This document describes the fabrication of a printed circuit board (PCB) and prototyping of a door-knock or vibration alarm circuit. It includes a list of components used - PCB, LED, diode, resistor, transistor, IC LM324. It provides the circuit schematic, board layout designed using EAGLE software, and the chemical etching process. It then describes how the circuit works using the quad op-amp LM324 as an amplifier, with a buzzer as the input sensor and transistors to drive the output buzzer or relay. Adjusting the reference voltage with a potentiometer controls sensitivity.

1. FABRICATION OF PCB AND PROTOTYPING
PRESENTED BY :-
B. Vamsi Krishna
Door-Knock or Vibration Alarm

2. Contents
 Introduction
 Components
 Circuit Schematic
 Board Layout
 Process
 Description of Components
 Circuit & Working

3. 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.

4. Components

5. 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.

6. 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.

7. 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.

8. 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

9. 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.

10. 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.

11. Circuit Schematic

12. Board Layout

13. Process
• Using EAGLE SoftwareCircuit
Schematic
•Using EAGLE Software
Board Layout
•Using Photo glossy paper
Print Out
•Chemical Solution
Fe2Cl3
Etching
Process
•Prototype DesignComponents
Fabrication

14. 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.

15. 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.

16. Circuit Fabrication