BASIC Stamp Alarm System

Prototype Design

I originally started designing this alarm system while experimenting with the EDE1144 Keypad Decoder IC. I was trying to think of good uses for it and of course, and alarm system is a perfect application.

I used my Board of Education to experiment with the IC and keypad for a while, but of course I didn’t really have any room to grow, so I was eventually forced to move over to the Professional Development Board (PDB). I also switched from using a 4×20 Parallel LCD with the PIC-an-LCD IC to using a 2×16 Parallax Serial LCD and finally a 4×20 Parallax Serial LCD.

Using the PDB I set up the eight (8) zones and experimented with different sensors, such as magnetic and PIR. With eight of the I/O pins used for zone input, the remaining I/O was used for controlling the LCD, alarm and relay output and of course, the keypad input, which used two I/O lines.

Milling The Enclosure

I chose a slope-front enclosure for this alarm since the cabinet was intended to sit on my bench next to my computer shop PC. The parts are all being milled on my coffee table at the time since I was home from the shop while working on this project. The copper-clad board shown in the bottom section of the enclosure was being fitted for a possible custom PCB. In the end I used a Super Carrier Board for the main control board.

Pilot holes were drilled and then the various sections such as LCD and keypad were cut out. Letters were rubbed on from a sheet and then sealed in with acrylic clearcoat. The piezo buzzer was hot glued in and all the hardware was mounted. The rear panel (not shown) was originally milled out for the power input / fuse, zone inputs, alarm / relay outputs (using spring terminal connectors) and optionally, a PINK Module (web server) for remote web access to the alarm system.

Completed Alarm System

The completed alarm system is shown here ready to be powered up. I wanted to be able to kill power quickly during software development since the BS2 doesn’t have interrupts and I was forced to do some clever coding which resulted in a few hang-ups during development. The power switch allowed me to kill power during those times when the alarm got stuck on.

The power LED was a 3mm blue I had in my parts bin. The four LEDs to the right of the keypad indicated status. The top two are quite obvious. The bottom two indicated loop status. Red meant the loop wasn’t ready or that a PIR was tripped. Green meant the system was ready to arm. A shift register was used to control the LEDs and the alarm / relay outputs.

The buzzer was originally a piezo speaker meant to use with the EDE1144 Keypad Decoder IC, however the one I installed in the cabinet was really not a good choice. In the end I connected the piezo speaker directly to the BS2 (via transistor) and mounted the original piezo speaker for the EDE1144 on the Super Carrier Board. All that speaker did was provide an audible chirp when keys were pressed on the keypad, so it wasn’t really significant. The main buzzer was used to provide audible tones for alarm status, especially when using entry / exit delays.

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