Sniffing Wired Garage Door Opener Signals


In addition to being something fun to do with an oscilloscope, this could be a valuable time-saver for anyone looking to tap into the wired communications on a garage door opener. If you own an older model you might be scratching your head. But newer units have more than just one button operation, usually extending to at least two extra buttons that control the lights on the motor unit and lock out wireless control. A quick probing turned up the communication scheme used by the button unit mounted next to the door into the house.

We’ve patched into our own garage door using a simple relay to interface with a microcontroller which will still work for opening and closing the door But if you’re looking for extended control you need to spoof one of the timing signals detailed in this post. We like the stated examples for future hacks: building a better wired button unit, or adding some type of RFID integration. We could see this approach for hacking in motion light control for door openers that don’t have it.

[Thanks Victor]

6 thoughts on “Sniffing Wired Garage Door Opener Signals

  1. when i was a crane driver, i also worked on tower cranes. one day i was buiding up the crane when a garage door in the same street openend. It was because the crane send out com signal on 7 frequencies. luckily the owner was home en coud turn the door off.

    1. We used to have some amateur radio equipment near the top of the 1000′ tower owned by channel 11 in Atlanta. It had the luxury of an elevator car that went all the way to the top. The original controller operated in the 27MHz band and used some kind of tone system to indicate up or down.

      To avoid false starts, the tone had to be present for 5 or 10 seconds. It worked well enough, but it made it next to impossible to jog the car very well. Once we reached the 960′ level to exit the car, we had to drop it about 10′ so we could open the equipment cabinet doors. We’d have to have someone on the ground to use the manual controls to do that.

      The fun part was when there was enough interference that the receiver at the tower base couldn’t hear the transmitter in the car. On some occasions, the car would suddenly stop for 15 or 20 seconds while Bubba, on his over-modulated 2KW “foot warmer” reporting the local bears or what seat-covers to check out ,passed by on the nearby interstate.

  2. I don’t know how new is new, but my ~10 year old Legacy 696CD/B used a couple resistors in the wired remote. The remote has the door opener button, the light button, and a switch to lock out the door from being opened with any remote. At one time I had the schematics for the remote, but I can’t find them now.

    I did the same old trick with the relay, so I could use the user-controlled outputs on the alarm panel to open and close the garage door with a keyfob remote that works with the alarm system for other purposes, and has FAR better range than the traditional garage remote.

  3. After slapping together an app with appinventor for my phone, hooking up a relay, bluetooth module, and an arduino micro to my garage door opener a few months ago…I was looking for a “phase 2”. How is it that HAD always seems to pull through with the inspiration I need right when I need it? Thanks to everyone involved for keeping the ball rolling.

  4. Anyone know if the LiftMaster unit is compatible with newer Genie “professional” units? My new house has the latter, yet my move here separated me from easy access to an oscilloscope. I’ll probably buy one of the usb jobs someone soon, just for this purpose.

    My openers also have open, light, and wireless lockout on a two wire system. Unfortunately, the wireless receiver fails to allow more than four remotes to associate, which stinks when you have two cars, a wireless keypad, and still want to have a couple of remotes for waking around or as a spare.

    I usually have my phone on me, and I get WiFi signal in the driveway. I’d like to leverage that. I do network security for a living, and I’d like a project that goes over the top, just for fun. I’m thinking this is the one.

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