electronics – Tim's Blog

Candle Flame Oscillations as a Clock

Todays candles have been optimized for millenia not to flicker. But it turns out when we bundle three of them together, we can undo all of these optimizations and the resulting triplet will start to naturally oscillate. A fascinating fact is that the oscillation frequency is rather stable at ~9.9Hz as it mainly depends on gravity and diameter of the flame.

We use a rather unusual approach based on a wire suspended in the flame, that can sense capacitance changes caused by the ionized gases in the flame, to detect this frequency and divide it down to 1Hz.

A surprising IC in a LED light chain.

LED-based festive decorations are a fascinating subject for exploration of ingenuity in low-cost electronics. New products appear every year and often very surprising technology approaches are used to achieve some differentiation while adding minimal cost.

This year, there wasn’t any fancy new controller, but I was surprised how much the cost of simple light strings was reduced. The LED string above includes a small box with batteries and came in a set of ten for less than $2 shipped, so <$0.20 each. While I may have benefitted from promotional pricing, it is also clear that quite some work went into making the product cheap.

Revisiting Candle Flicker-LEDs: Now with integrated Timer

Years ago I spent some time analyzing Candle-Flicker LEDs that contain an integrated circuit to mimic the flickering nature of real candles. Artificial candles have evolved quite a bit since then, now including magnetically actuated “flames”, an even better candle-emulation. However, at the low end, there are still simple candles with candle-flicker LEDs to emulate tea-lights.

I was recently tipped off to an upgraded variant that includes a timer that turns off the candle after it was active for 6h and turns it on again 18h later. E.g. when you turn it on at 7 pm on one day, it would stay active till 1 am and deactive itself until 7 pm on the next day. Seems quite useful, actually. The question is, how is it implemented? I bought a couple of these tea lights and took a closer look.