Introduction: Automatic Bulb Using PIR Sensor

Hello guys!!

Here I am introducing an automatic light that turns on within the sight of a human or a creature. The sensor utilized here is, the exceptionally renowned PIR is a basic circuit that is promptly accessible on the web. I purchased this sensor sometime in the past yet now I am using it. Different components required are recorded beneath. The 12V supply for powering the circuit is got from an SMPS board which is utilized for enlightening LED strips and it is accessible at a modest rate.

I kept all the circuit boards inside a plastic enclosure which is used to make switchboards. The bulb holder was kept on top of the enclosure, the sensor is placed below the enclosure directing the IR beam downwards.


  1. PIR sensor
  2. Diode 1N4007
  3. Resistor 1K/0.25W
  4. Transistor BC547
  5. 12V Relay - 240VAC, 7A rated
  6. Connecting Wires
  7. 12V -500ma SMPS
  8. 6x4 Plain box

Step 1: Circuit Diagram

The terminal J4 is where the input supply is given, the output from the SMPS is connected to this terminal. Next comes terminal J5 where the connection to the PIR sensor is made. The sensor consists of three pins-VCC, OUT, GND. This should be connected properly. Last comes the terminal J2 where the AC supply to the bulb is given. We can adjust the sensitivity and delay time by adjusting the pot on the sensor. To know more about the sensor adjustments check the datasheet.

To view the datasheet of the sensorClick here

Step 2: PCB Layout

The PCB layout is provided here. Place the components carefully and solder them properly. Provide suitable insulation to the AC mains track in the PCB to avoid any short circuit.

Step 3: Finished Board

After making the PCB connect the 12V supply, PIR sensor, and the AC supply. Adjust the sensitivity and delay time according to your situation and place of fitting the bulb. Then finally put all the things inside the enclosure and screw it on your wall.

I hope this instructable will be useful to the individuals who consistently neglect to kill the lights after use.