Z-Wave Garage Door Opener with Chamberlain HD220

I recently purchased a GoControl/Linear GD00Z-4 Z-Wave Garage Door Opener on clearance from Staples for about $40, quite the deal. However, after following the instructions to get it installed, it didn't work. (I would activate the door from my phone and the lights on the back of the garage door opener would flash, indicating that something was working, but the door wouldn't open or close.)

Turns out that my garage door opener (a Chamberlain HD220) is too new and fancy to work with a general door opener like this one. This Z-Wave opener has a relay that goes in parallel with the wall button and pulses it to simulate a button press. The button on the wall that came with the Chamberlain unit is actually more than just a contact -- there's a whole printed circuit board behind it and presumably it sends some sort of serial command when you press it.

A poor quality picture of the board behind my wall button. Note the clicky switch  SW2 on the left.

I briefly thought about putting a logic analyzer on the bell wire going out to the switch and putting a microcontroller in line to spit out the same commands, but that's way too much work.

Even though the wall button isn't just a button, there is a button on it (SW2 above). The relay in the Z-Wave unit just has to go in parallel with that button. It wasn't too pretty, but I soldered on a hobby JST connector (not the ideal wire because of its size and many strands, but it works) so that I could do a longer wire run to the Z-Wave unit which is next to the physical garage door opener.

The button board with JST pigtail connector.

Close-up of the switch and solder-job. I'm not proud.

The bell wire that pigtails out of the Z-Wave unit wasn't long enough, so I extended it with some old telephone wire that I knew I'd been saving for something, but any wire with 2 conductors in it would work.

The button back together and on the wall.

Now the Z-Wave unit can effectively push the button on the wall, which is how it is meant to operate.

I got the idea from this forum post. Note that this should work on Liftmaster, Chamberlain, and Craftsman garage door openers that have smart buttons.