xEM access controller for garage door question

Hey guys I found a video where someone who used their access controller to open their garage door. In the video the guy uses an automotive relay in the set up, is this necessary? I was just gonna use some bell wire from the xEM controller to the terminals on the garage door motor where the indoor controller attaches. Is there a reason this won’t work?


The controller won’t support much more amperage than necessary for a signal. If you pull too much, you’ll toast it. That being said, I don’t know how much amperage your circuit would pull. Better safe than sorry.

The relay is really easy if that helps. Plus there’s plenty of people here who would walk you through it.


Check these out, should give you a good starter…


Thanks I’ve seen both videos, I just wasn’t sure if I needed the relay or not, as far as I can tell the bell wire used by the original opener control carries a 12v signal to opener. If that’s the case it seems like just wiring the access controller should work, however sometimes I think I fall into that “knows just enough to be dangerous” catagory so I’m trying to learn why the relay needs to be there. I build circuit boards for a living but half the time I don’t know why a part goes where it does.

Yeah use a relay. The reasons are legion… but in short the garage door opener is an unknown circuit and you want to push power into it from a totally separate circuit. First you’d have to share grounds to make this work, and second it might not actually be power it’s expecting… meaning it might not be a chassy ground line on the garage door opener side… you could burn out one or both units connecting them directly together.

The garage door system is expecting a complete short (button press) and you’re accomplishing that with the relay while keeping the two circuits totally separate.


Since you have seen both (3) :wink: of the videos above did you also see the wiring diagram (the diode is back to front, so you will need to flip it.


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Lol ya thanks saw ALL the videos. What is the diode for in the circuit, and would a Reed relay be better than an automotive relay? I was hoping this would be a good lock down project but I don’t think I have anything I can pull a relay out of. Thanks for all the help guys. O and from my research it looks like the opener activates with a 12v signal.

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Diode is there to protect the xAC from a back current from the relay coil when deenergized.

The reason people use automotive is there 12v, plenty of amps, easy to get and cost little.


So I used the em controller to power a relay that just acts as a switch for a remote, you could use the same setup for a garage remote


actually this would likely result in something burning out… do not push power from one circuit into another. the door strike is not a circuit, it is a load… but the garage door opener button is not a load… it is at best a sensor for the button pressing circuit in the garage door opener… do not push power into foreign circuits… you’re gonna have a bad time.


Edited ( Removed ) statement


Ok so what I’m getting from all of this is I need to get a 12v spst automotive relay with the built in diode across the coils. And I should be safe wiring it the way the video shows? Is there anything else I’m missing. I think in the video comments you mention connecting the wires to the wall button, is that the best way or can I just run the wire from the relay to the terminals on the garage door opener?

I’ve seen relays with diodes internally. They’re used to dissipate (hopefully harmlessly) the voltage spike that happens when you turn off a relay.

The recommended setup is to install the diode between the relay and the XaC (in series), the internal ones are set up in parrallel with the coil. I don’t know for sure that the parallel setup would completely protect the circuit, but the series one (with a separate diode) will for sure.

Regarding the wall button. If it just contains a simple switch, then yeah you could just jack into that circuit anyplace. BUT>> If it has circuitry that communicates with some sort of signal, you can’t hope to duplicate that, and you’ll hafta hook in to the button so that the correct signal can be generated.

That second scenario seems unlikely, but I’ve not seen your garage door opener, and I just want you to make sure you get it on the first go.


The only reason I was looking at a relay with the internal diode is because that’s what he says he is using in the comments. I agree I definitely want to get this right the first time. In your opinion it would be better to just connect an external diode like a IN4001, or something similar. Like I said I know just enough to be dangerous lol. Thanks for the help.

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Pictures worth 1000 words take a look at this;

Basically the simplest way to hook it up would be to connect the relay to connect the 2 sides of the open button inside your garage. (Providing you can press open and it will open without you needing to hold it).

Not trying to dumb things down but just incase;

  • COM is common to both outputs its the input of the switch.
  • NO is normally open, com connects to this when a valid tag is scanned
  • NC is normally closed, com is connected to this when relay is un powered (no tag or invalid tag)

D1 prevents back feeding into the xAC output.
D2 (purple) provides emf suppression when the relay turns off.


Bingo! Diodes are cheap, and dollar for dollar one of the best things you can add to any circuit or home project!

Simple and really effective circuit protection, and even if your relay has a diode, or another circuit you connect to has a diode on the input side, another usually wont hurt (for power and 12v signals, for small signals its a different story)



Thanks believe me dumbing it down is not a problem I’m taking this a a learning experience as well as a project. It’s crazy with my job you give me the parts I need and I can put it all together and give u nice clean solder joints, most of the time I can even tell why something goes where, I can troubleshoot a board and find a problem but trying to figure this out is really hard. Thanks for the diagram and the explanation.


The gaming market agrees… REG L-E-DIODE ALL THE THINGS!

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9 posts were split to a new topic: Wiring Wiki / Video Discussion

Found another potential problem. My openers use security +2.0 so they use a rolling code system. It seems like I would have to pass a signal through one of them somehow. That seems like a bad idea. Any thoughts?

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