Darkness Detector with Beep Alarm Using LDR and 555 Timer

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.

Components

No.ComponentQuantity
1.Power supply (5V – 9V) 1
2.555 timer1
3.Piezo buzzer1
4.LDR1
5.2.2kΩ resistor1
6.10kΩ resistor1
7.1MΩ resistor1
8.1μF electrolytic capacitor1
9.100pF ceramic capacitor1

Circuit diagram

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.

Darkness Detector with Beep Alarm Using LDR and 555 Timer (Circuit Diagram)

Designed circuit

Circuit is designed on a breadboard.

Darkness Detector with Beep Alarm Using LDR and 555 Timer (Designed Circuit)

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