electronic candle - Elektor Iights a candle to wish all our readers a Merry Christmas and a Happy New Year

electronic candle elektor december 1984 .iench this candle, shown in figure 2, is early very simple. It consists of little ore than two ICs and two transistors. It so works in a very straightforward man- ar. There are two pick-ups (an LDR and i NTC), each of which is followed by an nplifier (Al and A2) and a flip-flop con- ining op-amps A3 and A4. The flip-flop vitches the lamp in the candle on and T via Ti and T2. iis is how the candle is lit. A burning atch is brought close to the LDR (R2) hose resistance then drops and reduces e potential at the non-inverting input of 1. A large negative voltage is output from is op-amp, making the output of A3 igh". The lamp is then lit via the two tran- stors. Positive voltages at the output of 1 have no effect because they are ocked by diode D1. The sensitivity of is part of the circuit (the light intensity at hich it reacts, in other words) is preset means of Pl. owing out the candle is a completely .fferent procedure. The NTC (R7) is pre- ...