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Eric T
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I'm planning to add a keep-alive to a small tank locomotive.
The keep-alive will be hidden in a tender, and I would like to have a backup light on the tender as well.

The locomotive's stock decoder has an embedded sound module, so I'd rather not replace the whole board,
but the decoder does not have an output for a backup light either.

In addition, I only want to run two wires to the tender to simulate air and fuel lines. 
(It will be an oil tender)

My proposed solution is to put a mobile decoder in the tender, that uses the same address as the locomotive,
with electrical pickup from the tender's wheels.
 
But I don't want the backup light to go out over un-powered turnout frogs or rough track,
so I'd connect it to the keep-alive as well since there isn't room for two keep-alives and a decoder in the tender shell I want to use.

Will this plan work if the two decoders are wired in parallel?


NathanO
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What decoder are you using right now?

Nathan

Eric T
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NathanO wrote: What decoder are you using right now?

The locomotive is a Bachmann On30 0-4-0 Porter.

I'm planning to use a TCS T1-LED in the tender.


NathanO
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What decoder do you have in the locomotive?

Nathan

Eric T
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NathanO wrote: What decoder do you have in the locomotive?

Nathan


I'm using the locomotive's stock decoder.

NathanO
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The instructions that came with the locomotive should say which Soundtraxx decoder it has.

Then you can go to the Soundtraxx web site and get the information on what they call the Current Keeper.

Nathan


NathanO
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If it is the 21 pin decoder then the backup light should be pin 7.

Nathan

Eric T
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Nathan,

I'm not asking whether a keep-alive/current-keeper can be added to my loco,

I'm asking whether a single capacitor can feed two decoders.


NathanO
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If you put a small diode to each one so they do not draw form each other it should work.

Nathan

NathanO
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This should work.

Nathan

Helmut
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@Nathan

Sorry to tell you that this circuit will NOT work.

Just follow the current path when discharging the capacitor ( the keep-alive case )


Eric T
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I don't really know how to read schematics anyway.

I did find a decoder with a built-in keep-alive plus resistors for LED lighting,
that should save enough space to work for the project without interfering with the locomotive's keep-alive.

Thanks anyway, guys.



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