accelerometer based tilt sensor for controlling wheel chair
TRANSCRIPT
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
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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.
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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
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Figure 2: Tilt Sensor
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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.
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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.
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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.
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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
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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
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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.
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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.
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DC MOTOR FORWARD REVERSE BIASED CIRCUIT
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Figure 3: DC Motor
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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.
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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()
{
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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)
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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;
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}
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)
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{
rel1=rel2=rel3=rel4=1;
rel1=rel3=0;
Lcd8_Write(0xce,'R');
}
else if(x1==0&&x>=8&&z<20)
{
rel1=rel2=rel3=rel4=1;
rel2=rel4=0;
Lcd8_Write(0xce,'L');
} else if(y1==1&&y>=7&&z<15)
rel1=rel2=rel3=rel4=1;
rel1=rel4=0;
Lcd8_Write(0xce,'F');
}
else if(y1==0&&y>=8&&z<15)
{
rel1=rel2=rel3=rel4=1;
rel2=rel3=0;
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Lcd8_Write(0xce,'r');
}
else
{
rel1=rel2=rel3=rel4=1;
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.
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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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Behind the Book
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