Cab lighting help

[kingarthur69]

Hi all.
I've recently added 2 Heljan locos to my collection, class 15 and a Western. Both have 8 pin hatton decoders fitted.
Does any one have any experience of adding interior cab lighting to these?
Thanks
Arthur

[Peterm]

Bumped for lack of replies. I've got a Heljan Western and it already has lights. Does yours not have any ?

[End2end]

I have not checked but I have just got a Heljan class 14 teddy and am now wondering the same.?
Thanks
End2end

[kingarthur69]

Both mine have exterior lights that are directional. So i can't wire into them for an interior light as I guess it will only come on in 1 direction. You could get power from the pick ups from the track but the lights would stay on.
Really we need to know a way to connect to a spare function from the decoder.

[Bigmet]

If wanting to use the Hattons decoder, the first question is whether it has the capability required. It will need to be a three (or more) function type for independent control of a cab light, as the A and B functions (white - pin 6, and yellow - pin 2) are already taken for operation of the front and rear lights. If a third function is available it will be on the green wire, pin 3, with common return on pin 7, blue wire.

[kingarthur69]

Hi there.
Thanks for the reply. The hattons decoder fitted is 4 function. Do you know if there us a way to do it from the pcb or other wiring si I wouldn't need to add wires between the decoder and plug? Just so if i need to change or upgrade the decoder i can still just unplug it. I guess I can get the common negative from any where if i test with a meter. But the possitive is the difficult one.

[Metadyneman]

As far as i know, you cannot add cab lights to a loco which hasn't already got them without tapping into the wires from the decoder and soldering directly to them unless there is somewhere on the circiuit board allowing you to plug the lights into. The head/tail lights on the Western has a bank of two pin interfaces for each light at each end of the circuit board but I don't think there is a spare interface for extra lighting. The way I've done it is to split the blue "common" wire and the two function wires (green & dark purple) and tap directly into them by-passing the 8-pin plug altogether. It will all still work plugged into the socket and the cab lights you fit will be independantly switchable via F1 and F2 on your controller. As to how you do this with a 21-pin interface I've no idea as I've never tried it and not sure I would know how to but as the locos you have described both have 8-pin sockets you should be ok with the above method.

[kingarthur69]

Thank you. I will have to do as you have. It's the best way really but thought I would check. Maybe as more people add non standard item to locos the manufacturer will add easy connections, even just allowing the loco side of the socket to be soldered onto.
Or how about a double sided plug that would fit between any 8 pin decoder and the loco socket with the common and functions having a small wire. Sort of like a splitter. Probably won't happen but could be cheep and easily swapable.