Tuesday, September 16, 2008

Sharing 16-20V AC accessory power between turnouts and lights

It's often said that incandescent lights on a layout, be they inside your structures or the streetlamp variety, look better and last longer if they are run below their rated voltage, for example running a 12V lamp at 9V. To do that, though, you can't just wire up all the lamps to your accessory power, you generally have to run them off the variable DC output of an extra transformer.

I have a nifty solution for this problem, which also reduces flicker in the lights if you use the same accessory power with remote turnouts. Using diodes, create two circuits off the accessory power with each circuit rectified in a different direction. The half-wave rectified power in one circuit is still plenty powerful for the coils in your turnouts. The other circuit goes to the lights, and since there is a lag when incandescent lights switch on or off, they appear to still be glowing continuously, albeit a bit dimmer.

Note that this doesn't work for any LED lights, the half-wave power will product a very noticeable flicker since LEDs shut on and off instantaneously.

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