Garage sensor: How do they work ?

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

I have RF-linked tilt switches on my doors (Chamberlain/Liftmaster) and the receiver plugged into an outlet in my office.

...Jim Thompson

As others have commented, these won't tell you if the door is opened slightly.

This type of sensor is designed to be floor-mounted (can be driven over) and will trip the circuit if the door is opened more than an inch or so

- see Overhead Door Contacts:

Here's a cheap wireless package that you could use as a starting point:

Or, you could just get a standard magnetic door sensor, mount it anywhere on the vertical edge of the door when it's closed, and it'll trip when the door opens.

HTH, Richard

Hello Rodo,

As Dave said, the obstruction sensors won't help you here. I do not know belt drives but figure they must have something similar to what our screw drive has at either end: End switches. These are simple mechanical switches and the one near the door closes (or opens, depending on model) when the door is fully closed.

Regards, Joerg

Is it a segmented-panel door? If so put the tilt switch on the topmost panel.

...Jim Thompson

Of course they do. If the "closed" switch isn't giving its "door closed" signal, then the door isn't closed. And if the switch at the top of the travel isn't giving its "the door is fully opened" signal, then the door is obviously someplace in between, which is what Rodo was asking for, as far as I can tell.

The elecronics comes into play when you decide to sense the state of both limit switches simultaneously. That's an "AND" gate.

Thanks, Rich

Hello Rich,

The Genie units usually have that already in them, along with another "one bit memory" that tells them in which direction the door had moved last.

Regards, Joerg

As has been said, a burglar-alarm magnetic switch is pretty easy. Also, if the motor unit has a light on it, and the light doesn't go out after the door has been open for a while, you might be able to use something like a cheap wall-wart plugged into the light socket to give you a signal when the door is open.

Matt Roberds

Hello Jim,

But the top panel moves...

Regards, Joerg

Uh, yeah, that's kinda the point, which would be obvious if whoever Joerg is responding to hadn't snipped everything.

Let's start plonking googlekiddies.

Thanks, Rich

Hello Rich,

Well, top panel mount would really only leave a wireless solution with batteries. A few hot weeks like out here right now and the batteries are toast. Garage door panels can become so hot that even a brief touch with a finger leaves a blister.

Seems overkill to me since the usual door drive already has two end switches. On our system (Genie screw drive) you could buy or make a spare set of end switches and mount them on the other side of the track if you wanted to have a completely isolated setup. If they are wired so they close when the door moves away from the end point they could simply be hooked up in series with a lamp or whatever to indicated a door that was left open. No electronics required. Anything mounted to the door itself is likely to get banged up.

Regards, Joerg

Hmmmm? My doors have about 1" of some kind of insulation between the metal panels.

...Jim Thompson

Hello Jim,

You must live in a pretty new house then or have newer doors. Ours are top quality but 30+ years old. Almost undentable metal but insulation or even double walled? Nope. When someone touches or accidentally leans against the inside of such a door on a hot summer day you'll hear a "tsssst", then an expletive, followed by an involuntary tarantella dance.

Regards, Joerg

...Jim Thompson

Hello Jim,

Then you do have a new house. Ours was built in 1970. Good quality stuff so most of the original hardware is still in place.

I grew up in Europe where a building under 50 years is considered quite new. The Romans probably thought more along the lines of 400-500 years.

Regards, Joerg

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

Original requirement:

--------------------- "I want to make a circuit that will beep (or something like that) for when I have the garage door semi-open."

Re-stated requirement:

---------------------- "I just want to have something beep if a critter (or not so critter) comes into the garage."

Glad I didn't attempt to contribute earlier! 13 replies so far, all based on your misleading spec.

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

Begging answers to those, I'd be thinking along the lines of either an interrupted IR beam or adapting a proximity detector (PIR).

Wouldn't that make it a little inconvenient to drive in or out? ;-)

Thanks, Rich

Go out and buy a standard electric cattle fence and mount a couple of isulators so that you can string a wire across the opening a few inches above the floor. No human intervention needed, and no need to move a signal from the garage to the house.