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. | Component | Quantity |
---|---|---|
1. | Power supply (5V - 9V) | 1 |
2. | 555 timer | 1 |
3. | Piezo buzzer | 1 |
4. | LDR | 1 |
5. | 2.2kΩ resistor | 1 |
6. | 10kΩ resistor | 1 |
7. | 1MΩ resistor | 1 |
8. | 1μF electrolytic capacitor | 1 |
9. | 100pF ceramic capacitor | 1 |
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)](/uploads/posts/content/2021/02/darkness_detector_with_beep_alarm_using_ldr_and_555_timer_circuit_diagram.png?v=1659785572)
Designed circuit
Circuit is designed on a breadboard.
![Darkness Detector with Beep Alarm Using LDR and 555 Timer (Designed Circuit)](/uploads/posts/content/2021/02/darkness_detector_with_beep_alarm_using_ldr_and_555_timer_designed_circuit.png?v=1659785572)
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