Seeing a car loitering off the end of our driveway, on a shared gravel driveway. I want to put in a security light to discourage this.

PIR sensors will not work well because they use heat, and a car body may be pretty much at ambient temperature. I have often driven up to our garage, which has one, and it doesn't trigger until I get out of the car (showing my warm face and body).

I want all of the equipment to be on our property.

  • 2
    Your PIR sensor is faulty, or incorrectly mounted. (They depend on the object traversing special facets in the lens to modulate the IR energy) They definitely detect cars, even though they are at ambient temperature because the emissivity of the car metal is different from the ground.
    – user71659
    Commented Feb 13, 2018 at 17:23
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    If you can dig and bury there’s nothing better than hardwired vehicle detection probes. Not a product recommendation as I just googled but this is the class of product I mean: diycontrols.com/… there are many manufacturers of similar systems. The eliminate false movement that many PIRs pick up. I agree with @user71659 there is something wrong with your existing PIR experience.
    – Tyson
    Commented Feb 13, 2018 at 17:56
  • Inductive sensors, much like most roads have. en.wikipedia.org/wiki/Induction_loop (Only slightly joking, but it could work)
    – Hari
    Commented Feb 14, 2018 at 1:29
  • beam interruption is the most reliable, that's why they use them with garage doors.
    – dandavis
    Commented Feb 14, 2018 at 20:00
  • I had motion sensor lights at each end and the center of a large circular driveway, the lights would turn on when a car went by or pulled to the mail box, I adjusted the sensor because kids were messing with our mailboxes after setting the sensor the lights came on and no more mangled mailboxes for me and several neighbors.
    – Ed Beal
    Commented Feb 14, 2018 at 20:18

1 Answer 1


I think hall effect sensors may work (like those used to synch. traffic lights), laser/IR gates (such as 'garage-door' stop-close sensors) or a computer vision based 'car-detection' system, but just a background-suppression system will work.

If you're good at programming, computer vision system may be better and most-effective (you can get easy notifications and also add a 'people detector' at little effort). Only things you need are: low-end computer (for simple BS), IR webcam and IR lamp.

But PIR may also do this job (it has to be adjusted) and is absolutely the cheaper.

... But if you like twitter notifications go for CV [Computer Vision].

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