutes. I also tested the quick raise in track voltage to activate the horn and it works also. After the run I reduced the track voltage to 0 and let it sit for 60 seconds before using the switch turned it off. The unit sat for two days and this morning I moved the switch to the ON position and the sound started immediately. Applied track power and all is well. 
Observations: The 2A bridge rectifier got warm during the initial start up when the system was drawing in excess of 3A, but once everything got charged the amps dropped to a very acceptable level and the rectifier cooled. Am still going to replace it with a higher rated unit. I also noted when there is track power and the system is running, turning the switch to the off position does nothing until the track power goes to 0 then it shuts right off, and I believe the caps will still hold the charge.
Still playing with the ability to use the 6V relay contacts as the on/off switch, no success at this time.


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## toddalin (Jan 4, 2008)

As I said, when the cap first charges, the circuit sees it as a dead short for a moment. That's why we put in the 4 ohm, 10 watt resistor. The short now becomes a minimum of 4 ohms, for a moment.

Using a value of 7 volts, this is 12.25 watts ((7 x 7) / 4), but for just a moment. 

12.25 watts / 4 ohms = 3.1 amps, but for just a moment.

This is how I determined what values to use.


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## Nick Jr (Jan 2, 2008)

toddalin: I now understand the reason for R1 (as I said, not trained in design only trouble shoot and follow schematics) and will add that to the circuit, thank you for explaining. That will take the load off the start up and probably will stop the heating of the rectifier, so will leave the 2A unit in place, for now. Will order the 4 ohm resistors. Do you have any advice on the cap size to slow down the release of the 6V relay so I can order several things at the same time and not incur shipping on each piece? You previously mentioned a 100mfd cap, do you still feel that will do it, and would a potentiometer be needed to fine tune it? Thank You Very Much


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## toddalin (Jan 4, 2008)

Let me get a noise study for the City of Anaheim Public Utilities Commission out of the way today/tomorrow and I will look into it and do a schematic later this week. I'll go back over the thread to see what is necessary.


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## Nick Jr (Jan 2, 2008)

Thank You very much, anxiously await.


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## Nick Jr (Jan 2, 2008)

Interesting observation: I ran several times, each time allowing the system to run different times, at 0 track power, before shutting off. The more the caps were discharged the higher the amps on the next start up. If the system is allowed to run 60 seconds or less the rectifier doesn't heat as much. Having said that, I did order the 4ohm resistors and will add one to the existing board and include it in the ones for my other loco's.


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## Greg Elmassian (Jan 3, 2008)

When fully discharged, the caps are like a dead short. As charge is stored, the current flow slows down. Todds suggestion of an inrush resistor to limit current flow is how it is done.

You are definitely putting your 2 amp diodes at risk.

Have you ever monitored current when charging batteries? Same thing.

Greg


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## toddalin (Jan 4, 2008)

If I'm not mistaken, I think this is what you want to do.

I think I have one of the relays so I can determine the value of C3 through experimentation. This will break the circuit between the wheels and Sierra Input as well as the supercaps and the "battery jack" when power is removed from the track after C3 discharges through the relay. The relay is actually a DPDT, and I've split the two sets of contacts in the schematic for ease of drawing/visualization. P1 sets the time the relay stays open. R2 ensures that when you turn the pot to the minimum value, you do not cause a short across the relay.

If this is what you think you want to accomplish, I'll play with the components to determine the value of the C3.


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## toddalin (Jan 4, 2008)

OK, I did some testing and 24,000 mfd (a big cap) will hold teh relay open for ~15 seconds, so figure a minute is about 100,000 mfd. That's a *BIG* cap, unless you use supercaps. In which case C3 is three supercaps together, just like C2, and put a 4 ohm, 10 watt resistor between BB1 and D2 to reduce the inrush. 

And these supercaps can be smaller in Farads if desired. The three 6F caps (2 F), will hold the relay open for lots of minutes. I got tired of waiting after over 3 minutes so the board would time out time after time if the pot were not there to let this "bleed down" quicker.

There is also a way to use the three existing supercaps and I'll do the schematic next.


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## toddalin (Jan 4, 2008)

I fixed the last schematic to include the second set of supercaps. These don't need to be as big. We double R1's value so as not to overtax the B/B, bridge, etc. with the addition of the second set.


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## Nick Jr (Jan 2, 2008)

toddalin: first thank you very much for taking the time to do this, and timed relay release operation is exactly what I am looking for. My only concern is you mention with C3 at 1F will give the relay 3 minutes of open. That is much too long as the board shuts down at 75 seconds and the Sierra stutters at the next start up.. Can P1 be adjusted down to about 60 seconds? or do other changes need to be made to accomplish that? Much appreciated.


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## toddalin (Jan 4, 2008)

By my estimate, P1 can turn it down to ~30 seconds. Ideally, we would want to find supercaps (C3) with a value of about 0.5 farad which would take this down to about 15 seconds minimum and 1-1/2 minute max.

This can also be adjusted by decreasing the value of R2. Instead of 100 ohms, 50 ohms reduces the minimum time by ~half, but you would want to increase the value of the resistor to 1 watt.


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## toddalin (Jan 4, 2008)

OK, 0.5 F, 2.7 volt supercaps do in fact exist, so use those instead of the 1 farad and leave the resistors as shown. This will also be a bit "easier" on the system reducing the necessary charge/short time accordingly.

10pcs 2.7V 0.5F KAMCAP Farad Super Capacitor Ultra Capacitor | eBay

2.7V 1F-6F 2F 4.7F 20F 15F 3.3F 10F Super Farad Capacitor Supercapacitor | eBay


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## toddalin (Jan 4, 2008)

I made the changes to the schematic.


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## Nick Jr (Jan 2, 2008)

toddalin: 15 - 90 seconds is great and allow for minor variances in mass produced components, track and locomotive variables and personal preferences. While waiting I was doing more playing:
For my first conversion I am using an Aristocraft FA locomotive set. The motors on these units start the wheels rolling at 4 volts at the track, same as the boost board coming into effect. To give myself a small window of operation I added diodes to drop the track voltage to the trucks. The wheels now start to move at 5.5V. I will have to change Set Up Step 1: Start Voltage setting on the Sierra board to correspond with the new movement.
toddalin, thank you again for taking the time and your expertise helping us revive what is a good and still usable sound system. Creating a shopping list and will post your SUCCESS in a couple of weeks.


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## toddalin (Jan 4, 2008)

Ideally, P1 should be a variable resistor, rather than a pot, because you can get them to handle more watts. You would still look for 10,000 ohms, but mabe a couple watts.

Something like this would be appropriate:

Resistor variable PPB-2A 2 Watt 10 kOhm USSR Lot of 1 pcs | eBay

Resistor variable PPB-3B 3 Watt 10 kOhm USSR Lot of 1 pcs | eBay


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## Nick Jr (Jan 2, 2008)

toddalin, thank you for the update, modifying shopping list which also changes source of some items. The pots I had on the list were only good for 250mw, the variable resistors are good for 5w. Still havin' fun.


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## toddalin (Jan 4, 2008)

After you have it up and running, with your selected voltage from the B/B, take a voltage reading across the relay. The inline diode will reduce this a bit (~0.7 volt). If you find it is over ~6.5 volts, put a 1 amp diode in series with the relay to reduce its voltage by about 0.7 volt and make it easier on the relay's life span. This will also reduce the timing a bit because the relay will kick out a lower voltage due to this voltage reduction.


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## Nick Jr (Jan 2, 2008)

toddalin: will print the above and save it, along with all your other postings on this topic. It will be a couple of weeks before I have all the components for the timing relay. 
Made another board, this time I have the 4ohm resistors, which I will add another in series or replace with an 8 when I add the timing board. Can see the difference on the meters. The initial surge is reduced and takes a bit longer for the caps to reach the output value of the regulator, which isn't noticed as the system is generating sound while the caps are charging.


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## Nick Jr (Jan 2, 2008)

toddling: did some playing with the relays I have, exact part number you advised. Found they go off normal at 2.5VDC, is that how you figured the release circuit and timing? Thank You


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## toddalin (Jan 4, 2008)

No, I simply took a relay and charged up a ~24,000 mfd cap, and timed how long it stayed open, about 15-16 seconds.

From there you can calculate timing value as a fairly linear relationship, (i.e., 100,000 mfd ~ 1 minute)

0.5F = 500,000 mfd

1/((1/0.5)+(1/0.5)+ (1/0.5)) = 0.1667F

166,667F/100,000F = 1.6667 x 1 min = 1.6667 min x 60sec/min = 100 seconds (give or take)

IIRC, the relay is listed at 80 mA at 6 volt or ~450 ohms

1/((1/450) + (1/10,000)) = 430 ohms

430 ohm/450 ohms x 100 sec = ~95 sec. max time

Turn pot to min:

1/((1/450) + (1/100)) = 82 ohms

82 / 450 x 100 = ~18 sec


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## toddalin (Jan 4, 2008)

BTW, I would urge you to also perform this experiment.

You have the relays. Just take a big capacitor of known value and charge it up to the voltage that C3 would be expected to see (after the B/B and big diode), disconnect it from the power source, put it across the relay leads, and you will hear the relay click closed. Time how long it takes to click open.

From there, the timing is a ~linear relationship based on the size of from the cap (mfd) and the resistance (ohm) across it.

You can also see what it does to the timing if you put a diode between the cap and relay as this will knock down the voltage a bit.


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## Nick Jr (Jan 2, 2008)

toddling, I did just what you described, several days ago, with the super caps and resistors I have on hand. I wouldn't be able to hear the relay operate, but did use a meter across the make contacts so I could see it. The best I was able to come up with, using the caps I have, and by adding resistors took over an hour for the caps to discharge to the point the relay released. I was headed in the right direction, but the answer was out of my grasp, I ran out of options. Being able to calculate the needed values permits you to go directly to the answer, I don't have that ability so have to keep adding or removing components to get to where I want to be, and that doesn't always work. Again thank you for your time and expertise.


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## Nick Jr (Jan 2, 2008)

I didn't abandon the project, it took a while to receive all the components for the time out circuit. I tested using power from a transformer and an ohm meter to watch the contacts.
A BEAUTIFUL SIGHT. Variable resistor came from factory set in the center, measured 5K ohms. The input voltage also effects the relay hold time. Using 6V the hold time was 45 sec, 7V was 60 sec. So between the input voltage and the variable resistor there should be a very wide range of cut off timing. Interfacing the two boards is a simple matter of picking up power from the limiter output and using the NO contacts in place of the I/O switch. Before I do that I want to play some more. I'm sure this has helped many of us make use of existing if outdated sound systems. Toddalin, great engineering and design and once again THANK YOU VERY MUCH. I had fun and the outcome is very rewarding.
EDIT: left is the timing circuit, right is the battery replacement board.


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## toddalin (Jan 4, 2008)




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## Nick Jr (Jan 2, 2008)

Made another timing board this morning, with a wiring error, easy fix. Cataract surgery '21 days and a wake up', can't come soon enough.


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## Nick Jr (Jan 2, 2008)

Playing: using 7V input, after the initial charge takes minimum 60 sec to get a full charge, longer had no effect but shorter lessened the time out. Using the uxcel Variable Resistors 10K ohm 5W from Ebay. (ref the pic) from factory A-B is 55K, B-C50k, pretty close to the 60 sec I wanted. Found 2 revolution of the adjustment screw changed the release time by 4 seconds, up or down depending on which connections you used and what direction you turned the screw. 
B-C CCW raised, CW lowered resistance----- A-B CCW lowered, CW raised. Hope that makes it easier for those doing this. 19 days and a wake up.


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## Nick Jr (Jan 2, 2008)

As I mentioned I advanced the Super Cap circuit to the Sierra board using the existing battery leads, leaving the I/O switch as ONE way to turn it off.. Using this option gives an instant start as long as the switch goes OFF within the 90 seconds of full discharge. Second option using the timing circuit. This caused the sound board to give a very short grunt while the caps on the timeout board charged. Either way is totally acceptable. This will be my last posting on this subject. Toddalin, again thank you very much for your time and expertese. I will continue to play with these circuits and convert my other Sierra's to this system.


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## Nick Jr (Jan 2, 2008)

Just a word of caution: the Sierra circuit output to charge the battery is 7.0VDC, so set the limiter board to that.


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