srodgers - good tip with the two contacts - for full open vs. just not closed.
Most people use a contact like
THIS or
THIS (I use the latter) - so you need a pair of wires at each door for the contact sensor.
For control of the door, really it depends on you and the opener. In the old days it was much easier - you just short the button wires at the motor and that triggers the door. However, most modern day openers come with the smart control panels. They're still 2 wires to the motor, and honestly you can still usually just short the 2 wires at the motor to cycle the door, but these things that have clocks and temperature sensors and all that - it makes them reset when you do a hard short on the wires. This has posed a dilemma in automating garage doors the last few years. People are stuck with:
1) not caring about the smart panels (they're not required - you can replace with regular buttons and they'll function just fine) - then you can still wire to the motor;
2) Wire to your wall buttons and solder to the button contact points. This simulates pressing the button on the controller without screwing with all the other electronics on the thing.
3) Hack a remote -
here's a writeup showing how... this is especially helpful if you don't have wiring near your buttons - but with these new controllers it has the drawback of being disabled by the smart controller turning off remote access (a feature of many of them).
In my opinion, I'd like the option to disable the built-in wireless controller completely and use my solution only - requiring hardwiring at the motor or switch. At least, that's best case scenario. I haven't done it and haven't been motivated enough - but if I have my security hat on, I want something even more secure than the run of the mill RF remotes that every garage door in America comes with augmented with my own security. What I did get to is throwing the smart buttons in the trash and using regular buttons - then I can do regular momentary contact closures at the motor. Additionally, the wiring goons who prewired this house used Cat5 to the sensor eyes so there are extra pairs there - I used those for my contact sensors - so I only had to run a single Cat5 across my garage ceiling by the motors to pick up both doors and both sensors over to my little sub-panel.
