Darkness Detector with Beep Alarm Using LDR and 555 Timer

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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