Stay Alive for caboose lighting

[B. Bryce]

I am installing a powered truck on the rear of my cabooses with a white interior LED light and a flashing red LED on the rear of the car which will be run on track voltage, 13.8 volts DCC.  The caboose is already weighted, but I am afraid I may still get some slight flickering of the interior white light if the truck looses contact anywhere or encounters any dirt.

I would like to install a poor mans version of a Stay Alive circuit inside the caboose.  It is DCC and I will probably use a 470uf capacitor, but I am not sure where to wire it in, before or after the bridge recifier to the LED.  I am assuming it would go between the bridge rectifier and the LED bulb, as I believe it must work on DC current, not the AC sine wave of DCC. 

Anyone done this before?

 

[rrinker]

 Has to be AFTER the rectifier, a standard electrolytic capacitor is polarized and will (literally, in some cases) explode if subject to being hooked up backwards.

 I'm actually planning to put function-only decoders in some of my cabeese, as in my era they still used oil lights and not electric, so the flicker effect offered in the decoder will be perfect. Either that or I will build my own little random flicker circuit, but with a standard decoder you can attach any sort of keep alive - might even be neat to have the interior light flickering away for significant time after the caboose is set off, while the crew enjoys dinner at the end of a day.

                                         --Randy

 

[gmpullman]

B. Bryce

Anyone done this before?

Hi,

This circuit works great for me:

DCC_light2 by Edmund, on Flickr

I've used several combinations of series or parallel LEDs and played with different R2 resistor values. I have fed up to a dozen LEDs in passenger cars and will get about ten seconds of light after lifting the car off the rails. With only a few LEDs in series you can get even longer stay alive or go with a bigger cap.

You have to remember it is DCC only, as Randy says, the cap can pop if DC is fed backwards.

For a caboose you don't want very bright light, although the Aladdin caboose kerosine lamp burns with a greenish/white glow about equal to a 75W. incandescent.

Good Luck, Ed