Simple Alarm System

Author: Kirill Yelizarov

The Software, which you can find here, is free. I do not warrant the information or Software or results obtained by using this information, or Software. I will not be liable to you for any damages, lost savings or other consequential damages arising from your use of this information, documentation, or Software.
YOU USE THIS SOFTWARE, INFORMATION, DOCUMENTATION ON YOUR OWN RISK.

I'm receiving lots of letters about car alarm system based on PIC 12C508 Version 1.0 (link broken). The system described was introduced as a simple circuit only. I tried to focus on using one and the same pin as input and output in different situations. Parts of code were taken from my previous alarm projects (AS1 and AS2), which were a success. The code wasn't totally debugged and I have no time to revise it now. Instead, I'm introducing a new Version 1.1.

Version 1.1

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A PIC12C508 based security system is described in this project. It implements the folowing features:

IR remote keyless system
72 bits transmission length (64bits password, 4bit CRC, and 4bits for commands)
Arm/Disarm
Immobilizer
Two stage sensors, door and shock sensor trigger inputs
Locking/unlocking of doors
Normal/Silent modes
Inside zone intrusion memory
Transmitter low battery indication

This system is a perfect solution for unidirectional remote keyless entry systems and access control systems. Such system may be implemented in:

Automotive alarm systems
Automotive immobilizers
Gate and garage door openers
Burglar alarm systems

This Alarm Sytem is based on two PIC12C508 (one is used in transmitter and the other one in the main unit). The following PICs are supported: 12c508, 12c509, 12c508a, 12c509a, 12ce518, 12ce519, 12f508, 12f509, 16f84 and 16f84a. Transmitter uses infra red beam to send code name to main unit. The commands are:

Arm/Disarm
Silent Arm/Disarm
Weak battery in transmitter

Figure 1: CODE WORD TRANSMISSION FORMAT

Each pulse in a packet sets a bit in a message. Pulse width is 256 us. This pulse is modulated at 38kHz. Delay between pulses sets the bit value. Single delay (256us) means "0" bit, double delay (512us) means "1" bit, and tripple delay (768us) is a start bit. It is used to synchronise two RC generators in the main unit and in the transmitter and it shows the start of a new packet. Packets are 72 bits long. First 64 bits are password key. The last byte is divided into two nibbles. One for commands and another for CRC. Code word transmission format is shown in figure 1. It took about ~36ms (min) to ~56 ms (max) to send a message. With more than 10¹⁹ combinations and minimum delay between packets of about 110ms it will take almost 3,2*11¹⁰ years to scan the code.

Figure 2: CODE WORD ORGANIZATION

Transmitter

Transmitter schematic diagram is shown in figure 3.

Figure 3: TRANSMITTER SCHEMATIC DIAGRAM

Transmitter Parts List

Capacitors:

C1 - 1nF (10V min)

C2 - 0.1uF (10V min)

C3 - 2x470 uF 6,3V (electrolytic)

Diodes:

D1 - Red light emitting diode

D2 - CQY99 (Infra Red light emitting diode)

D3,D4 - any type diodes

Resistors:

R1 - 300 Ohm (.125W)

R2 - 100 kOhm (.125W)

R3 - 300 Ohm (.125W)

R4 - 1 kOhm (.125W)

R5 - 1 Ohm (.125W)

Miscellaneous:

U1 - PIC12C508 programmed with transmitter code

S1-S2 - normally open pushbutton switches

Click to view a larger picture (76Kb)

Here you can find transmitter assembler code (updated on March 11, 2008) and a password.inc file. Don't forget to change processor type in MPLAB or you will get errors. I've added PIC16F84 family processors for debug.

Main Unit

Figure 4: MAIN UNIT SCHEMATIC DIAGRAM

Main Unit Parts List

Capacitors:

C1 - .1 uF

C2 - 470 uF 25V (electrolytic)

C1 - 10 uF 6,3V (electrolytic)

Diodes:

D1-D12,D14-D17,D20-D24 - 1N4148

D18,D19 - 1 amp rectifiers

D13 - blinking LED

Resistors:

R1-R4 - 300 Ohm (.125W)

R5-R8 - 33 kOhm (.125W)

R9-R12,R14-R18 - 4,7 kOhm (.125W)

R19-R23 - 1,5 kOhm (.125W)

R13 - depends on the type of LED you will use

Miscellaneous:

Q1-Q4 - BC547

Q5-Q9 - 2N2222A

U1 - PIC12C508 programmed with main unit code

U2 - 78L05

Click to view a larger picture (364Kb)

Figure 5: IR RECEIVER SCHEMATIC DIAGRAM

IR Receiver Parts List

Capacitors:

C1 - 47 uF (electrolytic)6,3V

C2 - 1000 pF

C3 - 3900 pF (NP0, +30...-75ppm/C)

C4 - 0,1 uF

Resistors:

R1 - 30 kOhm (.125W)

R2 - 1 kOhm (.125W)

R3 - 100 kOhm (.125W)

R4 - 10 kOhm (.125W)

R5 - 1,5 kOhm (.125W)

R6 - 10 kOhm (.125W)

R7 - 47 Ohm (.125W)

Miscellaneous:

Q1 - BC557

U1 - TSOP1738, BRM1020

U2 - CD4011

Figure 6: IR RECEIVER SCHEMATIC DIAGRAM (TBA2800 BASED)

IR Receiver Parts List

Capacitors:

C1 - 4,7 uF (electrolytic)6,3V

C2 - 1200 pF

C3 - 0,01 uF

C4 - 1500 pF

C5 - 47 uF (electrolytic)6,3V

C6 - 3900 pF (NP0, +30...-75ppm/C)

C7 - 0,1 uF

Diodes:

D1 - BPW41 (Photo diode)

Resistors:

R2 - 1 kOhm (.125W)

R3 - 100 kOhm (.125W)

R4 - 10 kOhm (.125W)

R5 - 1,5 kOhm (.125W)

R6 - 10 kOhm (.125W)

R7 - 47 Ohm (.125W)

Miscellaneous:

Q1 - BC557

U1 - TBA2800

U2 - CD4001

Here you can find main unit assembler code (updated on March 11, 2008). This is a Release Candidate version 6. Don't forget to change processor type in MPLAB or you will get errors. I've added PIC16F84 family processors for debug. And here is a picture of a test alarm (153Kb) I built using PIC16F84.

Click to view a larger picture (21Kb)