Other uses for garage door eyes

[AGCB]

As a residential contractor I sometimes replace garage door openeners for one reason or another. As such I have a collection old photo eyes and have wondered if they could be of use in my electronics hobby. I do not know how they work but they must be more complicated than just a DC transmitter/receiver pair. Anyone put a pair to good use or can explane the system? Aaron

 

[Gary B]

Normally, there is a light source and detector in a box with a retro-reflector mounted on the other side. When the beam is broken, either a solid state switch or relay is activated. That will in turn provide either a ground on one wire or a dry closure between two wires. I would guess that if it has three wires, two are power and the third is the control lead that will either add or remove a ground upon breaking of the beam. If it has four wires, two are for the lamp power the other two are the relay contacts.

The best way to know for sure is to pull one apart and draw out the schematic since you have several examples to play with.

 

[#12]

I worked on a garage door opener where both modules were wired, as in "no mirror". One of them pulsed and the other received. The receiver changed a voltage and the brain board decided what to do about it.

 

[AGCB]

I worked on a garage door opener where both modules were wired, as in "no mirror". One of them pulsed and the other received. The receiver changed a voltage and the brain board decided what to do about it.

This sounds like it. I did pull one apart and there is quiet a complicated circuit with several ICs, one of them being a dual comparitor, plus a half dozen or so caps and a bunch of resistors. This was the emiter side. I gues it's more complicated than it's worth to try and use. I'll bet it's this complicated to make disabling the system nearly imposible for the home owner and therefore litigation proof! Aaron

 

[RMMM]

I doubt that is the reason.

I would think the complex circuit is to produce a modulated light, so the receiver is tuned to see it. This way, regular sunlight wont trigger the unit.

Like how TV remotes work. They modulate the signal at 38hz. The receiver ignores anything but a 38hz signal to keep the TV from changing channels, turning off, etc.. because of sunlight or other sources of IR light.

 

[AGCB]

You may be right but just google "GARAGE DOOR EYE" and see how many people are wanting to disable their's.