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This simple circuit can tell the difference between darkness and light, making it very useful for switching on and off signs, porch lights or other things when it gets dark or light. this circuit control the relay that will be switching if there are any difference between darkness and light. parts : R1————————————- 100K (to [...]

This circuit using photo-sensitive resistor as a sensor and LED that will starts flashing when the photo resistor is scarcely illuminated, very simple circuit operate with 3V batteries. The oscillation frequency is about 1Hz and set by C1 value. The onset of flashing can be set by trimming R2. The best result in flashing frequency [...]