Garage door opener sensors - how do they work?

In addition to the photo sensor, there are also usually two "sensitivity" limit adjustments for maximum force to both open and close the door. Check your owners manual and learn which of these controls the down force limit. You should verify that the door springs, rollers, etc. are all operating as designed and there is no binding or a mechanical problem. You can do this by removing the door emergency release latch and operating the door normally by hand. It should go down and up fairly easily and stop at around mid-door on its own if the springs are calibrated properly. If this all looks OK, re-engage the eclectic opener on the door and experiment with increasing the down limit sensitivity to see if this is the problem.

Based on the photo detector lights being illuminated, I'd suspect the door close force limit is the problem and it might be as simple as greasing the drive and track to reduce the friction and get it back to where the limit was previously set. (This is set for safety just in case something or someone is under the door while it is closing.)

Good luck!

Bob

Chamberlain. Brand name is "Access Master" but they also sell

Liftmaster.

overhead light flashes 10 times. Door can be made to close

signal from the photo sensors, yet the lights on both

be the sensors or the logic board in the unit.

how the sensors work and I don't. "Transmitter" and

figuring what signal's going where and how, is it AC or

but any info at all is appreciated.

In one of my former lives (Errr... wait... it was this life, wasn't it?) I logged a goodly number of hours installing or otherwise working on garage doors (with and without openers), and this screams "The sensors can't see each other" at me. If they're out of alignment (Tabs bent, turned on their mounting screws/bolts, etc) so that the can't "look each other in the eye", it's just the same as if they were broken. Basically, the concept involved is that each one of the units has a light source, usually quite directional, and sometimes a specific color, and a light sensor (tuned specifically for the color being used in the ones that are particuarly finicky). When the door-travel path is clear, each one can see the other's light, and is probably sending a "1" signal as long as the beams are unbroken. "AND" the two signals together at the controller logic-board to get "1", and the opener works. Block one or both beams, and one or both of them switch to sending a "0". "0 AND anything" equals zero, so the controller says "PROBLEM!!!!" and refuses to work without going into some sort of "override" mode. (your "hold the hardwired button down" process)

Just because they're pointing roughly at each other doesn't mean that either one is able to see the other's light...

You're probably going to need to rig some sort of "beeper" to help you re-aim the sensors - Something that, when the sensor says "I see the light!!!", gives you some indication that it noticed. We had a little gizmo that clipped onto the sensor wires and made a quiet, but quite effective, "beep beep beep" as long as the sensor could see the light source, and went silent when it couldn't. The aim is surprisingly critical.

it's probably DC at that point, but that's not a certainty. AC is almost certainly only connected to the motor itself, with a DC supply for the logic board/controller.

Bob,

Thanks for the info but I've actually checked that already!

The "force sensor" isn't actually a force sensor at all, rather it detects changes in the motor's RPM (there's a photointerrupter sensor on the motor shaft) and senses the load that way. Therefore to measure force, the motor must be turning. In the case of my unit, it doesn't activate the motor at all - it immediately goes to "flashing lights" mode as soon as you press the button.

Eric

Don,

Thanks, but the sensors definitely are "seeing" each other. Both LED's are lit (continuously - I know flickering is bad), and when I block the beam with my hand the receiver LED goes out. I've heard of sunlight causing problems, and the sun does shine toward the receiver in the afternoon, but when I shade the sensor it still doesn't work.

Eric

lit (continuously - I know flickering is bad), and

sunlight causing problems, and the sun does shine

doesn't work.

-- Sunlight... Grrr....

Our garage door faces north, so we only had a problem in the summertime. For the first 3 years in our new house, until the landscaping grew enough to block the setting sun, we had to send somebody out of the car to provide shade for the receiver in the late afternoon/early evening, or we couldn't close the garage door.

If the LED on the receiver goes out when interrupted, AND you have a good connection from the receiver to the opener, the only other thing left is the controller in the opener. Have you checked continuity of the wires from the receiver to the opener? If the wires are OK, put a voltmeter across the wires at the opener, see if you have a different voltage with the receiver blocked vs. not blocked. If you see a difference, I would suspect the controller in the opener.

--

Jerry Maple General Dynamics C4 Systems Scottsdale, AZ Ofc:480-441-2700 Fax:480-675-1449 snipped-for-privacy@gdds.com

lit (continuously - I know flickering is bad), and

sunlight causing problems, and the sun does shine

doesn't work.

I've had the same issue several times with a Sears opener, despite the LEDs being on, re-aiming has always solved the problem. The aim has to be way off for the led to start flickering or ven go out. Try cleaning the lens faces too.

-Chris

(continuously - I know flickering is bad), and

sunlight causing problems, and the sun does shine

doesn't work.

I work in the Apt. industry. I have adjusted over a hundred garages. Those leds on the sensor can stay on and the sensor still might not see the other one. The sensor is much faster then the light. It could be right on the edge of seeing the other sensor and that is why the lights are on. Try moving the sensors around a little and retest the door. 90% chance this is just a sensor alignment problem.

are lit (continuously - I know flickering is bad), and

of sunlight causing problems, and the sun does shine

doesn't work.

Chamberlain.

Liftmaster.

"ok"

either be

idea how

time

no

subject.

Brand name is "Access Master" but they also sell

light flashes 10 times. Door can be made to close

signal from the photo sensors, yet the lights on both

the sensors or the logic board in the unit.

the sensors work and I don't. "Transmitter" and

figuring what signal's going where and how, is it AC or

any info at all is appreciated.

My first guess would be a shorted photo-cell wire as in a staple being too tight somewhere & therefore the logic board isn't seeing the proper voltage from the sensors. Try running a temporary wire from the operator to the photo-cells to verify.

If they are both lit solidly, obviously they are both working & the board is putting out the proper voltage (it's low DC but I don't remember what it actually is). However if they are lit but "dim" that may be a different story.

Doordoc

Took the logic board out of the opener last night to see if I could figure out how the circuit works. Took all of 45 seconds to realize that *that* wasn't going to happen, but noticed one lead on a surface-mount device on the back of the board that wasn't soldered properly. 2 minutes with the iron, reinstalled board, works like a champ!

Thanks everyone for your help!

Eric Law

Brand name is "Access Master" but they also sell

light flashes 10 times. Door can be made to close

signal from the photo sensors, yet the lights on both

the sensors or the logic board in the unit.

the sensors work and I don't. "Transmitter" and

figuring what signal's going where and how, is it AC or

any info at all is appreciated.

Good job at sticking with it - it's always nice to come out the winner.

WT

out how the circuit works. Took all of 45 seconds to

surface-mount device on the back of the board that wasn't

a champ!

Chamberlain. Brand name is "Access Master" but they also sell

Liftmaster.

overhead light flashes 10 times. Door can be made to

"ok" signal from the photo sensors, yet the lights on both

be the sensors or the logic board in the unit.

how the sensors work and I don't. "Transmitter" and

time figuring what signal's going where and how, is it AC

but any info at all is appreciated.

Eric -

Like you, I live on the ocean, and I had a very similar problem. I futzed around with the aiming, the lens cleaning, the force adjustments, etc, for days, with no luck. Eventually, what I found was that the salt air had penetrated a tiny nick in the insulation of the small wires that connect the transmitter and receiver, and had corroded the copper wire inside the insulation. The only clue was a tiny dot of green crud on the insulation at the site of the nick. I cut the wires at the nick, stripped back the insulation, removed the corroded portion, soldered the ends, and sealed the joint with a dab of vaseline inside some shrink some sleeving. It started working immediately, and has worked perfectly for three years now.

I never figured out how the LEDs could indicate proper optical alignment when one of the wires was corroded, but corrosion may be something you could check for. Those tiny little conectors look especially vulnerable to me.

Bill Jeffrey ===================

EL wrote:

Brand name is "Access Master" but they also sell

light flashes 10 times. Door can be made to close

signal from the photo sensors, yet the lights on both

the sensors or the logic board in the unit.

the sensors work and I don't. "Transmitter" and

figuring what signal's going where and how, is it AC or

any info at all is appreciated.

out how the circuit works. Took all of 45 seconds to

surface-mount device on the back of the board that wasn't

a champ!

Congrats, slightly more complex than a normal repair then

Pull it to bits full of hope Look at the board Few expletives about little people with fingers like mice and a few expletives about disposable society Put it back together and test It works Make out bill Give back to customer Pocket cash.