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Can two LiftMaster 882LMW multi-function control panels be wired in parallel? Has anyone looked at the PCB to see what it is populated with?

The opener is a LiftMaster 8365W.

Thank you.

  • Seems like this would be a good question to pose directly to the manufacturer. Check for a "contact us" link on their web page. – FreeMan Jun 9 at 17:24
  • I have contacted the manufacturer and they were not helpful. They cried liability blah blah blah. My educated guess is that it is just a resistor network which creates an analog control loop of various voltage or currents depending on which switch is pressed. I’ve ordered another switch for reverse engineering and testing. – mike Jun 9 at 17:49
  • Glad to hear you took that step. It's generally good to include that in the initial question so people don't have to ask/suggest it. Based on your profile, sounds like you may be one of the better qualified people around here to do the experimentation necessary to find out if this is possible and to make it work if it is! If you do some experiments, it would be great if you came back and posted your results as an answer to share your knowledge with the rest of the community. When you need a break from tinkering, you'll find it helpful to take the tour and browse the help center. – FreeMan Jun 9 at 17:54
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    It'll be a few weeks, but yes I can share the results. – mike Jun 9 at 18:12
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The short answer to the question is yes, two LiftMaster 882LMW door openers can be wired in parallel and work.

Please note that you cannot simply place a doorbell switch or any dry contact in parallel and expect this to work.

The long answer is that the 12Vdc coming from the garage opener itself is not just a DC voltage; there is a variable frequency PWM signal riding on top of this which communicates to an embedded STM8S103F2 microcontroller in the 882LMW.

I did not take my scope to the PWM signal, but my multimeter picked up a frequency range of ~6-14kHz. The MCU likely uses input capture mode on a timer, and then returns the message with another PWM signal superimposed on the 12Vdc, or something like that.

Here is a picture of the back of the PCB.

enter image description here

My requirement is to make use of a computer controlled relay (dry contact) to open my garage. I simple soldered two leads across the micro pushbutton and wired them to the relay. My wires from the garage are now screwed to the terminals labelled red and white.

This works in parallel to the other 882LMW that's located in the entryway of my house.

I am not tinkering with this any further as I won't be able to reverse engineer the embedded firmware in the MCU, and it works the way I left it.

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My recollection from playing with LiftMaster multi-function controls several years ago, though not specifically that model, is that they couldn't handle having multiple multi-function controls attached to a single opener. Seems like I found that it uses a digital (serial) communication between the control and the opener. IIRC I also found that it would not operate properly with one multi-function and one pushbutton switch.

Your best wired alternative is probably to set the multi-function control aside and instead use multiple normal "dumb" switches (an unlighted doorbell button, for example).

An easy option is to install the 882LMW in the primary location and mount battery-powered remotes (like what you'd keep in a car) in the other location(s).

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