electronics - burglar alarm project

8/10/2019 Electronics - Burglar Alarm Project

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Problem Situation

Burglar Alarm Project

PROBLEMSITUATION

An Alarm company is developing a simple low cost security system for use in a new blockof small flats

The pressure mat gives a high (1) output when stood on.

The alarm arm switch is incorporated into the the front door key lock. Locking the doorwill set the alarm giving signal high (1).

A Reed switch and magnet are mounted on the door and frame and gives a low(0)signal when the door is opened

The electronic control sub-system is based on a combinational logic circuit whichoperates the alarm via a transistor


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Design Brief


Design an electronic logic control sub-system to process the signal from the

Inputs in order to operate the Alarm buzzer as described above

DESIGNBRIEF


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Systems Approach


PROBLEMSITUATION

DESIGNBRIEF

SYSTEMANALYSIS

SPECIFICATION

SOLUTION

ResourceSelection

Build & Test

ComputerSimulation

DATA SHEETS

Evaluation
http://e/Simulation1.cythttp://e/Simulation1.cythttp://e/Simulation1.cyt


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Systems Approach

PROCESSINPUTOUTPUT

Any device or system can be analysed interms of INPUT, PROCESS & OUTPUT

The universal System Diagram



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The universal System Diagram

Burglar

AlarmINPUT

OUTPUT

A) Arm Key Activated

B) Burglar Through Door

C) Burglar Through Window

Z) SCARY SOUND ENERGY


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The system diagram can be broken down into a subsystem diagram:



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A

B

C

ZSCARYSOUNDENERGY

Arm Key Activated

Burglar Thru Door

Burglar ThruWindow

System Boundary

Subsystem

Inputs

Subsystem

Outputs

Process

Subsystems

ReedSwitch N/C

Micro

Switch N/O

PressureSwitch N/O

Inverter OR

AND LATCH DRIVER

BUZZER

Sub System Diagram

Manual Reset

D

Push ButtonN/O


System

OUTPUTS

System

INPUTS


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Systems ApproachBurglar Alarm Project

PROBLEMSITUATION

DESIGNBRIEF

SYSTEMANALYSIS

SPECIFICATION

SOLUTION

ResourceSelection

Build & Test

ComputerSimulation

DATA SHEETS

Evaluation


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The System Must:

1) Detect a Burglar entering through the door or the window

2) Enable owner to disable it to go about their businesswithout setting it off

3) It must give a continuous audible warning to deterburglars, and should be reset by owner

4) It should be low cost, reliable and durable

5) Sensor should be unobtrusive

SPECIFICATION


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PROBLEMSITUATION

DESIGNBRIEF

SYSTEMANALYSIS

SPECIFICATION

SOLUTION

ResourceSelection

Build & Test

ComputerSimulation

DATA SHEETS

Evaluation


12/33Solution


SIMULATION LINK
http://e/Simulation1.cythttp://e/Simulation1.cyt


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SIMULATION LINK


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SIMULATION LINK


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SIMULATION LINK


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A(Arm Key)

B(Reed Switch)

C(Pressure Mat)

Buzzer

0 0 0 0

0 0 1 0

0 1 0 0

0 1 1 0

1 0 0 1

1 0 1 1

1 1 0 0

1 1 1 1 SIMULATION LINK


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PROBLEMSITUATION

DESIGNBRIEF

SYSTEMANALYSIS

SPECIFICATION

SOLUTION

ResourceSelection

Build & Test

ComputerSimulation

DATA SHEETS

Evaluation


18/33SubsystemINPUTDevices

MicroSwitch N/O

ReedSwitch N/C

PressureSwitch N/O


Selection of Resources

For detecting pressure under mat whenburglar comes through window

For detecting when door is lockedArming the alarm

For detecting when the door is open.(This switch is high when the door is closed)


19/33Subsystem PROCESSDevices

Integrated circuits consist of plastic cases filled with electronic circuitry.There are many resistors, transistors and other components packed intothe chips. There are literally thousands of ICs on the market, all designedto do different jobslogic gates, amplifiers, timers, etc.In this work we will be using the TTL (transistortransistor logic) range ofchips.

TTL chips require a stable 5V supply to work properly. (Great difficultieswill be met if any other voltage is used.) Any unconnected pinsautomatically go to logic 1. In other words, if a wire connected to a pinis connected to the 0-volt rail (logic 0), it will go to logic 0. If the wire isdisconnected from the 0-volt rail it will go to logic 1. However, it is good

practice to connect pins to high or low as needed.

All TTL chips have a four-digit code number, which always starts with 74.For example, a 7400 is a quad two-input NAND chip.Although the chip contains complex circuitry, the internal wiring can beshown as simple logic circuits with the inputs and outputs of each logicgate shown. This is called a pin-out diagram.


Selection of Resources


20/33Subsystem PROCESS Devices

OR (TTL 7432) NOR (TTL 7402)

AND (TTL 7408) INVERTER (TTL 7408)


Used to detect when the arm key is activatedAND a burglar is in the system

Used to detect when a burglar comesthrough the Door OR through the window

2 cross coupled Nor Gates make an SRFLIP-FLOP Keeping the output high if a

burglar closes the door or steps off the mat

Inverts out put from N/C reeds switch todetect when Door is open


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PROBLEMSITUATION

DESIGNBRIEF

SYSTEMANALYSIS

SPECIFICATION

SOLUTION

ResourceSelection

Build & Test

ComputerSimulation

DATA SHEETS

Evaluation


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DATA ON TTL 74HC04 INVERTER CHIP



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DATA ON TTL 74HC32 OR CHIP



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DATA ON TTL 74HC08 AND CHIP



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DATA ON TTL 74HC02 NOR CHIP



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PROBLEMSITUATION

DESIGNBRIEF

SYSTEMANALYSIS

SPECIFICATION

SOLUTION

ResourceSelection

Build & Test

ComputerSimulation

DATA SHEETS

Evaluation


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BREAD BOARD



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BREAD BOARD



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BREAD BOARD



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BREAD BOARD



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RESET


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PROBLEMSITUATION

DESIGNBRIEF

SYSTEMANALYSIS

SPECIFICATION

SOLUTION

ResourceS l ti

Build & Test

ComputerSimulation

DATA SHEETS

Evaluation

electronics - burglar alarm project

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