Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!att!tsdiag!pedsga!jeffj
From: jeffj@pedsga.UUCP (Jeff Jonas)
Newsgroups: sci.electronics
Subject: Re: How can I fool the motion sensors connected to our lights?
Summary: it is OR or ultrasonic detection?
Message-ID: <926@pedsga.UUCP>
Date: 10 Jul 89 17:43:03 GMT
References: <358@gorn.santa-cruz.ca.us>
Distribution: usa
Organization: Concurrent Computer Corp. Tinton Falls, N.J.
Lines: 39

In article <358@gorn.santa-cruz.ca.us>, logo@gorn.santa-cruz.ca.us (David Kiviat) writes:
> 
> I have just started work somewhere where the lights are controlled by a system
> of motion sensors-if nothing moves in a pre-determined amount of time
> the lights go off.

You didn't mention how the motion was detected.
The most popular kind of detection these days for non-critical
applications (like lighting control) is using the
Passive Infra Red (PIR) detectors.
It's an infrared detector on a chip, usually with a fresnel lens over
it to give a better range of view.
You can see these things up close at most hardware/home imprevement
centers: they have a milky plastic window.
It works by sensing changes in infrared light.

What I'd do is look up the frequencies of sensitivity of the detector
(possibly on one of the brochures that I can't reach until the weekend),
and build a little box as follows:
there's an infrared LED on the top, aimed at the sensor.
There's a momentary pushbutton.
Push the button and for 30 minutes, the LED blinks at a slow rate
(once every 10 seconds), just enough to trigger the motion detector.
The timer is a 'pop up' timer (resettable one shot), so pushing
the button gives you 30 more minutes.

Battery powered, a walkman sized case would be generous.

__________
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Jeffrey Jonas

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