This project uses the 12F675, it was chosen because of its low cost, A/D convertor and flash memory. This security system was designed to be used in a simple installation with just a hidden switch and not a keyboard. There are several features such as a battery monitor built into the code that also make it good for remote locations just run off a battery. Also all the delays and and other parameters are put into flash memory just by using a visual basic program and the serial port of a PC.
As you can see in the photo there are unused holes in the board, the board was designed for several different variations and future applications. Also the picture shows a optional header. This header connects to a switch on my programmer so that I flip the switch to “load” press the program button then switch to “run”. If I need to change the program all I need to do is flip the switch to “load” press the program button then switch to “run”, no need to unplug the IC or anything.If the header is to be used the 4 thin traces between the header need to be cut. The ground trace remains intact.