How to integrate 'Liftmaster' garage door..

[felixrosbergen]

Hi all,

My garage door is a new 'liftmaster'. The wall control has 3 buttons (Open/Close, Light, Lock)..however there's only 2 wires going to the control. This must mean that there is some sort of protocol that the keypad unit used to communicate with the motor unit. Either that or different voltage levels or something.

Anybody integrated a liftmaster unit? This doesnt appear to be as simply as putting a relay in parallel to the button between the 2 wires.

 

[beelzerob]

Ya, I had thought that too with my genie. But then I decided just to short the contacts on the back, and sure enough, it opened!

Turns out the light button controls some kind of modulation of the signal, or something like that. So there is no protocol. Just short 'em and it should work.

I was worried too since the wall control is lit, so that meant it was getting power somehow, and so I didn't feel like shorting that. But it has no ill effect.

 

[CollinR]

Be aware that although it's very easy to control the door, it's very expensive if you lower it on your car. So you might expand on the existing photo beams to prevent issues like that.

Also DEFINATELY read over BSR's writeup he did on garage doors, very good info in there.

 

[Lagerhead]

This doesnt appear to be as simply as putting a relay in parallel to the button between the 2 wires.

FWIW. YMMV. Etc.

Actually it probably is that simple. I have one of these button sets and have it working off my M1. First, the opener provides AC low voltage (14V?) on the two wires to the button set. This provides illumination as well as sensing.

The "Open" function puts a dead short across the pair. The "Lock" functcion puts a single diode across the pair. These two functions I have implemented with relays in a M1XRB, one shorting the pair and the other with a diode (simple like a 1N4002) in series. A 1-sec activation of either relay will activate the function.

The "Light" function it seems has three diodes in series. I have not needed this so have not messed with it.

 

[hucker]

Ditto for a genii garage door opener. Short the contacts and you are good to go. I have it hooked up to my HomeVisionPro on a relay. I don't use it to close the door unattended but I have used it to open the door for people when nobody was home.

 

[beelzerob]

Be aware that although it's very easy to control the door, it's very expensive if you lower it on your car. So you might expand on the existing photo beams to prevent issues like that.

Hmm...even I wouldn't mind adding another pair at car level. How would you add more sensor beams? Do you just get another pair and wire them in series?

 

[dutchyn]

The "Open" function puts a dead short across the pair. The "Lock" functcion puts a single diode across the pair. These two functions I have implemented with relays in a M1XRB, one shorting the pair and the other with a diode (simple like a 1N4002) in series. A 1-sec activation of either relay will activate the function.

What direction for the diode -- I know, there's only two possibilities ...

Also, any idea how the sensor beams signal? Is it a simple close/no-close signal?

Chris D.

 

[sic0048]

Be aware that although it's very easy to control the door, it's very expensive if you lower it on your car. So you might expand on the existing photo beams to prevent issues like that.

Hmm...even I wouldn't mind adding another pair at car level. How would you add more sensor beams? Do you just get another pair and wire them in series?

I would assume this is correct. If the beam is broken on either sensor, it would cause a break in the circuit. I could definitely see the advantage to adding a beam at the 2.5' height. Any part of a car that was in the way of the door should break the beam at this height. I lower beam may only be broken by the tires. It obviously depends on the height of the lower beam and the height of the car frame, but I think most beams would not be broken by a car that is half in and half out of the garage.

 

[dutchyn]

If the beam is broken on either sensor, it would cause a break in the circuit. I could definitely see the advantage to adding a beam at the 2.5' height. Any part of a car that was in the way of the door should break the beam at this height. I lower beam may only be broken by the tires. It obviously depends on the height of the lower beam and the height of the car frame, but I think most beams would not be broken by a car that is half in and half out of the garage.

If the 30" height is better, why not put the beams there in the first place?

Chris D.

 

[Herdfan]

[If the 30" height is better, why not put the beams there in the first place?

I would not be able to detect a child laying on the ground. The real purpose of the sensors is to protect children, not cars.

And I know this has been covered, but a reminder that you should never automate any type of motor or mechanical device when you can't see it operate.

 

[hucker]

If you want multi beams I wouldn't bother with extra active hardware, I'd get two (or more) mirrors and bounce the beam back and forth. I'd make the mirrors by gluing them to angle iron or something beefy. Before trying this make sure if there is not a distance limitation on the beam/detector.

one downside of this is that you can't activate the opener and run out of the garage...

 

[Lagerhead]

The "Open" function puts a dead short across the pair. The "Lock" functcion puts a single diode across the pair. These two functions I have implemented with relays in a M1XRB, one shorting the pair and the other with a diode (simple like a 1N4002) in series. A 1-sec activation of either relay will activate the function.

What direction for the diode -- I know, there's only two possibilities ...

I'm pretty sure it doesn't matter (AC, and both wires are white), but as you point out, if it doesn't work just reverse the diode.

Also, any idea how the sensor beams signal? Is it a simple close/no-close signal?

It's messy, at least for the unit that I have. See this post:
http://www.cocoontech.com/index.php?showto...ost&p=95536

 

[Lagerhead]

one downside of this is that you can't activate the opener and run out of the garage...

I thought I was the only person who does that.

 

[BraveSirRobbin]

Remember, you can always hack the remote as another option!

 

[dBeau]

Remember, you can always hack the remote as another option!

Hacking the remote was the only option for one of my openers. The problem was that anything longer than a 3/4 second press would only turn the light on. If you want the door to operate you have to be quick. As the "door bell" button got old, it got to be really hard to time it right. I thought the system was broken. The 20 year old opener came with the house so I never knew what it was supposed to be like. Since the Elk's relays shortest pulse is 1 second, I had to hack the remote. It didnt make the distinction between "only turn on the light" and "operate the door".