DIY Motion Sensor Light

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Project 4: DIY Motion Sensor Light

Objective:

To build a motion-activated LED light using a PIR (Passive Infrared) sensor that turns ON when motion is detected and turns OFF automatically after a few seconds.

Components Required:

  1. PIR Motion Sensor (HC-SR501)
  2. NPN Transistor (BC547)
  3. Resistors – 330Ω
  4. LED – Any color
  5. Battery – 9V
  6. Relay Module (for controlling high-power devices)
  7. Diode – 1N4007 (for relay protection)
  8. Breadboard & Connecting Wires

Circuit Diagram:

(You can design the schematic using Tinkercad, Fritzing, or any circuit design tool.)

Step-by-Step Instructions:

Step 1: Connect the PIR Sensor

  • The PIR sensor has three pins:
    • VCC → Connect to +9V (or 5V).
    • GND → Connect to ground (-).
    • OUT → Connect to the base of BC547 transistor via a 330Ω resistor.

Step 2: Connect the Transistor

  • The collector of the BC547 transistor connects to the negative leg of the LED.
  • The emitter connects to ground (-).

Step 3: Connect the LED or Relay

  • The positive leg of the LED connects to +9V via a 330Ω resistor.
  • If using a relay module, connect it to control AC appliances like a bulb or fan.

Step 4: Power the Circuit

  • Connect a 9V battery or 5V adapter to power the circuit.

How It Works:

  1. When motion is detected, the PIR sensor sends a HIGH signal to the transistor.
  2. The transistor activates, allowing current to pass through the LED or relay, turning it ON.
  3. After a few seconds (adjustable via the PIR sensor’s delay knob), the LED turns OFF automatically.

Customization Ideas:

💡 Adjust PIR Sensitivity: Use the PIR module’s sensitivity knob to control the detection range.
💡 Use an Arduino: Add an Arduino board to program advanced features like timers or day/night detection.
💡 Control High-Power Devices: Use a relay module to automate home lights, fans, or alarms.



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