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I add Tomar LED lamps to my cabooses. I wanted a way to shut off the lamps when not in use on a siding. I don’t run interior lights. I was intrigued by Rivarossi’ magic  wand in their HO cars. Not available at this time. I find this on Amazon. A turns the lights On. B shuts them off. Pretty simple and works as advertised.


Got it working using track power. Worked well but at times it would go out. Probably from dirty track, rollers or wheels. You would have to reactivate it to get it back working. Figured I’d try a battery. Less drag without rollers and wipers. Figured the amount they would actually get used the battery would last a good long time.

Hook up is simple. Red and Black go to a 9v battery. The other 2 control a relay for the lights. I used a resistor to get just under 3v for the lights. Seems simple enough. Except the battery drains a little each day. Somehow it must have a draw on it. My guess is after a weeks time it wouldn’t have enough to power up the board. I’m somewhat electrically challenged. I can follow instructions if someone has any ideas on how to isolate the battery when not in use.


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Last edited by Dave_C
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Thanks John. I made a similar setup for your Chuff Generator to get 5v based on a diagram you posted. I just thought the lights drew so little a battery would last a good long time.  Didn’t think of factoring the receiver into the equation. Your diagram shows a capacitor. Will that keep everything alive on a long switch or a brief interruption ? I’m using Atlas caboose trucks and cobbled up wipers to ride on the axles to possibly help. Between the rollers and wipers it seems like you are adding 5 more cars to the consist.
The remote works well enough with track voltage. I guess I’ll just focus on getting good contact to the rails and I’ll give building your board a shot.

I’m guessing the first component is a Choke ?

Yep, you might want a larger cap, depending on how much current the LED's draw.  It'll also help keep the receiver alive during those same track power interruptions.  I'd probably consider something like a 470uf cap for your purposes.

The choke is only there if you run DCS, but I throw it in any design that might affect the DCS signal since it's a really cheap component.

quiescent current

In the Amazon item description for what looks like a similar product, the quiescent current is spec'd at 5mA.  And then when the relay is ON, the operating current jumps up to 20-30mA; of course add to that whatever the LEDs are drawing...maybe another 20mA.

Anyway, a typical 9V alkaline has a capacity of 550 mAh.  So the battery will deplete in several days just sitting there powering the radio receiver waiting for a remote command to turn on.

It's interesting to read the Amazon user reviews.  Several 1-star (lowest rating) reviews complaining about how their 9V battery only lasted a few days...when the item is supposedly "low power."  Then again I don't think "quiescent" is a commonly used word...seems more like one of those Spelling Bee words!


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