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The Electronic Candle

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July 21, 2004

My ex-wife loves candles. She would buy all sorts of colored candles, scented candles, slim candles, fat candles – you get the picture, she loved candles. She would often light her candles in the evening and turn the electric lights off, to get the mood to a peaceful, serenity, which helped her wind down from a stressful day at work. It worked well, usually, and she wouldn’t go overboard doing it either. Just once in a while, maybe a couple of times a week. She would get a bit miffed when one of her favorite candles finally burned all the way down to the bottom because then she would have to figure out where she got that particular candle and then go and buy it. She isn’t one of those people who love to shop, but she would finally get around to getting her replacement.

This brings me to where I come in. I decided to create a candle that would never burn out (as long as electricity was supplied). I thought about the problem and decided that the way to approach this problem was not just an ordinary light bulb inside a hollow candle, no, this candle had to flicker. That’s what candles do, flicker, and the flicker adds to the enviance. So I had to come up with a way to make the little flashlight bulb give the effect of flickering. The candle that I used was already burned down to almost nothing, but it was a 3” diameter candle, so it had burned out a hollow in the center. The candle had melted sides, so it would look like a real burned candle. For the circuit, I started out with a simple tank circuit that would create a slow sine wave of electricity to power the light bulb. In effect, the sine wave would cause the light bulb to slowly dim and then brighten. This was OK, but the effect didn’t seem random enough. The frequency that I chose for the sine wave was about 3 Hz. I then added a second sine wave at about 5 Hz. Voila! The effect was perfect!

 I turned off the lights in my lab and invited my (then) wife to come see the candle burning in my lab. She looked at the candle and said “So, it’s a candle.”, but then I showed her that I had a light bulb inside the candle and she couldn’t believe it: An electronic candle that flickered like a real candle.

I will add my circuit schematic for this flickering candle at a later date, but you can come up with your own, now that you understand how!

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