motion sensor light switch is great way of saving energy short fall period.  A PIR sensor light switch will automatically detects when someone enter the room or any place where motion sensor is set. Then, after a few minutes(adjusted by your desires) where no movement has been detected, the lights will then automatically turned  off. Although a motion sensor switch is indeed a big and important invention . In fact, you can install a motion sensor light switch much in the same way as you would a single pole light switch. 


Components Needed for this project

SRComponents/PartDetailQTY
1AC/DC Adapter6v 1
2Relay6v 1=amp1
3TransistorBC 547/BC548 or equivalent 1
4Resistor1K Ohm1
5Diode1N 40071
6PIR sensor3.3 to 20V DC input1
7Bulb AC bulb or DC bulb can be used1
8BCBYour can use it without PCB1

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All living things (human or animals), whose body temperature is more than 0 degree Centigrade , emit the heat in form of infrared radiation through their body, also called as thermal radiations. This Radiated energy is invisible to human eye. These heat Signals can be detected by using PIR sensor which is specially designed for such purpose.

This is a motion detector sensor which detects movement of human beings and triggers its output to High state (low or high). It operates in two modes low and high. The mode is selected by the jumper provided on the rear side of the PIR sensor PCB that is shown on figure given below. If sensor with input voltage capability of 12V is not in your reach, use LM 7805/7806 regulator to control the 12v current if you give 12v current directly the sensor may be damaged.

Modes of PIR sensor 

Normal Mode: When the Passive infrared sensor detects motion it sets output to High until  set time end, independent of the movements during the output HIGH time. This is One-time triggering mode.

Re-Triggering Mode: When the PIR sensor detects motion, it sets the output to High until a set time become Low, but if it detects motion during its output High state 1, it again triggers the timer making it to count from zero.N

Sensitivity Adjust

Sensitivity Adjust

With this potentio meter you can set the range which you want.

You will have to play a little with this to see what is the appropriate setting for your desired purposes.

An increased sensitivity can be beneficial for when using a PIR sensor for long range, say up to 6 meters or more. 

A decreased sensitivity is good for a very short range say maximum range or up to 10 feet. Which in turn could miss movements at a longer range.

Delay Time Adjust

The Delay Time indicates  how long the PIR sensor will keep the Output High (ON) as detecting motion.

For example, when motion has been detected, you could set this somewhere between a few seconds  up to a few minutes time period.


Yaqoob Gillani

I am yaqoob gillani electronics engineer and in this website i am going to show you very simple electronic circuits and also i am giving training about basic programming languages.

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