Bi-Directional Lighting

[Anonymous]

Good morning, everyone!

I model a small industrial switching operation in a waterfront area, so I'm still with DC rather than DCC. Many, MANY years ago, I wired a steam loco that would light the headlight on the smokebox when operating forward and the one on the tender when in reverse. I do remember that I had to pick up some simple supplies from Radio Shack in addition to grain-of-wheat bulbs (now that really dates me!) and CalScale headlight castings, but my many moves since then has caused me to misplace the directions for the project AND the engine!

Can anyone give me a VERY SIMPLE explanation of how this can be done? I know it isn't really prototypical for the 1940's, BUT I LIKE IT!

[Anonymous]

You could try using a couple of Light Emitting Diodes (LEDs) - these only light up when power flows through them one way, so if you wire them so one lights up when going forward and the other when going backwards, this should create the effect you're after. Just make sure they're suitably rated - that they can handle the voltage/current/etc that you'll be putting through them.

If anyone knows a suitable rating for LED headlights I'd be glad to hear about it as I'm planning to fit one to an Athearn F7 I'm superdetailing!

[Jetrock]

If you're using GOW bulbs or LED's for directional lighting, pick up a pair of diodes! These pass electricity in one direction but not the other, which will allow directional lighting when installed in the right direction--like so:

(+)-----0---|<------(-)
(+)----->|--0-------(-)

0 =GOW bulb (or LED, facing the same direction as the diode)
>| =diode
(+) (-) = Power leads

You will note that you'll have two separate circuits, parallel to each other--the diodes face opposing directions. When power runs one way, one bulb will light but the other won't--the diode blocks the current from completing a circuit. When power is reversed, the other light lights up.

I suppose one could just use LED's without diodes, but it is my understanding that LED's don't like having current reversed through them and tend to burn out more quickly--the diode becomes a safety feature.

[preceng]

Try "Model Railroad Electronics 1" by Rutger Friberg. This book has real nice illustrations, parts lists, etc. I built some, and they actually worked.

Have fun