Light ON at night and light OFF in day all automatic!
All this is done with one LDR and a BC547 transistor.
This Smart Street Light Control Circuit is a easy and simple way to save energy.
There is no manual effort and no energy waste.
Circuit Working:
Parts List:
| Component Name | Specification | Quantity |
|---|---|---|
| Resistors | 100k 1/4 watt | 1 |
| 330Ω 1/4 watt | 1 | |
| LDR | 1 | |
| Semiconductors | Transistor BC547 NPN | 1 |
| LED any color 5mm 20mA | 1 | |
| Battery 6V DC | 1 |
LDR change resistance when light change.
In bright light the resistance go low.
In dark the resistance go high.
LDR and resistor R1 make voltage divider.
This voltage go to base of transistor BC547.
When light fall the base voltage goes low.
Transistor does no work and LED goes OFF.
When dark come then base voltage is high.
Transistor get bias and turns ON.
And with this LED glows automatic.
Formula with Calculation:
Base current (Ib) = (Vb – Vbe) / R1
Collector current (Ic) = β × Ib
Assume transistor gain β = 100, Vbe = 0.7V.
If voltage at base is around 0.7V or more then transistor turns ON.
LED current = V / R2 = 6V / 330Ω = 18mA approx.
This is safe for LED.
How to Build:
To build a Smart Street Light Control Circuit follow the below steps:
- Take all parts as shown in circuit diagram.
- Emitter of transistor Q1 goes to ground (0V).
- Collector connects to negative side of LED.
- LED positive side goes to battery positive through resistor R2.
- Base pin connects between LDR and resistor R1.
- R1 goes to positive terminal.
- LDR goes to ground.
- Power supply is +6V battery.
Conclusion:
This Smart Street Light Control Circuit works automatic.
Light turns ON at night and OFF in day.
No need to press switch.
Good for school and home projects.
Easy to make and works well with LDR and BC547.