xEM access controller for garage door question

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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Hmm, depends on how you want to go about it. Are you sacrificing a remote or do you have wall mounted buttons you want to use?


Janky solution that could save you a remote is to use a motor to press the button on the remote :man_shrugging:

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That would still mean a remote permanently occupied. Unless your talking about a wall mounted remote in which case ther usually wired and are just dumb.

Even then if its a wireless wall mounted remote I still see no problem.

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Sorry should have been clearer. I was talking about not modifying a remote. I keep that stuff in mind as I rent so even if it’s reversible I wouldn’t risk my garage remote. :grin:

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Ahh I see. I mean you could definitely do it in a way that was non destructive and would not look suspect from outside the box.

But I mean yeah ofcourse you could use a servo with a little arm to press the buttons.

I never tend to think like that as the stuff I do is usually permanently fitted or atleast done in a way that can be detached and still work as “factory”


You maybe, but I am not so sure about me…



Pretty much any system is going to have a point of access. No matter how secure the communcations are, somewhere there is a button that you can push to activate it. That button pushes on a switch. A switch is nothing more than a connection that is opened or closed.

Regardless of how nice or getto you go about it, all you have to do is find the switch, and attach a wire to each side of it, then connect or disconnect as required via a relay controlled by the power of SCIENCE!!!

First law of ODaily, the first step to fixing anything is to break it so badly that it wants to be fixed.





When it is available

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Be good or the Toggleator will get you!!!


I have a wall mounted push button. I thought it was wirless but I took a look after I posted and it is the only thing in the garage that they actually ran wires through the wall for. So it looks like it’s just a normal push button opener. The only reasons it has a pcb inside is for it’s lock and learn functions.


Hey fellas… Couple questions…

  1. can I use a regular 87 relay or do I need an 87A? I bought an 87 by not paying attention and the auto parts are all closed right now (11pm my time)

  2. will this diode work?

The controller is reading the tag, but garage door is not opening or closing… And my diode should be on my signal wire with the silver band towards the controller correct?

The band should be towards the relay. You can double check with a test light. Clamp it on the negative and test before AND after the diode. You should get light on both sides if it’s correct. If the light only works before the diode, then it’s backwards. Think of it this way, the power is SUPPOSED to go through to the relay, so hot on both sides, but if the power is coming from the relay (BAD) then it should be stopped by the diode. So only hot on one side.

This confuses me. The relay should have 4 or 5 terminals (connectors, or pins). They are all labeled. If you have a 5 pin, one of them will be labeled 87A, but you won’t actually use it. Assuming we are talking about the same thing, then the answer is the one you have is fine. This may help. https://www.12voltplanet.co.uk/relay-guide.html

That diode will work fine.

About the Relay;

The terminals are labeled by numbers.
85 & 86 are the ones used to control the relay. One should be connected to ground. The other should be hooked to the white controller wire (with diode in between).

87 & 30 are connected when the relay is activated. You can hook them to the door circuit, or you can hook one to 12v and the other to something that will be turned on by that 12V

IF you use a capacitor, (this gives it a little time delay / hang time, but is NOT mandatory), then that get hooked between ground, and whichever terminal is hooked to the white wire. This should be between the diode and relay. So after the diode, but before the relay.

Also if you use an electrolytic capacitor, they can only be hooked up one way, the negative side is marked with a stripe on the side.

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I have a 4-pin relay… My garage door switch has two wires a red and a black. I have 12 volt positive to number 30. Ground to 85. Signal wire from controller (with diode) to 86. And my red wire from my garage door controller to pin number 87