Sort-Of Electronic Candle

摘要

This simple circuit is a brave effort at simulating a candle flame using an LED. Generated by electronics only and using just two AA or AAA batteries the simulated flame avoids the nuisance of smoke and the dangers of a real flame, particularly if you forget to quench it before you leave the room. The little project along the schematic in Figure 1 consists of a small microcontroller type PIC12F675 suitably programmed to generate a PWM (pulse-width modulation) signal which powers a single LED, effectively varying the duty cycle of the signal, resulting in intensity control of the LED. To simulate a softly flickering flame the PWM drive randomly varies its value using a pseudo-random bit sequence (PRBS) values. Each signal change occurs within a period small enough to enable your spell-bound visitors to note the change in LED brightness as if staring into a little flame flickering from a whiff of air ( Like a Candle in the Wind).