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.
Best Answer
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.