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Control Bi-Colour LEDs

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Gino:
Greg

The locomotive is a GP30 that I purchased used. One of the class lights PCB has a date code on it, April,06,02. The boards are factory and they have the 3 lead LEDs.
The problem is that the LEDs are common cathode and do not play well with trying to turn them on using the +5V supply. But common cathode LEDs work well with the ability to reverse the polarity in a DC system.

You can wire them to work using the +5V but you end up using too many outputs.

I also have an SD40-2 that I purchased used with classification lights but they appear to be single colour, Red.
Now come to think about it I never did try to see if they were bipolar. I just wired them as a one colour LED.
I will take the locomotive apart to confirm that the LEDs are in fact just one colour.
If they are bipolar then it be be back to the drawing board to wire them to take advantage of the find.

If the LEDs are just a single colour and the locomotive is apart anyway I will rewire the class lights with the extra 3 lead red/green LEDs that I purchased.

Gino

gregeusa:
Thanks Gino, I have mostly older design USAT, PA, F3, NW2, etc.

Sound like they modernized a bit.

The real difficulty is finding a common anode white/green led... class lights were never red.

Greg

Gino:
Greg,

Some of the locomotives I purchased used have an LM317 regulator to provide constant voltage to the lamps in the units. This way they can use lower voltage bulbs and not worry too much about burnt bulbs using direct power from the rails.

I did not know that class lights were only Green and White, my bad!
I did some looking and found a 5mm common cathode Green/White LED. No luck on a common anode version.

But now that I have purchased the Red/Green LEDs I will install them in the locomotives I have with class lights. Not prototypical as noted but under the circumstances this is my railroad, ha, ha, ha.

The upside is that I can also use the bi-colour LEDs for signaling.

Gino

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