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no image Friday, October 13, 2017 by Simon PEREMANS

PIR Project

Good evening,

I am doing a project in work. I am in the army and i am looking at making a PIR sensor to detect the movement of enemy troops outside of a harbour area, at a max distance of 20 feet and once triggered to alert the sentry positon covertly. Is there anyway or component that can be used in conjuction with the sensor to give an indication of the distance as well? So for instance something as simple as the closer the distance the more LEDs light up. Any help or ideas would be much appreciated.

Kind Regards,




  • by  Gustavo Cedron

    If you need a sensor, maybe yhis web can help you:

    • by  Simon PEREMANS

      hello Gustavo,  thank you for the reply but I am not after buying a sensor as a whole.

  • by  Simon PEREMANS

    hello Gustavo,  thank you for the reply but I am not after buying a sensor as a whole.

  • by  Elizabeth Simon

    A PIR by itself won't give you distance if that's what you are asking. Since it's a passive sensor, it only detects a change in the infrared coming in.

    I suppose if you had one with an analog output, you could get a relative closeness by how strong the signal is and use that to turn on an LED bar graph. It's only going to be relative though because the enemy could bundle up or hide behind a shield to make themselves look further away.

  • by  David Ashton
    Simon...have you considered using ultrasonic distance sensing?  Similar to a reverse parking sensor.  the commercial reverse parking sensors only alarm when obstacles (ie detected objects) are a few feet away.  But ultrasonic distance measuring devices give a very precise indication of the distance to a reflecting surface.  Their beam might be a bit narrow for your requirements, though.   You'd probably have to design your own or adapt something commercial.  As pointed out, a PIR only detects infrared...a close dog will look the same as a further away human.
  • by  Kevin Angelo Ma
    I would go with david here. Although the type of ultrasonic sensor would also matter. I have done a similar project like this, the response time is quite nice. I would just not suggest much in terms of so many obstacles included in the environment since the reflection of the sound would be difficult to retrieve. Somewhat in my experience, it has diffraction. Also, ultrasonic sensors would cost you more.

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