Motion sensing light without Arduino.

Motion sensing light without Arduino.

A few decades ago no one would have thought about automatic lights as a reality. But now a days it is possible with the help of some budget friendly electronic components. You just go into the room and see the magic happen, your LED bulb will glow automatically. The project we are going to discuss in this article does the same, we named it as “Motion sensing lights”.

Motion sensing LED

Now you might be wondering about the working of these lights, well the key component of these lights is “Passive Infrared Sensor”, abbreviated as PIR senor. Upon which Motion sensing lights work.

PIR Sensor


Our X factor for these lights is PIR module. PIR detects the Infrared radiations of the nearby objects or person, after that these radiations convert into electrical signal according to the strength of the radiations and LED will be triggered to light up your room. Actually the PIR sensor detects the radiations in the form of heat energy. The two pyroelectric sensors inside the PIR sensor setting besides one another. Entry of a person creates a differential between two sensors. Hence PIR sensor will be engaged.

PIR Sensor sensing the IR radiations


PIR module – It consists of 2 pyroelectric sensors to find heat radiations from the surroundings. When the signal between two sensors changes hints the sensor that someone has just entered the room. PIR has 2 potentiometers. To make the ideal conditions, set first at high sensitivity and second at 1 minute.

Relay module – LED works on 220v AC. We need relay to control the voltage.

Power supply – Power supply has a simple work to convert 220v AC to 5v DC, so that PIR and relay can work. We can easily get a power supply module from mobile charger.

NPN and PNP transistors – To amplify the 3v output to PIR sensor, so that 5v relay can be triggered we need a transistor in between. In this project we have used BC558 PNP transistor. NPN can also be used.


LED bulb


Carefully open upper cover of the bulb without breaking it. Remove the LED plate by unsolder the main AC wires. There you can find enough space to fit the circuit easily. According to the circuit diagram connect the whole circuit.

Actual Circuit

Carefully fit the relay, power supply, transmitter circuit behind the LED plate. Make sure that wires are not touching each other without feeling any strain. Now place PIR outside i.e. on the top of the LED plate. Furthermore, we need to cover the bulb with the plastic bulb cover, but this time we have to create a huge hole at the center of the cover so that PIR can fit and detect the radiations properly. After that paste the PIR sensor with the plastic cover of the bulb. Finally plug it into the bulb holder and enjoy the convenience of motion sensing light.


Power going to the LED plate is controlled by relay. The relay is being controlled by PIR sensor. PNP transistor is working as a bridge between PIR 3v output and relay 5v input. Lastly power supply is supplying 5v to the modules

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