Accelerometer Based Tilt Sensor for Controlling Wheel Chair

Accelerometer Based Tilt Sensor for Controlling Wheel Chair A Project Report

Technology Edition by Shahzad Saeed

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Table of content

Abstract ......................................................................................................................................................... 2

Introduction .................................................................................................................................................. 2

Embedded system ................................................................................................................................. 2

Photographs .................................................................................................................................................. 3

BLOCK DIAGRAM ........................................................................................................................................... 5

Literature Review .......................................................................................................................................... 5

PIC Microcontroller(16F877) ................................................................................................................. 5

Features ................................................................................................................................................ 5

Temperature Sensor ..................................................................................................................................... 7

Tilt Sensor ..................................................................................................................................................... 8

BASIC BLOCK DIAGRAM ................................................................................................................................ 9

Relay ............................................................................................................................................................ 10

DC MOTOR .................................................................................................................................................. 11

DC MOTOR FORWARD REVERSE BIASED CIRCUIT ....................................................................................... 12

OVERALL CIRCUIT ........................................................................................................................................ 14

Battery......................................................................................................................................................... 14

Software ...................................................................................................................................................... 15

Program....................................................................................................................................................... 15

Applications and merits .............................................................................................................................. 20

Result .......................................................................................................................................................... 21

Conclusion ................................................................................................................................................... 21

Behind the Book .......................................................................................................................................... 22


Abstract The objective of the project is to control a certain object with the

help of the movement of the palm.

The design has a microcontroller, temperature sensor,

accelerometer, driver circuits, LED Display along with motor and

wheel chair

The movement represents different operations such as forward,

reverse, left and right.

By using this mechanism we move a wheel chair here by the

movement of the palm.

Introduction The machine is loaded with several units such as microcontroller,

TILT Sensor, Temperature Sensor, relay and driver circuits.

Microcontroller is the heart of the device.

The microcontroller used is PIC 16F877 microcontroller.

It is a flash type reprogrammable memory.

It also provides sufficient power to inbuilt peripheral devices.

Embedded system

The system used here is embedded systems.


The application of this system makes user friendly cheaper

solutions and enables to add features otherwise impossible to

provide other means.

The software used for the embedded system is called firmware.

The languages used can be C or C++.

They need no or minimal inputs from the user, hence the

interface like keyboard may be minimal

Photographs

Figure 1: Wheel Chair using Tilt Sensor


Figure 2: Tilt Sensor


BLOCK DIAGRAM

Literature Review

PIC Microcontroller(16F877)

The PIC microcontroller is the first RISC based microcontroller

fabricated in CMOS that uses separate bus for the instruction and

data allowing simultaneous access of program and data memory.

Features

All single cycle instructions for program branches which are two

cycle.


Eight level deep hardware stack.

Direct, Indirect and relative addressing modes

Programmable code protection

Power saving sleeping mode

Low power, High Speed CMOS

Only single 5V source needed dor programming capability.

Wide operating voltage.


Temperature Sensor The thermistor is a type of resistor varies with temperature. The

word when split gives thermal and resistor.

The thermistors are unlike the Resistance Temperature Detectors

because the material used are pure metals rather than ceramic or

polymers.

Moreover the temperature response is also different because

RTD’s are inefficient at low temperatures.

The relationship between resistance and temperature is linear.

ΔR = kΔT

Where

ΔR = change in resistance

ΔT = change in temperature

k = first-order temperature coefficient of

resistance.

Based on this the thermistors are divided in two types.

Positive temperature coefficient(PTC) thermistor

Negative temperature coefficient(NTC) thermistor

In PTC the resistance decreases with increasing temperature and vice-

versa in NTC.


Tilt Sensor A tilt sensor can measure the tilting in often two axes of a

reference.

The tilt angle is measured with reference to the earths ground

plane, which uses an Accelerometer.

Accelerometer measures proper acceleration related to freefall.

When held fixed in a gravitational field by, for example, applying a

ground reaction force or an equivalent upward thrust, the


reference for an accelerometer accelerates upwards with respect

to a free-falling reference frame.

The acceleration is quantified in SI units meters per second per

second(m/s²)

Conceptually, an accelerometer behaves as a damped mass on a

spring. When the accelerometer experiences an acceleration, the

mass is displaced to the point the spring is able to accelerate the

mass at the same rate ad the casing.

BASIC BLOCK DIAGRAM


Relay A relay is an electrical switch and opens closes under the control

of another circuit. The relay actually uses an electromagnet to

open or close.

When a current flows through the coil, the resulting magnetic

field attracts an armature that is mechanically linked to a moving

contact which leads to the switching ON and OFF the device.

Relays allow one circuit to switch a second circuit which can be

completely separate from the first.


DC MOTOR The motor is used here to rotate the wheels. Actually a set of 2 DC

motors are used here which can move in both forward and

reverse directions.

The basic mechanism is based on simple electromagnetism.

Here motors with cores are used because coreless motors are

prone to excess heating.


DC MOTOR FORWARD REVERSE BIASED CIRCUIT


Figure 3: DC Motor


OVERALL CIRCUIT

Battery The battery used here is a 12V re-chargeable battery.

The main use of the battery is to provide electric current for the

functioning of the whole circuit including the DC motors.

These give a continuous flow in the working of the circuit as well

as the movement of the wheel chair.


Software The software used here is MICROSIM.

It is used to program the PIC microcontroller which controls the

functioning of the circuit.

The compiler used here is KEIL COMPILER. This is used to solve the

problems facing embedded software developers.

It helps to understand hardware configurations and avoids time

wasted on setup problems.

Program #include <pic.h>

#include "pic_acce.h"

#include "pic_lcd8.h"

#include "pic_adc.h"

unsigned char x,y,z,h,value;

bit val1,val2,val3,x1,y1,z1;

#define rel1 RB0

#define rel2 RB1

#define rel3 RB2#define rel4 RB3

void main()

{


rel1=rel2=rel3=rel4=1;

TRISD=0x00;

TRISC=0xc0;

TRISB=0x00;

ADCON1=0x09;

TRISA=0xff;

Lcd8_Init();

Acc_Init();

Lcd8_Display(0x80,"Acc_meter Based ",16);

Lcd8_Display(0xc0," Tilt sensor ",16);

Delay(65000);Delay(65000);

Lcd8_Display(0x80," X: 000 Y: 000 ",16);

Lcd8_Display(0xc0," Z: 000 T: ",16);

Delay(65000);Delay(65000);

while(1)

{

value=Adc8_Cha(0);

Lcd8_Decimal3(0xca,value);

Acc_Write(0x07,0x01);Delay(2000)


x=Acc_Read(0x00);Delay(1000);

TRISC=0xc0;

if(x>30)

{

Lcd8_Write(0x83,'-');

x= 63-x;

x1=1;

}

else

{

Lcd8_Write(0x83,'+');

x1=0;

}

Lcd8_Decimal3(0x84,x);

y=Acc_Read(0x01);Delay(1000);

if(y>30)

{

Lcd8_Write(0x8b,'-');

y=63-y;

y1=1;


}

else

{

Lcd8_Write(0x8b,'+');

y1=0;

}

Lcd8_Decimal3(0x8c,y);

z=Acc_Read(0x02);Delay(1000);

if(z>30)

{

Lcd8_Write(0xc3,'-');

z=63-z;

z1=1;

} else

{

Lcd8_Write(0xc3,'+');

z1=0;

}

Lcd8_Decimal3(0xc4,z);

if(x1==1&&x>=8&&z<20)


{


rel1=rel3=0;

Lcd8_Write(0xce,'R');

}

else if(x1==0&&x>=8&&z<20)

{


rel2=rel4=0;

Lcd8_Write(0xce,'L');

} else if(y1==1&&y>=7&&z<15)


rel1=rel4=0;

Lcd8_Write(0xce,'F');

}

else if(y1==0&&y>=8&&z<15)

{


rel2=rel3=0;


Lcd8_Write(0xce,'r');

}

else

{


Lcd8_Write(0xce,'S');

}

}

}

Applications and merits MERITS

1] Low cost to design the circuit

2] Maintenances of the circuit is good

3] Reliability

4] Compatibility

5] Easy convenience to handle

APPLICATIONS

This project is very useful for physically challenged.


Result A working model of Accelerometer based Tilt sensor for the movement

of the wheel chair was prepared with the help of a PIC microcontroller,

two DC motors and the necessary equipments which resulted in the

proper movement of the wheel chair in all the four directions.

Conclusion Tilt sensors have a secure place in the movement of equipment based

on actions done. The system can be made free from challenges and will

be cost effective in the near future.


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Date post:	08-Apr-2015
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Accelerometer Based Tilt Sensor for Controlling Wheel Chair

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