DaveJfr0 posted:
Some questions:

1. Do you have a suggestion for a mouser part number for the 5F caps? I'd like to try one of those in case I think I actually need more juice for certain power hungry locomotives I have (like the Weaver VO1000)

2. I noticed the alternate zener diodes you listed have different forward voltages and impedance than the part that's out of stock.  I'm pretty sure that doesn't matter in this circuit, but just checking.

3. I saw the previous questions, but to adjust and benchtest, to be clear:  You throw power on this, let it charge, then voltmeter test (no load) the U+ to GND and turn the knob on the converter until you achieve ~12.5V voltage.  Is that is sufficient or do I need to actually have this connected to the locomotive its intended to go into and adjust it until it can make the motors turn enough to get over dirty spots/gaps in the track (at slow speed)?

Thanks again for sharing this design and your logic behind it.

  1. 5F 5.5V capacitor is the one I've used.
  2. Yeah there are minor differences in the specs, no impact for our use here.
  3. Yep, power it with 5V on the bench and then set the regulator to your desired output. The regulation is very good, so it won't change with load. Make sure you discharge it before doing anything else with it by connecting the 5V and ground leads for a few minutes.

12.5V is what works for me at 16V DCC voltage. You may need to experiment, and maybe go a bit lower, if you are using a lower DCC voltage.

Make sure you build one or two and test them out, before you go building 10 of them. I'd hate to be responsible for all that time and effort if they didn't work out for some reason! 

DaveJfr0 posted:
I'm looking at making 10 of these to compare with the soundtraxx currentkeeper installations I have with my Loksound decoders and make a decision on what I do going forward. I currently run my Digitrax system on the HO 15V setting. I think the parts list above should suit me fine.

Just occurred to me - are you running HO, and the standard Loksound decoders, or O, with the Loksound L?

If the former - definitely build one and test. I have one that I just recently put in my Lionel docksider with an HO decoder, and it is not working as expected at the moment. The cap and regulator are working (charging, etc.), but I'm not getting any run time after removal of power. Haven't had time to chase that one down yet.

Loksound L in O scale 2R.  I just use the HO setting on the Digitrax for 15V.  Works fine for me.  

Other than consuming less power out of the capacitors (and lasting longer), I don't see how lowering the input voltage to the decoder from the keepalive will change its behavior as the processor should remain on, maintaining constant speed to the motors, powering the sound, lights etc.

I'll order parts for 10, and then build one, test, and then build the rest if they work better than the soundtraxx keepalives, which after reading through what you said earlier, probably will be the case.

DaveJfr0 posted:

Other than consuming less power out of the capacitors (and lasting longer), I don't see how lowering the input voltage to the decoder from the keepalive will change its behavior as the processor should remain on, maintaining constant speed to the motors, powering the sound, lights etc.

From my original post:

The output of the converter is tied to the high (track) voltage bus U+ on the decoder. The capacitor on the converter output is important because the high voltage bus on the decoder actually fluctuates quite widely. Without a capacitor on the output of the converter, anytime the bus voltage drops below the converter output, it draws energy from the supercap to maintain it, and the supercap will never charge.

and:

I set the boost converter output to 12.5V. This number is important, and somewhat layout-dependent, since the high voltage bus on the decoder depends on your track voltage. Too low, and you will have a noticeable drop in speed when the keepalive kicks in. The ESU Powerpack actually exhibits this. Too high, and the supercap will never charge, because the converter will be intermittently supplying power to the high voltage bus. Testing on my layout showed the 12.5V provided nearly seamless transitions from track power to supercap, and charged reliably.

So it may be fine at 15V DCC voltage (I think it probably will). But, it may also be that the decoder bus voltage drops below the regulator output voltage occasionally, which will be more likely with a lower track voltage.

thor73 posted:
DaveJfr0 posted:

Other than consuming less power out of the capacitors (and lasting longer), I don't see how lowering the input voltage to the decoder from the keepalive will change its behavior as the processor should remain on, maintaining constant speed to the motors, powering the sound, lights etc.

From my original post:

The output of the converter is tied to the high (track) voltage bus U+ on the decoder. The capacitor on the converter output is important because the high voltage bus on the decoder actually fluctuates quite widely. Without a capacitor on the output of the converter, anytime the bus voltage drops below the converter output, it draws energy from the supercap to maintain it, and the supercap will never charge.

and:

I set the boost converter output to 12.5V. This number is important, and somewhat layout-dependent, since the high voltage bus on the decoder depends on your track voltage. Too low, and you will have a noticeable drop in speed when the keepalive kicks in. The ESU Powerpack actually exhibits this. Too high, and the supercap will never charge, because the converter will be intermittently supplying power to the high voltage bus. Testing on my layout showed the 12.5V provided nearly seamless transitions from track power to supercap, and charged reliably.

So it may be fine at 15V DCC voltage (I think it probably will). But, it may also be that the decoder bus voltage drops below the regulator output voltage occasionally, which will be more likely with a lower track voltage.

I missed that.  Sorry.  I'll play with it and let this thread know how it goes.

Thanks again for your idea and your help!

You didn't mention is this was a 2-rail or 3-rail context, but feeding power into the closure rails on larger Ross turnouts prevents stalling. You take advantage of the Tortoise Motor "relay" contacts. Basically, you feed power into the unused closure rail (the one the wheels aren't rolling on) and energize them as a hot-lead extension, while putting the closure rail being used to common. This gives you full power through the turnout.  If this is a 2-rail situation, you can just wire the closure rails to the corresponding main running rails since the frog is insulated.

Hope this helps.

 

Matt Jackson
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i think this diy powerpack is the bomb and one has become a permanent install on my loksound test bench fixture.

select L is the only loksound I have used. recently, I received my first loksound 5 L DCC. threw it on the test fixture, and it seemed dead. sent it back and replacement came. scared to try again with the powerpack, but don't know if that is what killed it. the 5 new L DCC claims to have "on-board" powerpack, but the manual does describe hooking to an external one, but of course the manual says only use a loksound powerpack.

has anyone used thor73's design on the new loksound?

thanks

 

No reason I can see that it wouldn't work with the v5, although I don't have one (yet...) to test it with. Proceed carefully, however. 

In my experience, even the XL with its onboard powerpack did not provide as much runtime as I wanted. I would expect the powerpack on the 5L would be smaller.

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