This small LDR Based Dark Sensor Circuit is very smart.
It can see light and dark using LDR.
When there is light, everything stay quiet.
When it becomes dark then LED start to glow and buzzer makes sound.
No need to touch anything it works by itself.
It is easy to make with low cost and is good for small school projects.
Circuit Working:
Parts List:
| Component Name | Specification / Type | Quantity |
|---|---|---|
| Resistors | 1k 1/4 watt | 1 |
| LDR | 1 | |
| Semiconductors | Transistor BC547 NPN | 1 |
| LED 5mm any color | 1 | |
| Buzzer 5V or 9V DC | 1 | |
| Battery 9V | 1 |
This circuit is like light sensor switch.
It control one LED and one buzzer.
Power come from 9V battery.
LDR see the light around.
BC547 transistor act like small switch.
It make LED and buzzer ON or OFF.
LDR and resistor share voltage.
When light is bright, LDR resistance become low with LED and buzzer stay OFF.
When dark come then LDR resistance go high.
Then transistor turn ON and LED start to glow, buzzer give sound.
How to Build:
To build a LDR Based Dark Sensor Circuit follow the below steps:
- Assemble all the parts as shown in circuit diagram.
- Emitter connects to ground negative of battery.
- Collector is connected to LED(–) + Buzzer(–) through R1 resistor to positive of battery
- Base is connected to one end of LDR and other end connected to LED and Buzzer positive.
Conclusion:
This LDR Based Dark Sensor Circuit work auto with light.
In light, all stay OFF.
In dark, LED glow and buzzer sound.
No switch need.
Simple, cheap and good for small project.