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    The motion sensor switch circuit can automatically turn on a water sprinkler but you can easily use it as a motion sensor light switch or motion activated alarm too. Before beginning the construction contact your nearest electronics component vendor and procure a readymade box-type Passive Infrared (PIR) Motion Sensor unit.
    Such units, packed in a compact enclosure with power input and relay output terminals are widely available.

    In prototype, an unbranded (Made in China) PIR Motion sensor with the following specifications are used.

    • Detection Range:10Meter Maximum
    • Supply Input:12V DC, <500mA
    • Relay Output :Common(C),Normally Closed(N/C),Normally Opened(N/O)
    • Relay ON time: 15 Secs (Not Adjustable)

    pir motion sensor unit

    Now install the PIR module hanging from a 3 metre high mast (to cover 10 metre radius area) and connect its supply and relay terminals to our finished and enclosed circuit, observing right polarity. A 4-core screened cable can be used for this interconnection. Power the circuit from a regulated 12VDC adaptor/solar power box.

    Whenever the PIR module detect movement of a live body its relay output toggles and the switching mosfet (T1) in the circuit is switched to on via resistor R1 and related parts. As as result, the EM relay at the output of T1 is activated and the electric sprinkler gets its supply through the relay (RLY1) contacts. This contacts (or spare contacts) can also be used to activate a high-power warning alarm.

    Please note that, here T1 is wired as a mini electronic timer. Even after the PIR relay switched off, output relay (RLY1) remains in on state for a short duration decided by the value of timing capacitor C2.

    Motion Sensor Switch Circuit Schematic

    motion sensor switch circuit schematic

    The Electric Sprinkler

    electric sprinkler

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    43 Responses to "Motion Activated Switch for Alarm, Light or Water Sprinkler"

    1. helo,i am interested with this circuit,,pls give me info abt d PIR unit..name and brand coz i dnt knw were to find here saudi arabia…tnx

      also abt d timer ckt,can i add a diode forwrd to the gate of mosfet?so that when PIR switch off,no voltge reach on its output frm the charged capacitor…hope u knew weat i mean,sori for my poor english,,tnx,more power!!!

    2. Thanks for your interest! Readymade PIR sensor boxes are easily available and you can purchase the same from electronics super markets too.Otherwise search in google to locate the nearest dealer in Saudi Arabia.

      No need to add a diode because,the low value capacitor C2 slowly discharges through R2.Futher when PIR is in off state,the relay contacts are also in “open”condition.If you wish to use a PIR with solid-state output (ie transistor switched output instead of the relay),such an alteration may become necessary.

      • ayinde olayiwola says: on February 5, 2012 at 7:53 pm

        sir, i really appreciate your contribution in electronics, sir i want to join you and really want to work with you sir. am 19 years of age from Nigeria, i will be so happy if you accept my wish sir . thanks

    3. Thanks for the ckt. i am interested PIR based motion detector, could you explain how to connect 3 terminal PIR sensor (i.e. Drain, source and gate type) with your ckt.
      Thanks in advance,

      • T.K.Hareendran says: on December 10, 2010 at 2:37 pm

        You can’t directly connect a 3-pin PIR sensor component in this circuit.Addition of a complex signal conditioning& switching circuit is required to drive the output relay.Here we are using a ready-made PIR sensor module.Anyway,I will try to add a circuit using the sensor component,mentioned by you in near future.

      • Thanks for your early prompt reply. could you give hint on how to test 3 pin sensor and connections to drive relay or LED. I have tested the same sensor by connecting source pin to +5V DC, drain to Amp i/P, GND pin to ckt comman GND. Contineous o/p of 1.565-1.655V at Amp o/p was measured, but no change in voltage when human body comes within the coverage. Please help to solve the problem.

    4. I am working in project and i want to ask about its connection with PLC if its possible to do so ,and isn’t it comes with its own conditioning circuit ?
      thanks for your effort :)

    5. Hello………….
      i want to know how to make motion sensor circuit.so if you know some information about that circuit.plz inform me…….

    6. sir i want to make a security alarm with automatic light switch..can you help me in making my project.

    7. hello sir i analyzed the circuit above.I have a question to ask that,will this circiuit serve for switching on a normal room light.

    8. Helo sir,
      I just wnat to know that is there any specific number or code for PIR for this circuit?

    9. hi i have a question about the circuit above i see you are using a ready made pir sensor and im trying to use one as well Honeywell IS-215T and the pins that are avaiable on the senor are +,-, C, N/C and 2 x T i was wondering if it is possible to use the circuit above to this pir sensor and if possible where to i connect the N/O part as it is not on the Pir sensor i have

      Thank you

    10. sir,
      i seen your circuit which is very reliable circuit but it should be light dependent. plz send me thecircuit which is light dependent

    11. how can i connect this cct with 16f84 pic

    12. Hi, I’m also interested in this circuit. But my problem is the only PIR available here in our country has only 3 pins. Can you help me solve my problem and apply this kind of PIR in your circuit? tnx.

    13. hey i am using first time PIR sensor gor motion detection of robots……i have no idea how can i use these sensors with my PIC18F452…..if anybody know plz help me
      Any drive circuts…..!!!

    14. Hi
      Iam interested in building the motion sensor/sprinkler as above.I am having difficulty in locating suppliers of a 240v soleniod switch and the PIR .im in the UK and suggestions or at least the manufacturer of the one shown

    15. Hola me interesa tener mas informacion sobre un aspersor de agua que se active con el movimiento, una cosa mas bien domestica, yo estoy en bogota, Colombia. Importante precios

    16. Hi sir, I want to make a solar powered motion detector sensor. My plan is that during the day, it will collect the solar power and store in a charger. At night, the sensor will be activated and if there’s anyone walks towards the house, the security alarm will function. So, do you know how to connect the solar charger to the sensor? Thank you.

    17. sir, i want circuit diagram for detect the motion to activate floor light/staircase lighting plz help me for my project.
      send the circuit to my mail id
      Thank you sir

    18. heloo. sir i want to make this circuit. I am in now Quetta Pakistan.R tha PIR senser avail in Quetta, if avail then pls send location.thanks.

    19. Basically all I need for my motion sensor lights project is the PIR sensor and this circuit? I want to install this in my block corridor so it turns on the light when it senses movement and then turn it off after a certain amount of time.

    20. Sir is this circuit can we directly connect tubelights and other lights???

      • Yes, you can connect light bulbs. As you can see there is a relay that acts like a switch, turning on the light for 15 seconds. It can be used to turn ON the lights in an apartament building saving electricity.

    21. Is it possible to glow the light continuously until the human getting away from the room,bcoz i like this circuit and planned to do as a mini project…

    22. @ P.Marian :-
      sir can u reply to my above comment

    23. Sir,
      Is it possible to detect the human with no movement???

      I want to detect the Human without motion by him.

      Please Help me…

      • tiger_rajas says: on March 9, 2013 at 8:28 pm

        No it is not possible,even through human is in PIR SENSING area if no movement in human body means the sensor gets off,i have checked this last week.

    24. I regret, I can’t understand your doubt. Please clarify what you mean by “detecting human without a motion”. Or give some details about your project.

      • tiger_rajas says: on March 9, 2013 at 8:25 pm

        i started doing this as my mini project,in bread board connection the o/p is not coming correctly.The i/p coming for relay during human motion will be 12 v and during no human motion the i/p for relay is only derceased to 11.2v.Can u provide me a solution for my problem?

      • tiger_rajas says: on March 9, 2013 at 8:38 pm

        Totally there are only 3 pins in PIR SENSOR in the order of +ve,output,-ve.But in the above circuit diagram u r giving 12v to sensor through diode and another 12 v giving directly to PIR SENSOR.In which pin you are giving that 12 v directly.

    25. First of all note that this circuit is built around a readymade box-type Passive Infrared (PIR) Motion Sensor unit. Such units, packed in a compact enclosure with power input and relay output terminals are widely available.

      I think you are using a ready-made PIR module with + , – and o/p terminals. If you wish to construct a circuit using this type of module, just leave this circuit & switch to my new circuit http://electroschematics.com/8425/led-security-light-with-pir-motion-sensor/

      This will give you an idea about the wiring!

    26. hello everyone,
      please how can I configure a PIR circuit to sense presence of occupant in a room without need for the person to move about?

    27. how to connect pir sensor to close a door of dog cage

    28. Hi Hareendran
      I would like to know how modify my Key cam to activate the recording ,if it detects motion.Please help because some one stole my Laptop Charger from my desk in my office.I would like to have a spy cam on my desk which i set it on after ofice hours so that if anyone goes to my desk this CAM start recording.

      Thank you very much in advance.

    29. Hi
      How can I use a standard box type PIR with only a normally closed relay output to trigger the sprinkler or light and how can I adjust the timing?

    30. Hi sir,

      i am also using a Passive PIR with normally closed relay output also. pls help.


    31. Sir, i am interested in Pir sensor , and delay off switch , i live in islamabad can you guide me where to get it or how to make one
      i have some basic electrical knowledge.

    32. Sir,
      The n channel enhancement mosfet needs to have a limiting resistance for drain current..
      The FET here used has a relay driver has no limit resistance for the driving side..
      12V gets driven through relay and ground..
      Please revert it

    33. Good day , please I need a fitter circuit for fittering inverter’s output . You can reach me via ,goldin321@yahoo.com

      Thanks .

    34. Hi. im dani from thrissur , kerala. im intrested to buy this product.. so please give me the contact details.. Mob: 9995546007

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