It is an independent base station for RFID controlled access to your home. Control is monitored by permissions of the users and an RTC which does have a coin cell that is not listed. The keypad allows for name input and changing privileges and even has password control which may be turned on and off. Repair is easy enough using the manual for a user-end reset. An external EEPROM is added because the PIC 18F series only has so much memory. The door is opened and closed by an electronic door strike which is set off and powered by a Mosfet using a nice 5/12V DC-DC flyback (happen to have one that I go for $2 – score!). The base station was designed to be the controller of several peripherals and could always be expanded using the Dallas 1-wire port that was left open and unpopulated. There are header files you can add for the PIC which will allow for them to be used with Dallas 1-wire for expansion. A very cool potential use for this was to actually create a small antenna for data to be transferred through the electrical wiring of the house, making each piece truly easy to set up and requiring nothing more than a walwart power supply and some industrial-strength Velcro to hold it up (amazing stuff there).
The BOM comes to around $280, but in this case the Display and the RFID Antenna (as we wanted a powerful one so that you could simply open your door when you got to it) made up for $220 of that total cost! Realistically, you could buy an RFID Antenna and Cards from Sparkfun or similar for appx $40-50, a Display for $25 (35 with I2C converter), and keypad debouncer chip for $10 with very little change in the code. The price would have been much cheaper if places like MakerShed, Sparkfun, Adafruit, LittleBird, etc. were well known 2.5 years ago, enough that a school would feel comfortable buying a bunch of stuff from them. As such, you will see that the parts are primarily from Digikey. Plus, our school already had several PIC programmers and Arduino boards were not the beast that they are now.
What is not listed in the BOM is the enclosure that we got from Hammond or the fact that what we turned in was wired on a small breadboard. We did plan on PCB’s, but we did not have a 3-week “setup time” available to us. PCB’s would have been around $50 each for two with 100% test and double layer 2oz traces with ground and voltage planes for anyone who is wondering.
User Manual: http://www.sendspace.com/file/dkjk6r
Repair Manual: http://www.sendspace.com/file/wq4tw8
Design Doc: http://www.sendspace.com/file/t0tso5
This code uses a lot of the built-in PIC library functions so it is easy enough to understand for anyone who has worked with an Arduino before and is a nice step up in complexity when you are ready to try some harder stuff. Personally, I love Arduinos and the code libraries make every little project run that much easier!
**Will edit this post with some pictures of the thing, once I can find them!***