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 Head of Department

Mr. Arun C.R.

Mrs. Tushara H.P.

Project Coordinator

Project Guide

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.

i

ABSTRACT Tongue

Drive

unobtrusive

System

(TDS)

assistive

can potentially provide people with effective

computer access

is

a

tongue-operated

technology, with severe

which disabilities

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. ii

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 iii

LIST OF FIGURES

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

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Figure No.

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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.

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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.

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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.

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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.

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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.

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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.

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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,

mobility,

the hole mobility and

the hole concentration,

the electron

the absolute value of the electronic charge.

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

with

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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

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Chapter 5

BLOCK DIAGRAM

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

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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.

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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.

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Chapter 7

CIRCUIT DIAGRAM

Figure 7.1: Circuit Diagram of Tongue Motion Controlled Wheel Chair

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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 Halleffect sensors are mounted on a headset outside the mouth. The output of all t he 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 t he 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 wit h pickit2 programmer is also provided for incircuit 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.

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Chapter 9

PCB LAYOUT

Figure 9.1: PCB Layout of Tongue Motion Controlled Wheel Chair

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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.

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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.

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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.

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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.

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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.

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Chapter 13

PROGRAM

#include #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_A2, 1); output_bit( PIN_A3, 1); output_bit( PIN_D4, 1); // Motor1 forward output_bit( PIN_D5, 0); output_bit( PIN_D6, 1); // Motor2 forward output_bit( PIN_D7, 0); } else if( !input(PIN_A1) ) // if o/p from sensor 1 is detected { output_bit( PIN_A0, 1); output_bit( PIN_A2, 1); output_bit( PIN_A3, 1); output_bit( PIN_D4, 0); // Motor1 backward output_bit( PIN_D5, 1); output_bit( PIN_D6, 0); // Motor2 backward output_bit( PIN_D7, 1); }

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else if( !input(PIN_A2) ) // if o/p from sensor 2 is detected { output_bit( PIN_A0, 1); output_bit( PIN_A1, 1); output_bit( PIN_A3, 1); output_bit( PIN_D4, 1); // Motor1 forward output_bit( PIN_D5, 0); output_bit( PIN_D6, 0); // Motor2 stops output_bit( PIN_D7, 0); } else if( !input(PIN_A3) ) // if o/p from sensor 3 is detected { output_bit( PIN_A0, 1); output_bit( PIN_A1, 1); output_bit( PIN_A2, 1); output_bit( PIN_D4, 0); // Motor1 stops output_bit( PIN_D5, 0); output_bit( PIN_D6, 1); // Motor2 forward output_bit( PIN_D7, 0); } else

// if no sensor o/p is detected

{ output_bit( PIN_D4, 0); // Both motors stop output_bit( PIN_D5, 0); output_bit( PIN_D6, 1); output_bit( PIN_D7, 1); output_bit( PIN_A0, 1); output_bit( PIN_A1, 1); output_bit( PIN_A2, 1); output_bit( PIN_A3, 1); } } }

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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.

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Chapter 15

COMPONENT LIST AND PRICE

Sr. No.

Equipment

Quantity

Rate (Rs.)

1 2 3 4 5 6 7 8 9

PIC 16F877A Microcontroller Battery (12V) Voltage Regulator 7805 Hall Effect Sensor Crystal Oscillator Geared DC Motors L293D Motor Driver IC LED Switch

1 1 1 4 1 2 1 5 2

200 100 20 300 5 400 70 10 8

10

PCB + Fabrication

600

11

Connectors

1 -

TOTAL

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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.

Department of Electronics Engineering

24

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 tongueoperated 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

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

Company Name and Product Category Lead Free

MH:MST Hall Effect/MP:MST Power MOSFET

Part number Handling Code

181,182,183,184,185,248,249…

Temperature range Package Identification

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

Package type Sorting Code

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

Sorting Package type

α,β β,Blank…..

Package Identification Code Temperature code

01,02,03…..

Handling Code Part number

BLANK: ESD bag, TR: Tape & Reel

Lead Free Code Company Name and Product Category

101807

BLANK: Lead Free Device ,G: Green

Page 1 of 7

Rev. 009

MH 183 CMOS Unipolar Hall Switch

Part No. 183

Temperature Suffix K (-40℃ ℃ to + 125℃ ℃)

Package Type UA ( TO-92S)

Package Identification 01

K (-40℃ ℃ to + 125℃ ℃) E (-40℃ ℃ to + 85℃ ℃) E (-40℃ ℃ to + 85℃ ℃)

SO (SOT-23 ) UA ( TO-92S) SO (SOT-23 )

05 01 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 2 of 7

Rev. 009

MH 183 CMOS Unipolar Hall Switch MH-183 Electrical Specifications DC operating parameters: TA = 25℃, VDD=12VDC (unless otherwise specified).

Parameter

Symbol

Test Conditions

Supply Voltage

VDD

Operating

Supply Current

IDD

Average

Output Leakage

IOFF

Saturation Voltage

Min. Typ. Max. Units 2.5

27

V

5.0

mA

BBop

0.5

V

Output Rise Time

Tr

Vdd=12V,RL=1.1Kohm,CL=20pf

.04

Output Fall Time

Tf

Vdd=12V,RL=1.1Kohm,CL=20pf

.18

2.5

µS 70.0

µS

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

Parameter

Symbol

Operating Point

BOP

Release Point

BRP

Hysteresis

BHYS

Test Conditions

Min. Typ. Max. Units 25 5

mT mT

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

BBop

low

high

North pole

South pole

101807

OUT=low(Vdson)

OUT=low(Vdson)

SO package

UA package

Page 3 of 7

Rev. 009

MH 183 CMOS Unipolar Hall Switch Performance Graphs

101807

Page 4 of 7

Rev. 009

MH 183 CMOS Unipolar Hall Switch

101807

Page 5 of 7

Rev. 009

L293D L293DD

®

PUSH-PULL FOUR CHANNEL DRIVER WITH DIODES 600mA OUTPUT CURRENT CAPABILITY PER CHANNEL 1.2A PEAK OUTPUT CURRENT (non repetitive) PER CHANNEL ENABLE FACILITY OVERTEMPERATURE PROTECTION LOGICAL "0" INPUT VOLTAGE UP TO 1.5 V (HIGH NOISE IMMUNITY) INTERNAL CLAMP DIODES DESCRIPTION The Device is a monolithic integrated high voltage, high current four channel driver designed to accept standard DTL or TTL logic levels and drive inductive loads (such as relays solenoides, DC and stepping motors) and switching power transistors. To simplify use as two bridges each pair of channels is equipped with an enable input. A separate supply input is provided for the logic, allowing operation at a lower voltage and internal clamp diodes are included. This device is suitable for use in switching applications at frequencies up to 5 kHz.

SO(12+4+4)

Powerdip (12+2+2)

ORDERING NUMBERS: L293DD

L293D

The L293D is assembled in a 16 lead plastic packaage which has 4 center pins connected together and used for heatsinking The L293DD is assembled in a 20 lead surface mount which has 8 center pins connected together and used for heatsinking.

BLOCK DIAGRAM

July 2003

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L293D - L293DD ABSOLUTE MAXIMUM RATINGS Symbol

Parameter

Value

Unit

VS

Supply Voltage

36

V

VSS Vi Ven

Logic Supply Voltage Input Voltage

36 7

V V

Enable Voltage Peak Output Current (100 µs non repetitive)

7 1.2

V A

Io Ptot Tstg, Tj

Total Power Dissipation at Tpins = 90 °C Storage and Junction Temperature

4

W

– 40 to 150

°C

PIN CONNECTIONS (Top view)

Powerdip(12+2+2)

SO(12+4+4)

THERMAL DATA Symbol

Decription

Rth j-pins Rth j-amb

Thermal Resistance Junction-pins Thermal Resistance junction-ambient

Rth j-case

Thermal Resistance Junction-case

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

2/7

DIP

SO

Unit

max. max.

– 80

14 50 (*)

°C/W °C/W

max.

14

–

L293D - L293DD ELECTRICAL CHARACTERISTICS (for each channel, VS = 24 V, VSS = 5 V, Tamb = 25 °C, unless otherwise specified) Symbol VS VSS IS

ISS

Parameter

Test Conditions

Min.

Typ.

Max.

Unit

Supply Voltage (pin 10)

VSS

36

V

Logic Supply Voltage (pin 20) Total Quiescent Supply Current (pin 10)

4.5

V mA

Total Quiescent Logic Supply Current (pin 20)

VIL

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

VIH

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

Vi = L ; IO = 0 ; Ven = H

2

36 6

Vi = H ; IO = 0 ; Ven = H

16

24

mA

44

4 60

mA mA

Ven = L Vi = L ; IO = 0 ; Ven = H Vi = H ; IO = 0 ; Ven = H

16

22

mA

Ven = L

16 – 0.3

24 1.5

mA V

2.3 2.3

VSS 7

V V

– 10

µA

100

µA

– 0.3

1.5

V

2.3 2.3

VSS 7

V V

– 100

µA

± 10

µA

VSS ≤ 7 V VSS > 7 V

IIL

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

VIL = 1.5 V

IIH

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

2.3 V ≤ VIH ≤ VSS – 0.6 V

30

Ven L

Enable Low Voltage (pin 1, 11)

Ven H

Enable High Voltage (pin 1, 11)

VSS ≤ 7 V VSS > 7 V

Ien L

Low Voltage Enable Current (pin 1, 11)

Ven L = 1.5 V

Ien H

High Voltage Enable Current (pin 1, 11)

2.3 V ≤ Ven H ≤ VSS – 0.6 V

VCE(sat)H

Source Output Saturation Voltage (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 (*) Turn-on Delay (*) Turn-off Delay (*)

0.9 to 0.1 VO 0.5 Vi to 0.5 VO 0.5 Vi to 0.5 VO

250 750 200

ns ns ns

ton toff

– 30

(*) See fig. 1.

3/7

L293D - L293DD Figure 1: Switching Times

TRUTH TABLE (one channel) Input

Enable (*)

Output

H L H L

H H L L

H L Z Z

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

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

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