Wireless IR Headset Project Report

College of Eng: Munnar Dept. of ECE

WIRELESS IR HEADSET

Minor project Report
Submitted in partial fulfillment of the requirements
For the award of B.Tech Degree in

Electronics & Communication Engineering

Of the Cochin University of Science and Technology

By

AKHIL M 13102602

NIDHEESH V.V 13102626

SOORAJ.S 13102639

Under the guidance of
Mr. Jayakrishnan K.R & Mr. Albert Jose

APRIL 2012

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

COLLEGE OF ENGINEERING

MUNNAR-685612

Wireless IR Headset Page 1


ACKNOWLEDGEMENT

We express our thanks to Dr K.G.Balakrishnan, Principal, College Of Engineering, Munnar, for all
necessary help extended to us in the fulfilment of this minor project.

We express our thanks to Mr Biju V.G, Head of the Department of Electronics and Communication
Engineering, College of Engineering, Munnar, for all necessary help extended to us in the fulfilment of this
minor project.

We have great pleasure to express our gratitude and obligations to Mr K.R. Jayakrishnan, Assistant
Professor Department of Electronics and Communication Engineering, College of Engineering, Munnar, for
his valuabl

e guidance, constant encouragement and creative suggestions to make this minor project a great success.

We have great pleasure to express our gratitude and obligations to Mr Albert Jose, Lecturer
Department of Electronics and Communication Engineering, College of Engineering, Munnar, for his
valuable guidance, constant encouragement and creative suggestions to make this minor project a great
success.

We also express our sincere gratitude to all the Staff Members of Department of Electronics and
Communication Engineering, College of Engineering, Munnar, for their valuable help and encouragement,
which lead to the successful accomplishment of this minor project.

We are also thankful to my friends for their valuable suggestions and encouragements.

Above all I thank the ALMIGHTY, without whose blessing we would ever be able to complete
our work.

AKHIL M

NIDHEESH V.V

SOORAJ S



ABSTRACT
Infrared Rays form a part of the electromagnetic spectrum which has a wavelength ranging
from 0.7 to 400 um. It is known widely for its heating effects and the role it plays in atmosphere.
Infrared rays find large applications in electronic and wireless applications due to certain
advantages provided by its inherent properties.

In the past few decades, an unprecedented demand for wireless technologies has been taking
place. Mobiles, Laptops, assistants (PDAs), and mobile phones, to name just a few examples, are
becoming part of the everyday life of a growing number of devices that communicate wirelessly.
Radio and infrared (IR) are currently the main parts of the electromagnetic spectrum used to
transmit information wirelessly. IR is becoming more popular every day and it is being preferred
due to its inherent advantages like low power requirements, security, effective short distance
communication as compared to its Radio counterpart.

In this project we aim to design and build a hardware model of IR transmitter and receiver that
is capable of communicating data over a short range. The device we plan to build could be
integrated with the digital devices to transmit signals in the audio frequency range of 20Hz to
20000Hz over a range of 4 to 5 metres. Also we aim to study the properties of the IR
communication in terms of the range acquired and the power requirements of the system.



CONTENTS
No Content Page No

1. Overview 3-7

1 .1 Introduction 3

1.2 Technology Overview 4

1.3 Evolution of Infrared Communication System 5

1.4 System configuration of Wireless IR Communication Systems 7

2. Objectives 8

3. Infrared Systems 9-13

3.1 Properties 9

3.2 Advantages 10

3.3 Disadvantages 11

3.4 Applications 11

4. Hardware description 14-19

4.1 Design Considerations 14

4.2 Block Diagram 15

4.3 Circuit Diagram 17

4.4 Working 18

4.5 Power Consideration 19



5. Simulation, Analysis and Amendments 20-21

5.1 Simulation 20

5.3 Observations 21

5.4 Amendments 21

6. PCB Fabrication 22

7. PCB Layout 26

8. List of components 27

9. Results and Inference 28

10. References 28

11. Datasheets 29



1. OVERVIEW

1.1 Introduction

In the past few decades, a demand for wireless technologies has tremendously increased.
Both industrial and private customers are demanding products -for a wide range of applications-
that incorporate wireless features, which allow them to exchange, receive, or transmit information
without the inconvenience of having to be fixed to any particular location.

The benefits of wireless technologies are not limited to user convenience- in terms of mobility-
and flexibility in the placement of terminals. Significant reductions in cost and time also can be
achieved, in a number of applications, using wireless solutions. Reconfiguring computer terminals
or microcontroller systems (in places such as laboratories, conference rooms, offices, hospitals,
production floors, or educational institutions), for instance, can be done relatively cheaply and
quickly with wireless networks. Maintaining and reconfiguring wired networks, on the other hand,
is usually carried out in more expensive, time-consuming, and complicated ways (especially in
situations where cables are grounded or installed in inaccessible places). Furthermore, cables are
susceptible to damage, which means potential disruption to the network operation. Radio and
infrared (IR) are currently the main parts of the electromagnetic spectrum used to transmit
information wirelessly. By the term “radio”‖ we refer to the radiofrequency and microwave parts
of the spectrum, and “IR”‖ to the Near-infrared part of it.

In homes, some member prefers to watch television while others don’t. It becomes difficult for
younger member to go against the will of elder, especially in Indian scenario, so younger have to
suffer in most of cases. Wired headphones do not give flexibility for mobility and more users to
accommodate (usually due to predefined design), so wireless headphones are required to meet
the requirement. We in this project intend to make wireless system using Infrared technology, so
as to counter this problem. Thus, Infrared cordless headphones would be used for watching TV
and movies with full enjoyment but without disturbing the peace at home



1.2 Technology Overview

Radio and infrared (IR) are currently the main parts of the electromagnetic spectrum used to
transmit information wirelessly. By the term “radio”‖ we refer to the radiofrequency and
microwave parts of the spectrum, and “IR”‖ to the near infrared part of it. Infrared rays have a
wavelength ranging from 0.7 to 400 µm which corresponds to a frequency ranging from 1THz to
400 THz.

Most of today’s wireless communication is based on radio frequency but IR frequency is also
being used and is becoming popular these days (due to its inherent advantages) over its radio
counterpart for a number of applications.

From a spectrum management point of view, for example, IR offers potentially huge
bandwidths that are currently unregulated worldwide. The radio part of the spectrum, on the
other hand, gets more congested every year, and the allocation of radio frequencies is increasingly
difficult and expensive. Moreover, due the fact that the authorities that regulate the allocation of
radio frequencies vary from one country to another so device are to be modelled accordingly in
different country.

Another advantage of IR over radio is its immunity to electromagnetic interference (EMI).This
makes IR the preferred option in environments where interference must be minimized or
eliminated. In addition, IR does not interfere with and is not affected by radio frequencies, which
is particularly relevant in hospitals, as explained in a number of published articles in the area.

IR also presents advantages over radio in terms of security. Because IR radiation behaves like
visible light, it does not penetrate walls, which means that the room where the energy is
generated encloses the emitted signal completely (assuming there are no windows or transparent
barriers between rooms). This prevents the transmitted information from being detected outside
and implies intrinsic security against eavesdropping. Further advantages of IR over radio include
the low cost, the small size, and the limited power consumption of IR components.

Despite the advantages presented by the infrared medium, IR is not without its drawbacks.
Infrared wireless links are susceptible to blocking from persons and objects, which can result in the
attenuation of the received signal. In addition, wireless IR systems generally operate in
environments where other sources of illumination are present. If this background illumination has
part of its energy in the spectral region used by wireless IR transmitters and receivers, it
introduces noise in the photo detector, which limits the range of the system.

Moreover, optical wireless systems are also affected by the high attenuation suffered by the IR
signal when transmitted through air, and by atmospheric phenomena such as fog and snow that
further reduce the range of the system and deteriorate the quality of the transmission when
operating outdoors.



1.3 Evolution of Infrared Communication Systems

Optical wireless communication systems have experienced a huge development since the
late1970s when IR was first proposed as an alternative way (to radio) to connect computer
networks without cables.

IBM was one of the first organizations to work on wireless IR networks. The first reports on
IBM’s experimental work were published between 1978 and 1981. They have described a duplex
IR link that achieved a bit rate of 64 kbps using PSK and a carrier frequency of 256 kHz

In 1983, Minami et al. from Fujitsu described a full-duplex LOS system that operated under
the same principles as the network described by Gfeller. That system consisted of an optical
satellite attached to the ceiling and connected to a network node via a cable, and of a number of
computer terminals that communicated to the server via the optical satellite. It operated at 19.2
kbps (over 10 m) with an error rate of 10−6 when working under fluorescent illumination. By 1985,
the Fujitsu team had managed to improve the data rate of its system to48 kbps, as reported by
Takahashi and Touge.

In the same year (1985), researchers from two other companies (Hitachi and HP Labs)
presented their own work in the area of wireless IR communications. In the case of Hitachi, Nakata
et al. reported a directed-LOS network system that replaced the optical satellite on the ceiling with
an optical reflector. This system achieved a data rate of up to 1 Mbps with a BER of less than 10−7
for a distance of 5 m.

In 1987, AT&T Bell presented their work on optical wireless communications. They reported a
directed-LOS system that operated at 45 Mbps over a wavelength of 800 nm.

More recently, Showa Electric reported a 100-Mbps short-range IR wireless transceiver that
operated over a maximum range of 20 m and used LEDs for the transmitter and avalanche photo-
detector (APDs) for the receiver. Another system, proposed by Singh et al. in 2004 [24], was based
on the idea of a base station attached to the ceiling and connected to the network via a backbone.

The proposed network operated at 100 Mbps and was based on DPPM with carrier sense
multiple access with collision detection (CSMA/CD) for the Media Access Control (MAC) protocol



Fig 1.3.1 Chronology of indoor optical wireless communication research



1.4 System Configurations of Wireless IR Communication Systems

Optical wireless systems for indoor and outdoor use can be arranged in a number of configurations
depending on the specific requirements of a system. In general, the topologies used for indoor optical
wireless communication systems are classified according to two parameters: (1) the existence of a nun
obstructed path between the transmitter and the receiver (LOS– non-LOS), and (2) the degree of
directionality of the transmitter, the receiver, or both (directed, non-directed, or hybrid).



2. OBJECTIVE

The objective of the project is to design an efficient infrared transmitter-receiver system
that would be capable of transmitting Infrared electromagnetic signals in the audio frequency
range of 20Hz to 20 KHz over a range of 4 to 6 metres. The device would be used in conjunction
with the multimedia devices, Computers and Laptops to transmit music from one place to a pair of
cordless headphones by employing the principles of wireless infrared communication without any
degradation in the quality of the music. Also we intend to study the properties of the system in
terms of the range and the power requirements.

Special emphasis is being laid into the communication of the music signals over a large range
and to study the degradation of the signal over a range. Also measures are being taken and a study
is being done to increase the angular range and the linear range of the system. The objective at
end is to obtain a low cost effective IR system ready for marketing purpose.



3. Infrared Systems

3.1 Properties of Infrared System:
Infrared radiation (IR) is electromagnetic radiation with a wavelength between 0.7 and 300micrometres,
which equates to a frequency range between approximately 1 and 430 THz. Its wavelength is longer (and
the frequency lower) than that of visible light, but the wavelength is shorter (and the frequency higher)
than that of terahertz radiation microwaves.

Fig. 3.1.1 Infrared Spectrum

Infrared Radiation behaves similar to the visible light, so it exhibits all the properties that light does such as

a) Reflection
b) Refraction
c) Diffraction
d) Diffusion

Attenuation
Atmospheric attenuation is defined as the process whereby some or all of the energy of an
electromagnetic wave is lost (absorbed and/or scattered) when traversing the atmosphere.

Absorption
Absorption, in the context of electromagnetic waves and light, is defined as the process of conversion of
the energy of a photon to internal energy, when electromagnetic radiation is captured by matter. When
particles in the atmosphere absorb light, this absorption provokes a transition (or excitation) in the
particle’s molecules from a lower energy level to a higher one.



Scattering
Scattering is defined as the dispersal of a beam of particles or of radiation into a range of directions as a
result of physical interactions. When a particle intercepts an electromagnetic wave, part of the wave’s
energy is removed by the particle and re-radiated into a solid angle centred at it. The scattered light is
polarized, and of the same wavelength as the incident wavelength, which means that there is no loss of
energy to the particle

3.2 Advantages over RF
a) Wider and Unregulated Spectrum
From a spectrum management point of view, for example, IR offers potentially huge bandwidths
that are currently unregulated worldwide. The radio part of the spectrum, on the other hand, gets
more congested every year, and the allocation of radio frequencies is increasingly difficult and
expensive. Moreover, due to the fact that the authorities that regulate the allocation of radio
frequencies vary from one country to another. Device needs to be modelled accordingly for
different country so as to avoid a potential risk of system or production compatibility in different
geographical locations.
b) High noise immunity:
Another advantage of IR over radio is its immunity to electromagnetic interference (EMI).This
makes IR the preferred option in environments where interference must be minimized or
eliminated. In addition, IR does not interfere with and is not affected by radio frequencies, which is
particularly relevant in hospitals, as explained in a number of published articles in the area.
c) Higher security:
IR also presents advantages over radio in terms of security. Because IR radiation behaves like
visible light, it does not penetrate walls, which means that the room where the energy is generated
encloses the emitted signal completely (assuming there are no windows or transparent barriers
between rooms). This prevents the transmitted information from being detected outside and
implies intrinsic security against eavesdropping. In addition, IR offers the possibility of rapid
wireless deployment and the flexibility of establishing temporary communication links. Further
advantages of IR over radio include the
d) low cost
e) The small size (Portable) and
f) The limited power consumption.
This is explained by the fact that wireless IR communication systems make use of the same Opto-
electronic devices that have been developed and improved over the past decades for optical fibre
communications and other applications. One such component is the light-emitting diode (LED),
which, due to its now faster response times, high radiant output power, and improved efficiency,
is becoming the preferred option for short-distance optical wireless applications.



3.3 Disadvantages:
a) Direct line of sight communication

Optical wireless links are susceptible to blocking from persons and objects, which can result in
the attenuation of the received signal or in the disruption of the link (depending on the
configuration of the system).That is the Wireless IR systems operate only in direct line of sight
communication.

b) Shorter Range

Wireless IR systems generally operate in environments where other sources of illumination
are present. This background illumination has part of its energy in the spectral region used by
wireless IR transmitters and receivers, and introduces noise in the photo detector, which limits the
range of the system .Moreover, optical wireless systems are also affected by the high attenuation
suffered by the IR signal when transmitted through air, and by atmospheric phenomena such as
fog and snow that further reduce the range of the system and deteriorate the quality of the
transmission when operating outdoors.

3.4 Applications
a) Infrared filter
Infrared (transmitting/passing) filters can be made from many different materials. One type is
made of polysulfone plastic that blocks over 99% of the visible light spectrum from “white” light
sources such as incandescent filament bulbs. Infrared filters allow a maximum of infrared output
while maintaining extreme covertness. Currently in use around the world, infrared filters are used
in Military, Law Enforcement, Industrial and Commercial applications. Active-infrared night vision:
the camera illuminates the scene at infrared wavelengths invisible to the human eye. Despite a
dark back-lit scene, active-infrared night vision delivers identifying details, as seen on the display
monitor.

b) Thermography
Infrared radiation can be used to remotely determine the temperature of objects (if the
emissivity is known). This is termed thermography, or in the case of very hot objects in the NIR or
visible it is termed pyrometry. Thermography (thermal imaging) is mainly used in military and
industrial applications but the technology is reaching the public market in the form of infrared
cameras on cars due to the massively reduced production costs.



Thermo graphic cameras detect radiation in the infrared range of the electromagnetic
spectrum (roughly 900–14,000 Nano meters or 0.9–14 µm) and produce images of that radiation.
Since infrared radiation is emitted by all objects based on their temperatures, according to the
black body radiation law, thermography makes it possible to "see" one's environment with or
without visible illumination. The amount of radiation emitted by an object increases with
temperature; therefore thermography allows one to see variations in temperature.

c) Tracking: Infrared homing
Infrared tracking, also known as infrared homing, refers to a passive missile guidance system
which uses the emission from a target of electromagnetic radiation in the infrared part of the
spectrum to track it. Missiles which use infrared seeking are often referred to as "heat-seekers",
since infrared (IR) is just below the visible spectrum of light in frequency and is radiated strongly
by hot bodies.

d) Infrared heating
Infrared radiation can be used as a deliberate heating source. For example it is used in infrared
saunas to heat the occupants, and also to remove ice from the wings of aircraft (de-icing). FIR is
also gaining popularity as a safe method of natural health care & physiotherapy. Far infrared
thermometric therapy garments use thermal technology to provide compressive support and
healing warmth to assist symptom control for arthritis, injury & pain. Infrared can be used in
cooking and heating food as it predominantly heats the opaque, absorbent objects, rather than
the air around them.

e) Communications
IR data transmission is also employed in short-range communication among computer peripherals
and personal digital assistants. These devices usually conform to standards published by IrDA, the
Infrared Data Association. Remote controls and IrDA devices use infrared light-emitting diodes
(LEDs) to emit infrared radiation which is focused by a plastic lens into a narrow beam. The beam
is modulated, i.e. switched on and off, to encode the data. The receiver uses a silicon photodiode
to convert the infrared radiation to an electric current. It responds only to the rapidly pulsing
signal created by the transmitter, and filters out slowly changing infrared radiation from ambient
light. Infrared communications are useful for indoor use in areas of high population density. IR
does not penetrate walls and so does not interfere with other devices in adjoining rooms. Infrared
is the most common way for remote controls to command appliances.



f) Spectroscopy
Infrared vibrational spectroscopy (see also near infrared spectroscopy) is a technique which can be
used to identify molecules by analysis of their constituent bonds. Each chemical bonding a
molecule vibrates at a frequency which is characteristic of that bond. A group of atoms in a
molecule (e.g. CH2) may have multiple modes of oscillation caused by the stretching and bending
motions of the group as a whole. If an oscillation leads to a change in dipole in the molecule, then
it will absorb a photon which has the same frequency. The vibration all frequencies of most
molecules correspond to the frequencies of infrared light. Typically, the technique is used to study
organic compounds using light radiation from 4000–400 cm−1, the mid-infrared. A spectrum of all
the frequencies of absorption in a sample is recorded. This can be used to gain information about
the sample composition in terms of chemical groups present and also its purity (for example a wet
sample will show a broad O-H absorption around 3200 cm−1).



4. Hardware description
4.1 Design Consideration:
Optical fibre technology has undergone major developments in the past decades; and as
wireless IR communication systems use some of the same components employed in optical fibre
systems, wireless IR systems benefit from mature and efficient devices that are available at a
relatively low cost The selection of the opto-electronic components for the transmitter and the
receiver is generally done according to the configuration desired for a system. Directed topologies
require directed sources and detectors, while non-directed links require wide emission beams and
wide FOVs. One of the things that can be observed from the information of different systems
developed so far is that wireless IR communications employs (1) light emitting diodes and (2) laser
diodes for wireless IR transmitters. LEDs present wider emission beams than LDs, which makes
them the preferred option of the indoor non-directed and the hybrid configurations. In addition,
they are generally considered as eye safe, which means that they can be used at higher emission
powers than LCD

4.1.1 Channel model from transmitted signal power to generated photocurrent :( intensity
modulation and direct detection)



Block Diagram

BLOCK DIAGRAM EXPLANATION

Transmitter

Infrared headphone has a transmitter connected to audio output from anv audio source like TV,
radio etc. The transmitter has 5 parts

1) Audio Device
2) Audio Interface
3) Audio Amplifier
4) IR Driver
5) IR LED



Audio device is as explained before. The audio output is given to an audio interface circuit
which is a transformer connected in step up mode. The output is given to an audio amplifier
mainly RC coupled amplifier where it is amplified to drive the IR driver. The IR driver has a High
current transistor which is used to drive IR LED connected to emitter. The IR LED generates the
infrared radiation corresponding to audio Input.

Receiver

The receiver section is what the user carries with him. The receiver section has 4 points.

1) IR Interface
2) Audio Amplifier
3) Audio Interface
4) Headphone

The IR interface is photo transistor. Then receives the IR radiations and produces
corresponding electrical signals. This is given to audio amplifier where it is amplified and given to
audio interface circuit. It gives the input to the headphone where the transmitted audio signal is
received



Circuit diagram

Transmitter

Receiver



4.4 Working of the circuit:
The circuit essentially can be divided into two major sub circuits:

1. The transmitter circuit 2. The Receiver Circuit

The transmitter Circuit:
The transmitter circuit consists of a transformer and the two transistor amplifier stage which is
used to amplify the audio signals supplied to the circuit. The audio signal ranges within frequency
from 20Hz to 20,000Hz. The transformer is connected in inverse so as to amplify signals and offers
impedance matching. The signal is then given to an audio amplifier. The three resistors R1, R5 and
R2 are used for the dc biasing of the transistorQ1 which is BC547A a NPN transistor having a Base
to Emitter Voltage rating of 6.0 V. The Red LED is used for the biasing of the transistor Q2 which is
a BD140 transistor which is a PNP transistor capable of handling high currents. The resistance R4 is
used to control the emitter current. When base voltage increases the transistor is ON and the
collector voltage decreases simultaneously. The red LED connected to its collector glows when
collector voltage decreases. The voltage is given to the base of transistor BD 140. The low voltage
makes the BD 140 transistor off and its collector voltage increases and the LED emits radiations. A
9v battery or adapter provides voltage supply.

The Receiver Circuit:
The transmitted IR rays are received by a photo transistor and converted to corresponding
electrical signals. This is amplified by audio amplifier comprising of T4 and T5. When base voltage
of T4 increases making it ON and thus collector voltage decreases. This is given to base of IS and it
becomes OFF and its collector voltage increases. This amplified signal is given to audio interface
where it is given to head set and the audio signal is received.



4.5 Power Budget Considerations
The power budget is one of the most important considerations when designing a Wireless
communication system because it defines the battery size and the operation time of portable
units. Power consumption is determined by a number of factors, such as the electronic and the
optical components used, the modulation scheme, the topology, and the emitted power of a
wireless system. The type of technology used also affects power consumption.

IR transceivers present a lower power requirement than their RF counterparts. An optical
wireless transceiver operating at 1 Mbps consumes 150 mW, while a radio LAN transceiver
consumes 1.5 W, which corresponds to a 25 Percept extra drain on the power supply of a laptop.

The power consumption of a system is strongly affected by the power emitted by the
transmitter. This power should be high enough to cover the desired range of a particular system,
as well as to supply the receiver with sufficient energy.

The power at the receiver is determined by the range of the link, the topology used the
geometry of the room where the system is operating, and the reflective properties of its walls and
ceiling. In addition, the use of an optical collimating element can minimize the power consumption
at the transmitter by transforming an extended source into a concentrated source with narrow
emission angles. When this is the case, care must be taken to comply with eye safety regulations.
The use of collimated sources also allows the use of narrower receivers, which, due to their
directive nature, can present high optical gain increasing the sensitivity of the receiver and
reducing the need for a high transmitted power for a given distance. The use of angle-diversity
receivers and multi-spot transmitters also help to reduce power consumption while maintaining
wide coverage.

Optical Concentrators and Power Requirements

Another way of improving power consumption is through the use of an optical concentrator at
the receiver. This is possible due to the fact that an optical concentrator improves the sensitivity of
the receiver, which means that a lower emitted power may be required at the transmitter (for a
given range) compared to the same system without a concentrator. To optimize the power
consumption, it is also important to transmit only the relevant information, to use an effective
signal coding, and to perform the required signal processing at low power if possible



5 Simulation, Analysis and Amendments

5.1Simulation:

The circuit was simulated by the LT Spice Software to obtain the following plots at
the transmitter.

Figure: - Spice Output wave form.



5.2 Observation:

In order to study the range of the IR Transmitter-Receiver system, we supplied the transmitter
with a sinusoidal signal and observed the output wave form at the DSO. The output received at the
receiver and the DSO was also observed to be sinusoidal for a range of 3 metres. The quality of the
music received was exceptionally good for a range of 1.5 metre after which it started deteriorating.
An Optical Concentrator was then employed at the transmitting LED side. It was observed that the
volume and the quality of the music received were highly improved.

5.3 Amendments

1. Wider Line of Sight
Infrared Communication is line of sight communication. Due to this if there is an obstruction
placed between the transmitter and the receiver then the transfer of the data stops.
Improvements to this headphone technology will be provided by the project team, where we will
use a lens in front of the LEDs to diffuse the light to provide a wider line of sight for the infrared
headphones to catch–there by reducing chances of losing the signal .This method of diffusing the
infrared beam also means the listener needs no longer to sit directly in front the infrared
transmitter which plugs into your TV or other audio source. When it comes to TV/movie watching
and untainted enjoyment of the sound infrared cordless headphones have a number of advantages
which make them ideal for a comfy relaxing viewing experience.

2. Better Range
Use of power amplifiers and an array of high power LEDs arranged at different angles will be
used to increase the range of infrared transmission to cover more area.

3. Use of Optical Concentrator
By using Optical Concentrator at the Transmitting end, the IR Power gets concentrated and a
higher volume of the music and a better quality of music can be obtained.



6. PCB Design and Fabrication
Nowadays the Printed Circuit Board here after mentioned as PCBs makes the electronic circuit
manufacturing as easy one. In olden days vast area was required to implement a small circuit to
connect the leads of the components and separate connectors were needed. But PCBs connects
the two by copper coated lines. In the single sided PCBs the copper layer is on both sides. Some
cases middle layer is also possible than the two sides.
In our project we have done the PCB design with the help of OR-CAD software. The different
steps in the PCB design and how the same was done by us are explained below.

6.1 BOARD TYPES

The most popular board types are:
1. Single-sided boards: They are mainly used in entertainment electronics where
manufacturing costs have to be kept minimized.
2. Double-sided boards: Double sided PCBs can be with or without plated through holes. The
product of boards with plated through holes is fairly expensive.
We have used double-sided board here taking into account the size of the board and ease of
installation. Figure 5.1a is the bottom layer and figure 5.1b is the top layer.

6.2 MANUFACTURING PROCESS

The different steps involved in the design and fabrication of PCB are explained below. We,
observing the necessary precaution during the entire fabrication period have been carefully
followed these steps.

6.3 LAYOUT APPROACHES

The first rule is to prepare each and every PCB layout as viewed from the component side.
Another important rule is not to start the designing of a layout unless an absolutely clear circuit
diagram is available, if necessary with components list. Among the components the larger ones
are placed first and the space between is filled with smaller ones. Components requiring
input/output connections come near the connectors. All components are placed in such a manner
that de-soldering of other components is not necessary if they have to be replaced.

The layout for our circuit was obtained with the help of OR-CAD software. For this, as the first
step we drew our circuit with the help of the software obtaining the required components from
the library files. These components have been properly placed avoiding a large number of
interconnections and crossovers. To develop the layout at first the schematic of the circuit is done
which is then converted into a single layered board design to obtain the layout.



6.4 BOARD CLEANING

The cleaning of the copper surface prior to resist applications is an essential step for any types
of PCB process using etch or plating resist. Insufficient cleaning is one of the reasons most often
encountered for difficulties in PCB fabrication although it might not always be recognized as this.
But it is quite often the reasons of poor resist adhesion, uneven photo-resist films, pinholes, poor
plating adhesion etc.
The cleaning of the board was done with just a sink with running water, pumice powder,
scrubbing brushes and suitable tanks.

6.5 SCREEN PRINTING

The screen-printing process is very simple. For this reason fabric with uniform meshes and
opening is stretched and fixed on a solid frame of metal or wood. The circuit pattern is then
photographically transferred onto the screen, leaving the meshes in the pattern open, while the
meshes in the rest of the area are closed. In the actual printing step, ink is forced by moving
squeegee through the open meshes onto the surface of the material to be printed.

6.6 PLATING

The plating was done expecting the circuit board to retain its solder ability for long periods of
several months so that reliable solder joints can be produced during assembly. Plating of a metal
can be accomplished on a copper pattern by three methods. They are:
1. Immersion plating
2. Electro less plating
3. Electroplating.

6.7 ETCHING

This was done manually by immersing the board into a solution of formic chloride and
hydrochloric acid and finally cleaning the board y soap. The copper pattern was formed by
selective removal of all unwanted copper which is not protected by an etch resist. Factors like
under etching and overhang which complicate the matter especially in the production of fine and
highly precise PCBs have been carefully dealt with. This can also be done using a spray type
etching machine.



6.8 COMPONENT PLACING

In the circuit, components having considerably more connecting points than the others have
been placed first and remaining ones were grouped around them. This will result in a minimum
overall conductor length. This was done aiming to get shortest possible interconnections. The
bending of the axial component leads was done to guarantee an optimum retention of the
component of the PCB while a minimum of stress is introduced on the solder joint. Horizontally
mounted resistors have to touch the board surface to avoid lifting of solder joints along with the
copper pattern under pressure on the resistor body. Vertically mounted resistors should not be
flush to the board surface to avoid strain on the solder joints as well as on the component lead
junction due to different thermal expansion coefficients of lead and board materials, where
necessary resilient spaces have to be provided.

6.9 DRILLING

Drilling was done by mechanical machining operation in PCB production processes. Holes were
made by drilling wherever a superior hole finish for plated through hole processes is required and
where the tooling costs for a punching tool cannot be justified. Therefore drilling is applied by all
the professional grade PCB manufacturers and generally in smaller PCB production laboratories.

6.10 SOLDERING

Soldering is a process for the joining of metal parts with the aid of a molten metal
(solder),where the melting temperature is suited below that of the material joined and whereby
the surface of the parts are wetted, without then becoming molten.

Soldering generally implies that the process occurs at temperature below 450 degree
centigrade. Solder wets and alloys with the base metals and get drawn, by capillary action into the
gap between them. This process forms a metallurgical bond between the parts of the joint.
Therefore solder acts by
1) Wetting of base metal surfaces forming joint.
2) Flowing degree centigrade. Solder wets and alloys with the base metals and gets drawn by
capillary action into the between these surfaces, which result in a completely filled space between
them.
3) Metallurgical bonding to these surfaces when soldered.

If the basic constituents in making a soldered joint are represented in a diagram, it will look as
follows:



Figure 6.1: Soldering Joint Constituents

Soldering was done by placing the components at the right position, wetting these surfaces
with molten solder and allowing the solder to cool down until it has been solidified. During this
soldering operation, an auxiliary medium, flux, was used to increase the flow properties of molten
solder and to improve the degree of wetting. Following characteristics are required in the flux:

It should provide a liquid cover over the materials and exclusive air up to the soldering
temperature.
It should dissolve any oxide on the metal surface or on the solder and carry such unwanted
elements away.
It should be readily displaced from the metal by the molten soldering operation.
Residues should be removable after completion of the soldering. To achieve a soldered joint,
the solder and the base metal must be heated above the melting point of the solder used. The
method by which the necessary heat is applied among other things depends upon:
Nature and type of the joint
Melting point of the solder
Flux
Generally applied soldering methods are iron soldering, torch soldering, electrical soldering,
furnace soldering etc. of which we have gone for iron soldering. Components are mounted on only
one side of the board. In double sided PCBs, the component side is usually opposite to the major
conductor pattern side, unless otherwise dictated by special design requirements.
The performance and reliability of solder joints give best result covered with solder and
herewith contributing to the actual solder connections. However, lead cutting after soldering is
still common in particular in smaller industries where hand soldering is used.
With the soldered PCB, many contaminants can be found which may produce difficulties with
the functioning of the circuit. The problems usually arise at a much later than during the final
functioning testing of the board in the factory. Among the contaminants, we can typically find flux,
chips of plastics, metals and other constructional materials, plating salts, oil greases,
environmental soils and other processing materials.
At the end, a cleaning procedure with an appropriate cleaning medium was done. The
following performances are expected from the cleaning procedure:
Dissolution or dissolving of organic liquids and solids, Eg. oils, greases, resin, flux
Removal of plating salts and silicone oils
Displacing of particulate and other insoluble matters, e.g., chips, dust and lint



No severe attacks on boards and components to be cleaned, no alteration of ink or paint
notations and last but not the least, compatibility with healthy environmental working conditions.

7. PCB Layout

Transmitter

Receiver



8. List of Components
Sl. No COMPONENTS QTY PRICE
(Rs)
1 Audio Transformer 1 10
Transistors
BC547 1 1
2 BC549 2 1
BD139 1 7
BD140 1 7
3 IR Photo transistor 1 80
4 IR LED 2 2
5 LED 1 1
Resistors 3
22k 1
10k 1
4.7k 3
6 2.2k 1
2.7k 1
100R 1
10R, 1W 1
470R 1
Potentiometer 2
100k 1
7 10k 1

Capacitors 12
2200uF, 16V 1
8 0.1uF 2
0.01uF 2
47pF 1
9 Battery 9V 2 40
Total 155


College of Eng: Munnar Dept.
of ECE

9. Result and Inference

9.1 RESULT:

The IR Cordless headphones were successfully built and a detailed study of the
Wireless IR Communication was carried out. The range of the system was
increased by using array of LEDs. Also optical concentrators were used to
improve the power ratings, the amplification and quality of the music received.
Diffusers were also used successfully to increase the angular range.

9.2 FUTURE WORK

In future we plan to study and work more on the IR systems. The IR systems
provide a potential for future research work for short range communication
because of its inherent advantages. We plan to work on increasing the bit rate
transfer of the IR systems so that they can be used effectively in future for
faster communication.

10. Reference:

1. Electronic Devices And Circuit Theory-Robert L.Boylestad,Louis Nashelsky
2. Electronic Devices And Circuits-J.B Gupta
3. Electronics for You
4. http://en.wikipedia.org
5. http://www.alldatasheets.com/


Wireless IR Headset Project Report

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