I found this Magtek card reader in a surplus shop. It was meant to read paper cards in a parking garage. I wasn't quite sure what to do with it but then I realized it would make a nice big ugly door lock.
Besides, that big Glowing VFD in a dark hallway seems to just say "KEEP OUT"
It had a VFD display but it was damaged. The gas seal was broken. Luckily I had one on hand that would almost fit. I say almost because it was just a little too wide. I trimmed the width on a band-saw and had to hot glue it in but from the outside it looks great.
It had nice lamp holders on the front already but they had old style incandescent lamps. I replaced them with 10mm White LED's. To control the LED's I used a small PIC micro controller that would watch the serial data to the display and used certain control characters to trigger the LEDs. I almost added a code to trigger the strike but that would make it too easy to bypass the lock if you ripped the face off the wall.
There was a power switch and reset button I left disconnected. I probably could use the push button for a doorbell.
The completed head unit only has 2 connectors. Power and serial data. For power I used a standard Wall Wart. I used a 1/8 stereo headphone Jack for the serial data.
The original reader mechanism was designed or paper cards. It almost looked like it could be used to read punch cards. I removed it and replaced it with a serial insertion reader. I have a few different ones around the larges ones seen above came from a Gas Pump and are the best. The smaller ones use a clock and data interface. No big deal since I already have a PIC on board. It could easily handle that too.
I used a standard RS232 driver chip. I added a standard DB-9 connector. I did a quick check to see that everything clears the LinkIt's mount. Then I went the parts bins to get a Darlington transistor and a decent relay. The one I picked is rated at 5A so it should be more than enough for any household door strike. make sure you match the relay to the intended load.
By putting the relay here and not in the head unit its much harder to bypass.
You could program it to match any card on hand or custom program your own cards. I kept the messages simple and to the point. I just got a SIM card so I have to activate it. Then I can add SMS notifications of any swipes.