Modding a Door Lock Rev 3

Alright, back again. For those uninitiated with this saga, I’d recommend you check out my original post and follow up post to get the full scope of what’s going on.

I recently got a xEM AC V2 and have been playing around with those two crucial top wires (see last post) and seeing where things go. I’ve tried all manner of configuration with the yellow and white AC cables, as well as shorting the top two wires when reading the ID card. If I short them with an exposed strip in the middle this while connecting top pin to top hole and second pin to second hold, the reader flashes green for a second and then orange. No luck on actually getting it to open, though. I wondered at first if it was a voltage error since the AC outputs 9 to 12 v while the motors in the door take 4.5V at most, but no dice even after running it through a stepper. I thought given it was only two wires that it couldn’t be super complex, but that is probably why I am not an electrician.

Another proposition. With an xEM AC V2, I’m wondering if I grab a servo like so and then just rig it up to either turn the internal door knob directly with brute force and a big enough servo arm or utilize its large turn radius with an attached string for the servo to pull that is subsequently attached to the inside handle, like some sort of horrible tooth extraction. Granted this all assumes the xEM AC is capable of giving a signal to the servo in the way that I need it to. Unless what I need is more in line with a DC motor? My knowledge of electronic ends just about at the concept of positive and negative. What do you guys think?

Note: The inside handle of the door is always unlocked for easy egress


Unfortunately it will not. The output of the XAC is just but a relay, which connects two pins together at a time (NC and COM, and NO and COM). You’ll need some sort of microcontroller to convert the connections from the XAC to ones which the servo will accept (PWM / pulsed output signal).

Potentially a DC motor could work, given a proper power source. Main challenge will be torque / mechanism which would rotate / pull it back to locked in an unpowered state.

In regards to previous discussions - the options for working out what happens on those two wires, in (generally) increasing cost are: digital multi-meter (DMM), logic analyser and oscilloscope. Even a $10 - $20 USD DMM could provide some insight into the logic level / polarity of the signal going to the lock.

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This might be part of the issue: afaik XAC does not output a voltage, instead it is a relay which, like my above message says, actually just connects two pins / wires together - idk exactly how you wired it, but you need an external / additional power source.

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