Simple photo-sensitive circuit, 3V battery supply This circuit adopts the rather unusual Bowes/White emitter coupled multivibrator circuit. The oscillation frequency is about 1Hz and is set by C1 value. The LED starts flashing when the photo resistor is scarcely illuminated. The onset of flashing can be set by trimming R2. Parts: R1 = LDR R2 [...]
Most darkness activated alarms employ opamps and some logic ICs. Here, a less expensive approach is shown based on the eternal 555, this time in monostable multivibrator mode. Components R2 and C1 represent a one-second network. When the LDR (light dependent resistor) is in the dark, its resistance is high, pulling pin 2 of the [...]
This is automatic light circuit when be become dark. It by use LED Lamp, be a place gives the light and this circuit has small-sized use volt supply 3V only. The work of the circuit be when there is the light affects LDR1 will valuable the resistance at LDR1. It be down make Q1 work [...]
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