The making of: My smart doorknob

  • My doors’ latch mechanism completely broke several months ago, as a result of the “spring” being permanently deformed, and rendered useless.
  • Metalworking is by no means my ::forte::, and given that the lock mechanism is circa 1900, my attempts to fix it were unsuccessful.
  • A doorknob is an item that is purpose built for being rotated many thousands of times, so would likely be durable enough for the project
  • It’s cool. And it feels like an, albeit nerdy, James Bond gadget

How I made it

  • Includes a 2xAA battery pack, so could be powered without a plug
  • Includes a Bluetooth radio, capable of sending UART messages
  • Can read analog resistance values
  • The kit it came with included crocodile clips, which are easier (and less permanent) than soldering*
Pardon the dirty table

Micro:Bit Code

The complete Micro:Bit code
  1. Checks whether another device (i.e. my RPi) is connected, and hence enables the UART service and sets the “connected” variable to true

Raspberry Pi Code


The basic internals of a doorknob
The result of attempting to drill the gears.
  • Glue: Not durable enough, and I didn’t want to permanently modify my potentiometer
  • Drilling a hole through the centre of the rod: This is a lot harder than it sounds, especially without a drill press, or the correct bits. The rod was also very narrow, and I wasn’t confident in the tools or my own abilities to continue this approach.
A wooden popsicle stick next to a joined spindle and potetiometer with a wooden spline

Final Assembly




I like programming and using technology to make awesome stuff

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Wyatt Sell

Wyatt Sell

I like programming and using technology to make awesome stuff

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