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.


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, 2017 at 19:09
  • Call and talk to Chamberlain.
    – Paul Logan
    Nov 28, 2017 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, 2017 at 20:49
  • I know this is almost 3 years old, but did you find a solution by reading the signal from the opener? I'm running into a similar problem trying to use my Particle door opener device that worked great for my previous garage door opener. Trying to figure out if I should go through the hassle of writing something to sample the opener signal.
    – Chris
    Jun 29, 2020 at 3:48
  • I actually took one of the remotes (I had 4 b/c we have 2 garage doors) and unsoldered the button connections and hooked them up to the PI so I could just "push" the buttons like that.
    – mikeb
    Jun 30, 2020 at 10:51

3 Answers 3


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.


  • 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, 2017 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, 2017 at 20:54
  • Didn't work, I tried .1, .2, .5 and 1 second.
    – mikeb
    Dec 1, 2017 at 20:33
  • Called them, see my edit, basically they won't support it.
    – mikeb
    Dec 1, 2017 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, 2017 at 22:02

I know this is an old thread but I figured out a work around. Just need 22 gauge wire(security?) and a soldier gun. You can still use a standard relay by 5 minutes of tinkering with the encrypted wall openers. Just connect these soldered leads. Touching these cable together opens the doorsThis technique works on both types of Chamberlain wall switches I have


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, 2017 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, 2017 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, 2017 at 16:35

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