This small LDR Based Dark Sensor Circuit is very smart, as it can see light and dark using LDR.
When there is light, everything stay quiet and when it becomes dark then LED start to glow and buzzer makes sound; also there is no need to touch anything it works by itself.
In addition, it is easy to make with low cost and is good for small school projects.
Circuit Working:
Parts List:
| Components | Values | 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 |
To begin with, this circuit is like light sensor switch, which control one LED and one buzzer.
Here, power come from 9V battery, LDR see the light around and then BC547 transistor act like small switch and it also makes LED and buzzer ON or OFF.
Then LDR and resistor share voltage.
When light is bright, LDR resistance become low with LED and buzzer stay OFF and when dark come then LDR resistance go high; after that the transistor turn ON and LED start to glow and finally buzzer give sound.
How to Build:
To build a LDR Based Dark Sensor Circuit follow the below steps:
- First, assemble all the parts as shown in circuit diagram.
- Next, emitter connects to ground negative of battery.
- Then collector connected to LED(–) + Buzzer(–) through R1 resistor to positive of battery
- After that, base connected to one end of LDR and other end connected to LED and Buzzer positive.
Conclusion:
Overall, this LDR Based Dark Sensor Circuit work auto with light; in light, all stay OFF and in dark, LED glow and buzzer sound.
Also, no switch needed, as this circuit is a simple, cheap and good for small project.