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I have one of these: http://support.chamberlain.com/articles/How_To/Chamberlain-Models-B550-B750-Owner-s-Manual

On my old door, I wired a relay in to the same terminals the push-buttons (like doorbells) on the wall used to open the door. The new opener uses 2 wires (in fact the same wires the old switches used) but they have lights and programming and opener buttons on them. They must be doing some magic on the circuit to tell the door what to do. How can I get my relays to work again?

I do not see any places to put push-button switches into the unit on the ceiling. Any suggestions for how to do this? I'm controlling the relays with a Raspberry Pi via the Internet, and the open/close sensors are working fine.

EDIT

I tried .1, .2, .5 and 1 second and nothing works.

Called Chamberlain and they said I have to buy some hardware and have a "partner agreement" with them to have my own software work with it.

Boo Chamberlain, next time I'll be buying something else.

  • I guess you tried the old-style doorbell buttons and that didn't work? – JPhi1618 Nov 28 '17 at 19:09
  • Call and talk to Chamberlain. – Paul Logan Nov 28 '17 at 19:47
  • I called chamberlain and they were useless - won't work unless you have a partner agreement with them. I'd have bought something else if I knew that. – mikeb Dec 1 '17 at 20:49
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Your existing setup will still work even with the new magical control panel that works with 2 wires. A relay wired in parallel that momentarily closes the circuit will activate the garage door. The most likely cause is that your relay is staying closed too long, so adjust it so it's only closing the circuit for 0.2 seconds. You can test a few timing values to find the best one, it might work best as quick as 0.1 seconds or as long as 0.5 seconds.

Test this first by shorting the terminals on the back of your control panel for a split second to verify that this action activates the garage door.

If the test works and the relay still doesn't work, make sure that you wired it in parallel and not in series.

Controls

  • This works for me - my opener has the fancy multi-button light and program button on the wall on one side of the garage and a standard old-fashioned doorbell button on the other side. The doorbell button works as long as you press it for the correct amount of time, around half a second. – Moshe Katz Nov 29 '17 at 18:32
  • Thanks, I will try this and report back. I'm using a Raspberry PI to drive the output to the relay so I can adjust the relay firing time. – mikeb Nov 29 '17 at 20:54
  • Didn't work, I tried .1, .2, .5 and 1 second. – mikeb Dec 1 '17 at 20:33
  • Called them, see my edit, basically they won't support it. – mikeb Dec 1 '17 at 20:50
  • @mikeb I read your update, you can wire the relay directly to the PCB push button switch inside the control panel. – Dotes Dec 1 '17 at 22:02
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Since you are using a Raspberry Pi, why not connect the control wires to your Pi and write a simple program to sample the input port you connect them to? Then just hit the open button and see what it's sending to the opener. Once you have that signal recorded, you just repeat that exact signal as an output.

  • I guess that's what I'll try next. The Pi only has digital inputs, but I suppose I could read the up/down timings and figure it out, is that what you mean? – mikeb Dec 2 '17 at 16:04
  • Yes, if the control pad is sending a signal to the garage door, it's almost certainly a digital signal. By sampling every X times per second, you will see what it's sending, and by just recording that and playing it back out, it will likely open the door. I doubt the hardwired control pad is secured and that the output is likely to change over time. – alfreema Dec 3 '17 at 17:53
  • OK, thanks, I'm going to try this. The Pi API has a feature that allows you to detect "edge" events, which are an up/down state change on a DI. I can just log the DI state changes with a timestamp (to the millisecond) to determine the pattern. I just have to figure out how to get the wires to where I need them. – mikeb Dec 4 '17 at 16:35

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