project report 1

TONGUE MOTION CONTROLLED WHEEL CHAIR

MINI PROJECT REPORT

Submitted by

AMIT PHILIP

JAMES SABY

KISHOR S. BABU

MAAHIR MEHABOOB CHAKKARATHODI

PRAVEEN P. AUGUSTINE

in partial fulfilment for the award of the degree

of

Bachelor of Technology

in

ELECTRONICS AND COMMUNICATION ENGINEERING

of

COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY

DEPARTMENT OF ELECTRONICS ENGINEERING

MODEL ENGINEERING COLLEGE

COCHIN 682 021

APRIL 2012

MODEL ENGINEERING COLLEGE

THRIKKAKARA, KOCHI–21

DEPARTMENT OF ELECTRONICS ENGINEERING

COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY

BONAFIDE CERTIFICATE

This is to certify that the mini project report entitled

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Submitted by

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

is a bonafide account of the work done by him/her under our

supervision

Dr. Mini M.G Mr. Arun C.R. Mrs. Tushara H.P.

Head of Project Coordinator Project Guide

Department

i

ACKNOWLEDGEMENT

This project would remain incomplete if the mention of gratitude to

the following people were forgotten, whose aspirations, suggestions,

guidance and encouragement were priceless for the success of this

project.

First and foremost, we would like to express our heartfelt thanks to

our principal Prof. Dr. T.K. Mani who is the leading light of our

institution. We would also like to thank Dr. Mini M.G, Head of the

Department, Electronics & Communication Engineering; Project

Coordinator Mr. Arun C.R and Project guide Mrs. Tushara H.P, for

their valuable guidance, ideas and support towards the project from the

beginning to the end and acknowledge the technical assistance given to us

by Mr. Shalumon P.S, Mrs. Suma, Mrs. Geetha and other lab

technicians for the project.

Above all, we thank Lord Almighty for providing us with the

courage and confidence to take up this project.

ii

ABSTRACT

Tongue Drive System (TDS) is a tongue-operated

unobtrusive assistive technology, which

can potentially provide people with severe disabilities

with effective computer access and environment control.

Alternative and effective methods for controlling powered wheelchairs

are important to such individuals with tetraplegia and similar

impairments whom are unable to use the standard joystick. This project

describes a system where tongue movements are used to control a model

of a powered wheelchair thus providing users, with high level spinal cord

injuries, full control of their wheelchair.

It translates users’ intentions into control commands by detecting

and classifying their voluntary tongue motion utilizing a small

permanent magnet, secured on the tongue, and an array of

magnetic sensors mounted on a headset outside the mouth. The

magnetic sensors are nothing but hall-effect sensors. A Hall Effect sensor

is a transducer that varies its output voltage in response to changes in

magnetic field. The control system consists of Hall Effect sensor and

microcontroller. Microcontroller collects data from the sensor and

Microcontroller makes to move the motors of the wheel chair in

appropriate direction.

iii

TABLE OF CONTENTS

CONTENTS Page No. 1. ACKNOWLEDGEMENT i

2. ABSTRACT ii

3. INTRODUCTION 1

4. TONGUE DRIVE SYSTEM 4

5. HALL EFFECT 6

6. HALL EFFECT SENSORS 8

7. BLOCK DIAGRAM 9

8. BLOCK DIAGRAM DESCRIPTION 10

9. CIRCUIT DIAGRAM 12

10. CIRCUIT DIAGRAM DESCRIPTION 13

11. PCB LAYOUT 14

12. PCB FABRICATION 15

13. SOLDERING AND DESOLDERING 17

14. DEVELOPMENT TOOLS 19

15. PROGRAM 20

16. SYSTEM PERFORMANCE RESULT 22

17. COMPONENT LIST AND PRICE 23

18. CONCLUSION AND FUTURE SCOPE 24

REFERENCES

APPENDIX

iv

LIST OF FIGURES

Figure No.

Description Page No.

Figure 5.1 Block Diagram - Tongue controlled system 9

Figure 7.1 Circuit Diagram - Tongue controlled system 12

Figure 9.1 PCB Layout - Tongue controlled system 14

Model Engineering College Tongue Motion Controlled Wheel Chair

Department of Electronics Engineering 1

Chapter 1

INTRODUCTION

1.1 Overview

Assistive technologies are critical for people with severe disabilities to lead a

self-supportive independent life. Persons severely disabled as a result of causes

ranging from traumatic brain and spinal cord injuries to stroke generally find it

extremely difficult to carry out everyday tasks without continuous help. Assistive

technologies that would help them communicate their intentions and effectively

control their environment, especially to operate a computer, would greatly improve

the quality of life for this group of people and may even help them to be employed.

A large group of assistive technology devices are available that are controlled

by switches. The switch integrated hand splint, blow-n-suck (sip-n-puff) device, chin

control system, and electromyography (EMG) switch are all switch based systems and

provide the user with limited degrees of freedom. A group of head-mounted assistive

devices has been developed that emulate a computer mouse with head movements.

Cursor movements in these devices are controlled by tracking an infrared beam

emitted or reflected from a transmitter or reflector attached to the user‟s glasses, cap,

or headband. Tilt sensors and video-based computer interfaces that can track a facial

feature have also been implemented. One limitation of these devices is that only those

people whose head movement is not inhibited may avail of the technology. Another

limitation is that user‟s head should always be in positions within the range of the

device sensors. For example the controller may not be accessible when the user is

lying in bed or not sitting in front of a computer.

Another category of computer access systems operate by tracking eye

movements from corneal reflections and pupil position. Electro-oculographic (EOG)

potential measurements have also been used for detecting the eye movements.



A major limitation of these devices is that they affect the users‟ eyesight by

requiring extra eye movements that can interfere with users‟ normal visual activities

such as reading, writing, and watching. The needs of persons with severe motor

disabilities who cannot benefit from mechanical movements of any body organs

are addressed by utilizing electric signals originated from brain waves or muscle

twitches. Such brain computer interfaces, either invasive, or non-invasive have been

the subject of major research activities. Brain Gate is an example of an invasive

technology using intracortical electrodes, while Cyberlink is a non-invasive interface

using electrodes attached to the forehead. These technologies heavily rely on signal

processing and complex computational algorithms, which can results in delays or

significant costs. Think-a-Move Inner voice is yet another interface technology

platform that banks on the capabilities of the ear as an output device. A small earpiece

picks up changes in air pressure in the ear canal caused by tongue movements, speech,

or thoughts.

Up until now, very few assistive technologies have made a successful

transition outside research and widely utilized by severely disabled. Many technical

and psychophysical factors affect the acceptance rate of an assistive technology.

Among the most important factors are the ease of usage and convenience in control.

Operating the Device assistive device must be easy to learn and require minimum

effort on the users' part. Finally, a factor that is often neglected is that the device

should be cosmetically acceptable. The last thing a disabled person wants is to look

different from an intact person.

1.2 Use of tongue for manipulation

Since the tongue and the mouth occupy an amount of sensory and motor

cortex that rivals that of the fingers and a dental retainer and attached on the outside

of the teeth to the hand, they are inherently capable of sophisticated motor measure

the magnetic field from different angles and provide control and manipulation tasks.

This is evident in their usefulness in vocalization and ingestion.



The tongue is connected to the brain by the cranial nerve, which generally

escapes severe damage in spinal cord injuries. It is also the last to be affected in most

neuromuscular disorders. The tongue can move very fast and accurately within the

mouth cavity. It is thus a suitable organ for manipulating assistive devices. The

tongue muscle is similar to the heart muscle in that it does not fatigue easily.

Therefore, a tongue operated device has a very low rate perceived exertion.

An oral device involving the tongue is mostly hidden from sight, thus it is

cosmetically inconspicuous and offers a degree of privacy for the user. The tongue

muscle is not afflicted by repetitive motion disorders that can arise when a few

exoskeletal muscles and tendons are regularly used. The tongue is not influenced by

the position of the rest of body, which may be adjusted for maximum user comfort.

The tongue can function during random or involuntary neurological activities such as

muscular spasms. Also non-invasive access to the tongue movements is possible.

The above reasons have resulted in development of tongue operated assistive

devices such as the TongueTouch Keypad (TTK), which is a switch based device.

Tongue-mouse is another device that has an array of piezoelectric ceramic sensors,

which elements can strength and position of a touch by the tongue. The sensor module

is fitted within the oral cavity as a dental plate. Tonguepoint is another tongue

operated device that adapts the IBM Trackpoint pressure sensitive isometric joystick

for use inside the mouth. The latter two devices have fairly large protruding objects

inside the mouth, which can cause inconvenience during speaking or eating.



Chapter 2

TONGUE DRIVE SYSTEM

2.1 Overview

In the Tongue Drive system, the motion of the tongue is traced by an array of

Hall-effect magnetic sensors, which measure the magnetic field generated by a small

permanent magnet that is contained within a nonmagnetic fixture and pierced on the

tongue. The magnetic sensors are mounted on a dental retainer and attached on the

outside of the teeth to measure the magnetic field from different angles and provide

continuous real-time analog outputs. In this project, we have made use of four Hall

Effect sensors, each of which are used for the movement of the wheel chair in

different directions. The four Hall Effect sensors are placed on the dental retainer. The

output of the first sensor (from the left) assists the forward motion. The outputs of the

second and third sensors are used for turning left and turning right respectively. The

output of the fourth sensor helps in backward motion.

2.2 Advantages

The signals from the magnetic sensors are linear functions the magnetic field,

which is a continuous position dependent property. Thus a few sensors are able to

capture a wide variety of tongue movements. This would provide a tremendous

advantage over switch based devices in that the user has the options of proportional,

fuzzy, or adaptive control over the environment. These would offer smoother, faster,

and more natural controls as the user is saved the trouble of multiple on/off switch

operations. Alternative assistive technologies that emulate a computer mouse use an

additional input device such as a switch for the mouse button clicks besides the

primary method for moving the pointer. In the Tongue Drive system on the other

hand, the additional switches are unnecessary since a specific tongue movement can

be assigned to the button press.



The permanent magnet which generates the magnetic field is a small, passive,

and inherently wireless component leading to user convenience and additional power

saving. The mouthpiece electronics can be integrated on an application specific

integrated circuit (ASIC). The ASIC along with the transmitter antenna can be

incorporated into a miniaturized package that may be fitted under the tongue as part of

the dental retainer. Due to the proximity of the magnet and Hall-effect sensors in the

oral cavity, the Tongue Drive system is expected to be more robust against noise,

interference, and involuntary movements compared to alternative technologies. Many

aspects of the system can be customized and fine-tuned through software for a

particular individual's oral anatomy, requirements, and disabilities. Therefore, the

Tongue Drive system can serve as a platform to address a variety of needs of different

individuals.



Chapter 3

HALL EFFECT

3.1 Introduction

The Hall-Effect principle is named for physicist Edwin Hall. In 1879 he

discovered that when a conductor or semiconductor with current flowing in one

direction was introduced perpendicular to a magnetic field a voltage could be

measured at right angles to the current path.

The Hall voltage can be calculated fromVHall= σB where:

VHall = emf in volts

σ = sensitivity in Volts/Gauss

B = applied field in Gauss

I = bias current

3.2 Hall Effect Senor IC Categories

Bipolar Hall Switch

Unipolar Hall Switch

Latch Hall Sensor IC

Ratiometric linear hall Effect IC

3.3 Advantages over other methods

Hall Effect devices when appropriately packaged are immune to dust, dirt,

mud, and water. These characteristics make Hall Effect devices better for position

sensing than alternative means such as optical and electromechanical sensing.

When electrons flow through a conductor, a magnetic field is produced. Thus,

it is possible to create a non-contacting current sensor. The device has three terminals.

A sensor voltage is applied across two terminals and the third provides a voltage

proportional to the current being sensed. This has several advantages; no additional

resistance (a shunt, required for the most common current sensing method) need be

inserted in the primary circuit. Also, the voltage present on the line to be sensed is not

transmitted to the sensor, which enhances the safety of measuring equipment.



3.4 Disadvantages compared with other methods

Magnetic flux from the surroundings (such as other wires) may diminish or

enhance the field the Hall probe intends to detect, rendering the results inaccurate.

Also, as Hall voltage is often on the order of millivolts, the output from this type of

sensor cannot be used to directly drive actuators but instead must be amplified by a

transistor-based circuit.

3.5 Hall Effect in Semiconductors

When a current-carrying semiconductor is kept in a magnetic field, the charge

carriers of the semiconductor experience a force in a direction perpendicular to both

the magnetic field and the current. At equilibrium, a voltage appears at the

semiconductor edges.

The simple formula for the Hall coefficient given above becomes more

complex in semiconductors where the carriers are generally both electrons and holes

which may be present in different concentrations and have different mobilities. For

moderate magnetic fields the Hall coefficient is

where is the electron concentration, the hole concentration, the electron

mobility, the hole mobility and the absolute value of the electronic charge.

For large applied fields the simpler expression analogous to that for a single carrier

type holds.

with

http://en.wikipedia.org/wiki/Transistor

http://en.wikipedia.org/wiki/Semiconductor

http://en.wikipedia.org/wiki/Electrons

http://en.wikipedia.org/wiki/Electron_hole

http://en.wikipedia.org/wiki/Electron_mobility

http://en.wikipedia.org/wiki/Absolute_value



Chapter 4

HALL EFFECT SENSORS

4.1 Introduction The Hall Effect sensor used in this project is MH 183. MH 183 is a unipolar

Hall Effect sensor IC. It incorporates advanced chopper stabilization technology to

provide accurate and stable magnetic switch points. The design, specifications and

performance have been optimized for applications of solid state switches. The output

transistor will be switched on (BOP) in the presence of a sufficiently strong South

Pole magnetic field facing the marked side of the package. Similarly, the output will

be switched off (BRP) in the presence of a weaker South field and remain off with “0”

field. The package type is in a lead (Pb)-free version was verified by third party

organization.

4.2 Features and Benefits

CMOS Hall IC Technology

Solid-State Reliability

Chopper stabilized amplifier stage

Unipolar, output switches with absolute value of South pole from magnet

Operation down to 2.5V

High Sensitivity for direct reed switch replacement applications

Small Size in To 92S or Sot 23 package.

100% tested at 125 for K Spec.

Custom sensitivity / Temperature selection are available.

4.3 Applications

Solid state switch

Limit switch

Current limit

Interrupter

Current sensing

Magnet proximity sensor for reed switch replacement



Chapter 5

BLOCK DIAGRAM

Figure: 5.1: Block Diagram of Tongue Motion Controlled Wheel Chair



Chapter 6

BLOCK DIAGRAM DESCRIPTION

6.1 Microcontroller

The central element of the system is the PIC16F877A 8-bit microcontroller. It

continuously takes in information from the Hall-effect sensors to make decisions on

driving the DC motors.

6.2 Hall-Effect Sensors

The Hall-effect sensors, mounted on the tongue piece, communicate to the

microcontroller when they are driven low, indicating the direction of the wheelchair.

Depending on which sensor is driven low, the microcontroller determines the

direction of motion of the wheelchair. The microcontroller continuously monitors the

output of all the four Hall-effect sensors.

6.3 Crystal Oscillator

A 12MHz crystal is used as clock source for the microcontroller with its necessary

filter capacitors.

6.4 DC Motor Driver

The output of microcontrollers is given to the inputs of motor driver L293D. It is a

monolithic integrated high voltage, high current four channel driver designed to

accept TTL logic levels and drive inductive loads. A single DIP package can drive

two DC motors.



6.5 DC Motors

Two 12V/60rpm DC motors are used to drive the wheelchair. The necessary power

required is provided through the motor driver IC. The driver also controls the

direction of rotation.

6.6 Power Supply

We are using a 12V battery as the power source and it is given to the motor driver IC

directly for the motors. It is also regulated to 5V using a voltage regulator IC 7805 and

is given as the supply for the microcontroller and the sensors.



Chapter 7

CIRCUIT DIAGRAM

Figure 7.1: Circuit Diagram of Tongue Motion Controlled Wheel Chair



Chapter 8

CIRCUIT DIAGRAM DESCRIPTION

In this circuit, four Hall-effect sensors are used to detect the tongue motion of

the user. A small permanent magnet, secured on the tongue, and an array of Hall-

effect sensors are mounted on a headset outside the mouth. The output of

all the sensors remains high unless a magnetic field of sufficient strength

is detected. The output of each of the sensor are connected to pins RA0,

RA1, RA2, RA3 of Port A and these pins are configured as input pins. The

microcontroller cont inuously monitors the outputs of these sensors. When

any of the sensor output is driven low, microcontroller provides its

corresponding output signals to the motor driver‟s input pins. Pins RD4,

RD5, RD6 and RD7 of Port D are configured as the output pins. These

pins are connected to corresponding input pins of the motor driver.

A crystal oscillator of 12MHz is used as the clock source of the

microcontroller. MCLR pin of the microcontroller is pulled up to +5V

through a 10K resistor. A reset switch is provided to reset the controller

whenever necessary. A protection diode is also provided. A 5pin

connector compat ible with pickit2 programmer is also provided for in-

circuit programming while test ing and debugging the circuit. A 12V battery

as the power source and it is given to the motor driver IC directly for the motors. It is

also regulated to 5V using a voltage regulator IC 7805 and is given as the supply for

the microcontroller and the sensors. Motor driver IC used is L293D. It is a monolithic

integrated high voltage, high current four channel driver designed to accept TTL logic

levels and drive inductive loads.

A single DIP package can drive two DC motors. Connecting the pulse width

modulated output to its enable can be used to control the speed of the motors. Two

12V/60rpm motors have been used. Led indicators are provided at the regulated

output of 7805 and at the sensors outputs.



Chapter 9

PCB LAYOUT

Figure 9.1: PCB Layout of Tongue Motion Controlled Wheel Chair



Chapter 10

PCB FABRICATION

The materials required for PCB fabrication are copper clad, ferric chloride

solution, paint and drilling machine.

The PCB fabrication involves the following steps:

1. Preparation of the PCB Layout

First the circuit is drawn using Express schematic and PCB layout is prepared

using PAD 2 PAD as explained in the layout making procedure. The mirrored

image of layout of bottom layer PAD 2 PAD software is printed on an A4 size

translucent tracing sheet or butter paper. Using this, the thin film can be made

and is exposed to the UV.

2. Film Preparations

In this process, the negative of the plate is made into photographic film. For

this the printed image of the layout in the butter paper is placed over the film

and is exposed to UV rays from the top so that the film will be exposed to the

UV rays from the top so that the film will be exposed to the UV rays in the

region other than the layout. The developer solution then the reaction will take

place, then the region not exposed by UV rays will become transparent and the

other regions are dark in color. Thus the negative is produced. Then the film is

washed in fixing solutions. After that the solution is kept for drying.

3. Transferring the layout to copper clad sheet

Traditional Toner Transfer Method is used here. Here we make use of an

ironer to copy the impression of the layout into the copper clad. First the thin

film is kept over the copper clad such that the impression of the layout lying

on the copper clad. We ten press the thin film using a

switched on ironer. The heat produced by the iron box must be sufficiently

high that the impression of the layout is copied on to the copper clad surface.



4. Etching of the board

When the board is ready for etching, it is placed in the Ferric Chloride solution

of required concentration. It is checked in regular intervals to prevent over

etching and successive damage to the part. After the etching is complete the

board is taken out of the etch and washed in water to remove the excess ferric

chloride. The D13X NC Thinner is applied to remove any dew or paint

material on copper tracks. Then the sheet is cleaned by using steel scrubber

and washed again in water. Now the copper lines are exposed and hence the

body is checked with the magnifying glass to see whether all the lines in the

layout are clearly formed. Now the board is ready for tinning.

5. Drilling

The next process is drilling. In this, holes of required sizes are drilled in the

PCB wherever needed using a PCB drilling machine.

6. Finishing

In the process after drilling holes on PCB, the board is taken and a light coat

of air dying insulating varnish is applied to the bottom side carefully avoiding

the pad areas The PCB is then left till the insulating varnish dry up. The

application of the insulating varnish prevents any type of oxidation on the

track further proving better safeguard to the tracks after tinning.



Chapter 11

SOLDERING AND DESOLDERING

11.1 Soldering

Soldering is the process of joining two or more dissimilar metals by melting another

metal having low melting point.

11.2 Soldering Tools

Soldering Iron

It is the tool used to melt the solder and apply at the joints in the circuit. It

operates in 230V main supply. The normal power ratings of the soldering iron are

10W, 25W, 35W, 65W and 125W. The iron bit at the top of it gets heated up within

a few minutes. 10W and 25W soldering irons are sufficient for light duty works.

Soldering Station

The soldering station consists of a handheld hot air blow gun and the base station

comprising of air flow and temperature controls to the hot air blow gun. Tip

temperature is maintained by feedback control loops. Soldering guns usually have

a trigger switch which controls the AC power.

11.3 Making Soldering Joints

Hold the soldering like a pen, near the base of the handle. Remember to never

touch the hot element or tip.

Touch the soldering iron onto the joint to be made. Make sure it touches both

the component lead and the track. Hold the tip there for a few seconds.

Feed a little solder on the joint. It should flow smoothly onto the lead and

track to form a volcano shape. Make sure you supply the solder to the joint,

not to the iron.

Remove the solder, then the iron, while keeping the joint still. Allow the joint

a few seconds to cool before you move the circuit board.



Inspect the joint closely. It should look shiny and have a „volcano‟ shape. If

not, you will need to reheat it and feed in a little more solder. This time ensure

that both the lead and track are heated fully before applying solder.

11.4 Desoldering

It is the removal of the solder from previously soldered joint. There are two ways to

remove the solder.

Using De-soldering Pump (Solder Sucker):

De-solder pump is a commonly used device for this purpose. When the solder melts

by the action of the soldering iron, the trigger on the de-solder pump should be

activated to create a vacuum. This vacuum pulls the solder into the tube.

Set the pump by pushing the spring loaded plunger down until it locks.

Apply both pump nozzle and the tip of your soldering iron to the joint.

Wait a second or two for the solder to melt.

Then press the button on the pump to release plunger and suck the molten

solder into the tool.

Repeat if necessary to remove as much solder as possible.

The pump will need emptying occasionally by unscrewing the nozzle.

11.5 Safety Precautions

Never touch the element or tip of the soldering iron. They are very hot (about

673K) and will you a nasty burn.

Take great care to avoid touching the mains flex with the tip of the iron. The

iron should have a heatproof flex for extra protection. Ordinary plastic flex

melts immediately if touched by a hot iron and there is a risk of burns and

electric shock.

Always return the soldering iron to its stand when it is not in use.

Allow joints a minute or so to cool down before you touch them.

Work in a well-ventilated area. The smoke formed as you melt the solder is

mostly from the flux and quite irritating. Avoid breathing it by keeping your

head to the side of, not, above your work.

Wash your hands after using solder.



Chapter 12

DEVELOPMENT TOOLS

Features of EAGLE:

System Requirements:

EAGLE is a powerful graphics editor for designing PC board layouts and

schematics. In order to run EAGLE the following is required:

o Windows 2000, XP, or Vista.

o A hard disk with a minimum of 70 MByte free disc space.

o A minimum graphics resolution of 1024 x 768 pixels.

Different editions of EAGLE:

o Professional Edition

o Standard Edition

o Light Edition

For our application we chose the light edition.

The following restrictions apply to the EAGLE Light Edition:

o The board area is restricted to 100 x 80 mm (about 3.9 x 3.2 inches).

Outside this area it is not possible to place packages and draw signals.

o Only two signal layers can be used (no inner layers).

o A schematic can consist of only one single sheet.

Larger Layout and Schematic files can be printed with the higher editions. The

CAM processor can generate manufacturing data as well. It is not possible to

combine modules of different editions. The Light Edition is available as

Freeware for testing, evaluation, and non-commercial use.



Chapter 13

PROGRAM

#include <16F877A.h>

#fuses NOWDT, HS

#use delay (clock=12000000)

void main()

while(1)

if( !input(PIN_A0) ) // if o/p from sensor 0 is detected

output_bit( PIN_A1, 1);



output_bit( PIN_D4, 1); // Motor1 forward

output_bit( PIN_D5, 0);



else if( !input(PIN_A1) ) // if o/p from sensor 1 is detected




output_bit( PIN_D4, 0); // Motor1 backward


output_bit( PIN_D6, 0); // Motor2 backward










output_bit( PIN_D6, 0); // Motor2 stops






output_bit( PIN_D4, 0); // Motor1 stops




else // if no sensor o/p is detected

output_bit( PIN_D4, 0); // Both motors stop










Chapter 14

SYSTEM PERFORMANCE RESULTS

After completing the hardware and software design, the circuit was tested. The

distance between the Hall Effect sensor and the magnet was varied by displacing the

magnet and the approximate range for obtaining the output was determined.

In order to implement the project, the requirement of a super rare earth magnet

placed on the tongue using tissue adhesive was unavoidable. Unfortunately, owing to

the unavailability of this magnet variant in India, alternate magnets had to be used.

Super rare earth magnets were available at the United States but they could be only

shipped within America. Instead, we made use of magnets found inside the computer

hard disk. Using this magnet, the output could be obtained at an approximate

maximum distance of 2.5cm from the Hall Effect sensor. The magnetic field was also

found to pass through skin and phalanges (finger bones) upon testing. PWM (Pulse

Width Modulation) has not been used in this project as appreciable speed has been

obtained without modulation.

A bus wire of approximately 1m length has been used to interconnect the

wheel chair model to the dental retainer. Initially, 4m of bus wire was used but owing

to attenuation of power due to increased length of wire, the length of the wire was

limited to 1m. The limit for the length of the wire to be used for a 5V supply to obtain

a good output is available in the data sheet and is approximately 1.5m.

A maximum supply voltage of 28V is possible for the Hall Effect sensor. In

this project, a 5V supply has been used for the Hall Effect sensor. The sensor was

tested 12V supply voltage and it had no effect on the range of the magnet.

As per the design, all the requirements were met leading to a successful project.



Chapter 15

COMPONENT LIST AND PRICE

Sr. No.

Equipment Quantity Rate (Rs.)

1 PIC 16F877A Microcontroller 1 200

2 Battery (12V) 1 100

3 Voltage Regulator 7805 1 20

4 Hall Effect Sensor 4 300

5 Crystal Oscillator 1 5

6 Geared DC Motors 2 400

7 L293D Motor Driver IC 1 70

8 LED 5 10

9 Switch 2 8

10 PCB + Fabrication 1 600

11 Connectors - 100

TOTAL 1813



Chapter 16

CONCLUSION AND FUTURE SCOPE

As to conclude the report, we would like to share our gratitude and thanks

towards our Project Guide, Mini Project Coordinator, and all our supporting friends.

The aim of our project was to achieve excellence in the technical and social aspect of

the initiative. The project is a symbol of the motto, „by the society for the society‟. As

a personal side of the group, we would like to always motivate such kind of projects.

Building the project was a long journey, starting from the idea to design,

implementation and finally debugging. Apart from the theoretical knowledge, we

could successfully learn the application of the concepts and implementation of an

idea, using the knowledge. It was a good experience to learn working as a team to

make a working model out of just the blue prints.

Tongue Controlled Wheelchair, is one of the major assets in the Bio-medical

arena, where a crippled loss of his/her motor abilities can still be encouraged of

his/her right to explore the surroundings. Our next steps would be trying to implement

„Tongue Controlled Computer Mouse‟. The scope of the idea is huge, and can be

transformed into many attributes of innovations for a man incapable of his/her motor

abilities.

Much further reach of the idea is to replace remote controls. Every human can

control almost everything just by the slip of his/her tongue. The project is the

testimony to the might of electronics and its impact to human life. We conclude our

report, with a promise to encourage and motivate innovations using the wide spectrum

of electronics for Humans in the coming time.

REFERENCES

[1] Morten Enemark Lund, Henrik Vie Christiensen, Hector A Caltenco

“Inductive Tongue Control Of Powered Wheelchairs,” in EMBS 2010,

32nd

Annual International Conference of the IEEE, Argentina, 2010

[2] Gautham Krishnamurthy and Maysam Ghovanloo “Tongue Drive: A

Tongue Operated Magnetic Sensor Based Wireless Assistive

Technology for People with Severe Disabilities,” IEEE ISCAS, 2006

[3] Xueliang Huo, Jia Wang, Maysam Ghovanloo “Introduction and

preliminary evaluation of the Tongue Drive System: Wireless tongue-

operated assistive technology for people with little or no upper-limb

function,” Journal of Rehabilitation Research & Development,

Volume 45, Number 6, 2008

[4] In-O Hwang “The design and development of a head mounted

Tongue Drive Power Wheelchair Controller,” Georgia Institute of

Technology

[5] PIC Microcontroller Datasheets, www.microchip.com

[6] Hall Effect Sensor Datasheets, Allegro Microsystems Inc.

APPENDIX

101807 Page 1 of 7 Rev. 009

MH 183

CMOS Unipolar Hall Switch

MH 183 is a unipolar Hall effect sensor IC. It incorporates advanced chopper stabilization

technology to provide accurate and stable magnetic switch points. The design, specifications

and performance have been optimized for applications of solid state switches.

The output transistor will be switched on (BOP) in the presence of a sufficiently strong

South pole magnetic field facing the marked side of the package. Similarly, the output will be

switched off (BRP) in the presence of a weaker South field and remain off with “0” field. The package type is in a lead (Pb)-free version was verified by third party organization.

Features and Benefits CMOS Hall IC Technology Solid-State Reliability Chopper stabilized amplifier stage Unipolar, output switches with absolute value of South pole from magnet Operation down to 2.5V High Sensitivity for direct reed switch replacement applications Small Size in To 92S or Sot 23 package. 100% tested at 125 for K Spec. Custom sensitivity / Temperature selection are available.

Applications Solid state switch Limit switch Current limit Interrupter Current sensing Magnet proximity sensor for reed switch replacement in low duty cycle applications

Ordering Information

XX-XXX X XX-X-XX XX-X

Lead Free

Handling Code

Package Identification

Sorting Code

Package type

Temperature code

Part number

Company Name and Product Category

Company Name and Product Category

MH:MST Hall Effect/MP:MST Power MOSFET

Part number

181,182,183,184,185,248,249…

Temperature range

E: 85 Degree C, K: 125 Degree C, L: 150 Degree C

Package type

UA:TO-92S,SO:SOT-23,ST:Tsot-25,SU:USON

Sorting

αααα,ββββ,Blank…..

Package Identification Code

01,02,03…..

Handling Code

BLANK: ESD bag, TR: Tape & Reel

Lead Free Code

BLANK: Lead Free Device ,G: Green

101807 Page 2 of 7 Rev. 009

MH 183


Part No. Temperature Suffix Package Type Package Identification

183 K (-40 to + 125) UA ( TO-92S) 01

K (-40 to + 125) SO (SOT-23 ) 05

E (-40 to + 85) UA ( TO-92S) 01

E (-40 to + 85) SO (SOT-23 ) 05

K spec is using in industrial and automotive application. Special Hot Testing is utilized.

Functional Diagram

Note: Static sensitive device; please observe ESD precautions. Reverse VDD protection is not included. For reverse

voltage protection, a 100Ω resistor in series with VDD is recommended.

Absolute Maximum Ratings

Supply Voltage (Operating), VDD 28V

Supply Voltage (Reverse) VDD -0.3V

Supply Current (Fault), IDD 50mA

Output Voltage, VOUT 24V

Output reverse Voltage, VOUT -0.3V

Output Current (Fault), IOUT 50mA

Operating Temperature Range “K”, TA -40 to +125

Operating Temperature Range”E”, TA -40 to +85

Storage Temperature Range, TS -55 to +150

Note: Do not apply reverse voltage to VDD and VOUT Pin, It may be caused for Missfunction or damaged device.

101807 Page 3 of 7 Rev. 009

MH 183


OUT=low(Vdson)

North pole

OUT=low(Vdson)

SO package UA package

MH-183 Electrical Specifications

DC operating parameters: TA = 25, VDD=12VDC (unless otherwise specified).

Parameter Symbol Test Conditions Min. Typ. Max. Units

Supply Voltage VDD Operating 2.5 27 V

Supply Current IDD Average 2.5 5.0 mA

Output Leakage IOFF B<Brp,Vout=20V 10.0 µA

Saturation Voltage VSAT Iout=20mA, B>Bop 0.5 V

Output Rise Time Tr Vdd=12V,RL=1.1Kohm,CL=20pf .04 µS

Output Fall Time Tf Vdd=12V,RL=1.1Kohm,CL=20pf .18 70.0 µS

Magnetic Specifications

DC operating parameters: TA = 25, VDD=12VDC (unless otherwise specified).

Parameter Symbol Test Conditions Min. Typ. Max. Units

Operating Point BOP 25 mT

Release Point BRP 5 mT

Hysteresis BHYS 4.5 mT

Note: 1 mT = 10 Gauss.

Custom sensitivity selection is available.

Output Behaviour versus Magnetic Pole

DC Operating Parameters Ta = -40 to 125, Vdd = 2.5 to 27V (unless otherwise specified)

Parameter Test condition(SO) OUT(SO) OUT(UA)

South pole B<Brp high Low

Null or weak magnetic field B=0 or B < BRP high high

North pole B>Bop low high

South pole

101807 Page 4 of 7 Rev. 009

MH 183


Performance Graphs

101807 Page 5 of 7 Rev. 009

MH 183


L293DL293DD

PUSH-PULL FOUR CHANNEL DRIVER WITH DIODES

600mA OUTPUT CURRENT CAPABILITYPER CHANNEL 1.2A PEAK OUTPUT CURRENT (non repeti-tive) PER CHANNELENABLE FACILITY OVERTEMPERATURE PROTECTION LOGICAL "0" INPUT VOLTAGE UP TO 1.5 V(HIGH NOISE IMMUNITY)INTERNAL CLAMP DIODES

DESCRIPTIONThe Device is a monolithic integrated high volt-age, high current four channel driver designed toaccept standard DTL or TTL logic levels and driveinductive loads (such as relays solenoides, DCand stepping motors) and switching power tran-sistors.To simplify use as two bridges each pair of chan-nels is equipped with an enable input. A separatesupply input is provided for the logic, allowing op-eration at a lower voltage and internal clamp di-odes are included.This device is suitable for use in switching appli-cations at frequencies up to 5 kHz.

The L293D is assembled in a 16 lead plasticpackaage which has 4 center pins connected to-gether and used for heatsinkingThe L293DD is assembled in a 20 lead surfacemount which has 8 center pins connected to-gether and used for heatsinking.

July 2003

®

BLOCK DIAGRAM

SO(12+4+4) Powerdip (12+2+2)

ORDERING NUMBERS:

L293DD L293D

1/7

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

VS Supply Voltage 36 V

VSS Logic Supply Voltage 36 V

Vi Input Voltage 7 V

Ven Enable Voltage 7 V

Io Peak Output Current (100 µs non repetitive) 1.2 A

Ptot Total Power Dissipation at Tpins = 90 °C 4 W

Tstg, Tj Storage and Junction Temperature – 40 to 150 °C

THERMAL DATA

Symbol Decription DIP SO Unit

Rth j-pins Thermal Resistance Junction-pins max. – 14 °C/W

Rth j-amb Thermal Resistance junction-ambient max. 80 50 (*) °C/W

Rth j-case Thermal Resistance Junction-case max. 14 –

(*) With 6sq. cm on board heatsink.

PIN CONNECTIONS (Top view)

SO(12+4+4) Powerdip(12+2+2)

L293D - L293DD

2/7

ELECTRICAL CHARACTERISTICS (for each channel, VS = 24 V, VSS = 5 V, Tamb = 25 °C, unlessotherwise specified)

Symbol Parameter Test Conditions Min. Typ. Max. Unit

VS Supply Voltage (pin 10) VSS 36 V

VSS Logic Supply Voltage (pin 20) 4.5 36 V

IS Total Quiescent Supply Current(pin 10)

Vi = L ; IO = 0 ; Ven = H 2 6 mA

Vi = H ; IO = 0 ; Ven = H 16 24 mA

Ven = L 4 mA

ISS Total Quiescent Logic SupplyCurrent (pin 20)

Vi = L ; IO = 0 ; Ven = H 44 60 mA

Vi = H ; IO = 0 ; Ven = H 16 22 mA

Ven = L 16 24 mA

VIL Input Low Voltage (pin 2, 9, 12,19)

– 0.3 1.5 V

VIH Input High Voltage (pin 2, 9,12, 19)

VSS ≤ 7 V 2.3 VSS V

VSS > 7 V 2.3 7 V

IIL Low Voltage Input Current (pin2, 9, 12, 19)

VIL = 1.5 V – 10 µA

IIH High Voltage Input Current (pin2, 9, 12, 19)

2.3 V ≤ VIH ≤ VSS – 0.6 V 30 100 µA

Ven L Enable Low Voltage(pin 1, 11)

– 0.3 1.5 V

Ven H Enable High Voltage(pin 1, 11)

VSS ≤ 7 V 2.3 VSS V

VSS > 7 V 2.3 7 V

Ien L Low Voltage Enable Current(pin 1, 11)

Ven L = 1.5 V – 30 – 100 µA

Ien H High Voltage Enable Current(pin 1, 11)

2.3 V ≤ Ven H ≤ VSS – 0.6 V ± 10 µA

VCE(sat)H Source Output SaturationVoltage (pins 3, 8, 13, 18)

IO = – 0.6 A 1.4 1.8 V

VCE(sat)L Sink Output Saturation Voltage(pins 3, 8, 13, 18)

IO = + 0.6 A 1.2 1.8 V

VF Clamp Diode Forward Voltage IO = 600nA 1.3 V

tr Rise Time (*) 0.1 to 0.9 VO 250 ns

tf Fall Time (*) 0.9 to 0.1 VO 250 ns

ton Turn-on Delay (*) 0.5 Vi to 0.5 VO 750 ns

toff Turn-off Delay (*) 0.5 Vi to 0.5 VO 200 ns

(*) See fig. 1.

L293D - L293DD

3/7

TRUTH TABLE (one channel)

Input Enable (*) Output

HLHL

HHLL

HLZZ

Z = High output impedance(*) Relative to the considered channel

Figure 1: Switching Times

Figure 2: Junction to ambient thermal resistance vs. area on board heatsink (SO12+4+4 package)

L293D - L293DD

4/7

project report 1

Documents

halleffect sensors

hall effect sensors

control system

tongue movements

voluntary tongue motion

environment control

control commands

array of magnetic sensors