The CIRCUIT
The circuit is very simple. All the work is done by the micro.

The micro is designed to work on 5v and the supply to it must not be more than 5.6v.
The alarm is supplied from a 12v battery and a very clever voltage-dropping arrangement has been provided to delver a maximum of 5v6 to the micro.
This is the section of the circuit that will be taking current when the project is turned ON. That's why we have taken special care to keep the current very low, so the circuit can operate on a rechargeable battery or even two lantern batteries.
The supply contains two high-brightness LEDs to drop the 12v supply by 1.7v for each LED. This delivers 12.6v - 1.7v - 1.7v = 9.2v to the right end of the 1k5 resistor. The left side is a maximum of 5v6 and the difference is 3.6v. This produces a current of 2.4mA.
This current is available for the micro.
When the micro is in the "detection mode" is takes less than 1mA and the remainder of the current flows though the 5v6 zener.
When one of the indicator LEDs is flashing, or button A is pressed, or the piezo buzzer is sounding, or the piezo siren is active, the 5v section takes more than 1mA and can take up to 2.4mA. At this point the circuit takes all the current that is available via the 1k5 resistor and the voltage drops to 5.5v. This takes the zener out of conduction and the micro consumes all the current.
The flashing LEDs will take more than 2.4mA for a short period of time and the 100u electrolytic will deliver this extra current and charge during the "off time."
This arrangement takes the least current from the battery as a 78L05 requires 10mA and you would need to use a special low-current regulator to achieve what we have done. 
The circuit has been designed around easy-to-obtain components.
There are two clever features that need describing.
The 4 inputs are monitored by turning on the 47k pull-up resistors inside the micro and this creates a voltage-divider between the external resistors and the internal 47k's.
The 1k resistor across the LEDs keeps the "bottom resistor" in the divider very low and prevents 1.7v developing across the LEDs as this would be detected as a HIGH (the chip detects anything above about 1v5 as a HIGH).
The 22n across switch A is charged by the program for a very short period of time then the pin is turned into an input to see if the capacitor is still charged. SwA will discharge the 22n very quickly if it is pushed. 
This is the only way to detect if SwA is pressed. The internal 47k's cannot pull the input high enough to record a HIGH when the 10k is used as a base resistor.
The siren piezo has a transistor driver to produce maximum output and the buzzer piezo has a transistor driver and 10mH choke to increase the output. This allows you to use low-cost piezo diaphragms for both.

 
CONSTRUCTION
You can build the circuit on matrix board or use the ALARM 4-ZONE Printed Circuit board included in the kit.
The kit of components comes with all the parts you need to get the project working, including a pre-programmed chip.
If you want to burn your own chip or modify the program, you will need a PICkit-2 programmer and this comes with 2 CD's containing all the software needed for In-Circuit Programming.
You will also need a lead (comes with PICkit-2) to connect the programmer to your lap top via the USB port and an adapter we call 6pin to 5 pin Adapter to connect the PICkit-2 to your project.

FITTING THE ALARM
The board comes with screw terminals for the 4 inputs and a set of terminals for the 12v supply as well as the leads to the piezo siren.
This makes it easy to install.
Simply build the circuit and mount it inside a cupboard where it will not be seen.
2 x 6v lantern batteries will last 3,000 hours (125 days) or a 12v gel cell will last 6 months. But the alarm is only active for a few hours each day and the battery-life will not be a problem.
Mount the siren piezo some distance from the alarm in a high location. It will be so loud that the burglar will leave the premises.
You can add a second siren piezo and mount it outside.
Any unused inputs need to have a "shorting link" added across the terminals of the unused input.
Cover the hole in the piezo to reduce the sound when initially testing the project.
The alarm will wail constantly if you have chosen the first flashing LED via the mini tactile switch "A." or it will only sound for 5 minutes if the middle LED is flashing.
 

PROGRAMMING THE CHIP
The kit comes with a pre-programmed PIC chip but if you want to program your own chip or modify the program, the .hex file is available as well as the assembly file, so you can see how the program has been written and view the comments for each line of code.
The PIC12F629 is one of the smallest micros in the range but you will be surprised how much can be achieved with such a tiny micro.
The program contains sub-routines to produce delays, sequences on the display and both read and write EEPROM; jobs that require accurate code - including a special sequence - called a handshaking sequence that prevents the EEPROM being written due to glitches. 
Even a program as simple as this is not easy to put together and to assist in this area, we have provided a whole raft of support material.
Not only do we provide a number of programs with full documentation but our approach to programming is simple.
It involves a method of "copy and paste" whereby sub-routines are taken from previously written code and copied into your program. Any modifications are made in very small steps so that each can be tested before adding more code.
This is exactly how we produce a complex project. Each step is written and tested before adding the next step.
This saves a lot of frustration as it is very easy to add a line of code that is incorrect and get an unsuspected result. 
If you follow our suggestions you will buy a programmer ("burner") called a PICkit-2 if you are using a laptop. It is the cheapest and best on the market and comes with a USB cable and 2 CD's containing the programs needed to "burn" the chip. If you are using a desk-top and/or tower with a serial port, you can use a cheaper programmer called MultiChip Programmer from Talking Electronics. You will also need NotePad2 to write your .asm program. This can be downloaded from Talking Electronics website. You will use Alarm4Zone.asmm or Alarm4Zone-asm.txt as a basis and it is best to change only a few lines at a time to see what effect is created. You will also need a 6 pin to 5 pin connector that fits between the burner and the project. This is also available on Talking Electronics website.
As we said before, this project is for medium-to-advanced programmers as it is very compact and does not have in-circuit programming pins.
To be able to modify the chip you will need a programming socket and this can be obtained from one of our other projects that contains the 5 pins for in-circuit programming. Or you can build a programming socket by adding a socket to a surface-mount PC board and solder 5 pins to one edge and connect the socket to the pins.
You can then put the chip into the socket and program it.

PROGRAMMING LANGUAGE
There are a number of kits, programs and courses on the market that claim and suggest they teach PIC Programming.
Most of these modules and courses use a PIC microcontroller as the chip carrying out the processes, but the actual programming is done by a proprietary language invented by the designer of the course.
Although these courses are wonderful to get you into "Programming Microcontrollers" they do not use any of the terms or codes that apply to the PIC microcontroller family.
All our projects use the 33 instructions that come with the PIC Microcontroller and these are very easy to learn.
We use the full capability of the micro and our pre-programmed chip is less than the cost of doing it any other way.
In addition, anything designed via our method can be instantly transferred to a PIC die and mass produced. And we use all the input pins and all the memory of the chip. The other approaches use less than 25% of the capability of the memory and one of the pins is not available.
In fact it would be difficult to reproduce this project via any of the opposition methods. It would require a larger chip and more expense. 
You can use our method or the opposition. Just be aware that the two are not interchangeable.
Ours is classified as the lowest "form" (level) of programming - commonly called machine code - invented in the early days of microprocessors - and now called mnemonic programming as each line of code is made up of letters of a set of words. The opposition uses a higher level language where one instruction can carry out an operation similar to a sub-routine.
But you have to learn the "higher level language" in order to create a program. And this requires a fair amount of skill and capability.  
It sounds great and it is a good idea. But if you want to learn PIC programming, it does not assist you. It is "a step removed" from learning PIC language. The other disadvantage of the opposition is the "overhead." The 1,000 spaces allocated for your program is filled with pre-written sub-routines. You may require only 10 of these sub-routines but ALL of them are loaded in the memory space. And they take up all the memory.
You have no room for your own program.
To get around this the opposition uses the 128 bytes in EEPROM to deliver instructions on how to apply the sub-routines. This provides about 30 powerful instructions using their language called BASIC (or a similar language). 
It's a bit like selling a diary filled with all the paragraphs you need to express yourself, and leaving a few blank pages at the back for you to write single lines such as: see page 24, paragraph 7, see page 63 paragraph 4, to create your diary entries.
It depends on how much you want to be in charge of writing a program. Using our method is like writing your own auto-biography. Using the opposition is like getting a "ghost writer."
When using a higher level language to create a program, you have absolutely no idea how the code is generated for the micro.
In some of the developmental kits, the code is "locked away" and you are NEVER able to access it.
Everything runs smoothly until a fault appears. With our method you can see the code. With the other methods, you cannot see the code - it's like doing key-hole surgery without the advantage of an illuminated endoscope to see what you are doing.
Everything has its place and our method of hand-assembly is only suitable for very small micros and you will eventually need to "learn a high level language."   The PIC12F629 has over 1,000 locations for code and this equates to more than 20 pages when printed, so this is about the limit to doing things by hand.
But our drive is to show how much can be done with the simplest devices on the market, at the lowest cost.
Anyone can show you high-technology at a high price but this is not where you start and this is not where you get enthusiasm.
We provide the things to get you started. That's the difference.

BURGLAR ALARM   4-ZONE
This circuit uses a dedicated alarm chip from Talking Electronics (TE555-BA4). The chip costs $2.50 and contains a 4-zone Burglar Alarm circuit. All you need are the surrounding components to complete the project. These components are available as a kit for $20.00 including the dedicated chip and this makes it one of the cheapest kits on the market (postage for kit $6.50). Click HERE to order the chip or the kit.
The only additional parts you require are 4 reed switches. These can be purchased on eBay for $5.38 for a set of 5 Normally Open switches (post free).
Here is the link:
http://www.ebay.com/itm/5-Set-Door-Or-Window-Safety-Contact-Magnetic-Alarm-Reed-Switch-NO-with-Screws-/290746194636?pt=LH_DefaultDomain_0&hash=item43b1d2dacc