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Garage Door Opener - Electric Eye

Have a neighbor w/ garage door troubles. Can someone explain (from a voltmeter's perspective) how these things work?

I can get it to work right if I aim the electric eye sensors directly into each other and tape them up, but if I try to actually aim them across the opening, the door will not close. (It may not open either, but I never tested that..)

With both eyes disconnected, the terminals on the back of the main unit read about 12 volts. With one eye connected, that drops to about

7.8 volts, and with both sensors, it drops to about 7.3 volts or so. However, I can't really see much meter deflection whether the eyes are aimed or not, even when they are taped together.

However, when taped directly together (so that one sees directly into the other and there is no possible chance for misalignment!!), the door does indeed work correctly.

I'm assuming these electric eyes are current mode?? That might at least explain the lack of a discernable voltage when aligned, not-aligned...?

There are no polarity markings on the electric eyes, and opening up both showed a full-wave bridge (4 diodes anyway that look suspiciously like a bridge!), so I'm assuming polarity does not matter. (?) Either way, the voltage magnitudes did not change much when trying the wires reversed.

Any ideas what could be going on here? Can this really be just an alignment problem, or to you think the eyes are defective? They are newly replaced (before I got involved). I have no idea where the orignal ones went off to.

Thanks in advance!!

-mpm

It's a Sears unit, "Genie", I think? Pretty hefty size door. 2-car with hurricane braces. Probably a 3/4 horse.

Reply to
mpm
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4

Oh, I should also have added... Each electric eye has an LED.

I suspect one is a transmitter and the other is a receiver. (?)

Anyway, the one with the GREEN LED is on all the time. The other one (receiver?) has a RED LED which toggles on or off depending on whether the beam is obstructed. RED =3D Clear, RED off =3D obstructed.

Please note that the LED's behave this way when (I'm pretty damn certain) they are aimed correctly, yet the door will not close. (It also might not open, but I didn't test that). And as I mentioned previously, the DC voltage doesn't seem to change much, if at all regardless of what the LED's are doing.

-mpm

Reply to
mpm

Start here:

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--Winston

Reply to
Winston

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3/4

The signal could be pulsed (modulated), and you won't see them with a DC meter.

Reply to
linnix

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a 3/4

Good point. I honestly didn't think of that. I just assumed something as "industrial" as a garage door opening would be "simple".

Reply to
mpm

No, they are usually modulated to prevent problems from other light sources.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
Reply to
Michael A. Terrell

In today's world, nothing is simple!

A common scheme is to pulse the led, and measure the drop on the receiver's power suppply. This is done by wiring both to the same (current limited) power source, sending a pulse and looking at the current drawn. Too little current, and the system knows the sensor eye is blocked, enough current and it knows the sensor is seeing the pulse from the LED. Pulsing is used to both allow comphensation for ambient light, and to provide a basic reference point for the blocked sensor mode (OK, these are basically the same thing...)

Reply to
PeterD

That's exactly how this one's wired. So, I guess it really is an alignment issue.... Sure didn't look like it though. Maybe I can tie a string (tight) across the door opening and aim them that way???

This sounds like a pain in the ass...

Reply to
mpm

(...)

Did operation improve after you cleaned the lenses?

--Winston

Reply to
Winston

On Tue, 18 May 2010 05:41:34 -0700, mpm wrote: [snip]

Try a laser pointer or one of those levels with a laser.

The opener I have the receiver LED turns on when they are aligned.

--
Joe Chisolm
Marble Falls, Tx.
Reply to
Joe Chisolm

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