Door Unlockerator Project

Last night, Ash came to the meeting with an RFID reader and a couple cards and an idea to turn it into an automatic door locker/unlocker by hooking it up to a motor and a small microprocessor. I liked the idea enough to toss it up as a project.

The reader speaks 2400 baud 8N1, so it’s a piece of cake to interface, and the cards are only $1.19 each. We’d probably have to mount the reader outside the metal-covered door, but that’s about the only hassle I forsee. This is certainly the path of least resistance — we could have a working system up in a week or so. The downsides from a tech/fun perspective are that the reader we’ve got only works with its own cards, and that the whole project is just a little too easy. Plus, we’d have to get the reader out of Ash’s hands…

Cooler still would be a homebrew RFID reader that allowed us to read whatever RFID tags you’ve got in your wallet or purse. This may be non-trivial and will certainly require building up a receiver. It might be as easy as these guys had it, or it might be truly impossible. Could be super fun, could be a dead end. Anyone have DIY RFID experience? Know how to build a SmartTrip reader?

Other, less-secure and less-tech but nonetheless-groovy ideas include:

  • Knock-pattern sensor: Detects rhythmic series of knocks and pauses. I’ve implemented one of these before, and it’s a fun toy. The biggest obstacles are if some members have bad rhythm or our neighbors have particularly good rhythm. The keyspace isn’t really all that huge either. But it’s a classic.
  • Phone-dialing entry: Re-use a telephone (rotary is coolest, touch-tone will work in a pinch) as an entry keypad. It’s fun to open doors by dialing.

In any case, none of this is to replace the real keys, and so whatever mechanism we choose has to be key-overridden. It’d be no good if it crashed and locked us all out, and I don’t want to make anyone learn the secret knock or implant an RFID chip if he/she doesn’t want to. And if we can keep the systems cheap, it won’t be a big hassle to switch from a knock-lock to an RFID lock, or heck, use both/either.

What else do you folks think would be a good or fun? How can we lock and unlock the door?

Post comments and/or e-mail Elliot or Ash if you’re interested.