Originally posted on Hackaday:
Candle flicker LEDs are a one part replacement for a real candle. They contain both a yellow LED and a control chip that modulates the light to create a candle effect. [Cpldcpu] took a deep look into reverse engineering one of these LEDs.
To analyze the circuit, which is potted into the LED itself, a shunt sense resistor was connected to the LED. By connecting this resistor to a logic analyzer, the control signal could be observed.
This control signal looked like pulse width modulation, with some randomness to the duty cycle. [Cpldcpu] determined that a linear feedback shift register was most likely used to generate a pseudeorandom bitstream, and some shaping was applied to make the LED look more like a real candle.
It turns out a blinking LED can be quite complex, and this takes a deep look into it by analyzing the signal. [Cpldcpu] took the…
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