Garage sensor: How do they work ?

[Rodo]

Hmmm. I guess I didn't make myself too clear on this one . I'm not
interested in the state of the door. I know the door will be open
(slightly) because I opened it. I just want to have something beep if a
critter (or not so critter) comes into the garage. My condo sits on top of
the garage and I just want to cool it down on summer days by leaving the
door open a bit. It is also not intended to be open overnight.

Thanks



"Rodo" <dsp1024@yahoo.com> wrote in message
news:5uxje.2972$6d.2606@trnddc02...

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 ?

Thanks

BTW the motor is a Genie unit (belt driven ...very quite kind).

 

[Bob Monsen]

Rich Grise wrote:

On Wed, 25 May 2005 01:27:35 +0000, Rodo top-posted:


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.

"Terry Pinnell" <terrypinDELETE@THESEdial.pipex.com> wrote in message
[snip]


What size of critter must be detected? (Mouse, rat, cat, squirrel,
Alsatian, neighbour's baby, teenage vandal, 300 lb escaped
convict...?)


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

http://www.goldmine-elec-products.com/prodinfo.asp?number=G4567&variation=&aitem=35&mitem=38