Led lights for switches and other stuff

TinMan3railOGR Forum Member DIGITAL SUBSCRIBERFORUM SPONSOR

I noticed a couple of different circuits that Lionel used in their newer switches. The simplest one is a simple 1n1005 diode in series with a 1k resister between the center rail power and the LED. the other lead of the LED went to the outside rails.

A second design was basically the same except instead of the 1n1005 they used a surface mount full wave bridge.

the third design was similar except the resistor was attached to the center rail power, then the LED then the 1n1005 reversed biased directly to ground. They all seemed to function ok except for the final one drew a lot more current. Opinions? I have heard some comments about circuits like this causing issues with some of the newer electronics??

1/9/153:18 PM

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gunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

I can't imagine why the one drew a lot more power, the LED running at more than 30-40 MA would probably die.

1/9/157:23 PM

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TinMan3railOGR Forum Member DIGITAL SUBSCRIBERFORUM SPONSOR

I don't know either, but it did. Do you see any potential issues with the first design, as far as interference with other devices?

1/10/159:24 AM

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gunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

The only issue I see is the remote possibility of issues with DCS, whenever I suspect it might be a problem, I include a 22uh RF choke in the mix.

1/10/1510:02 AM

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TinMan3railOGR Forum Member DIGITAL SUBSCRIBERFORUM SPONSOR

Thanks, I assume you are concerned about the 1/4 wave causing a rf spike, good point. Probably should add a cap too. Unfortunately, do not have a scope here to watch it. I have read on one of the forums, of concerns of mixing DC with ac, but, the whistle circuits have been using that forever, so I kind of poo pooed that, but the continuous high speed pulse from all these LED's could be another matter. By the way, did you get the pliers I sent you?

1/10/152:47 PM

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gunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

I did indeed get them, I meant to send you an email. I actually loaned them out to a guy that's doing a bunch of tubular track on his layout, I'm waiting to get a usage report coming back.

I also thought the little plug that lets you power the switch and the track from one drop was a pretty interesting idea, I would have never thought of that.