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Is anyone here electrically inclined?

by Jack Gordon
11 replies
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My office has a steel door.

It also has a biometric fingerprint lock (gotta keep out the riffraff). You can see it here

When I touch the biometric lock on either side of the door, it beeps at me. Sometimes when I just touch the door, it beeps at me. It has also been known to shock me. None of those things are supposed to happen. It should only beep when I press the button on the outside telling it that it is time to read a fingerprint.

I can't help but suspect this is some sort of a grounding issue, but it only uses a battery. Clearly, I am out of my depth.

Is that enough information to offer any kind of a preliminary diagnosis?
  • Profile picture of the author Frank Donovan
    Jack, can't help you with a diagnosis, but now I have this picture in my mind of your office:

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  • Profile picture of the author dremy154
    Sounds like ground or short. Shocking would be ground, the unexplained beeping, a short I would say. This unit is essentially self-sustaining, meaning it has a battery, and most certainly a capacitor. The capacitor draws energy from the battery and stores it for later discharge. Hard to say without seeing a schematic/wiring diagram. No expert. HVAC/refrigeration in the Army 25 years ago, but also trained on power generation.

    By the looks, it uses electromagnetism to unlock.

    The capacitor must be releasing a good amount of current for it to noticeably shock you.

    Short(beeping), and/or ground(shocking), possibly the unit itself is grounding out on the door?

    Check if there's any contact between the locking unit and the door(any metal to metal)

    Hope this helps?
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    • Profile picture of the author Jack Gordon
      Originally Posted by dremy154 View Post

      Sounds like ground or short. Shocking would be ground, the unexplained beeping, a short I would say. This unit is essentially self-sustaining, meaning it has a battery, and most certainly a capacitor. The capacitor draws energy from the battery and stores it for later discharge. Hard to say without seeing a schematic/wiring diagram. No expert. HVAC/refrigeration in the Army 25 years ago, but also trained on power generation.

      By the looks, it uses electromagnetism to unlock.

      The capacitor must be releasing a good amount of current for it to noticeably shock you.

      Short(beeping), and/or ground(shocking), possibly the unit itself is grounding out on the door?

      Check if there's any contact between the locking unit and the door(any metal to metal)

      Hope this helps?
      That does help, quite a bit. I had a nagging feeling it was going to be something like that, but I don't really know what I don't know, and wasn't sure I would recognize what to look for if I did open it up.

      One thing I am unsure of is if the fact that it is a steel door makes this issue unsolvable, because of course metal will be touching metal, or if there is a specific point of contact that can be nullified.

      I'll break it open and see if I can get a feel for that.

      Thank you!
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      Fifteen Lessons I have learned over 15 years and six businesses (or, My 1000th-Post Manifesto)
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      • Profile picture of the author dremy154
        Originally Posted by Jack Gordon View Post

        That does help, quite a bit. I had a nagging feeling it was going to be something like that, but I don't really know what I don't know, and wasn't sure I would recognize what to look for if I did open it up.

        One thing I am unsure of is if the fact that it is a steel door makes this issue unsolvable, because of course metal will be touching metal, or if there is a specific point of contact that can be nullified.

        I'll break it open and see if I can get a feel for that.

        Thank you!
        Well, there are two parts to the mechanism that mount on the outside of the door; take them off. There should be either an o- ring type, or boot type rubber piece. Start with the simplest possible cause, and go from there. Hell, it could possibly be a loose screw on the back of one of those two parts.

        Hope this has helped.
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  • Profile picture of the author goneill
    To add to what Dremy154 says,

    Does it happen when the door is open or closed ? (possibly pinched wiring)

    other possibilities damp (condensation)

    If you follow Dremy154 logic, I am sure you will find the cause
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    George ONeill

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  • Profile picture of the author dremy154
    Sometimes though, it takes some knowledge, and a multimeter unfortunately.
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  • Profile picture of the author goneill
    Hi again

    If you can access the keypad easily, remove battery and use a spray pcb board cleaner and allow to dry

    (follow instructions on can) then replace with a new battery and see what happens?

    (usually it blows the bloody door off, sorry British humour)
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    George ONeill

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