Large Scale Central

Wiring a keep alive capacitor?

I don’t even know if this is possible but I have the capacitor shown and I would like to add it to a car to give the lights and sound a backup over rough track. Is there a wiring diagram I can use? Can this just be connected to the pickup wires off the truck and then to the led lights and ITT sound card?

This simple diagram may help…

That is very simple but instead of a battery I’m using track power so is the wiring the same?


You might want to read this page about keepalive caps and sound decoders.

It appears that some decoders have a spot to add capacitors.

I worry that, in general, it is slightly more tricky than just wiring the capacitor in. My EE training from loooong ago has me worried.

Some things that can be a problem: the voltage from track pickups switch plus/minus if you turn the loco around (full wave rectifier), you may need to be careful how fast you allow the capacitor to charge or discharge (resistors in and out), you may want to clip the voltage stored in the capacitor so it doesn’t blow your sound card (zener diode).

Presumably the sound card has all that built in and you are just supplying the capacitor.

Thanks for chiming in Jim. After looking at the info in that link I’m going to give up on this plan. The card is an ITT engineering one that I put in my party car. It works well on the test track but out on the main it is sketchy. I could add another power pickup truck or a battery. The small LEDs use 3 AA which is not enough for the sounds. The flashing ones and piano sounds come from the track power. The last thing I want is to blow something up.