What's Inside Keep Alive?

[8-Mile]

Hello All,
Back in the hobby after a hiatus. I have a number of loco's, one of which has a KeepAlive system that works brilliantly. It was expensive when I bought it so got to wondering what is an inexpensive way of doing this. I'd like to use a Digitrax DH126, and according to Digitrax's page (https://www.digitrax.com/tsd/KB1059/pow ... atibility/) these are compatible with their PowerXtender addon board.

My question is, do I need the proprietary PowerXtender, or is it just a case of plugging an appropriate capacitor into the two pin port of the DH126? In other words, what is inside their PX112-2?

Thanks in advance. The daily challenges of modeling UK outline traind from the 80's, while living in Michigan
/Andy!

[Bigmet]

Don't know anything about digitrax product, so cannot give an answer. The vital component is a capacitor to hold charge - that you know - but regulation of charging and detection of loss of track power to trigger release of the capacitor's charge to the decoder requires a small circuit of additional components. The difficulty is that the answer will depend on what's on the decoder in the way of any circuit components to manage a stay alive, or 'none whatsoever'. In your shoes I would go searching for digitrax online support or a discussion forum with digitrax content. You are far more likely to find information in the homeland of the manufacturer would be my feeling.

[Roger (RJ)]

Article about stay alives by Nigel Cliffe. Refers to stay alives in general, not specific to digitrax
https://www.2mm.org.uk/articles/DCC%20S ... index.html

[8-Mile]

Thank you for your help. I will get one, and might be tempted to take a look inside...!

[centenary]

Thank you for your help. I will get one, and might be tempted to take a look inside...!

Be careful if you do! A fully charged small capacitor can still give you a nasty shock.

[Peterm]

I can't help with Digitrax decoders, but certainly with Zimo, you can use stay alives. Some come with dedicated wires and circuits to connect stay alives to, and with others, you use the blue (common positive) and the black ground wire. Those with the dedicated circuit can have capacitors connected directly and those without need the small, simple charge circuit. I use Lais stay alives which come with that circuit and in various configurations and only need two wires to connect. They aren't expensive and work really well.

There are other decoders that can work with these, but I only use Zimo except for one loco with an ESU, but that's another story.