So I’ve started in on my first Arduino project - an automatic combination lock opener. It’ll automatically turn and guess the combination for a Master lock. It’ll have a screen to display its current combination attempt, and will spin the dial itself. I thought for a while about it, and I think I have some really neat ideas to make it more interesting:

  • An optimization can be made by taking advantage of the lock’s imperfect positioning, and instead of trying every number, trying every other number first.
  • Based on where 1 spin ends, you can make the next move you choose to make start close to the end position of your last move.
  • The last turn, you can spin the lock and continually attempt opening, without re-trying the combinations.

So, my hopes are that with these optimizations, I can go from:

  • 1st dial - 40 possibilities
  • 2nd dial - 40 possibilities
  • 3rd dial - 40 possibilities
  • 40 * 40 * 40 = 64000 combinations


  • 1st dial - 20 possibilities
  • 2nd dial - 20 possibilities
  • 3rd dial - spinning as I go
  • 20 * 20 * 1 = 400 combinations

I’ll post here updates as I have them, and hopefully soon we’ll have a cool combination lock unlocker.