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PIR Sensor

Mar 12 2012 | 7:21 pm

I’m working on my first Max/MSP project for a sound art installation, and so far everything is going great. For one portion of the patch, I would like to have PIR sensors dictate the frequency of some recordings, but I’m not getting any variable numbers from the sensor. Does any one know if the PIR sensors are able to output variable data, or just high and low?


Mar 12 2012 | 8:26 pm

Have you tried turning it off and on again?

Mar 12 2012 | 8:42 pm

Most PIR sensors are wired up as logical motion detectors (on/off) for ease of use. Think of those porch lights that turn on automatically when people walk by. I think it’s possible to get analog data from a PIR, but it would probably require quite a bit of op-amp fiddling to get something usable. AFAIK, there is no easy out-of-the-box PIR analog sensor that gives usable voltages(although the PIR itself is an analog sensor).
You might be happier with an infrared ranger, an ultrasonic ranger, or camera detection.

Mar 12 2012 | 9:06 pm

That’s what I was afraid of, but thanks for the input. I think radio shack is getting tired of my returns…

Mar 13 2012 | 3:10 pm

Andrew’s right, PIR’s are best used as a switch. Oddly, the straight analog sensor is expensive:

I’ve used it, and you can get a general idea of direction of motion, sometimes, but it is very twitchy. It’s more accurate, but less sensitive, without the lens. There’s a great information resource here:

Mar 13 2012 | 4:30 pm
Mar 13 2012 | 6:26 pm

Thanks for the input everybody! I returned the PIR sensors and picked up a sonar, too bad the sonar isn’t 10 bucks.

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