Hi all,I want to make a circuit that will beep (or something like that) for when I have the garage door semi-open. Since the system already has sensor in it, I figure I can just interface to them.I measure the terminals of the two sensors that stop the door from closing when interrupted. One shows a 12vdc and the other a 3.6vdc. If I place an object in the path, the 12vdc goes to 13.6vdc. The other does not change. How do these things work ?I figure one is an IR Tx and the other Rx. The beam is interrupted and the voltage changes (and the LED on it blinks), right ? I measure no AC or frequency from any of the two sensors ( at any time).I'm planning to use a PIC18. I'm just puzzled by the 1.6v difference ? Is that all that they use ?ThanksBTW the motor is a Genie unit (belt driven ...very quite kind).

If you do this your beeper will only sound when there is an obstructionbetween the sensors. The door can be opened without the obstructionsensors activated (my door will stop when button is pressed whenmotion).I use a reed switch and magnet to sense if the door is not closed. Imade my own (I'm cheap) from junk parts but they can be purchased fromRadio Shack in N/O or N/C types.Dave

Garage sensor: How do they work ?

May 21, 2005 22 Replies

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Rodo 21 years ago

Dog, cat as long as they're smaller than the 300lb convict :-). Seriously, I just want to leave it open a couple of feet. I don't mind that someone or something goes inside, I just want to be alerted so I can go check.

Thanks to all for the replies and I apologize for the misinformation.

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Rich Grise 21 years ago

How about one of those PIR motion sensor yard lights? I think it's possible to get just the sensor part, or you could just unscrew the bulb and operate a 120VAC relay; and they have adjustable sensitivity. Maybe two - one for each side.

Good Luck! Rich

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Bob Monsen 21 years ago

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