Light-Activated LED Dimmer Circuit

This Project is sponsored by JLC PCB. You can check out JLC PCB at : https://jlcpcb.com/HAR

Theory & Logic:

The circuit works on the principle of feedback control. The LDR, which varies its resistance based on light intensity, is used as a sensor. The Op-Amp is configured as a voltage comparator. When the ambient light is low, the resistance of the LDR increases, resulting in a higher voltage at the inverting input of the Op-Amp. This causes the Op-Amp to output a high voltage, turning on the transistor and allowing more current to flow through the LED, making it brighter.

Conversely, when the ambient light is high, the LDR resistance decreases, causing a lower voltage at the inverting input of the Op-Amp. The Op-Amp then outputs a low voltage, reducing the current through the LED and dimming it.

Procedure:

Stepwise Procedure:

1.Connect Op-Amp:

• Connect the LM741 Op-Amp to the breadboard.
• Connect pins 2 and 3 of the Op-Amp to the LDR and the potentiometer (10k), respectively.
• Connect pin 6 to the ground and pin 7 to the positive rail.

2.Configure Op-Amp:

• Connect pin 2 (inverting input) to pin 6 (non-inverting input) through a 1k ohm resistor.
• Connect pin 2 to the output (pin 6) through a 2.2k ohm resistor.
• Connect pin 6 to the ground through a 4.7k ohm resistor.

3.Connect Transistor:

• Connect the collector of the BC547 transistor to the positive rail.
• Connect the emitter of the transistor to the ground.

4.Connect LED:

• Connect the base of the transistor to the output of the Op-Amp.
• Connect the anode of the LED to the collector of the transistor.
• Connect the cathode of the LED to the ground.

5.Power Supply:

• Connect the positive and negative terminals of the power supply to the positive and negative rails of the breadboard, respectively.

6.Adjust Potentiometer:

• Adjust the potentiometer to set the threshold light level for LED dimming.

7.Testing:

• Shine light on the LDR and observe the LED's brightness change based on the ambient light.

Conclusion:The light-activated LED dimmer circuit successfully adjusts the LED brightness based on ambient light conditions. The Op-Amp, LDR, and transistor work together to create a feedback control system that regulates the current through the LED.

Applications:

• Ambient Lighting Control: Use in rooms to adjust the brightness of LED lights based on natural light levels.
• Energy Savings: Implement in outdoor lighting systems to save energy by dimming lights during daylight.
• Security Systems: Integrate into security cameras with infrared LEDs for optimal night vision without excessive brightness.