Light ON at night and light OFF in day all automatic! A single LDR and a BC547 transistor perform all these functions.
This Smart Street Light Control Circuit is a easy and simple way to save energy and also there is no manual effort and no energy waste.
Circuit Working:
Parts List:
| Components | Values | 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 and in dark the resistance go high.
Then LDR and resistor R1 make voltage divider and this voltage go to base of transistor BC547.
After that, when light fall the base voltage goes low and transistor does no work and LED goes OFF and when dark come then base voltage is high.
Now 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.
Hence, this is safe for LED.
How to Build:
To build a Smart Street Light Control Circuit follow the below steps:
- First, take all parts as shown in circuit diagram.
- Next, emitter of transistor Q1 goes to ground (0V) and collector connects to negative side of LED and then base pin connects between LDR and resistor R1.
- Then LED positive side goes to battery positive through resistor R2.
- Also, R1 goes to positive terminal and LDR goes to ground.
- Finally, power supply is +6V battery.
Conclusion:
To conclude, this Smart Street Light Control Circuit works automatic; light turns ON at night and OFF in day and there is no need to press switch.
Furthermore, it saves power and time, is good for school and home projects and is also easy to make and works well with LDR and BC547.