RFID + Back door = Easy Access

Lately I have been lazy about getting into my home, early in the morning I dislike rummaging through my pockets to get out my keys just to go through 2 doors just to get in and sit down.  So I fixed this issue by making my patio door RFID accessible. With a few parts on hand and a whole bunch of time, I made a “patio un-locker”, because it only unlocks the patio door but does not lock it.

So to build your own, you will need:

  • Parralax RFID reader(serial) –  2400 baud
  • 1x tip120 darlington
  • msp430 of your choice
  • solenoid – purchased from American science and surplus(local)
  • Power supply 12v, 5v and 3.3v
  • various resisters, 1x 10k for rst, 1k for level translation, 100 for darlington base
  • wires and misc supplies and a bunch of Scotch Loks (I love those things)

The basic setup of the whole thing

From the RFID reader, I permanently attached the enable pin to 5V. The serial pin is connected through a 1k resister to P1.1 on the msp430(f2012). Next the I attached the darlington’s base with a 100ohm resistor to P1.7 on the msp430 (this is to turn on the solenoid). The solenoid is connected to +12v and the other side is connected to the darlington’s (emitter?). There is a 1n4001 diode hooked in parallel with the inductive load.

There are a bunch of ways to make this work, I could have used a relay or mosfet, or other digital switch to turn on the solenoid to get the process to work.

Hopefully in the near future I will be able to upgrade my Rube Goldberg like machine to a stepper motor, so it can lock and unlock my patio door.

On a side note, I had to run the msp430 at 8Mhz to be able to read the 2400 baud serial connection from the rfid reader. I used an msp430g2231 with the calibrations flashed in, but if you notice the code says its an msp430f2012, which is pretty much the same thing but with factory preset  calibrations.

My over kill Power supply, 500 watts of pure overkill

rfid reader duct taped to the window

solenoid zip tied to my shelves
ball bearing ina polishing clothe to soften the fall lol

Files for project:

rfidproject.zip – contains main.c and make file

main.c  just the main.c

rfidproj.tar contains main.c and make file