Microprocessor based home security system:-

In this advance world security system is in high end so the security breakers are. Now it’s time to live free, live secure. By keeping these all thing in mind (problem from burglary) the innovative group dreamlover technology designed a microprocessor based project “Microprocessor-Based Home Security System”. This advance security system not only let you know but also alert police immediately. In the project 8085 microprocessor based home security system we can control siren, telephone (via cradle and redial switches) and cassette player (alert message is recorded already)

Working of the system

The whole circuit of 8085 based home security system consist transmitter, receiver, Phase-Locked-loop and processing section as shown in Block diagram.

 

The mechanism of the project “Microprocessor Based-Home Security System” is very simple. As this project is IR based, the IR ray from transmitter is focused in the base of phototransistor of receiver fitted in opposite to each other. The property of phototransistor is that whenever the IR ray focused on its base is obstructed, the microprocessor as per program burnt in EPROM which further control siren, telephone and cassette player.

Circuit Description

The whole Project “8085-Microprocessor based security system” is divided into two main sections i.e. Hardware and Software.

 

Hardware: The complete circuit-Diagram of “Microprocessor Based Home Security System” is shown in figure 1. The transmitter section is designed and fabricate around timer IC NE555 wired as astable multivibrator followed by transistor T₁ and IR LED. The oscillated frequency of transmitter section is decided by resistor R₁and R₂, preset VR₁ with capacitor C₁. The output from pin 3 of IC₁ is given to base of transistor T₁ through resistor R₃ for amplification as per required and given to IR LED. The modulated IR signal is transmitted by IR LED₁.

The IR transmitted signal is focused on the base of photo transistor. The output from photo transistor is given to transistor T₃ followed by op-amp (IC₂) for amplification. The amplified signal from IC₃ is given to input pin 3 of Phase-Locked-Loop (PLL) IC LM567 (IC₃) through capacitor C₄. The normal use of PLL IC (IC₃) is frequency decoder so is here in order to drive the load. The tuning frequency is determined by variable resistor VR₂ and current controlled oscillator by resistor R₁₂. The tuning frequency (6-10 KHz) should match with modulating frequency transmitted by transmitter. Pin 8 of IC₃ is connected to base of transistor T₄ through resistor R₁₃. Glowing LED₁ indicate receiving signal is locked to transmitting signal. Transistor T₅ is used as relay driver in order to energize the relay RL₅. Relay RL₁ energized normally when transmitted IR signal falls on phototransistor T_2, at this time microprocessor does not get any input. But when IR signal is interrupted microprocessor get high (TTL-level) signal through port A of Programmable Peripheral Interface (PPI).

The microprocessor start working as per command loaded in the EPROM (IC₅) when high input is given from PLL. Octal latch (IC₆) is used for interface between low-order multiplexed address and latch lines AD₀ through AD₇ of microprocessor (IC₄) and EPROM in order to separate Address line A₀ through A₇ from data line D₀ to D₇ by latch-enable signal (ALE), while high-order address lines A₈ through A₁₀ is directly connected to EPROM.

ALE pin (30) of microprocessor is connected to pin 11 of IC₆. The output changed according to input data when ALE is high, if ALE goes low the lower-order address is latch at the output of IC₆.

RD and IO/M pin (32 and 34 respectively) of microprocessor (IC₄) is used to generate Chip-Select signal (CS) with the help of NAND gates.

Pin 18, 19, 20 and 25 of IC₇ are connected to base of relay driver transistor T₆ to T₉ through resistor R₁₉ to R₂₂ respectively. The high signal (interrupt of IR signal on the base of phototransistor) on these pin energizes the relay RL₁ to RL₄. For reset switch SW₁ is used.

Polarity reversed in the telephone line is build around optocoupler ICs (IC₈ and IC₉). As we all know that normal TIP of telephone set is positive in compare to Ring LED of telephone line. When the handset is in OFF-HOOK position, a loop current of 10mA is assumed for flowing in telephone line.

When the polarity reversed occurs from DC line the internal LED of IC₈ conduct which further glow LED₃ for indicating polarity reversed. Internal LED of IC₉ goes off and its pin 5 goes high in order to provide line reversed sense signal to microprocessor using pin 14 of programmable peripherals interface (PPI) IC (IC₇).

Relay connection

The cradle switch of telephone set is replaced by DPDT relay (RL₃). The four pads connection of PCB with cradle switch is now connected with relay. The two shorter distance pad when handset is placed in the cradle is connected to N/C contract of relay RL₃ where other two pad which is shorter distance when handset is off-hook are connected to N/O contract of same relay. Relay RL₂ is connected to redial bottom of telephone set parallel. When relay RL₃ is energized relay RL₂ is also energized to switch on the redial bottom which automatically dialed already loaded number (i.e. police or any help line). Relay RL₄ activate siren when ever receiving IR signal is interrupted until the reset bottom is pressed. Lastly relay RL₁ switched the audio cassette player in which victim detail is already recorded. The speaker connection of audio cassette player is connected to microphone of telephone to convey the alert message.

Software: The flowchart showed in figure: 6 shows the assembly language program. 99H word is used here to control device interface IC (IC₇) where port A and C as input port and B as output. At first microprocessor read the status of port A, when port A is high siren is activated, redial switch is activated and emergency number is dialed. After dialing number redial bottom gets switch off. Now microprocessor read the status of port C which further checks the polarity reversal of telephone line.  After detection of polarity reversal, the audio player is activated. When the message is finished the player automatic gets turned off.

 

Click to download program code for microprocessor-based home security system

PCB DESIGN: The actual size of PCB board must be 17.5cm×9.7cm

 

Click to download PCB Design in high resolution

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R1, R2 = 5.6 KΩ R3, R16, R18 – R22, R25 = 4.7 KΩ R4 = 100 Ω R5 = 3.9 KΩ R6, R8, R12, R15, R17 = 1 KΩ R7, R10, R11, R13, R14 = 10 KΩ R9 = 100 KΩ R23 = 120 Ω R24 = 470 Ω VR1 = 47 KΩ VR2 = 10 KΩ

Capacitors

C1 = 3.3 nF ceramic disc C2, C6, C13, C14 = 0.1 µF ceramic disc C3, C8 = 0.01 µF ceramic disc C4 = 1 nF ceramic disc C5 = 10 µF, 25V electrolyte C7 = 2.2 µF, 25V electrolyte C9 = 10 µF, 10V electrolyte C10, C11 = 10 pF ceramic disc C12 = 1000 µF, 50V electrolyte

Semiconductors

IC1 = NE555 (timer IC) IC2 = µA741 (operational amplifier) IC3 = LM567 (Phase-Locked-loop) IC4 = 8085 (Microprocessor) IC5 = 2732A (EPROM 4k) IC6 = 64LS373 (Octal Transparent Latch) IC7 = 8255 (programmable peripheral interface) IC8, IC9 = MCT2E optocoupler IC10 = 74LS00 (NAND gate) IC11 = 7809 (9V regulator) IC12 = 7812 (12V regulator) T1, T3 – T9 = BC548 (NPN transistor) T2 = L14G1 (Phototransistor) D1 = 1N4148 (Switching diode) D2 – D10 = 1N4007 (rectifier diode) LED1 – LED3 = Red LED IR LED1 = Infrared Led

Miscellaneous

X1 = 230V/50 Hz or 110V/60 Hz AC primary to 12V-0-12V, 300 mA secondary transformer XTAL = 3.5 MHz crystal SW1 = Push-to-on switch SW2 = On Off switch RL1, RL2, RL4, RL5 = 12V, 200 Ω, 1C/O relay RL3 = 12V, 200 Ω, 2C/O relay