I’m trying to connect an xEM Access Controller to my Liftmaster garage door opener following this video. The door opener I have is newer and has an LCD display and when I short out the terminals in the back it resets the opener. When I check out the voltage it’s 12v normally and drops to ~9V when I press the buttons. I say buttons because the big button actually actuates two microswitches on the panel. I am attaching pictures so you can see what I’m dealing with.
Taking it off to get that picture turned off the switch. I think what’s happening is that the wires provide power to the switch but it connects to the opener wirelessly. Which would explain why shorting them out reset the switch since it was losing power.
Yes this is like a dumb HVAC system supplying power to a digital thermostat through the temperature control wires. You can’t just short these because the device is “smart”. What you will have to do in this case is find this actual micro button switch on the PCB and carefully solder to either side of that switch only to short those paths that the switch normally shorts when you press it.
There are four posts on the switch, two of them are one side of the switched connection and two of them are the other side. There are four of them for stability and attachment to the pcb. The easiest way to test this is to simply use a paper clip to short two of these four connections together and if you short them and the door opens their closes then these are the two posts you need to solder the wires to that will lead back to their access controller relay.
There are two because the plastic “button” you actually press down on is so wide and it’s easy to put a switch on either side vs trying to balance the whole plastic thing on a single switch in the center… it would also cause stress on the microswitch if you normally press the plastic button on just the side and not dead center… better for longevity etc.
You might want to look around for places that have them for use. I’ve seen them in libraries, and you can find maker places (kinda like a gym membership, but with cool toys instead of sweaty machines).
It’s working!!!