Wednesday, August 17, 2022

Infrared Sensor Based Power Saver

--Fayaz Hassan He is a manager at Visakhapatnam Steel Plant, Visakhapatnam, Andhra Pradesh. His interest includes MCU projects, mechatronics and robotics

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Construction and testing

A single-side PCB for the PIR sensor based power saver is shown in Fig. 3 and its component layout in Fig. 4. Enclose the PCB in a small box in such a way that you can easily connect 230V AC input to CON1 and the light/fan to CON3 at rear end of the box. Connect the PIR using a 3-wire cable to the PCB at CON2 and install it at a suitable location in your room.

Before using the PIR in the circuit, manually check it by connecting Vcc and GND pins of PIR to a 9V (or 12V) battery. Then check for change in voltage at signal output pin with respect to ground by waving your hand in front of the sensor. Adjust sensitivity and time controls of the PIR as per requirement (else turn both presets clock-wise to have highest sensitivity and high time signal). The dome surface of the PIR should be clean for better sensing.

Fig. 3: Actual-size PCB pattern of PIR sensor based power saver
Fig. 3: PCB pattern of PIR sensor based power saver
Fig. 4: Component layout of the PCB
Fig. 4: Component layout of the PCB

Download PCB and component layout PDFs: click here

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After manually checking the PIR, remove the battery and connect the PIR to the PCB. You can assemble the circuit on the PCB with terminal connectors for CON1 (input) and CON3 (output).

Verify that voltages at the test points are as per the table before using the circuit. Check to see if LED2 is off and relay is energised. After some time, LED2 will glow and the relay will get de-energised. Your circuit is now ready!

EFY notes

Some PIR sensors require an initial stabilisation time of 10 to 60 seconds in order to function properly. During this time, any motion in its field-of-view (near 15m range) should be avoided.

Main DC voltage at TPI is unregulated.

Feel interested? Check out other electronics projects.


  1. Hello sir….
    I am Divyanshu
    Sir i am trying to make a circuit of Infrared Sensor Based Power Saver.I connected all the components as per your circuit diagram but my circuit is not work. Then I check the voltage of TP1 . only 3.5 volts at TP1
    Sir you tell what is wrong in my circuit plzzz

    • Your problem is not clear whether the components are heated up excessively while measuring the voltage at TP1. If yes, there is a possible short circuit.
      First make sure that transformer output is about 9V. Remove IC1 and T1 from circuit and check the voltage at TP1 again, it should be around 9V as listed in the test point table. Also check voltage between pin 3 and 4 of BR1 which should be about 9V.
      If not, double check BR1 connections or replace it with a fresh one. The circuit is simple and working perfectly. It will work if all components are connected properly in the circuit as shown in Fig.2.

    • To switch off the relay, no person should stand or move infront of the PIR and wait for long time.
      to change the delay of relay OFF time, adjust the 1M variable resistance.

  2. Can we use 9v supply to sensor input that you have given in circuit or we have to use a IC7805 extra to circuit you have guven to decrease voltage for sensor

  3. I made this project.It is in running condition but i found one major fault in this circuit. 220k ohm resistor causes too much voltage drop . I removed potentiometer of 1M ohm and 220k ohm resistor and and i placed 2.2k ohm in it.

    • @ Muhammad farhan. This is the reply from author Fayaz Hassan. I felt happy to know that somebody tried the circuit and it is working fine.
      The main purpose of the 1M and 220K resistance is to slowly charge the capacitor C3 (1000uF), so that it increases time delay of the PIR which has limited triggering time. In case, the capacitor has more internal leakage than the charge input through the 1M and 220K, then the capacitor C3 will never get charged and the output of IC1 (555) will never change. so use new and good quality capacitor with atleast 25V rating. By changing the charging resistance, only relay hold time will vary else the circuit will function normally.

  4. Sir ,
    Can this project automatically switch ON or OFF light and fan .
    Can This project automatically work if two man or three man enter but one man out in the room??
    Pls reply this question .
    If it is not work then how solve this problem.
    Its my CLG project.

    • This is the reply from the author. Yes, it works. It does not count the persons. Actually, the PIR sensor triggers whenever a person is moved in front of it. (of course, within its range. refer datasheet for full details) if the person is not moved for more time, the relay will be switched OFF.
      It means the relay may be switched OFF if the person is sleeping (if no movement is observed for a long time). So the time delay is adjusted with 1M variable resistance. Use good quality and fresh capacitor C3 (1000uF) to have low leakage and high delay time. Also please read 2nd paragraph of Construction and Testing section.

  5. Sir,
    please give me a block diagram of infrared sensor based power saver without using microcontroller. In the circuit diagram we are not use the microcontroller so please give me some idea about block diagram.

  6. I have prepared this project for our office corridor. while i was trying to check the voltage at Test point 1 (TP-1), multimeter was showing descending volt up to 0 volts instead of 9 volts. the transformer which I have used was showing 10 volts. and the DB107 rectifier showing 13 volts at its terminal. te voltage after filter capacitor is -6.5 volt. for any short circuit probability, i have brake the further circuit but it still showing the same result. please help me.

  7. for atleast how long will the electric appliance operate? how can we increase the time it operates? by decreasing the 1 mega ohm value of variable resistance?


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