This post presents circuit which detects darkness using light dependent resistor (LDR) and produces a beep alarm by piezo buzzer. Circuit is based on 555 timer in astable mode to generate a square wave output.
|1.||Power supply (5V – 9V)||1|
|8.||1μF electrolytic capacitor||1|
|9.||100pF ceramic capacitor||1|
If the light drops below a certain level, a beep alarm is produced. The value of R1 resistor affects the level of light the LDR will detect and circuit will produce a beep alarm.
Circuit is designed on a breadboard.