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