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Discussion Starter · #41 ·
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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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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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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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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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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Discussion Starter · #46 · (Edited)
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.


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

 

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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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Discussion Starter · #48 ·
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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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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Discussion Starter · #50 ·
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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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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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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Discussion Starter · #53 ·
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
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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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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Discussion Starter · #55 ·
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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Discussion Starter · #56 ·
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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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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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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Discussion Starter · #59 ·
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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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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