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Motion Activated Switch for Alarm, Light or Water Sprinkler

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

43 Comments

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  • T.K.Hareendran

    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

      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.

    • tiger_rajas

      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?

  • Bhavin_cp

    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

      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.

  • tiger_rajas

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

  • tiger_rajas

    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…

  • tiger_rajas

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

    • P. Marian

      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.

  • radiofanatic

    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.

  • Sultan

    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.

  • janshi

    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

  • REETHA

    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.

  • MarthaF

    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

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