After some cases of vandalism (objects inserted in the lock from outside) I would like to get rid of this single point of failure by adding, on the internal side of the lock, an electro-mechanical mechanism to turn the lock from the inside. It would be powered by an Arduino.

I know that there are electronic locks (the ones I saw had various issues) or anti-vandalism ones (no electronic parts) but I would like to try to roll out my own.

The problem I am having is that I could not find anywhere an insert which would be

  • normal on the outside part of the door (a classical hole for the key)
  • hackable on the inside part of the door,

probably something like this

enter image description here

where I could attach something (a motor for instance) instead of the knob.

Do such inserts (cylinders) exist?

  • 1
    How is this going to stop vandalism? Commented Sep 2, 2016 at 11:25
  • @CarlWitthoft: it is of course not going to stop vandalism. What I am mostly annoyed with is that each of such an event (when we are not home) means getting a locksmith urgently (premium rates) so that he spends a long time breaking in (with the family waiting outside), then getting a "whatever lock he has" to have a working door, etc. My aim is not to replace the lock (it could be used either traditionally with a key, or remotely via my system) but to be able to enter the apartment and change the lock with a quiet mind. There is no much vandalism but event two of such events are enough.
    – WoJ
    Commented Sep 2, 2016 at 11:31
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    What ever track you take make FULLY sure that the locking release can be easily manually operated from inside the structure. Last thing you want it to be is trapped inside when the electrical power is failed and flames are flashing around, flood waters are rising or a tornado is coming.
    – Michael Karas
    Commented Sep 2, 2016 at 21:37
  • Does the door use a standard door jamb strike. If so could you replace that with a electric strike using the Arduino to control it ( have done one of these). Likely easier then a lock core modification. Commented Sep 3, 2016 at 2:31

1 Answer 1


The "knob" cylinder shown in your picture is probably as close to ideal as you are going to get. Just modify the knob so you can attach your motor, directly or via drive belt or whatever.

It sounds like a better solution would be to either install a guard over the keyway so the kids can't tamper with it, or to switch to a keyless system so the problem can't varied in the first place.

I presume the apartment does not have a second door so you can't just go around that way.

  • Have the motor drive a belt that uses the knob as a pulley, or replace the knob with a pulley - and make sure it's set up so you can still operate it by hand, as noted by Michael Karas. And invest in a door camera (or two, one obvious, one not so obvious, so it can record the vandals attacking the obvious one)
    – Ecnerwal
    Commented Sep 3, 2016 at 2:14

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