Stay alive/keep alive for DC

[IanS]

I've searched and all I can find is info on using a stay alive for DCC.

I am (probably incorrectly) assuming that you can't simply place a 'stay alive capacitor and diode/resistor' into the power circuit. It occurs to me that you need two - one for forward motion and one for reverse motion - or some circuit to change it to always power in the correct direction required.

My electronics knowledge is so low that is a far as I get.

I'm hoping to introduce the stay alives temporarily on those locos where I've already installed an 8-pin socket ready for use with a decoder when funds allow so any assistance would be gratefully received.

[Steve M]

I’m pretty sure it won’t work the way you intend it.

On DCC, track power is a constant value with the decoder ‘telling’ the motor how fast to turn. On DC, track power has a variable value determined by the controller.
If you fit stay alives to DCC the decoder still determines the speed but on DC at best you would get full voltage and an uncontrolled runaway.
And that’s assuming they co7ld even be fitted on the first place - not sure electronic principles would allow it. But then my knowledge is just as basic as yours.

[Walkingthedog]

Not sure why you would need temporary stay alive because you have fitted an 8 pin socket for future use. If the loco is OK without the socket it will be OK with it.

[IanS]

Not sure why you would need temporary stay alive because you have fitted an 8 pin socket for future use. If the loco is OK without the socket it will be OK with it.

The same reason that those running DCC use stay alive, to keep 0-4-0 locos going over insulfrog points and less than perfectly clean track.

I've seen a seller on Ebay with what looks like a capacitor soldered onto a blanking plug for use with DC but can't see other circuitry, not even a resistor and diode as used on DCC locos. He's charging quite a lot more than for a capacitor and blanking plate. This is what prompted the simplistic question.

[Walkingthedog]

I was questioning why temporary but now I see, only temporary for the DC loco. Replaced by permanent version when decoder added.

I just added a permanent wagon/coach with extra pickups on 0-4-0 locos that were small.

Clean track solved most problems for me. Even more important when running DCC.

Remember what they say, a loco must work perfectly on DC if it is to be converted to DCC.

[Stese]

if you do want to do this still, a standard non polarized capacitor across the motor contacts will provide some 'keep-alive'

[teedoubleudee]

If you do this you are effectively putting the capacitor across the controller output.

[Stese]

teedoubleudee, don't most locos already have this in the form of suppressor capacitor?

[GeoffAlan3]

It has been done. The N gauge Society Hunslet DS has a built in stay alive and DCC chip, yet on DC the stay alive function is still working.

[IanS]

I've ordered one of the advertised 'Analogue stay alive' capacitor on an 8-pin blanking plug.

It should arrive today or tomorrow. I'll test it out and report back on the success (or otherwise). The seller says you can't use 'just any capacitor' but we'll see what he uses. It looks physically quite big, about the same diameter as the 8-pin plug is wide and about as long.

It shouldn't be too difficult to source a similar one if 'ordinary' capacitors don't or won't work.
(Famous last words of course!!!)