wireless ir headset_report

College of Eng: Munnar Dept. of ECE

Wireless IR Headset

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

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


Wireless IR Headset

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.


Wireless IR Headset

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


Wireless IR Headset

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


Wireless IR Headset

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


Wireless IR Headset

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.


Wireless IR Headset

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


Wireless IR Headset

Fig 1.3.1 Chronology of indoor optical wireless communication research


Wireless IR Headset

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).


Wireless IR Headset

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.


Wireless IR Headset

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.


Wireless IR Headset

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.


Wireless IR Headset

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.


Wireless IR Headset

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.


Wireless IR Headset

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).


Wireless IR Headset

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)


Wireless IR Headset

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


Wireless IR Headset

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


Wireless IR Headset

Circuit diagram

Transmitter

Receiver


Wireless IR Headset

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.


Wireless IR Headset

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


Wireless IR Headset

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.


Wireless IR Headset

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.


Wireless IR Headset

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.


Wireless IR Headset

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.


Wireless IR Headset

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:


Wireless IR Headset

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


Wireless IR Headset

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


Wireless IR Headset

8. List of Components

Sl. No COMPONENTS QTY PRICE (Rs)

1 Audio Transformer 1 10

2

Transistors BC547 BC549 BD139 BD140

1 2 1 1

1 1 7 7

3 IR Photo transistor 1 80

4 IR LED 2 2

5 LED 1 1

6

Resistors 22k 10k 4.7k 2.2k 2.7k 100R

10R, 1W 470R

1 1 3 1 1 1 1 1

3

7

Potentiometer 100k 10k

1 1

2

8

Capacitors 2200uF, 16V

0.1uF 0.01uF 47pF

1 2 2 1

12

9 Battery 9V 2 40

Total 155


Wireless IR Headset

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_report

Documents