FABRICATION OF PCB AND PROTOTYPING

PRESENTED BY :-

B. Vamsi Krishna

Door-Knock or Vibration Alarm

Contents

Introduction

Components

Circuit Schematic

Board Layout

Process

Description of Components

Circuit & Working

Introduction : Door Knock Alarm

This is a simple circuit that activates an alarm when there is a knock on the

door or there are any vibrations due to movement of heavy goods or

furniture. The circuit uses readily available components.

Components

Printed Circuit Board: -

A printed circuit board (PCB) mechanically supports and electrically connects

electronic components using conductive tracks, pads and other

features etched from copper sheets laminated onto a non-

conductive substrate. PCBs can be single sided (one copper layer), double

sided (two copper layers) or multi-layer (outer and inner layers). Multi-layer

PCBs allow for much higher component density. Advanced PCBs may contain

components - capacitors, resistors or active devices - embedded in the

substrate.

LED

A light-emitting diode (LED) is a two-lead semiconductor light source. It is a p–n junction diode, which

emits light when activated. When a suitable voltage is applied to the leads, electrons are able to recombine

with electron holes within the device, releasing energy in the form of photons.

Diode 1N4007

A diode is a specialized electronic component with two electrodes called the anode and the cathode. Most

diodes are made with semiconductor materials such as silicon, germanium, or selenium.The 1N4007 is a

family of popular 1.0 A (ampere) general purpose silicon rectifier diodes commonly used in AC adapters for

common household appliances.

Resistor

A resistor is a passive two-terminal electrical component that implements electrical

resistance as a circuit element. Resistors act to reduce current flow, and at the same time

act to lower voltage levels within circuits. In electronic circuits, resistors are used to

limit current flow, to adjust signal levels, bias active elements, and

terminate transmission lines among other uses

Transistor: -

A transistor is a semiconductor device used

to amplify and switch electronic signals and electrical power.

It is composed of semiconductor material with at least three

terminals for connection to an external circuit.

BC547 is mainly used for amplification and switching

purposes. It has a maximum current gain of 800. Its

equivalent transistors are BC548 and BC549.

IC LM324 Description

LM324 is a 14pin IC consisting of four

independent operational amplifiers (op-amps)

compensated in a single package. Op-amps are

high gain electronic voltage amplifier with

differential input and, usually, a single-ended

output. The output voltage is many times higher

than the voltage difference between input

terminals of an op-amp.

These op-amps are operated by a single power

supply LM324 and need for a dual supply is

eliminated. They can be used as amplifiers,

comparators, oscillators, rectifiers etc. The

conventional op-amp applications can be more

easily implemented with LM324.

Circuit Schematic

Board Layout

Process

• Using EAGLE SoftwareCircuit Schematic

•Using EAGLE SoftwareBoard Layout

•Using Photo glossy paperPrint Out

•Chemical SolutionFe2Cl3

EtchingProcess

•Prototype DesignComponentsFabrication

Circuit And Working

The circuit is built around quad-opamp LM324 (IC1), which is configured in

amplifier mode. It uses buzzer as the input sensor, two transistors BC547 (T1

through T2), a buzzer and some other components for the alarm circuit.

The reference voltage at pin 3 of IC1 is set by trimming potentiometer VR1.

The buzzer element plate is fixed at the center of the door. Apply a small

quantity of adhesive on the edges between the plates. Wires from the buzzer

are connected at CON2. These generate an input pulse when vibrations are

caused by knocking on the door. The pulse is amplified by op-amp A1 of IC1.

Remaining three op-amps of quad IC LM324 are not used here.

Cont…

The output of A1 of LM324 from pin 1 is further amplified by transistors T1

and T2 to drive the piezo buzzer or relay. Because of the presence of high-

value capacitor C5, the buzzer remains active for a few seconds. The circuit

is powered by 9V/12V power supply. Sensitivity of the circuit can be adjusted

by 1M potmeter VR1.

Circuit Fabrication