Passive Infrared (PIR) Sensor Tutorial


[ladyada] has a freshly-published and amazingly thorough tutorial on passive infrared (PIR) motion sensors. Most often seen in security floodlights and automatic doors, in creative hands these sensors can be put to other uses—cat flaps, camera triggers and purely artistic applications—as you’ll see in several demo projects and videos. For the curious, the tutorial provides a good amount of background theory on how PIR sensors work, along with the associated fresnel lens optics. And for those who just want to get hacking, most PIR sensors (like the one above) come in a simple-to-interface module containing all the support hardware and providing a simple digital output; the article wraps up with one such example.

18 thoughts on “Passive Infrared (PIR) Sensor Tutorial

  1. Basically: apply power. If something moves, then the signal will go high. Sometimes you need to use a transistor or analog pin if the high signal isn’t 5V TTL compatible. On another note, I got a bunch of great PIR sensors for $1 each at the Silicon Valley Electronics Flea Market. They run on 12V, and have adjustable sensitivity and timeout. Right now I actually have a PIR sensor watching my office and logging the motion to Pachube:

  2. I picked up a PIR sensor from Radio Shack a while ago. Great little gadget although not as powerful as the security-designed devices.

    Think RadioShack finally figured out that the hackers are their bread and butter. They’ve started carrying sensors from Parallax and can sometimes be cheaper than them at the store.

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