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Gadget Freak Case #209: Gradually Dimming Incandescent Bulb

To get immediate lighting while still conserving energy, Dick Bipes used an auxiliary incandescent lamp that would fade out as his CFL floodlights began to reach full brightness.

Like many gadget builders, Dick Bipes wanted to turn his windowless garage into a shop. That wasn’t easy with illumination coming from two bare 100W incandescent bulbs.

Since the garage is completely finished with gypsum board it was a challenge to run new wiring, so he used some surface wiring conduit to increase the shop’s light to eight floodlights.

Great, except the CFL floodlights take a long time to reach full brightness. Dick added an auxiliary incandescent lamp that would instantly turn on full brightness, then fade off as the CFL lamps brightened. He didn't want to use a commercial photocell device because they are mostly made for outdoor use and he wanted to make sure that they did not abruptly turn off. By using the dimming light, he is able to get immediate lighting while still conserving energy.

Dick Bipes's incandescent bulb gradually dims as the CFLs brighten, for a balanced lighting transition.

In the dark, the photocell’s resistance is high, and the voltage divider’s output is sufficient to charge the capacitor C2 quickly, achieve breakover voltage of the diac, turn the triac on, and bring the lamp to full brightness.

The auxiliary lamp and control combination is hard wired to the CFL overhead lights, so it turns on only when the light switch is thrown, and always turns off when the lights are shut off.

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