Shay Tips


Posted on Feb 5, 2014

The Shay is equipped with flickering ashpan and firebox lights. These are simulated with LEDs. The red and yellow ones both flicker, the red ones stay on about 2/3 of the time and the yellow ones 1/3 of the time. The effect is pretty good while it is going, but the engine has to be moving fairly fast, way faster than the prototypical maximum 10-12


Shay Tips
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mph, before the flickering will start. The speed that the flickering starts is somewhat dependent on your power pack. If you use pure DC, you might not see them start flickering at all. They work a little better with Aristo PWC power, but still not real well. My thanks to Garry Paine for taking the time to trace out the circuit. The top part consists of an adjustable regulator set to 9 volts and a cab light control circuit. The bottom part of the circuit is the multivibrator which flickers the LEDs. It will light the red LEDs at lower than 9 volts on the internal regulated bus, but does not start to flicker until a full 9 volts is reached. Due to the overhead of the LM317 regulator and the bridge rectifier, about 12 volts is needed on the track to get the circuit going. At 12 volts, the Shay is really trucking so its hard to see the lights anyway. If you run at anything like prototypical speeds, you`ll never get going that fast. I added a 50 micro farad capacitor to the output of the bridge rectifier that will charge off any peaks of power that might be applied to the track so that the regulator has the best chance of working at lower average input voltage. Since I use an Aristo Train Engineer which puts out full voltage pulses even at very low speed, the addition of this capacitor causes the cab light, headlights and the flickering lights to come full on just as the engine starts to move. With pure DC power there will be...




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