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I have all my accessories wired into a relay. I have a blinking billboard as part of this. My question is... How can I reduce the voltage going to the billboard, without lowering the voltage via the transformer, taking away needed voltage for the other accessories  to operate correctly. I am a rookie when it comes to electricity.

Thank you! Joe


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Last edited by Hippieroofer
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Out of curiosity, why do you want to lower the voltage to the billboard?


Per the first "Lionel blinking billboard" manual that popped up on a web search, it apparently operates over a fairly wide voltage range (11-16V AC).  Is the bulb burning out too often?

Perhaps you don't have an AC voltmeter but do you have an idea of what voltage you're presently sending to your accessories (via the relay)?


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@SteveH posted:

I'm surprised no one has mentioned using parallel diode ladders and/or bridge rectifiers to drop the voltage yet.  @Hippieroofer, if you're not in a hurry for your answer, you may want to wait a day or two to see what other less expensive and simple options are suggested, before ordering something.

You're right.  Any discussion about O-gauge AC voltage adjustment should include a cameo appearance by the diode/bridge dropping method.  There have been many OGR threads about this.  Here's a photo of the method from this OGR thread.


The math or electrical analysis of what's going on can be a bit intimidating so there is a certain leap-of-faith.  The method does work but does involve soldering or equivalent component-level fussing and mussing.  Each bridge component can be configured to lower the AC voltage about 1.4V.  So in your case, going from 16V AC down to 9V AC would require a 7V drop...or 5 bridge rectifiers (only 4 are shown in photo).  As shown, bridge rectifiers are inexpensive but the one shown in photo is eBay-Asia so with all those ships sitting off the Long Beach may be cooling your heals for quite a while!  Amazon prices are higher...for example:

amazon bridge

It should be pointed out that the bridge method retains the AC character of the voltage.  So you have AC in and AC out.

The thing is, when driving a light bulb, DC is just fine.  So the AC-to-DC converter module suggested earlier should do the trick.

ac dc stepdown modules

However, if I might make a suggestion, and I realize it's a bit more out-of-pocket (though you get 2 pieces) but I'd get a so-called "buck" converter module as shown above.  These modules are more electrically efficient than the so-called "LM317" modules. The electrical analysis can get a bit nerdy, but one way to think of it is the "buck" converters are digital and the "LM317" converters are analog.  This is a bit of semantic gymnastics but so be it.

In both cases you need a tiny jeweler type screwdriver to adjust the output voltage.  But no soldering is required as both modules have screw-terminal inputs and outputs.


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Last edited by stan2004

By the way, any chance you have a "loose" diode or even a bridge rectifier (as shown in previous post) sitting in a junk box or whatever?

amazon loose 1n4003

There is a even-odds chance that a single 5-cent diode could solve your problem...not that you can buy just 1 diode!

Anyway, inserting 1 diode in the wire to the lamp will cut the voltage roughly in half - it's not exactly 1/2 (again, the math is tedious).  The single diode is converting the 16V AC to a pulsed DC that just might work.  This technique was commonly used in rolling stock to dim bright incandescent bulbs when the conversion was made from conventional to command where 18V AC was now on the track overdriving the (typically) 14V bulbs used in passenger cars, cabooses, etc..


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Last edited by stan2004
@TedW posted:

@Hippieroofer, just curious, for our benefit, what voltage did you end up with which gave you the desired brightness and “blink” rate?  Thx

I did not test it at home. But I did take it to my train guy. He hooked up 18 volts to it & got it down to 15 volts out. I figured that's good. I have it hooked up to about 10-11 Volts in, so I figure its about 8.5 out to the accessory.

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