Model Railway Forum

Any one have any DCC blank plugs that you take out when fitting a new decoder. If so I can use them as I want to fit a capacitor for DC stay alive. Hornby locos Please have a look for me. Sandy

Sandy, how many pins on the plug?

I can't see how you can have a stayalive on dc. The capacitor will only discharge at full volts so every time you try to reduce the speed the capacitor will kick in and make it go full speed again until fully discharged.

As I said earlier, I have no need for a DC stay alive (DCC user and proud ) but I am intrigued how these could work in DC.
I’ve looked at some online photos and they seem to show a capacitor connected directly to two pins on an 8 pin plug with no other obvious components. Caps are, I believe, polarity sensitive and as polarity of the track is reversed when the controller direction is switched, I can’t see how they don’t go ‘bang’.
It’s difficult to see on the few photos I have seen but the rating of the caps may be 35v 100mf

It states that they have selected special capacitors, perhaps slow discharge, and do not use ordinary capacitors as they will cause damage.

You can get non-polarised capacitors - ones that work in both directions.

I bought some having seen something on YT but gave up quickly as I'm not educated enough about circuits.

While you two were typing I was reading a ten year old thread on another forum regarding ‘bipolar capacitors’.
I very quickly lost the will to live as I realised my curiosity did not stretch that far .

Sometimes it is best just to use things and not worry about how they work. Too much info can be a bad thing.

jed10 wrote: ↑Wed Dec 13, 2023 6:21 pm I can't see how you can have a stayalive on dc. The capacitor will only discharge at full volts so every time you try to reduce the speed the capacitor will kick in and make it go full speed again until fully discharged.

With DC the full volts will be the voltage you have the controller set to. Unlike DCC when the full voltage will be 15v and the Loco chooses the speed.

Steve M wrote: ↑Wed Dec 13, 2023 6:06 pm Sandy, how many pins on the plug?

Steve. There 8 pins On the two I looked at.