Motion sensor lights are very useful at home—they automatically turn ON when they detect movement, giving you hands-free lighting and saving electricity. This project uses a PIR (Passive Infrared) sensor, a BC547 transistor, and a few other simple parts to create such a smart light.
Components Required (Affiliate Links)
- PIR sensor ►https://amzn.to/34ht91n
- BC 547 transistor ►https://amzn.to/3wAgO4u
- 820 Ω resistor ►https://amzn.to/34i2jWD
- 5v dc supply
- 5v relay ►https://amzn.to/3vqBwnc
- Light bulb ►https://amzn.to/3wARwmJ
- Bulb holder ►https://amzn.to/2REhaZ3
- IN 4007 Diode ►https://amzn.to/2RNpLsj
Circuit
How It Works
- PIR Sensor Detects Motion
The PIR sensor has a special element that senses the heat energy from moving bodies. When someone passes in front of it, the sensor outputs a small voltage signal (HIGH). - Signal to BC547 Transistor
This small voltage from PIR sensor is sent to the base of the BC547 transistor through the 820 Ω resistor. This resistor limits current so the transistor doesn’t get damaged. - Transistor as a Switch
When the PIR sends voltage, the BC547 transistor turns ON. Think of it like pressing a button that closes a switch. - Activating the Relay
When the transistor switches ON, it completes the circuit for the relay coil, energizing it. The relay acts like a remote-controlled switch to turn ON the light bulb connected to the mains voltage or power supply. - Diode Protection
The IN4007 diode is connected across the relay coil to protect your circuit from sudden high voltage spikes when the relay turns OFF. This keeps your electronic parts safe. - Light Turns ON
As the relay closes, it connects the light bulb to the power, turning it ON automatically. When no motion is detected, the PIR output is LOW, making the transistor and relay turn OFF, and thus the light turns OFF.
Summary
- The PIR sensor acts like eyes that watch for movement.
- The BC547 transistor is like a helper that switches on the relay.
- The relay is a strong switch that controls the home light safely.
- The diode protects the circuit from damage.
- When you walk near the sensor, the light will ON. When you leave, it switches OFF automatically.
This simple project is perfect for beginners and helps you save power and have convenient automatic lighting at home.
This circuit provides an effective way to implement automatic, hands-free lighting, saving energy by ensuring the light is only on when motion is present.
Disclaimer:
This project involves working with AC mains voltage (220V AC), which can be very dangerous and potentially lethal if not handled properly. It is crucial to take all necessary safety precautions when dealing with AC power.
Watch the full video tutorial here: How to make a motion sensor light at home with explanation | PIR sensor | Transistor-BC547