Door knock alarm with timer

Door Knock Alarm With Timer
DOOR KNOCK ALARM WITH TIMER
A Project Report
Submitted in partial fulfillment of the requirement for the award of Degree of
Bachelor of Engineering in Electronics & Communication
Submitted to
RAJIV GANDHI PROUDYOGIKI VISHWAVIDHYALAYA,
BHOPAL(M.P.)
MINOR PROJECT REPORT
Submitted by
1.Sandeep Ghosh (0157EC091075) 2. Ankush Shivhare (0157EC091013)
3.Zeyaur Rahman (0157EC091090) 4.Pathik Sonkar (0157EC091056)
5.Kishor Kumar(0157EC091038)
Under the supervision of
Prof. Avinash Rai Prof.Priyanka Dubey
Department of Electronics and Telecommunication Engineering
LAKSHMI NARAYAN COLLEGE OF TECHNOLOGY &
SCIENCES,BHOPAL
SESSION-2011-2012
Department Of Electronics And Communication Engineering 1

LAKSHMI NARAIN COLLEGE OF TECHNOLOGY &
SCIENCE, BHOPAL (M.P.)
CERTIFICATE
This is to certify that the work embodied in this thesis entitled “DOOR KNOCK
ALARM WITH TIMER” has been satisfactorily completed by Sandeep
Ghosh,Ankush Shivara,Pathik Sonkar,Zeyaur Rahaman of pre final year. It is
a bonafied piece of work carried out under the supervision and guidance in the
Department Of Electronics And Communication Engineering in LAKSHMI
NARAYAN COLLEGE OF TECHNOLOGY AND SCIENCES for partial
fulfilment of the Bachelor Of Engineering In ELECTRONICS AND
COMMUNICATION AND ENGINEERING,during the academic year 2012.
Under the supervision of
…......................................... ……………………….
Prof. AVINASH RAI Prof. PRIYANKA DUBEY
(Project Guide) (Project Incharge)
Approved by
……………………………….
Prof. Soni Changlani
(Head Of Department)
Forwarded by
……………………
( Principal )

SCIENCE, BHOPAL
Department Of Electronics And Telecommunication Engineering
CERTIFICATE OF APPROVAL
This foregoing minor project work is hereby approved as a creditable study of
Engineering carried out and presented in a manner satisfactory to warranty its
acceptance as a prerequisite to the degree for which it has been submitted. It is
understood that by this approval the undersigned do not necessarily endorse or
approve any statement made, opinion expressed or conclusion drawn therein, but
approve the thesis only for the purpose for which it has been submitted.

,…………… SCIENCE, BHOPAL (M.P.)
DECLARATION
Sandeep Ghosh,Ankush Shivhare,Pathik Sonkar,Zeyaur Rahaman and Kishore
Kumar students of bachelor of engineering,branch Electronics And
Communication Engineering LAKSHMI NARAYAN COLLEGE OF
TECHNOLOGY AND SCIENCE,BHOPAL,hereby declare that the work
presented in this minor project report entitled “Door Knock Alarm With
Timer”outcome of our own work,is bonafide,correct to best of our
knowledge.This work has been carried out takink care of Engineering Ethics.This
work presented does not infringe any patented work and has not been submitted
to any university for the award of any degree or any professional diploma.
……………………….. ……………………….
Sandeep Ghosh Ankush Shivhare
(0157EC091075) (0157EC091013)
…………….................... …………………………
Pathik Sonkar Zeyaur Rahaman
(0157EC091057) (0157EC091090)
..........................................
Kishore Kumar
(0157EC091038) DATE-..............................

ACKNOWLEDGEMENT
Any work started and carried out with systemic approach turns out to be a success.
Any accomplishment requires the effort of many people and this work is outcome
of such one strenuous effort.The project was a challenge and was made more
difficult due to a number of varied reasons. Some of which were beyond our
capability.At time we were left with no options reguarding whwt to do next. It was
then the very assistance of the faculty members who helped us out of the
quicksand. We would be grateful to them for their inspiration, encouragement and
guidance in all stages of our project development process.
We feel extremely gratified to express out hearties thanks to Prof. Soni Changlani
HOD of Electronics and Communication Department for her constant
encouragement and valuable advice during the project development stages. We
wish to extend our thanks to all the faculty members who devoted their valuable
time for our project development.
Finally we would like to thank Prof. Priyanka Dubey mam and Prof. Avinash Rai
sir who tremendously contributed in this project either directly or indirectly. We
wish to express our sincere thanks to all those who may have contributed in the
project completion plan.

CONTENTS:
NAME OF TOPICS PAGE NO.
A PHOTOGRAPH OF PROJECT 3
B ABSTRACT 4
C PROJECT SPECIFICATION 5
D LIST OF FIGURES 6
E LIST OF TABLES 7
CHAPTER 1: INTRODUCTION 8
CHAPTER 2: THEORY/PRINCIPLE 9
CHAPTER 3: CIRCUIT ANALYSIS
3.1 CIRCUIT DETAILS 10
3.2 CIRCUIT LAYOUT 11
3.3 COMPONENT LIST 12
CHAPTER 4: PCB ANALYSIS
4.1 PCB DETAILS 13
4.2 PCB DESCRIPTION 19
4.3 PCB DESIGNING 21
4.4 PCB LAYOUT COMPONENT SIDE 24
4.5 PCB LAYOUT SOLDERED SIDE 25
4.6 PCB PROTECTION AND PACKAGING 26
CHAPTER 5: ASSEMBLY AND TESTING
5.1 BREADBOARD IMPLEMENTATION 27

NAME OF TOPIC PAGE NO.
5.2 PCB IMPLEMENTATION 33
CHAPTER 6: WORKING OF CIRCUIT 38
CHAPTER 8: EXPECTATION AND ACHIEVEMENTS 39
CHAPTER9: PROJECT COST 40
CHAPTER 10: COMPONENT DETAILS
10.1 PIEZOELECTRIC SENSORS 41
10.2 NE 555 IC 45
10.3 UM 66 MUSIC GENERATOR 48
10.4 RESISTOR 50
10.5CAPACITOR 52
10.6 VARIBLE RESISTOR 55
10.7 LOUDSPEAKER 58
10.8 ZENER DIODE 63
CHAPTER 11: SHORTCOMMINGS, LIMITATIONS AND
REMEDIES 66
CHAPTER 12: FUTURE APPLICATION AND SCOPE
OF PROJECT 67
CHAPTER 13: CONCLUSION 68
CHAPTER 14:REFERENCES AND BIBLIOGRAPHY 69

A- PHOTOGRAPH OF PROJECT

B- ABSTRACT
This low-cost circuit uses the piezoelectric element of a piezobuzzer as the input
sensor. When the door is knocked music is heard from the speakerLS1. After the set
time period, the melody sound stops. The circuit works off 5-12V DC. The music
time can be adjusted through VR1 by changing the R-C time constant of the timer.
This is the general functioning of the door knock alarm.
We have chosen the project as in day to day life it is not possible to have a watch over
every nook and corner. So to have a check on every aspect of a place we plan to
device a detector which is able to alert us of some change in the prevailing system.
There are many application of the concept behind the project. It can not only be used
for military purpose but also can be used in day to day like door knock alarm, bugler
alarm safety alarm.

C- PROJECT SPECIFICATION
Serial Number Component
description
Reference
Description
Quantity
1 IC NE555 IC 1 1
2 Resistor 10 K R4,R5,R8 3
3 Resistor 2.2 M R1 1
4 Resistor 270 K R2 1
5 Resistor 3.3 K R3 1
6 Resistor 470 K R 6 1
7 IC’S BC 547,BG
549,UM66,NE555
4
8 Resistor 1 K R 7 1
9 Variable Resistor
100 K
VR 1 1
10 9 Volt Battery - 1
11 Piezoelectric
element
- 1
12 Piezoelectriv
buzzer
- 1
Table 1
D- LIST OF FIGURES
FIGURE NO. FIGURE NAME PAGE NO.
Figure 1- Circuit Diagram 11

Figure 2- General PCB solder and component side 13
Figure 3- PCB Layout Component Side 24
Figure 4- PCB Layout Solder Side 25
Figure 5- Breadboard 28
Figure 6- PCB with test connection pads 33
Figure 7- Piezoelectric element 41
Figure 8- Schematic symbol and electronic model of a
piezoelectric sensor 42
Figure 9- Frequency response of a piezoelectric sensor;
output voltage v/s applied force 43
Figure 10- NE 555 45
Figure 11- Pin diagarm of NE 555 IC 45
Figure 12- Schematic of a 555 in monostable mode 46
Figure 13- UM66 48
..…………………
……….E- LIST OF TABLES
TABLE NO. TABLE NAME PAGE NO.
Table 1 Project Specification 5

Table 2 Component List 12
Table 3 Project Cost 40
CHAPTER 1
INTRODUCTION
sensor. The piezoelectric element plate is fixed at the centre of the door wing by using

a cello tape. Apply a small quantity of adhesive at the edges between the plate and the
door. Extend wires about 1-1.5 meters from the piezoelectric to the circuit. IC NE555
(IC1) is configured in monostable mode. When it gets an input pulse its output goes
high for a period set by VR1, resistor R5 and capacitorC3. IC UM66 (IC2) is used as a
melody generator. When the door is knocked at, the piezoelectric plate generates an
input pulse, which is amplified by transistor T1.The amplified signal triggers the timer
IC NE555 and its output pin 3goes high to enable the melody generator. Music is
heard from the speakerLS1. After the set time period, the melody sound stops.
Assemble the circuit on a general purpose PCB and enclose in a suitable case. Fix the
piezoelectric element at the door and place the speaker in a central room inside the
house using long wires. The circuit works off 5-12V DC. The music time can be
adjusted through VR1 by changing the R-C time constant of the timer.
CHAPTER 2
THEORY/PRINCIPLE
The basic principle behind operation of DOOR KNOCK ALAM WITH TIMER is
conservation of energy and transformation of one form of energy to another form of

energy. The law of conservation of energy states that “ Energy Can Neither Be
Created Nor Destroyed But It Can Be Changer From One Form To Another’’.
In DOOR KNOCK ALAM WITH TIMER we have conservation as well as
transformation of energy with of help of different type of transducers. A
TRANSDUCER is a special type of device which has the feature of converting one
form of energy to another form of energy. Initially the mechanical energy that is
pressure applied on the piezoelectric element is converted into its electrical equivalent
due to unique characteristic of the piezoelectric .Then the electrical energy is again
converted into sound energy with the help of UM66 IC which has the special
characteristic of converting electrical energy to its sound energy equivalent. This
successive transformation of energy takes place due to special type of transducers
i.e.UM66 (electrical to sound) and piezoelectric element (mechanical to electrical
energy) .
CHAPTER 3
3.1 CIRCUIT DETAILS

In DOOR KNOCK ALAM WITH TIMER we have conservation as well as
transformation of energy with of help of different type of transducers. A
TRANSDUCER is a special type of device which has the feature of converting one
form of energy to another form of energy. Initially the mechanical energy that is
pressure applied on the piezoelectric element is converted into its electrical equivalent
due to unique characteristic of the piezoelectric .Then the electrical energy is again
converted into sound energy with the help of UM66 IC which has the special
characteristic of converting electrical energy to its sound energy equivalent. This
successive transformation of energy takes place due to special type of transducers
i.e.UM66 (electrical to sound) and piezoelectric element (mechanical to electrical
energy) .
sensor. The piezoelectric element plate is fixed at the centre of the door wing by using
a cello tape. Apply a small quantity of adhesive at the edges between the plate and the
door. Extend wires about 1-1.5 meters from the piezoelectric to the circuit. IC NE555
(IC1) is configured in monostable mode. When it gets an input pulse its output goes
high for a period set by VR1, resistor R5 and capacitorC3. IC UM66 (IC2) is used as a
melody generator. When the door is knocked at, the piezoelectric plate generates an
input pulse, which is amplified by transistor T1.The amplified signal triggers the timer
IC NE555 and its output pin 3goes high to enable the melody generator. Music is
heard from the speakerLS1. After the set time period, the melody sound stops.
Assemble the circuit on a general purpose PCB and enclose in a suitable case.
3.2 CIRCUIT LAYOUT

Figure 1
1)T1,T2-TRANSISTORS 8)IC1 NE555-TIMER
2)GND-GROUND(0 VOLTS) 9)VR1-VARIABLE
RESISTOR
3)C1,C2,C3-CAPACITORS 10)LS1-LOUDSPEAKER
4)R1,R2,R3,R4,R5,R6,R7,R8-RESISTORS 11)PZ1-PIEZOELECTRIC
ELEMENT
5)ZD1-ZENNER DIODE
6)IC2 UM66-MELODY GENERATOR
3.3 COMPONENT LIST

description
Reference
Description
1 IC NE555 IC 1
2 Resistor 10 K R4,R5,R8
3 Resistor 2.2 M R1
4 Resistor 270 K R2
5 Resistor 3.3 K R3
6 Resistor 470 K R 6
7 IC’S BC 547,BG
549,UM66,NE555
8 Resistor 1 K R 7
9 Variable Resistor
100 K
VR 1
10 9 Volt Battery -
11 Piezoelectric
element
-
12 Piezoelectriv
buzzer
-
Table 2
CHAPTER 4
4.1 PCB DETAILS
MANUFACTURING
A PCB as a design on a computer (left) and realized as a board assembly populated
with components (right). The board is double sided, with through-hole plating, green
solder resist, and white silkscreen printing. Both surface mount and through-hole
components have been used.

The Component Side of a PCB in a computer mouse; some examples for common
components and their reference designation on the silk screen.
Figure 2
General PCB solder and component side
Conducting layers are typically made of thin copper foil. Insulating layers dielectric are
typically laminated together with epoxy resin prepreg. The board is typically coated
with a solder mask that is green in color. Other colors that are normally available are
blue, black, white and red. There are quite a few different dielectrics that can be
chosen to provide different insulating values depending on the requirements of the
circuit.
PATTERNING(ETCHING)
The vast majority of printed circuit boards are made by bonding a layer of copper
over the entire substrate, sometimes on both sides, (creating a "blank PCB") then
removing unwanted copper after applying a temporary mask (e.g., by etching), leaving
only the desired copper traces. A few PCBs are made by adding traces to the bare
substrate (or a substrate with a very thin layer of copper) usually by a complex process
of multiple electroplating steps. The PCB manufacturing method primarily depends
on whether it is for production volume or sample/prototype quantities. Double-sided

boards or multi-layer boards use plated-through holes, called vias, to connect traces
on either side of the substrate.
• Silk screen printing–the main commercial method.
• Photographic methods–used when fine linewidths are required.
• Print onto transparent film and use as photomask along with photo-sensitized
boards. (i.e., pre-sensitized boards), then etch. (Alternatively, use a film
photoplotter).
• Laser resist ablation: Spray black paint onto copper clad laminate, place into
CNC laser plotter. The laser raster-scans the PCB and ablates (vaporizes) the
paint where no resist is wanted. Etch. (Note: laser copper ablation is rarely used
and is considered experimental.)
• Use a CNC-mill with a spade-shaped (i.e., a flat-ended cone) cutter or miniature
end-mill to rout way the undesired copper, leaving only the traces.
HOBBYIST
• Laser-printed resist: Laser-print onto transparency film, heat-transfer with an
iron or modified laminator onto bare laminate, touch up with a marker, then
etch.
• Other labor-intensive techniques exist, only suitable for one-off boards (vinyl
film and resist, non-washable marker, and others).
There are three common "subtractive" methods (methods that remove copper) used
for the production of printed circuit boards:
• SILK SKIN PRINTING:uses etch-resistant inks to protect the copper foil.
Subsequent etching removes the unwanted copper. Alternatively, the ink may
be conductive, printed on a blank (non-conductive) board. The latter technique
is also used in the manufacture of hybrid -aided manufacturing circuit.
• PHOTOENGRAVING uses a photomask and developer to selectively remove
a photoresist coating. The remaining photoresist protects the copper foil.
Subsequent etching removes the unwanted copper. The photomask is usually
prepared with a photoplotter from data produced by a technician using CAM,
or compute software. Laser-printed transparencies are typically employed for
phototools; however, direct laser imaging techniques are being employed to
replace phototools for high-resolution requirements.
• PCB MILLING uses a two or three-axis mechanical milling system to mill
away the copper foil from the substrate. A PCB milling machine (referred to as
a 'PCB Prototyper') operates in a similar way to a plotter, receiving commands

from the host software that control the position of the milling head in the x, y,
and (if relevant) z axis. Data to drive the Prototyper is extracted from files
generated in PCB design software and stored in HPGL or Gerber file format.
"Additive" processes also exist. The most common is the "semi-additive" process. In
this version, the unpatterned board has a thin layer of copper already on it. A reverse
mask is then applied. (Unlike a subtractive process mask, this mask exposes those
parts of the substrate that will eventually become the traces.) Additional copper is
then plated onto the board in the unmasked areas; copper may be plated to any
desired weight. Tin-lead or other surface platings are then applied. The mask is
stripped away and a brief etching step removes the now-exposed original copper
laminate from the board, isolating the individual traces. Some boards with plated
through holes but still single sided were made with a process like this.General electric
made consumer radio sets in the late 1960s using boards like these.
The additive process is commonly used for multi-layer boards as it facilitates the
plating-through of the holes (to produce conductive vias) in the circuit board.
The dimensions of the copper conductors of the printed circuit board is related to the
amount of current the conductor must carry. Each trace consists of a flat, narrow part
of the copper foil that remains after etching. Signal traces are usually narrower than
power or ground traces because their current carrying requirements are usually much
less. In a multi-layer board one entire layer may be mostly solid copper to act as a
ground plane for shielding and power return. For printed circuit boards that contain
microwave circuits, transmission line can be laid out in the form of stripline and
microstrip with carefully controlled dimensions to assure a consistent impedence. In
radio-frequency circuits the inductance and capacitance of the printed circuit board
conductors can be used as a deliberate part of the circuit design, obviating the need
for additional discrete components.
CHEMICAL ETCHING
Chemical etching is done with ferric chloride, ammonium persulfate, or sometimes
hydrochloric acid. For PTH (plated-through holes), additional steps of electroless
deposition are done after the holes are drilled, then copper is electroplated to build up
the thickness, the boards are screened, and plated with tin/lead. The tin/lead becomes
the resist leaving the bare copper to be etched away.
The simplest method, used for small-scale production and often by hobbyists, is
immersion etching, in which the board is submerged in etching solution such as ferric

chloride. Compared with methods used for mass production, the etching time is long.
Heat and agitation can be applied to the bath to speed the etching rate. In bubble
etching, air is passed through the etchant bath to agitate the solution and speed up
etching. Splash etching uses a motor-driven paddle to splash boards with etchant; the
process has become commercially obsolete since it is not as fast as spray etching. In
spray etching, the etchant solution is distributed over the boards by nozzles, and
recirculated by pumps. Adjustment of the nozzle pattern, flow rate, temperature, and
etchant composition gives predictable control of etching rates and high production
rates.
As more copper is consumed from the boards, the etchant becomes saturated and less
effective; different etchants have different capacities for copper, with some as high as
150 grams of copper per litre of solution. In commercial use, etchants can be
regenerated to restore their activity, and the dissolved copper recovered and sold.
Small-scale etching requires attention to disposal of used etchant, which is corrosive
and toxic due to its metal content.
The etchant removes copper on all surfaces exposed by the resist. "Undercut" occurs
when etchant attacks the thin edge of copper under the resist; this can reduce
conductor widths and cause open-circuits. Careful control of etch time is required to
prevent undercut. Where metallic plating is used as a resist, it can "overhang" which
can cause short-circuits between adjacent traces when closely spaced. Overhang can
be removed by wire-brushing the board after etching.
A printed circuit board, or PCB, is used to mechanically support and electrically
connect electronic component using conductiv pathways, tracks or signal traces
etched from copper sheets laminated onto a non-conductive substrate. It is also
referred to as printed wiring board (PWB) or etched wiring board.
A PCB populated with electronic components is a printed circuit assembly (PCA),
also known as a printed circuit board assembly or PCB Assembly (PCBA). Printed
circuit boards are used in virtually all but the simplest commercially produced
electronic devices.
Alternatives to PCBs include wire wrap and point to point construction PCBs are
often less expensive and more reliable than these alternatives, though they require
more layout effort and higher initial cost. PCBs are much cheaper and faster for high-
volume production since production and soldering of PCBs can be done by
automated equipment. Much of the electronics industry's PCB design, assembly, and
quality control needs are set by standards that are published by the IPC organization.

Conducting layers are typically made of thin copper foil. Insulating layers dielectric are
typically laminated together with epoxy resin prepreg. The board is typically coated
with a solder mask that is green in color. Other colors that are normally available are
blue, black, white and red. There are quite a few different dielectrics that can be
chosen to provide different insulating values depending on the requirements of the
circuit.
Some of these dielectrics are polytetrafluroethene(Teflon), FR-4, FR-1, CEM-1 or
CEM-3. Well known prepreg materials used in the PCB industry are FR-2(Phenolic
cotton paper), FR-3 (Cotton paper and epoxy), FR-4(Woven glass and epoxy), FR-5
(Woven glass and epoxy), FR-6 (Matte glass and polyester), G-10 (Woven glass and
epoxy), CEM-1 (Cotton paper and epoxy), CEM-2 (Cotton paper and epoxy), CEM-3
(Non-woven glass and epoxy), CEM-4 (Woven glass and epoxy), CEM-5 (Woven
glass and polyester).
Thermal expansion is an important consideration especially with ball grid array(BGA)
and naked die technologies, and glass fiber offers the best dimensional stability.FR-4
is by far the most common material used today. The board with copper on it is called
"copper-clad laminate".
Copper foil thickness can be specified in ounces per square foot or micrometres. One
ounce per square foot is 1.344 mils or 34 micrometres
The vast majority of printed circuit boards are made by bonding a layer of copper
over the entire substrate, sometimes on both sides, (creating a "blank PCB") then
removing unwanted copper after applying a temporary mask (e.g., by etching), leaving
only the desired copper traces.
A few PCBs are made by adding traces to the bare substrate (or a substrate with a very
thin layer of copper) usually by a complex process of multiple electroplating steps.
The PCB manufacturing method primarily depends on whether it is for production
volume or sample/prototype quantities. Double-sided boards or multi-layer boards
use plated-through holes, called vias, to connect traces on either side of the substrate.

4.2 PCB DESCRIPTION
FR-4 (or FR4) is a grade designation assigned to glass-reinforced epoxy laminate
sheets, tubes, rods and printed circuit boards (PCB)fiberglass. FR-4 is a composite
material composed of woven cloth with an epoxy resin binder that is flame resistant
(self-extinguishing).
FR-4 glass epoxy is a popular and versatile high-pressure thermoset plastic laminate
grade with good strength to weight ratios. With near zero water absorption, FR-4 is

most commonly used as an electrical insulator possessing considerable mechanical
strength.
The material is known to retain its high mechanical values and electrical insulating
qualities in both dry and humid conditions. These attributes, along with good
fabrication characteristics, lend utility to this grade for a wide variety of electrical and
mechanical applications.NEMA is the regulating authority for FR-4 and other
insulating laminate grades. Grade designations for glass epoxy laminates are: G10,
G11, FR4 and FR5. Of these, FR4 is the grade most widely in use today. G-10, the
predecessor to FR-4, lacks FR-4's self-extinguishing flammability characteristics.
Hence, FR-4 has since replaced G-10 in most applications.
FR-4 epoxy resin systems typically employ bromine, a halogen, to facilitate flame-
resistant properties in FR-4 glass epoxy laminates. Some applications where thermal
destruction of the material is a desirable trait will still use G-10 non flame resistant
PRINTED CIRCUIT BOARD
FR-4 is the primary insulating backbone upon which the vast majority of rigid printed
circuit board (PCBs) are produced. A thin layer of copper foil is laminated to one, or
both sides of an FR-4 glass epoxy panel. These are commonly referred to as
"copperclad laminates."
FR-4 copper-clad sheets are fabricated with circuitry etched into copper layers to
produce printed circuit boards. More sophisticated and complex FR-4 printed circuit
boards are produced in multiple layers, aka "multilayer circuitry".
SPECIFICATION
In the USA, copper foil thickness is specified in units of ouncpeesr square foot
(oz/ft2
). One ounce copper foil has a weight of one oz/ft2
. This works out to a
thickness of 34.1 µm (1.34 mils). Some PCB manufacturers refer to one ounce copper
foil as having a thickness of 35 µm this may also be referred to as 35μ, 35 micron, or
35 mic. Two ounce would be 70 μ and half ounce would be 17.5 μ or thereabouts.
1/0 - denotes 1 ounce (28.3 gram) copper one side / with no copper on the other
side. 1/1 - denotes 1 ounce copper on both sides. Similarly: H/0 or H/H - denotes

half ounce copper on one and both sides, respectively. 2/0 or 2/2 - denotes 2 ounce
copper on one and both sides respectively.
4.3 PCB DESIGNING
Printed circuit board design was initially a fully manual process, where an initial
schematic diagram was converted into a layout of parts, then traces were routed
between package terminals to provide the required interconnections. Pre-printed non-
reproducing mylar grids assisted in layout, and rub-on dry transfers of common
arrangements of circuit elements (pads, contact fingers, integrated circuit profiles, and
so on) helped standardize the layout. The finished layout "artwork" wasn then
photographically reproduced on the resist layers of the blank coated copper-clad
boards.

Modern practice is less labor intensive since computers can inexpensively and
accurately perform many of the layout steps. The general progression for a
commercial printed circuit board design would include:
• Schematic capture through an Electronic design specification tool.
• Card dimensions and template are decided based on required heat sinks
circuitry and case of the PCB. Determine the fixed components anh heif
required.
• Deciding stack layers of the PCB. 4 to 12 layers or more depending on design
complexity. Ground plane and power plane are decided. Signal planes where
signals are routed are in top layer as well as internal layers.
• Line impedence determination using dielectric layer thickness, routing copper
thickness and trace-width. Trace separation also taken into account in case of
differential signals. Microstrip, stripline or dual stripline can be used to route
signals.
• Placement of the components. Thermal considerations and geometry are taken
into account. Vias and lands are marked.
• Routing the signal trace. For optimal EMI performance high frequency signals
are routed in internal layers between power or ground planes as power plane
behaves as ground for AC.
• Gerber file generation for manufacturing.
In layout of the board, a power plane is the counterpart to the ground plane and
behaves as an AC signal ground, whilst providing DC voltage for powering circuits
mounted on the PCB. Where possible it is good to have a power plane for each
ground plane on a board (known as a "plane pair"), as this reduces power supply
impedence to the components on the board. In electronic design automation(EDA)
design tools, power planes (and ground planes) are usually drawn automatically as a
negative layer. Adding primitive layout shapes (for example, a donut pad) on such a
layer automatically produces a negative of those primitives, placing copper wherever
there is no track or via.
After the printed circuit board (PCB) is completed, electronic components must be
attached to form a functional printed circuit assembly, or PCA (sometimes called a
"printed circuit board assembly" PCBA). In through-hole construction, component
leads are inserted in holes. In surface mount construction, the components are placed
on pads or lands on the outer surfaces of the PCB. In both kinds of construction,

component leads are electrically and mechanically fixed to the board with a molten
metal solder.
There are a variety of soldering techniques used to attach components to a PCB. High
volume production is usually done with SMT placement machine and bulk wave
soldering or reflow ovens, but skilled technicians are able to solder very tiny parts (for
instance 0201 packages which are 0.02 in. by 0.01 in. by hand under microscope, using
tweezers and a fine tip soldering iron,for small volume prototypes. Some parts may be
extremely difficult to solder by hand, such as BGA packages.
Often, through-hole and surface-mount construction must be combined in a single
assembly because some required components are available only in surface-mount
packages, while others are available only in through-hole packages. Another reason to
use both methods is that through-hole mounting can provide needed strength for
components likely to endure physical stress, while components that are expected to go
untouched will take up less space using surface-mount techniques.
After the board has been populated it may be tested in a variety of ways:
• While the power is off, visual inspection,automated optical,inspection. JEDEC
guidelines for PCB component placement, soldering, and inspection are
commonly used to maintain quality control in this stage of PCB manufacturing.
• While the power is off, analog signature analysis,power off testing
• While the power is on, in circuit testing, where physical measurements (i.e.
voltage, frequency) can be done.
• While the power is on, functional test, just checking if the PCB does what it
had been designed to do.
To facilitate these tests, PCBs may be designed with extra pads to make temporary
connections. Sometimes these pads must be isolated with resistors. The in-circuit test
may also exercise boundary scan test features of some components. In-circuit test
systems may also be used to program nonvolatile memory components on the board.
In boundary scan testing, test circuits integrated into various ICs on the board form
temporary connections between the PCB traces to test that the ICs are mounted
correctly. Boundary scan testing requires that all the ICs to be tested use a standard
test configuration procedure, the most common one being the Joint Test Action
Group (JTAG)standard.
The JTAG test architecture provides a means to test interconnects between
integrated circuits on a board without using physical test probes. JTAGtool vendors

provide various types of stimulus and sophisticated algorithms, not only to detect the
failing nets, but also to isolate the faults to specific nets, devices, and pins.
When boards fail the test, technicians may desolder and replace failed components, a
task known as rework.
4.4 PCB LAYOUT COMPONENT SIDE

Figure 3
4.5 PCB LAYOUT SOLDER SIDE

Figure 4
4.6 PROTCTION AND PACKAGING
PCBs intended for extreme environments often have a conformal coating, which is
applied by dipping or spraying after the components have been soldered. The coat
prevents corrosion and leakage currents or shorting due to condensation. The earliest

conformal coats were wax; modern conformal coats are usually dips of dilute
solutions of silicone rubber, polyurethane, acrylic, or epoxy. Another technique for
applying a conformal coating is for plastic to be sputtered onto the PCB in a vacuum
chamber. The chief disadvantage of conformal coatings is that servicing of the board
is rendered extremely difficult.
Many assembled PCBs are static sensitive, and therefore must be placed in antistatic
bags during transport. When handling these boards, the user must be
grounded(earthered). Improper handling techniques might transmit an accumulated
static charge through the board, damaging or destroying components. Even bare
boards are sometimes static sensitive. Traces have become so fine that it's quite
possible to blow an etch off the board (or change its characteristics) with a static
charge. This is especially true on non-traditional PCBs such as MCMs and microwave
PCBs.
CHAPTER 5
ASSEMBLY AND TESTING
5.1 BREADBOARD IMPLEMENTATION

A breadboard (protoboard) is a construction base for prototyping of electronics. The
term is commonly used to refer to solderless breadboard (plugboard).
Because the solderless breadboard does not require soldering, it is reusable. This
makes it easy to use for creating temporary prototypes and experimenting with circuit
design. Older breadboard types did not have this property. A stripboard(veroboard)
and similar prototyping printed circuit board, which are used to build permanent
soldered prototypes or one-offs, cannot easily be reused. A variety of electronic
systems may be prototyped by using breadboards, from small analog and digital
circuits to complete central processing units (CPUs).
In the early days of radio, amateurs nailed bare copper wires or terminal strips to a
wooden board (often literally a cutting board for bread) and soldered electronic
components to them. Sometimes a paper schematic diagram was first glued to the
board as a guide to placing terminals, then components and wires were installed over
their symbols on the schematic. Using thumbtacks or small nails as mounting posts
was also common.
Breadboards have evolved over time, with the term now being used for all kinds of
prototype electronic devices. For example, US Patent 3,145,483, filed in 1961 and
granted in 1964, describes a wooden plate breadboard with mounted springs and
other facilities. US Patent 3,496,419, filed in 1967 and granted in 1970, refers to a
particular printed circuit board layout as a Printed Circuit Breadboard. Both examples
refer to and describe other types of breadboards as prior art.
The breadboard most commonly used today is usually made of white plastic and is a
pluggable (solderless) breadboard. It was designed by Ronald J Portugal of EI
Instruments Inc. in 1971.
SOLDERLESS BREADBOARD
TYPICAL SPECIFICATION:

A modern solderless breadboard consists of a perforated block of plastic with
numerous tin plated phospher bronze or nickle silver alloy spring clips under the
perforations. The clips are often called tie points or contact points. The number of tie
points is often given in the specification of the breadboard.
The spacing between the clips (lead pitch) is typically 0.1" (2.54 mm). Integrated
circuit(ICs) in dual in package (DIPs) can be inserted to straddle the centerline of the
block. Interconnecting wires and the leads of discrete components (such as capacitors,
resistors, and inductor) can be inserted into the remaining free holes to complete the
circuit. Where ICs are not used, discrete components and connecting wires may use
any of the holes. Typically the spring clips are rated for 1 ampere at 5 volts and 0.333
amperes at 15 volts (5 watts).
Figure 5 Breadboard
Example breadboard drawing. Two bus strips and one terminal strip in one block. 25
consecutive terminals in a bus strip connected (indicated by gaps in the red and blue
lines). Four binding posts depicted at the top.
Close-up of a solderless breadboard. An IC straddling the centerline is probed with an
oscilloscope probe. The solderless breadboard is mounted on a blue painted metal

sheet. Red and black binding posts are present. The black one partly obscured by the
oscilloscope probe.
Solderless breadboards are available from several different manufacturers, but most
share a similar layout. The layout of a typical solderless breadboard is made up from
two types of areas, called strips. Strips consist of interconnected electrical terminals.
Terminal strips
The main areas, to hold most of the electronic components.
In the middle of a terminal strip of a breadboard, one typically finds a notch
running in parallel to the long side. The notch is to mark the centerline of the
terminal strip and provides limited airflow (cooling) to DIP ICs straddling the
centerline. The clips on the right and left of the notch are each connected in a
radial way; typically five clips (i.e., beneath five holes) in a row on each side of
the notch are electrically connected. The five clip columns on the left of the
notch are often marked as A, B, C, D, and E, while the ones on the right are
marked F, G, H, I and J. When a "skinny" Dual In-line Pin package (DIP)
integrated circuit (such as a typical DIP-14 or DIP-16, which have a 0.3 inch
separation between the pin rows) is plugged into a breadboard, the pins of one
side of the chip are supposed to go into column E while the pins of the other
side go into column F on the other side of the notch.
Bus strips
To provide power to the electronic components.
A bus strip usually contains two columns: one for ground and one for a supply
voltage. However, some breadboards only provide a single-column power
distributions bus strip on each long side. Typically the column intended for a
supply voltage is marked in red, while the column for ground is marked in blue
or black. Some manufacturers connect all terminals in a column. Others just
connect groups of, for example, 25 consecutive terminals in a column. The
latter design provides a circuit designer with some more control over crosstalk
(inductively coupled noise) on the power supply bus. Often the groups in a bus
strip are indicated by gaps in the color marking.
Bus strips typically run down one or both sides of a terminal strip or between
terminal strips. On large breadboards additional bus strips can often be found
on the top and bottom of terminal strips.
Some manufacturers provide separate bus and terminal strips. Others just provide
breadboard blocks which contain both in one block. Often breadboard strips or
blocks of one brand can be clipped together to make a larger breadboard.
In a more robust variant, one or more breadboard strips are mounted on a sheet of
metal. Typically, that backing sheet also holds a number of binding posting. These
posts provide a clean way to connect an external power supply. This type of

breadboard may be slightly easier to handle. Several images in this article show such
solderless breadboards.
DIAGRAM
A "full size" terminal breadboard strip typically consists of around 56 to 65 rows of
connectors, each row containing the above mentioned two sets of connected clips (A
to E and F to J). Together with bus strips on each side this makes up a typical 784 to
910 tie point solderless breadboard. "Small size" strips typically come with around 30
rows. Miniature solderless breadboards as small as 17 rows (no bus strips, 170 tie
points) can be found, but these are less well suited for practical use.
JUMP WIRES
Jump wires for solderless breadboarding can be obtained in ready-to-use jump wire
sets or can be manually manufactured. The latter can become tedious work for larger
circuits. Ready-to-use jump wires come in different qualities, some even with tiny
plugs attached to the wire ends. Jump wire material for ready-made or homemade
wires should usually be 22 AWG (0.33 mm²) solid copper, tin-plated wire - assuming
no tiny plugs are to be attached to the wire ends. The wire ends should be stripped
3/16" to 5/16" (approx. 5 mm to 8 mm). Shorter stripped wires might result in bad
contact with the board's spring clips (insulation being caught in the springs). Longer
stripped wires increase the likelihood of short-circuits on the board. Needle nose
pliers and tweezers are helpful when inserting or removing wires, particularly on
crowded boards.
Differently colored wires and color coding discipline are often adhered to for
consistency. However, the number of available colors is typically far fewer than the
number of signal types or paths. Typically, a few wire colors are reserved for the
supply voltages and ground (e.g., red, blue, black), some are reserved for main signals,
and the rest are simply used where convenient. Some ready-to-use jump wire sets use
the color to indicate the length of the wires, but these sets do not allow a meaningful
color-coding schema.
ADVANCED SOLDRERLESS BREADBOARD

Some manufacturers provide high-end versions of solderless breadboards. These are
typically high-quality breadboard modules mounted on a flat casing. The casing
contains additional equipment for breadboarding, such as a power supply, one or
more signal generators, serial interfaces, LED or LCD modules, and logic probes.
Solderless breadboard modules can also be found mounted on devices like
microcontroller evaluation boards. They provide an easy way to add additional
periphery circuits to the evaluation board.
LIMITATIONS
Due to large stray capacitance(from 2-25 pF per contact point), high inductanceof
some connections and a relatively high and not very reproducible contact resistance,
solderless breadboards are limited to operation at relatively low frequencies, usually
less than 10 MHz, depending on the nature of the circuit. The relative high contact
resistance can already be a problem for DC and very low frequency circuits. Solderless
breadboards are further limited by their voltage and current ratings.
Solderless breadboards usually cannot accommodate surface mount technology
devices (SMD) or components with grid spacing other than 0.1" (2.54 mm). Further,
they cannot accommodate components with multiple rows of connectors if these
connectors don't match the dual in line layout—it is impossible to provide the correct
electrical connectivity. Sometimes small PCB adapters called breakout adapters can be
used to fit the component to the board. Such adapters carry one or more components
and have 0.1" (2.54 mm) connectors in a single in line or dual in-line layout. Larger
components are usually plugged into a socket on the adapter, while smaller
components (e.g., SMD resistors) are usually soldered directly onto the adapter. The
adapter is then plugged into the breadboard via the 0.1" connectors. However, the
need to solder the components onto the adapter negates some of the advantage of
using a solderless breadboard.
Complex circuits can become unmanageable on a breadboard due to the large amount
of wiring required.
Alternative methods to create prototypes are point to point construction, reminiscent
of the original breadboards, wirw wrap, wiring pencil, and boards like the stripboard.
Complicated systems, such as modern computers comprising millions of transistors,
diodes, and resistors, do not lend themselves to prototyping using breadboards, as
their complex designs can be difficult to lay out and debug on a breadboard. Modern
circuit designs are generally developed using a schematic capture and simulation
system, and tested in software simulation before the first prototype circuits are built

on a PCB. IC designs are a more extreme version of the same process: since
producing prototype silicon is costly, extensive software simulations are performed
before fabricating the first prototype.
5.2 PCB IMPLEMENTATION

Figure 6
PCB with test connection pads
After the printed circuit board (PCB) is completed, electronic components must be
attached to form a functional printed circuit assembly,or PCA (sometimes called a
"printed circuit board assembly" PCBA). In through hole construction, component
leads are inserted in holes. In mount surface construction, the components are placed
on pads or lands on the outer surfaces of the PCB. In both kinds of construction,
component leads are electrically and mechanically fixed to the board with a molten
metal solder.
There are a variety of soldering techniques used to attach components to a PCB. High
volume production is usually done with SMT placement machine and bulk wave
soldering or reflow ovens, but skilled technicians are able to solder very tiny parts (for
instance 0201 packages which are 0.02 in. by 0.01 in.by hand under a microscope,
using tweezers and a fine tip soldering iron for small volume prototypes. Some parts
may be extremely difficult to solder by hand, such as BGA packages.
Often, through-hole and surface-mount construction must be combined in a single
assembly because some required components are available only in surface-mount
packages, while others are available only in through-hole packages. Another reason to
use both methods is that through-hole mounting can provide needed strength for
components likely to endure physical stress, while components that are expected to go
untouched will take up less space using surface-mount techniques.
After the board has been populated it may be tested in a variety of ways:
• While the power is off virtual inspection,automated optical inspection. JEDEC
guidelines for PCB component placement, soldering, and inspection are
commonly used to maintain quality contral in this stage of PCB manufacturing.
• While the power is off,analog signature analysis ,power off testing.
• While the power is on,in circuit testing,where physical measurements (i.e.
voltage, frequency) can be done.

• While the power is on,functionality test , just checking if the PCB does what it
had been designed to do.
To facilitate these tests, PCBs may be designed with extra pads to make temporary
connections. Sometimes these pads must be isolated with resistors. The in-circuit test
may also exercise boundary scan test features of some components. In-circuit test
systems may also be used to program nonvolatile memory components on the board.
In boundary scan testing, test circuits integrated into various ICs on the board form
temporary connections between the PCB traces to test that the ICs are mounted
correctly. Boundary scan testing requires that all the ICs to be tested use a standard
test configuration procedure, the most common one being the Joint Test Action
Group (JTAG) standard. The JTAG test architecture provides a means to test
interconnects between integrated circuits on a board without using physical test
probes.JTAG tool vendors provide various types of stimulus and sophisticated
algorithms, not only to detect the failing nets, but also to isolate the faults to specific
nets, devices, and pins.
When boards fail the test, technicians may desolder and replace failed components, a
task known as rework.
Lamination:
Some PCBs have trace layers inside the PCB and are called multi-layer PCBs. These are
formed by bonding together separately etched thin boards.
Drilling:
Holes through a PCB are typically drilled with small-diameter drill bits made of solid
coated tungsten carbide. Coated tungsten carbide is recommended since many board
materials are very abrasive and drilling must be high RPM and high feed to be cost
effective. Drill bits must also remain sharp so as not to mar or tear the traces. Drilling
with high-speed-steel is simply not feasible since the drill bits will dull quickly and
thus tear the copper and ruin the boards. The drilling is performed by automated
drilling machines with placement controlled by a drill tape or drill file. These computer-
generated files are also called numerically controlled drill (NCD) files or "Excellon files".
The drill file describes the location and size of each drilled hole. These holes are often
filled with annular rings (hollow rivets) to create vias. Vias allow the electrical and
thermal connection of conductors on opposite sides of the PCB.
When very small vias are required, drilling with mechanical bits is costly because of
high rates of wear and breakage. In this case, the vias may be evaporated by lasers.

Laser-drilled vias typically have an inferior surface finish inside the hole. These holes
are called micro vias.
It is also possible with controlled-depth drilling, laser drilling, or by pre-drilling the
individual sheets of the PCB before lamination, to produce holes that connect only
some of the copper layers, rather than passing through the entire board. These holes
are called blind vias when they connect an internal copper layer to an outer layer, or
buried vias when they connect two or more internal copper layers and no outer layers.
The walls of the holes, for boards with 2 or more layers, are made conductive then
plated with copper to form plated-through holes that electrically connect the conducting
layers of the PCB. For multilayer boards, those with 4 layers or more, drilling typically
produces a smear of the high temperature decomposition products of bonding agent in
the laminate system. Before the holes can be plated through, this smear must be
removed by a chemical de-smear process, or by plasma-etch. Removing (etching back) the
smear also reveals the interior conductors as well.
Exposed conductor plating and coating
PCBsare plated with solder, tin, or gold over nickel as a resist for etching away the
unneeded underlying copper.
After PCBs are etched and then rinsed with water, the soldermask is applied, and then
any exposed copper is coated with solder, nickel/gold, or some other anti-corrosion
coating.
Matte solder is usually fused to provide a better bonding surface or stripped to bare
copper. Treatments, such as benzimidazolethiol, prevent surface oxidation of bare
copper. The places to which components will be mounted are typically plated, because
untreated bare copper oxidizes quickly, and therefore is not readily solderable.
Traditionally, any exposed copper was coated with solder by hot air solder levelling
(HASL). The HASL finish prevents oxidation from the underlying copper, thereby
guaranteeing a solderable surface. This solder was a tin-lead alloy, however new solder
compounds are now used to achieve compliance with the RoHS directive in the EU
and US, which restricts the use of lead. One of these lead-free compounds is
SN100CL, made up of 99.3% tin, 0.7% copper, 0.05% nickel, and a nominal of
60ppm germanium.
It is important to use solder compatible with both the PCB and the parts used. An
example is Ball Grid Array (BGA) using tin-lead solder balls for connections losing
their balls on bare copper traces or using lead-free solder paste.
Other platings used are OSP (organic surface protectant), immersion silver (IAg),
immersion tin, electroless nickel with immersion gold coating (ENIG), and direct gold
plating (over nickel). Edge connectors, placed along one edge of some boards, are
often nickel plated then gold plated. Another coating consideration is rapid diffusion

of coating metal into Tin solder. Tin forms intermetallics such as Cu5Sn6 and Ag3Cu
that dissolve into the Tin liquidus or solidus(@50C), stripping surface coating or
leaving voids.
Electrochemical migration (ECM) is the growth of conductive metal filaments on or in a
printed circuit board (PCB) under the influence of a DC voltage bias. Silver, zinc, and
aluminum are known to grow whiskers under the influence of an electric field. Silver
also grows conducting surface paths in the presence of halide and other ions, making
it a poor choice for electronics use. Tin will grow "whiskers" due to tension in the
plated surface. Tin-Lead or Solder plating also grows whiskers, only reduced by the
percentage Tin replaced. Reflow to melt solder or tin plate to relieve surface stress
lowers whisker incidence. Another coating issue is tin pest, the transformation of tin
to a powdery allotrope at low temperature.
Solder resist:
Areas that should not be soldered may be covered with a polymer solder resist (solder
mask) coating. The solder resist prevents solder from bridging between conductors
and creating short circuits. Solder resist also provides some protection from the
environment. Solder resist is typically 20–30 micrometres thick.
Screen printing:
Line art and text may be printed onto the outer surfaces of a PCB by screen printing.
When space permits, the screen print text can indicate component designators, switch
setting requirements, test points, and other features helpful in assembling, testing, and
servicing the circuit board.
Screen print is also known as the silk screen, or, in one sided PCBs, the red print.
Lately some digital printing solutions have been developed to substitute the traditional
screen printing process. This technology allows printing variable data onto the PCB,
including serialization and barcode information for traceability purposes.
Testing:
Unpopulated boards may be subjected to a bare-board test where each circuit
connection (as defined in a netlist) is verified as correct on the finished board. For
high-volume production, a bed of nails tester, a fixture or a rigid needle adapter is
used to make contact with copper lands or holes on one or both sides of the board to
facilitate testing. A computer will instruct the electrical test unit to apply a small voltage
to each contact point on the bed-of-nails as required, and verify that such voltage
appears at other appropriate contact points. A "short" on a board would be a
connection where there should not be one; an "open" is between two points that
should be connected but are not. For small- or medium-volume boards, flying probe
and flying-grid testers use moving test heads to make contact with the

copper/silver/gold/solder lands or holes to verify the electrical connectivity of the
board under test. Another method for testing is industrial CT scanning, which can
generate a 3D rendering of the board along with 2D image slices and can show details
such a soldered paths and connections.
CHAPTER 6:

WORKING OF CIRCUIT
sensor. When the door is knocked music is heard from the speakerLS1. After the set
time period, the melody sound stops. The circuit works off 5-12V DC. The music
time can be adjusted through VR1 by changing the R-C time constant of the timer.
This is the general functioning of the door knock alarm.
We have chosen the project as in day to day life it is not possible to have a watch over
every nook and corner. So to have a check on every aspect of a place we plan to
device a detector which is able to alert us of some change in the prevailing system.
There are many application of the concept behind the project. It can not only be used
for military purpose but also can be used in day to day like door knock alarm, bugler
alarm safety alarm.
Alternative methods to create prototypes are point to point construction, reminiscent
of the original breadboards, wirw wrap, wiring pencil, and boards like the stripboard.
Complicated systems, such as modern computers comprising millions of transistors,
diodes, and resistors, do not lend themselves to prototyping using breadboards, as
their complex designs can be difficult to lay out and debug on a breadboard. Modern
circuit designs are generally developed using a schematic capture and simulation
system, and tested in software simulation before the first prototype circuits are built
on a PCB. IC designs are a more extreme version of the same process: since
producing prototype silicon is costly, extensive software simulations are performed
before fabricating the first prototype.

CHAPTER 8:
EXPECTATION AND ACHIEVEMENTS
The project is easy and can be implemented on both pcb and breadboard within
stipulated time. Minimal idea of circuit implementation on breadboard and pcb is
required for successfully carrying out the development process of the circuit. As we
had an idea of pcb and breadboard implementation we could easily carry out the
designing of the circuit. After the implementation of circuit on breadboard the main
hurdle was carrying out the fabrication process of the circuit on printed circuit board.
Initially we carried out the process of circuit layout manually. Later on we carried out
the process on special software called DIPTRACE.With the help of it we could easily
manage the layout diagram of the circuit. During the process we came to know about
the working of new software called DIPTRACE.Later on the fabrication process on
the pcb was carried out by us manually. We drew the layout on the unitched pcb and
then later on itched it to remove excess copper off the pcb board. The circuit was
ready for the drilling process. After the drilling process the components were placed
at their respective location and soldering of the components was carried out.After the
soldering process the development process was successfully carried out and the circuit
was tested. The project was a success at last.

CHAPTER 8:
PROJECT COST
description
Reference
Description
Cost
1 IC NE555 IC 1 10/-
2 Resistor 10 K R4,R5,R8 2/- (EACH)
3 Resistor 2.2 M R1 2/-
4 Resistor 270 K R2 2/-
5 Resistor 3.3 K R3 2/-
6 Resistor 470 K R 6 2/-
7 IC’S BC 547,BG
549,UM66,NE555
15/- (EACH)
8 Resistor 1 K R 7 2/-
9 Variable Resistor
100 K
VR 1 5/-
10 9 Volt Battery - 20/-
11 Piezoelectric
element
- 25/-
12 Piezoelectriv
buzzer
- 35/-
Table 3
CHAPTER 10:
COMPONENT DETAILS
10.1 PIEZOELECTRIC SENSORS

Figure 7
A piezoelectric disk generates a voltage when deformed (change in shape is greatly
exaggerated)
A piezoelectric sensor is a device that uses the piezoelectric effect to measure
pressure, acceleration strain and force by converting them to an electrical charge.
Principle of operation:
Depending on how a piezoelectric material is cut, three main modes of operation can
be distinguished: transverse, longitudinal, and shear.
Transverse effect
A force is applied along a neutral axis (y) and the charges are generated along the (x)
direction, perpendicular to the line of force. The amount of charge depends on the
geometrical dimensions of the respective piezoelectric element. When dimensions
apply,
,
where is the dimension in line with the neutral axis, is in line with the charge
generating axis and is the corresponding piezoelectric coefficient.
Longitudinal effect
The amount of charge produced is strictly proportional to the applied force and
is independent of size and shape of the piezoelectric element. Using several

elements that are mechanically in series and electrically in parallel is the only
way to increase the charge output. The resulting charge is
,
where is the piezoelectric coefficient for a charge in x-direction released by
forces applied along x-direction. is the applied Force in x-direction [N] and
corresponds to the number of stacked elements .
Electrical properties
Figure 8
Schematic symbol and electronic model of a piezoelectric sensor
A piezoelectric transducer has very high DC output impedance and can be modeled as
a proportional voltage and filter network.The voltage V at the source is directly
proportional to the applied force, pressure, or strain.The output signal is then related
to this mechanical force as if it had passed through the equivalent circuit.
Figure 9
Frequency response of a piezoelectric sensor;
output voltage vs applied force

A detailed model includes the effects of the sensor's mechanical construction and
other non-idealities. The inductance Lm is due to the seismic mass and inertia of the
sensor itself. Ce is inversely proportional to the mechanical elasticity of the sensor. C0
represents the static capacitance of the transducer, resulting from an inertial mass of
infinite size Ri is the insulation leakage rsistance of the transducer element. If the
sensor is connected to a load resistance, this also acts in parallel with the insulation
resistance, both increasing the high-pass cutoff frequency.
In the flat region, the sensor can be modeled as a voltage source in series with the
sensor's capacitance or a charge source in parallel with the capacitance.For use as a
sensor, the flat region of the frequency response plot is typically used, between the
high-pass cutoff and the resonant peak.
The load and leakage resistance need to be large enough that low frequencies of
interest are not lost. A simplified equivalent circuit model can be used in this region,
in which Cs represents the capacitance of the sensor surface itself, determined by the
standard formula for capacitance of parallel plate.It can also be modeled as a charge
source in parallel with the source capacitance, with the charge directly proportional to
the applied force, as above.
Sensor design
Metal disks with piezo material, used in buzzers or as contact microphones.
Based on piezoelectric technology various physical quantities can be measured; the
most common are pressure and acceleration.
For pressure sensors, a thin membrane and a massive base is used, ensuring that an
applied pressure specifically loads the elements in one direction. For
accelerometer,aseismometer is attached to the crystal elements. When the
accelerometer experiences a motion, the invariant seismic mass loads the elements
according to Newton’s second law of motion
.
The main difference in the working principle between these two cases is the way
forces are applied to the sensing elements. In a pressure sensor a thin membrane is
used to transfer the force to the elements, while in accelerometers the forces are
applied by an attached seismic mass.Sensors often tend to be sensitive to more than
one physical quantity. Pressure sensors show false signal when they are exposed to
vibrations.

Sophisticated pressure sensors therefore use acceleration compensation elements in
addition to the pressure sensing elements. By carefully matching those elements, the
acceleration signal (released from the compensation element) is subtracted from the
combined signal of pressure and acceleration to derive the true pressure
information.Vibration sensors can also be used to harvest otherwise wasted energy
from mechanical vibrations. This is accomplished by using piezoelectric materials to
convert mechanical strain into usable electrical energy.
10.2 NE555 IC
Figure 10

The 555 timer IC is an Integrated circuit (chip) used in a variety of timer, pulse
generation and oscillator applications. The 555 can be used to provide time delays, as
an oscillator, and as a flip flop element. Derivatives provide up to four timing circuits
in one package.
Introduced in 1971 by Signetics the 555 is still in widespread use, thanks to its ease of
use, low price and good stability, and is now made by many companies in the original
bipolar and also in low-power CMOS types.
PIN DIAGRAM:
Figure 11
Pin Name Purpose
1 GND Ground, low level (0 V)
2 TRIG OUT rises, and interval starts, when this input falls below 1/3 VCC.
3 OUT This output is driven to +Vcc or GND.
4 RESET A timing interval may be interrupted by driving this input to GND.
5 CTRL "Control" access to the internal voltage divider (by default, 2/3)
6 THR The interval ends when the voltage at THR is greater than at CTRL.
7 DIS Open collector output; may discharge a capacitor between intervals.
8
V+,
VCC
Positive supply voltage is usually between 3 and 15 V.
Modes:
The 555 has three operating modes:
• Monostable mode: in this mode, the 555 functions as a "one-shot" pulse
generator. Applications include timers, missing pulse detection, bounce free
switches, and touch switches, frequency divider, capacitance measurement,
pulse width modulation (PWM) and so on.
• Astable free running mode: the 555 can operate as an oscillator Uses include
LED and lamp flashers, pulse generation, logic clocks, tone generation, security
alarms, pulse and so on. Selecting a thermistor as timing resistor allows the use

of the 555 in a temperature sensor: the period of the output pulse is determined
by the temperature. The use of a microprocessor based circuit can then convert
the pulse period to temperature, linearize it and even provide calibration means.
• Bistable mode or Schmitt trigger the 555 can operate as a flip flop if the DIS
pin is not connected and no capacitor is used. Uses include bounce-free latched
switches.
Monostable
Figure 12
Schematic of a 555 in monostable mode
The relationships of the trigger signal, the voltage on C and the pulse width in
monostable mode
In the monostable mode, the 555 timer acts as a "one-shot" pulse generator. The
pulse begins when the 555 timer receives a signal at the trigger input that falls below a
third of the voltage supply. The width of the output pulse is determined by the time
constant of an RC network, which consists of capacitor(C) and a resistor(R). The
output pulse ends when the voltage on the capacitor equals 2/3 of the supply voltage.
The output pulse width can be lengthened or shortened to the need of the specific
application by adjusting the values of R and C.
The output pulse width of time t, which is the time it takes to charge C to 2/3 of the
supply voltage, is given by
where t is in seconds, R is in ohms and C is in farads.
While using the timer IC in monostable mode, the main disadvantage is that the time
span between the two triggering pulses must be greater than the RC time constant
Specifications
These specifications apply to the NE555. Other 555 timers can have different
specifications depending on the grade (military, medical, etc.).

Supply voltage (VCC) 4.5 to 15 V
Supply current (VCC = +5 V) 3 to 6 mA
Supply current (VCC = +15 V) 10 to 15 mA
Output current (maximum) 200 mA
Maximum Power dissipation 600 mW
Power consumption (minimum operating) 30 mW@5V, 225 mW@15V
Operating Temperature 0 to 70 °C
10.3 UM66 Music Generator Circuit

Figure 13
This is the UM66 music generator circuit, of course this circuit uses UM66 as the
main component to generate the signal of music / melody. UM66 operates on a
supply voltage of 3V. The required 3V supply is given through a zener regulator. The
transistor Q1 and Q2 is a push pull amplifier to drive the loudspeaker, so the music
signal from pin 1 IC UM66 can be heard loudly. A class A amplifier can be used
before push pull amplifier to minimize the noise and improve the output sound
quality. UM66 is a 3 pin IC package just looks like a BC547 transistor
COMPONETS
R1 = 4.7K Q1=SK100 SP=8 ohm
C1 = 10uF-25v Q2=SL100
D1 = 3.3v Zener IC=UM66
UM66 PIN CONFIGURATIONS:
• Output : Melody Output
• +Vdd : Positive Power supply
• -Vss : Negative Power supply
UM66T FEATURES:
• Voltage rating: 1.3V to 3.3 V
• 62 Note ROM Memory
• Power on reset
An audio amplifier is an electronic amplifier that amplifies low-power audio signals
(signals composed primarily of frequencies between 20 - 20 000 Hz, the human range

of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical
audio playback chain.
The preceding stages in such a chain are low power audio amplifiers which perform
tasks like pre-amplification, equalization, tone control, mixing/effects, or audio
sources like record players, CD players, and cassette players.
Most audio amplifiers require these low-level inputs to adhere to line levels. While
the input signal to an audio amplifier may measure only a few hundred microwatts, its
output may be tens, hundreds, or thousands of watts
10.4 RESISTOR
A resistor Is s passive two terminal electrical compnent that implements electrical
component as a circuit element. The current through a resistor is in direct proportion
to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied
across a resistor's terminals to the intensity of current through the circuit is called
resistance. This relation is represented by ohm’s law:
where I is the current through the conductor in units of ampers, V is the potential
difference measured across the conductor in units of volts, and R is the resistance of

the conductor in units of ohms. More specifically, Ohm's law states that the R in this
relation is constant, independent of the current. Resistors are common elements of
electrical network and electronic circuits and are ubiquitous in electronic equipment.
Practical resistors can be made of various compounds and films, as well as resistance
wire (wire made of a high-resistivity alloy, such as nickel-chrome). Resistors are also
implemented within integrated circuits, particularly analog devices, and can also be
integrated hybrid and printed circuit.
The electrical functionality of a resistor is specified by its resistance: common
commercial resistors are manufactured over a range of more than nine orders of
magnitude. When specifying that resistance in an electronic design, the required
precision of the resistance may require attention to manufacturing tollerance of the
chosen resistor, according to its specific application. The temperature coefficient of
the resistance may also be of concern in some precision applications. Practical
resistors are also specified as having a maximum power rating which must exceed the
anticipated power dissipation of that resistor in a particular circuit: this is mainly of
concern in power electronics applications. Resistors with higher power ratings are
physically larger and may require heat sink. In a high-voltage circuit, attention must
sometimes be paid to the rated maximum working voltage of the resistor.
Practical resistors have a series inductance and a small parallel capacitance; these
specifications can be important in high-frequency applications. In a low noise
amplifier or pre-ampilfier, noise effect characteristics of a resistor may be an issue.
The unwanted inductance, excess noise, and temperature coefficient are mainly
dependent on the technology used in manufacturing the resistor. They are not
normally specified individually for a particular family of resistors manufactured using
a particular technology.A family of discrete resistors is also characterized according to
its form factor, that is, the size of the device and the position of its leads (or
terminals) which is relevant in the practical manufacturing of circuits using them
The ohm is the SI unit of electrical resistance, named after Georg Simon Ohm. An
ohm is equivalent to a volt per ampere. Since resistors are specified and manufactured
over a very large range of values, the derived units of milliohm (1 mΩ = 10−3
Ω),
kiloohm (1 kΩ = 103
Ω), and megohm (1 MΩ = 106
Ω) are also in common usage.
The reciprocal of resistance R is called conductance G = 1/R and is measured in
siemens (SI unit), sometimes referred to as a mho. Hence, siemens is the reciprocal of
an ohm: . Although the concept of conductance is often used in circuit
analysis, practical resistors are always specified in terms of their resistance (ohms)
rather than conductance.
The behavior of an ideal resistor is dictated by the relationship specified by Ohm's
law:

Ohm's law states that the voltage (V) across a resistor is proportional to the current
(I), where the constant of proportionality is the resistance (R).
Equivalently, Ohm's law can be stated:
This formulation states that the current (I) is proportional to the voltage (V) and
inversely proportional to the resistance (R). This is directly used in practical
computations. For example, if a 300 ohm resistor is attached across the terminals of a
12 volt battery, then a current of 12 / 300 = 0.04 amperes (or 40 milliamperes) occurs
across that resistor.
10.5 CAPACITOR
A capacitor (originally known as condenser) is a passive two-terminal electrical
component used to store energy in an electric field. The forms of practical capacitors
vary widely, but all contain at least two electrical conductors separated by a dielectric
(insulator); for example, one common construction consists of metal foils separated
by a thin layer of insulating film. Capacitors are widely used as parts of electrical
circuits in many common electrical devices.
When there is a potential difference (voltage) across the conductors, a static electric
field develops across the dielectric, causing positive charge to collect on one plate and
negative charge on the other plate. Energy is stored in the electrostatic field. An ideal
capacitor is characterized by a single constant value, capacitance, measured in farads.

This is the ratio of the electric charge on each conductor to the potential difference
between them.
The capacitance is greatest when there is a narrow separation between large areas of
conductor; hence capacitor conductors are often called "plates," referring to an early
means of construction. In practice, the dielectric between the plates passes a small
amount of leakage current and also has an electric field strength limit, resulting in a
breakdown voltage, while the conductors and leads introduce an undesired inductance
and resistance.
Capacitors are widely used in electronic circuits for blocking direct current while
allowing alternating current to pass, in filter networks, for smoothing the output of
power supplies, in the resonant circuits that tune radios to particular frequencies, in
electric power transmission systems for stabilizing voltage and power flow, and for
many other purposes.
A capacitor consists of two conductors separated by a non-conductive region. The
non-conductive region is called the dielectric. In simpler terms, the dielectric is just an
electrical insulator. Examples of dielectric media are glass, air, paper, vacuum, and
even a semiconductor depletion region chemically identical to the conductors. A
capacitor is assumed to be self-contained and isolated, with no net electric charge and
no influence from any external electric field. The conductors thus hold equal and
opposite charges on their facing surfaces, and the dielectric develops an electric field.
In SI units, a capacitance of one farad means that one coulomb of charge on each
conductor causes a voltage of one volt across the device.
The capacitor is a reasonably general model for electric fields within electric circuits.
An ideal capacitor is wholly characterized by a constant capacitance C, defined as the
ratio of charge ±Q on each conductor to the voltage V between them:
Sometimes charge build-up affects the capacitor mechanically, causing its capacitance
to vary. In this case, capacitance is defined in terms of incremental changes:
Energy of electric field
Work must be done by an external influence to "move" charge between the
conductors in a capacitor. When the external influence is removed the charge
separation persists in the electric field and energy is stored to be released when the
charge is allowed to return to its equilibrium position. The work done in establishing
the electric field, and hence the amount of energy stored, is given by:

Current-voltage relation
The current i(t) through any component in an electric circuit is defined as the rate of
flow of a charge q(t) passing through it, but actual charges, electrons, cannot pass
through the dielectric layer of a capacitor, rather an electron accumulates on the
negative plate for each one that leaves the positive plate, resulting in an electron
depletion and consequent positive charge on one electrode that is equal and opposite
to the accumulated negative charge on the other.
.
Taking the derivative of this, and multiplying by C, yields the derivative form:
.
The dual of the capacitor is the inductor, which stores energy in a magnetic field
rather than an electric field. Its current-voltage relation is obtained by exchanging
current and voltage in the capacitor equations and replacing C with the inductance L.
The simplest capacitor consists of two parallel conductive plates separated by a
dielectric with permittivity ε (such as air). The model may also be used to make
qualitative predictions for other device geometries. The plates are considered to
extend uniformly over an area A and a charge density ±ρ = ±Q/A exists on their
surface. Assuming that the width of the plates is much greater than their separation d,
the electric field near the centre of the device will be uniform with the magnitude E =
ρ/ε. The voltage is defined as the line integral of the electric field between the plates
Solving this for C = Q/V reveals that capacitance increases with area and decreases
with separation
.The capacitance is therefore greatest in devices made from materials
with a high permittivity, large plate area, and small distance between plates.
However solving for maximum energy storage using Ud as the dielectric
strength per distance and capacitor voltage at the capacitor's breakdown voltage
limit V = Vbd = Udd.

We see that the maximum energy is a function of dielectric volume, permittivity, and
dielectric strength per distance. So increasing the plate area while decreasing the
separation between the plates while maintaining the same volume has no change on
the amount of energy the capacitor can store. Care must be taken when increasing the
plate separation so that the above assumption of the distance between plates being
much smaller than the area of the plates is still valid for these equations to be
accurate.
10.6 VARIABLE RESISTOR
Variable resistors consist of a resistance track with connections at both ends and a
wiper which moves along the track as you turn the spindle. The track may be made
from carbon, cermet (ceramic and metal mixture) or a coil of wire (for low
resistances). The track is usually rotary but straight track versions, usually called
sliders, are also available.
Variable resistors may be used as a rheostat with two connections (the wiper and just
one end of the track) or as a potentiometer with all three connections in use.

Miniature versions called presets are made for setting up circuits which will not
require further adjustment.
Variable resistors are often called potentiometers in books and catalogues. They are
specified by their maximum resistance, linear or logarithmic track, and their physical
size. The standard spindle diameter is 6mm.
The resistance and type of track are marked on the body:
4K7 LIN means 4.7 k linear track.
1M LOG means 1 M logarithmic track.
Some variable resistors are designed to be mounted directly on the circuit board, but
most are for mounting through a hole drilled in the case containing the circuit with
stranded wire connecting their terminals to the circuit board.
Linear (LIN) and Logarithmic (LOG) tracks
Linear (LIN) track means that the resistance changes at a constant rate as you move
the wiper. This is the standard arrangement and you should assume this type is
required if a project does not specify the type of track. Presets always have linear
tracks.
Logarithmic (LOG) track means that the resistance changes slowly at one end of the
track and rapidly at the other end, so halfway along the track is not half the total
resistance! This arrangement is used for volume (loudness) controls because the
human ear has a logarithmic response to loudness so fine control (slow change) is
required at low volumes and coarser control (rapid change) at high volumes. It is
important to connect the ends of the track the correct way round, if you find that
turning the spindle increases the volume rapidly followed by little further change you
should swap the connections to the ends of the track.
RHEOSTAT
This is the simplest way of using a variable resistor. Two terminals are used: one
connected to an end of the track, the other to the moveable wiper. Turning the
spindle changes the resistance between the two terminals from zero up to the
maximum resistance.

Rheostats are often used to vary current, for example to control the brightness of a
lamp or the rate at which a capacitor charges.
If the rheostat is mounted on a printed circuit board you may find that all three
terminals are connected! However, one of them will be linked to the wiper terminal.
This improves the mechanical strength of the mounting but it serves no function
electrically.
POTENTIOMETER
Variable resistors used as potentiometers have all three terminals connected.
This arrangement is normally used to vary voltage, for example to set the switching
point of a circuit with a sensor, or control the volume (loudness) in an amplifier
circuit. If the terminals at the ends of the track are
connected across the power supply then the wiper terminal will provide a voltage
which can be varied from zero up to the maximum of the supply.
PRESET
These are miniature versions of the standard variable resistor. They are designed to be
mounted directly onto the circuit board and adjusted only when the circuit is built.
For example to set the frequency of an alarm tone or the sensitivity of a light-sensitive
circuit. A small screwdriver or similar tool is required to adjust presets.

Presets are much cheaper than standard variable resistors so they are sometimes used
in projects where a standard variable resistor would normally be used.
Multiturn presets are used where very precise adjustments must be made. The screw
must be turned many times (10+) to move the slider from one end of the track to the
other, giving very fine control.
10.7 LOUDSPEAKER
A loudspeaker (or "speaker") is an electro acoustic transducer that produces sound in
response to an electrical audio signal input. Non-electrical loudspeakers were
developed as accessories to telephone systems, but electronic amplification by vacuum
tube made loudspeakers more generally useful. The most common form of
loudspeaker uses a paper cone supporting a voice coil electromagnet acting on a
permanent magnet, but many other types exist. Where accurate reproduction of sound

is required, multiple loudspeakers may be used, each reproducing a part of the audible
frequency range. Miniature loudspeakers are found in devices such as radio and TV
receivers, and many forms of music players. Larger loudspeaker systems are used for
music, sound reinforcement in theatres and concerts, and in public address systems.
The term "loudspeaker" may refer to individual transducers (known as "drivers") or to
complete speaker systems consisting of an enclosure including one or more drivers.
To adequately reproduce a wide range of frequencies, most loudspeaker systems
employ more than one driver, particularly for higher sound pressure level or
maximum accuracy. Individual drivers are used to reproduce different frequency
ranges. The drivers are named sub woofers (for very low frequencies); woofers (low
frequencies); mid range speakers (middle frequencies);tweeters (high frequencies); and
sometimes supertweeters, optimized for the highest audible frequencies. The terms
for different speaker drivers differ, depending on the application. In two-way systems
there is no mid-range driver, so the task of reproducing the mid-range sounds falls
upon the woofer and tweeter. Home stereos use the designation "tweeter" for the
high frequency driver, while professional concert systems may designate them as
"HF" or "highs". When multiple drivers are used in a system, a "filter network", called
a crossover, separates the incoming signal into different frequency ranges and routes
them to the appropriate driver. A loudspeaker system with n separate frequency bands
is described as "n-way speakers": a two-way system will have a woofer and a tweeter; a
three-way system employs a woofer, a mid-range, and a tweeter. Loudspeakers were
described as "dynamic" to distinguish them from the earlier moving iron speakers, or
speakers using piezoelectric or piezostatic systems as opposed to a voice call that
moves through a steady magnetic field.
Driver types
Individual electrodynamic drivers provide optimal performance within a limited pitch
range. Multiple drivers (e.g., subwoofers, woofers, mid-range drivers, and tweeters)
are generally combined into a complete loudspeaker system to provide performance
beyond that constraint.
FULL RANGE DRIVERS
A full-range driver is designed to have the widest frequency response possible. These
drivers are small, typically 3 to 8 inches (7.6 to 20 cm) in diameter to permit
reasonable high frequency response, and carefully designed to give low-distortion
output at low frequencies, though with reduced maximum output level. Full-range (or
more accurately, wide-range) drivers are most commonly heard in public address
systems, in televisions (although some models are suitable for hi-fi listening), small

radios, intercoms, some computer speakers, etc. In hi-fi speaker systems, the use of
wide-range drive units can avoid undesirable interactions between multiple drivers
caused by non-coincident driver location or crossover network issues. Fans of wide-
range driver hi-fi speaker systems claim a coherence of sound due to the single source
and a resulting lack of interference, and likely also to the lack of crossover
components. Detractors typically cite wide-range drivers' limited frequency response
and modest output abilities (most especially at low frequencies), together with their
requirement for large, elaborate, expensive enclosures—such as transmission lines, or
horns—to approach optimum performance.
Full-range drivers often employ an additional cone called a whizzer: a small, light cone
attached to the joint between the voice coil and the primary cone. The whizzer cone
extends the high-frequency response of the driver and broadens its high frequency
directivity, which would otherwise be greatly narrowed due to the outer diameter cone
material failing to keep up with the central voice coil at higher frequencies. The main
cone in a whizzer design is manufactured so as to flex more in the outer diameter than
in the center. The result is that the main cone delivers low frequencies and the
whizzer cone contributes most of the higher frequencies. Since the whizzer cone is
smaller than the main diaphragm, output dispersion at high frequencies is improved
relative to an equivalent single larger diaphragm.
Limited-range drivers, also used alone, are typically found in computers, toys, and
clock radios. These drivers are less elaborate and less expensive than wide-range
drivers, and they may be severely compromised to fit into very small mounting
locations. In these applications, sound quality is a low priority. The human ear is
remarkably tolerant of poor sound quality, and the distortion inherent in limited-range
drivers may enhance their output at high frequencies, increasing clarity when listening
to spoken word material.
SUBWOOFER:
A subwoofer is a woofer driver used only for the lowest part of the audio spectrum:
typically below 200 Hz for consumer systems,[17]
below 100 Hz for professional live
sound,[18]
and below 80 Hz in THX-approved systems.[19]
Because the intended range
of frequencies is limited, subwoofer system design is usually simpler in many respects
than for conventional loudspeakers, often consisting of a single driver enclosed in a
suitable box or enclosure.

To accurately reproduce very low bass notes without unwanted resonances (typically
from cabinet panels), subwoofer systems must be solidly constructed and properly
braced; good speakers are typically quite heavy. Many subwoofer systems include
power amplifiers and electronic sub-filters, with additional controls relevant to low-
frequency reproduction. These variants are known as "active" or "powered"
subwoofers.[20]
In contrast, "passive" subwoofers require external amplification.
WOOFER:
A woofer is a driver that reproduces low frequencies. The driver combines with the
enclosure design to produce suitable low frequencies (see speaker enclosure for the
design choices available). Some loudspeaker systems use a woofer for the lowest
frequencies, sometimes well enough that a subwoofer is not needed. Additionally,
some loudspeakers use the woofer to handle middle frequencies, eliminating the mid-
range driver. This can be accomplished with the selection of a tweeter that can work
low enough that, combined with a woofer that responds high enough, the two drivers
add coherently in the middle frequencies.
MID-RANGE DRIVER:
A mid-range speaker is a loudspeaker driver that reproduces middle frequencies. Mid-
range driver diaphragms can be made of paper or composite materials, and can be
direct radiation drivers (rather like smaller woofers) or they can be compression
drivers (rather like some tweeter designs). If the mid-range driver is a direct radiator, it
can be mounted on the front baffle of a loudspeaker enclosure, or, if a compression
driver, mounted at the throat of a horn for added output level and control of radiation
pattern.
TWEETER:
A tweeter is a high-frequency driver that reproduces the highest frequencies in a
speaker system. Many varieties of tweeter design exist, each with differing abilities
with regard to frequency response, output fidelity, power handling, maximum output
level, etc. Soft-dome tweeters are widely found in home stereo systems, and horn-
loaded compression drivers are common in professional sound reinforcement.
Ribbon tweeters have gained popularity in recent years, as their output power has
been increased to levels useful for professional sound reinforcement, and their output
pattern is wide in the horizontal plane, a pattern that has convenient applications in
concert sound.
CO-AXIAL DRIVER:
A coaxial driver is a loudspeaker driver with two or several combined concentric
drivers. Coaxial drivers have been produced by many companies, such as Altec,
Tannoy, Pioneer, KEF, B&C Speakers, BMS, Cabasse and Genelec.
Loudspeaker system design

Used in multi-driver speaker systems, the crossover is a subsystem that separates the
input signal into different frequency ranges suited to each driver. The drivers receive
power only in their usable frequency range (the range they were designed for), thereby
reducing distortion in the drivers and interference between them. No crossover can
be perfect (i.e., absolute block at the edges of the passband, no amplitude variation
within the passband, no phase changes across the frequency band boundaries the
crossover establishes, ..), so this is an idealized description.
Crossovers can be passive or active. A passive crossover is an electronic circuit that uses
a combination of one or more resistors, inductors, or non-polar capacitors. These
parts are formed into carefully designed networks and are most often placed between
the full frequency-range power amplifier and the loudspeaker drivers to divide the
amplifier's signal into the necessary frequency bands before being delivered to the
individual drivers. Passive crossover circuits need no external power beyond the audio
signal itself, but have disadvantages: high cost, large components (inductors and
capacitors), limited ability to adjust the circuit as desired due to limited choice of high
power level components, etc. They also cause substantial overall signal loss and a
significant reduction in damping factor between the voice coil and the crossover. An
active crossover is an electronic filter circuit that divides the signal into individual
frequency bands before power amplification, thus requiring at least one power amplifier
for each bandpass. Passive filtering may also be used in this way before power
amplification, but it is an uncommon solution, being less flexible than active filtering.
Any technique that uses crossover filtering followed by amplification is commonly
known as bi-amping, tri-amping, quad-amping, and so on, depending on the
minimum number of amplifier channels. Some loudspeaker designs use a combination
of passive and active crossover filtering, such as a passive crossover between the mid-
and high-frequency drivers and an active crossover between the low-frequency driver
and the combined mid- and high frequencies.
Passive crossovers are commonly installed inside speaker boxes and are by far the
most usual type of crossover for home and low-power use. In car audio systems,
passive crossovers may be in a separate box, necessary to accommodate the size of
the components used. Passive crossovers may be simple for low-order filtering, or
complex to allow steep slopes such as 18 or 24 dB per octave. Passive crossovers can
also be designed to compensate for undesired characteristics of driver, horn, or
enclosure resonances, and can be tricky to implement, due to component interaction.
Passive crossovers, like the driver units that they feed, have power handling limits,
have insertion losses (10% is often claimed), and change the load seen by the
amplifier. The changes are matters of concern for many in the hi-fi world. When high
output levels are required, active crossovers may be preferable. Active crossovers may
be simple circuits that emulate the response of a passive network, or may be more
complex, allowing extensive audio adjustments. Some active crossovers, usually digital

loudspeaker management systems, may include facilities for precise alignment of
phase and time between frequency bands, equalization, and dynamics (compression
and limiting) control.
Some hi-fi and professional loudspeaker systems now include an active crossover
circuit as part of an onboard amplifier system. These speaker designs are identifiable
by their need for AC power in addition to a signal cable from a pre-amplifier. This
active topology may include driver protection circuits and other features of a digital
loudspeaker management system. Powered speaker systems are common in computer
sound (for a single listener) and, at the other end of the size spectrum, in modern
concert sound systems, where their presence is significant and steadily increasing.
10.8 ZENER DIODE
A conventional solid-state diode will not allow significant current if it is reverse-biased
below its reverse breakdown voltage. When the reverse bias breakdown voltage is
exceeded, a conventional diode is subject to high current A zener diode is a special
kind of diode which allows current to flow in the forward direction in the same
manner as an ideal diode, but will also permit it to flow in the reverse direction when
the voltage is above a certain value known as the breakdown voltage, "zener knee
voltage" or "zener voltage." The device was named after Clarence Zener, who

discovered this electrical property. Many diodes described as "zener" diodes rely
instead on avalanche breakdown as the mechanism. Both types are used. Common
applications include providing a reference voltage for voltage regulators, or to protect
other semiconductor devices from momentary voltage pulses.
due to avalanche breakdown. Unless this current is limited by circuitry, the diode will
be permanently damaged due to overheating. A zener diode exhibits almost the same
properties, except the device is specially designed so as to have a greatly reduced
breakdown voltage, the so-called zener voltage. By contrast with the conventional
device, a reverse-biased zener diode will exhibit a controlled breakdown and allow the
current to keep the voltage across the zener diode close to the zener breakdown
voltage. For example, a diode with a zener breakdown voltage of 3.2 V will exhibit a
voltage drop of very nearly 3.2 V across a wide range of reverse currents. The zener
diode is therefore ideal for applications such as the generation of a reference voltage
(e.g. for an amplifier stage), or as a voltage stabilizer for low-current applications.[1]
Another mechanism that produces a similar effect is the avalanche effect as in the
avalanche diode. [1]
The two types of diode are in fact constructed the same way and
both effects are present in diodes of this type. In silicon diodes up to about 5.6 volts,
the zener effect is the predominant effect and shows a marked negative temperature
coefficient. Above 5.6 volts, the avalanche effect becomes predominant and exhibits a
positive temperature coefficient.[
In a 5.6 V diode, the two effects occur together and their temperature coefficients
nearly cancel each other out, thus the 5.6 V diode is the component of choice in
temperature-critical applications. Modern manufacturing techniques have produced
devices with voltages lower than 5.6 V with negligible temperature coefficients, but as
higher voltage devices are encountered, the temperature coefficient rises dramatically.
A 75 V diode has 10 times the coefficient of a 12 V diode.
All such diodes, regardless of breakdown voltage, are usually marketed under the
umbrella term of "zener diode".
Construction
The zener diode's operation depends on the heavy doping of its p-n junction. The
depletion region formed in the diode is very thin (<0.000001 m)and the electric field
is consequently very high (about 500000V/m) even for a small reverse bias voltage of
about 5V, allowing electrons to tunnel from the valence band of the p-type material to
the conduction band of the n-type material.
In the atomic scale, this tunneling corresponds to the transport of valence band
electrons into the empty conduction band states; as a result of the reduced barrier
between these bands and high electric fields that are induced due to the relatively high
levels of dopings on both sides.[2]
The breakdown voltage can be controlled quite

accurately in the doping process. While tolerances within 0.05% are available, the
most widely used tolerances are 5% and 10%. Breakdown voltage for commonly
available zener diodes can vary widely from 1.2 volts to 200 volts.
In the case of a large forward bias (current in the direction of the arrow), the diode
exhibits a voltage drop due to its junction built-in voltage and internal resistance. The
amount of the voltage drop depends on the semiconductor material and the doping
concentrations
Zener diodes are widely used as voltage references and as shunt regulators to regulate
the voltage across small circuits. When connected in parallel with a variable voltage
source so that it is reverse biased, a zener diode conducts when the voltage reaches
the diode's reverse breakdown voltage. From that point on, the relatively low
impedance of the diode keeps the voltage across the diode at that value.
In this circuit, a typical voltage reference or regulator, an input voltage, UIN, is
regulated down to a stable output voltage UOUT. The breakdown voltage of diode D is
stable over a wide current range and holds UOUT relatively constant even though the
input voltage may fluctuate over a fairly wide range. Because of the low impedance of
the diode when operated like this, resistor R is used to limit current through the
circuit.
In the case of this simple reference, the current flowing in the diode is determined
using Ohm's law and the known voltage drop across the resistor R. IDiode = (UIN -
UOUT) / RΩ
The value of R must satisfy two conditions:
• R must be small enough that the current through D keeps D in reverse
breakdown. The value of this current is given in the data sheet for D. For
example, the common BZX79C5V6device, a 5.6 V 0.5 W zener diode, has a
recommended reverse current of 5 mA. If insufficient current exists through D,
then UOUT will be unregulated, and less than the nominal breakdown voltage
(this differs to voltage regulator tubes where the output voltage will be higher
than nominal and could rise as high as UIN). When calculating R, allowance
must be made for any current through the external load, not shown in this
diagram, connected across UOUT.
• R must be large enough that the current through D does not destroy the
device. If the current through D is ID, its breakdown voltage VB and its
maximum power dissipation PMAX, then .
A load may be placed across the diode in this reference circuit, and as long as the
zener stays in reverse breakdown, the diode will provide a stable voltage source to the

load. Zener diodes in this configuration are often used as stable references for more
advanced voltage regulator circuits.
Shunt regulators are simple, but the requirements that the ballast resistor be small
enough to avoid excessive voltage drop during worst-case operation (low input
voltage concurrent with high load current) tends to leave a lot of current flowing in
the diode much of the time, making for a fairly wasteful regulator with high quiescent
power dissipation, only suitable for smaller loads.
These devices are also encountered, typically in series with a base-emitter junction, in
transistor stages where selective choice of a device centered around the avalanche or
zener point can be used to introduce compensating temperature co-efficient balancing
of the transistor PN junction. An example of this kind of use would be a DC error
amplifier used in a regulated power supply circuit feedback loop system.
Zener diodes are also used in surge protectors to limit transient voltage spikes.
Another notable application of the zener diode is the use of noise caused by its
avalanche breakdown in a random number generator that never repeats.
CHAPTER 11
SHORTCOMMINGS, LIMITATIONS AND
...................... ...................REMEDIES
The circuit was unable to detect mechanical force below a particular limit. Due to the
fixed specifications of the components used in circuit. Special efforts have been made
to enhance the sensitivity of the piezoelectric element used in the circuit. Many more
implementation can be brought about to further enhance the working and
performance of the circuit. By changing the capacitance and resistance used in the
circuit with one with higher specification we can enhance the functionality of the

DOOR KNOCK ALARM WITH TIMER to a greater extent. We can also increase
the time for which the alarm will ring in case of a door knock. But due to financial
constraints we could not use component which has best specifications. Moreover due
to some technical snag we were not able to fabricate the perfect combination of the
capacitor, resistor and variable resistor due to which we failed to harness the efficacy
of the DOOR KNOCK ALARM WITH TIMER to its optimum extent. However we
tried our best with best of our knowledge to make our circuit work with the best
possible condition keeping into mind all sort of technical and financial constraints.
CHAPTER 12
FUTURE APPLICATION AND SCOPE OF PROJECT
A)BUZZERS:
Basically it will convert the pressure applied on the piezoelectric element to sound
enegy.
B)KNOCK ALARMS:

The concept is same as buzzer but the application criteria and characteristic are quite
different.
C)PRESSURE DETECTORS:
Generally used in industries to detect the exact pressure of gases flowing via safety
valves and tubes.
D)BUGLAR ALARM:
A traditional use of it can be to spot the thief at times when we are not aware of their
presence around.
E)MECHANICAL ENERGY TO SOUND ENERGY CONVERTORS
Used in industries where the mechanical force is proportionally converted into
equivalent sound energy and used for varied application.
F)MECHANICAL SENSORS
G)WEIGHT LIMIT DETECTORS:
Can be used as a threshold weight detector where upto a limit the device allows the
application of weight but above it the detector alerts the user.
CHAPTER 13
CONCLUSION
“NOTHING IS MORE SWEETER THAN SUCCESS” is a very well said
quotation by someone.The successful execution of the project is of paramount
joy.The entire journey from collection of the components for assembly of the project
to the journey of implementing the circuit on the PCB was very interesting.But it was
not a cake walk for us.During the course we had to face a number of hurdles but as
it’s said God helps them those who help themselves.At last i would like to say that it
was a great time for our team during the entire process of project completion plan.

CHAPTER 14
REFERENCES AND BIBLIOGRAPHY
1. www.google.co.in
2. www.en.wikipedia.org
3. www.en.wikipedia.org/wiki/Resistor
4. www.en.wikipedia.org/wiki/Capacitor

5. www.datasheetcatalog.com/datasheets_pdf/A/T/8/9/AT89S52.shtml
6. www.en.wikipedia.org/wiki/Potentiometer
7. www.en.wikipedia.org/wiki/Diode
8. www.electronicsforu.com/electronicsforu/lab/
TECHNICAL INFORMATION FROM FOLLOWING BOOKS
1) Electronic devices and circuit theory By Robert.L.Boylestad, 4th
edition, 2004
2) Microelectronic circuits .By Adel.S. Sedra 5th
edition,2008
3) Electronics by R.S Sedha. 2nd edition,2002

Door knock alarm with timer

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