An Electronic Candle You Can Set On Fire

Candles are pretty to look at, but they tend to be rather a fire risk and a negative influence on air quality, too. If you want the vibe without the …. An Electronic Candle You Can Set On Fire.

If you want the vibe without the hassle, you might enjoy this skeuomorphic electronic candle from [Marek.] The build is deceptively simple for what it achieves. There is just one transistor, one thermistor, an LED, and a couple of resistors. You can “light” the candle just like a real one by heating the NTC thermistor.

That’s because it makes the thermistor’s resistance drop such that the gate voltage on the MOSFET goes high enough to turn on the LED. There’s a resistor in series with the LED, which gets warm enough to keep the thermistor conductive enough to keep the MOSFET conducting in turn. If you blow on the assembly, you’ll cool the thermistor enough that the MOSFET stops conducting and the LED turns off.

[Marek] notes that the design is finnicky and quite subject to the vagaries of heat transfer between components; it took some fine tuning to get it working as well as it does.