DIGITAL SPEEDOMETER WITH PASSWORD

ENABLE SPEED CONTROLLING

A PROJECT REPORT

ABSTRACT

The main aim of this project is to design a digital speedometer with

password enabled with speed limit controlling. This simple system shows the

ability to apply speed limit controlling techniques to the vehicle. Our digital

speedometer takes input from vehicle speedometer cable and executes the speed

limit controlling action.

The system comprises of keypad, LCD display and microcontroller unit. The

user interface includes keypad through which the password will be accepted by the

microcontroller. Microcontroller controls the over speed of vehicle.

List of Figures

Figure No. Figure Description Page No.

2.1 Basic Block Diagram 3

2.2 Circuit Diagram 4

2.3 Circuit Diagram of Speed Sensor input 5

2.4 Pin Diagram of IC LM324 7

2.5 Block Diagram of AT80S52 9

2.6 Pin Diagram of AT80S52 10

2.7 Pin Diagram of IC7805 15

2.8 Pin Diagram of EL1602 LCD 16

2.9 Circuit Diagram of keypad 18

2.10 Flowchart 19

List of Tables

Table No. Table Description Page No.

2.1 Pin Description of LM324 8

2.2 Pin Description of IC7805 16

2.3 Pin Description of EL1602 LCD 17

2.4 Keypad Output Arrangement 18

List of Abbreviation

Sr no. Short form Full form

1 LCD Liquid crystal display

2 LED Light emitting diode

3 OP-AMP Operational amplifier

4 RAM Random access memory

5 TTL Transistor transistor logic

6 IIL Integrated input logic

7 SFR Special function resister

8 ALE Address Latch Enable

9 PSEN Program Store Enable

10 EA External Access

11 ISP In-System Programmable

12 ASCII American standard coded

for information

interchange

13 PCB Printed circuit board

CONTENTS PAGE NO.

1 : Introduction 1

2 : Problem Identification & Methodology 2

2. Aim 2

2.1 Purpose 2

2.2 Working principle 2

2.3 System design 3

2.4 Working 6

2.4.1 IC LM324 7

2.4.2 Microcontroller AT80S52 9

2.4.2.1 PIN Description of AT80S52 11

2.4.2.2 Features of AT80S52 14

2.4.3 IC7805 15

2.4.4 EL1602 LCD 16

2.4.5 Keypad 18

3 : Software (as per project) 19

3.1 Flowchart 19

3.2 Program 20

4 : Application and Merits/demerits 25

4.1 Application 25

4.2 Merits 25

4.3 Demerits 25

4.4 Conclusion 25

5 : References 26

6 : Appendix 26

Chapter 1 : Introduction

1. INTRODUCTION

Digital speedometer with password and speed limit controlling is different think and technology

for automobiles. This instrument is normally used in maintaining the speed in that your vehicle is

operating, and is extremely useful in roadways and highways that have a fixed speed limit. The

system generally consists of numerical keypad, LCD and microcontroller unit. The speed sensor

system is easy to build. LCD and keypad are interfaced with microcontroller using program.

Keypad allows us to enter password to access the vehicle. Instead of the numerical password we

can also use the finger print scanner as a password. This speedometer system can be used in any

vehicle like bikes, cars, trucks, buses and any kind of vehicle. This system is very useful for the

beginner drivers and who drives over speedy in city and highways.

This research details the construction and building of a digital speedometer circuit that may be

interfaced to control the speed limit of vehicle. The circuit is trained to calculate the speed and

check that it is under speed limit or not. If it is over speedy than circuit controls the speed

automatically. This system increases the vehicle fuel efficiency and life.

Currently most vehicles are provided with analog speedometer which is less accurate than digital

speedometer. Also many vehicles are provided digital speedometer. The limitation of this

speedometer is that they don’ t have speed controlling facility. This limitation is overcome in

our project.

Chapter 2 : PROBLEM IDENTIFICATION &

METHODOLOGY

2. AIM

The aim of our project is to design a digital speedometer with password enable speed

controlling. Our speedometer can calculate and display the speed of vehicle and also control the

speed if it goes over speed.

2.1 PURPOSE

The purpose of the project is to develop a system, which to control the speed of vehicle in order

to avoid accidents occur.

2.2 WORKING PRINCIPAL

The system takes password input and check it is correct or not, if it is true than allows to drive

over speed but if it is false than activate the speed limit function.

The speed is sensed in form of pulse by op-amp comparator and given to microcontroller which

calculates the pulses per second and display the speed. It also compares the speed with stored

speed limit data and if it is over the speed limit than turn off the relay which is connected with

the ignition power supply. So speed will decreases and when it comes below speed limit than

turn on supply and continues.

2.3 SYSTEM DESIGN

This part introduces our approach of creating a system of a Digital speedometer which is

password enabled with speed controlling function.

Fig.2.1 Basic Block Diagram of Digital Speedometer with Password Enable Speed

Controlling

Fig.2.2 Circuit Diagram

Fig.2.3 Circuit Diagram of Speed Sensor input

2.4 WORKING

A digital speedometer is an instrument in a vehicle that is used for indicating the speed in which

it is actually traveling. It is at the same time useful for knowing the range that was traveled by

the vehicle.

First when the key is turn on a message “ ENTER PASSWORD” is displayed on the EL1602

16*2 LCD. The password is entered using 3*4 numeric keypad. Pre-defined password is stored

in the memory of microcontroller AT80S52. Entered password is compared with stored

password. If it’ s true than display the second menu display “ Drive” , “ Setting” . The setting

menu includes the facility to change the speed limit and password. By entering in the “ Drive”

menu user can drive above the speed limit.

If the password is false than system turn on the speed limit function, in which speed is

continuously compared with the stored speed limit and displayed on LCD. If speed is above the

limit than system turn off the relay which is connected with the ignition power supply, so power

is disconnected and speed decreases. Now, when speed comes below the speed limit, system turn

on the relay and continuously follows this process.

At speed sensor pulses are generated using infrared LED and receiver. It can be also generated

by using magnetic reed relay sensor. These pulses are given at the op-amp LM324 comparator

which produces pulse train. These pulses given to pin no.14, 15 of port 3.4 & 3.5 of

microcontroller 8052.

With the help of pulse input we can calculate the speed by calculating the frequency at input.

This frequency is multiplied by the distance travel by wheel in one rotation. The calculations are

as follow:

Circumference of the wheel= 2πr (where ‘r’ is in cm)

= 2×3.14×30

= 188.4 cm or 1.884 meters

Let’s assume that in 1 second the wheel completes one revolution. In other words, in one second,

the bike has covered 1.88 meters.

Therefore the speed in km/hour:

=N×1.88×3600/1000

= N×6.784 or N×6.8

Where ‘ N’ is the number of revolutions per second.

‘ 6.8’ is a constant and only ‘ N’ varies;

For example, if ‘ N’ is 5, the speed equals 5x6.8= 34 km/hour.

Lcd port 1

Keypad port 2.0 to 2.6

Output port 2.7

Input port 3.2 or port 3.3

2.4.1 IC LM324

LM324 is a 14pin IC consisting of four independent operational amplifiers (op-amps)

compensated in a single package. Op-amps are high gain electronic voltage amplifier with

differential input and, usually, a single-ended output. The output voltage is many times higher

than the voltage difference between input terminals of an op-amp.

Fig 2.4 Pin Diagram of IC LM324

These op-amps are operated by a single power supply LM324 and need for a dual supply is

eliminated. They can be used as amplifiers, comparators, oscillators, rectifiers etc. The

conventional op-amp applications can be more easily implemented with LM324.

Table 2.1: Pin Description of LM324

Pin

No

Function Name

1 Output of 1st comparator Output 1

2 Inverting input of 1st comparator Input 1-

3 Non-inverting input of 1st comparator Input 1+

4 Supply voltage; 5V (up to 32V) Vcc

5 Non-inverting input of 2nd comparator Input 2+

6 Inverting input of 2nd comparator Input 2-

7 Output of 2nd comparator Output 2

8 Output of 3rd comparator Output 3

9 Inverting input of 3rd comparator Input 3-

10 Non-inverting input of 3rd comparator Input 3+

11 Ground (0V) Ground

12 Non-inverting input of 4th comparator Input 4+

13 Inverting input of 4th comparator Input 4-

14 Output of 4th comparator Output 4

2.4.2 MICROCONTROLLER AT80S52

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes of in-

system programmable Flash memory. The device is manufactured using Atmel’ s high density

nonvolatile memory technology and is compatible with the industry standard 80C51 instruction

set and pin out. The on chip Flash allows the program memory to be reprogrammed in-system

or by a conventional nonvolatile memory programmer.

Fig 2.5 Block Diagram of AT80S52

By combining a versatile 8-bit CPU within system programmable Flash on a monolithic chip, the

Atmel AT89S52 is a powerful microcontroller which provides a highly flexible and cost effective

solution to many embedded control applications.

The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM, 32

I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a six vector two level

interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In

addition, the AT89S52 is designed with static logic for operation down to zero frequency and

supports two software selectable power saving modes. The Idle Mode stops the CPU while

allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning.

The Power down mode saves the RAM contents but freezes the oscillator, disabling all other

chip functions until the next interrupt or hardware reset.

Fig 2.6 PIN Diagram of AT80S52

2.4.2.1 PIN Description of AT80S52

VCC

Supply voltage.

Port 0

Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each pin can sink eight

TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-impedance inputs.

Port 0 can also be configured to be the multiplexed low-order address/data bus during accesses

to external program and data memory. In this mode, P0 has internal pull-ups. Port 0 also

receives the code bytes during Flash programming and outputs the code bytes during program

verification.

Port 1

Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers can

sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the

internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being

pulled low will source current (IIL) because of the internal pull-ups. In addition, P1.0 and P1.1

can be configured to be the timer/counter 2 external count input (P1.0/T2) and the

timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown in the following table. Port 1

also receives the low-order address bytes during Flash programming and verification.

Port Pin Alternate Functions

P1.0 T2 (external count input to Timer/Counter 2), clock-out

P1.1 T2EX (Timer/Counter 2 capture/reload trigger and direction control)

P1.5 MOSI (used for In-System Programming)

P1.6 MISO (used for In-System Programming)

P1.7 SCK (used for In-System Programming)

Port 2

Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers can

sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the

internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being

pulled low will source current (IIL) because of the internal pull-ups. Port 2 emits the high-order

address byte during fetches from external program memory and during accesses to external

data memory that uses 16-bit addresses (MOVX @ DPTR). In this application, Port 2 uses strong

internal pull-ups when emitting 1s. During accesses to external data memory that uses 8-bit

addresses (MOVX @ RI) Port 2 emits the contents of the P2 Special Function Register. Port 2

also receives the high-order address bits and some control signals during Flash programming

and verification.

Port 3

Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers can

sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by the

internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being

pulled low will source current (IIL) because of the pull-ups. Port 3 receives some control signals

for Flash programming and verification. Port 3 also serves the functions of various special

features of the AT89S52, as shown in the following table.

Port Pin Alternate Functions

P3.0 RXD (serial input port)

P3.1 TXD (serial output port)

P3.2 INT0 (external interrupt 0)

P3.3 INT1 (external interrupt 1)

P3.4 T0 (timer 0 external input)

P3.5 T1 (timer 1 external input)

P3.6 WR (external data memory write strobe)

P3.7 RD (external data memory read strobe)

RST

Reset input. A high on this pin for two machine cycles while the oscillator is running resets the

device. This pin drives high for 98 oscillator periods after the Watchdog times out. The DISRTO

bit in SFR AUXR (address 8EH) can be used to disable this feature. In the default state of bit

DISRTO, the RESET HIGH out feature is enabled.

ALE/PROG’

Address Latch Enable (ALE) is an output pulse for latching the low byte of the address during

accesses to external memory. This pin is also the program pulse input (PROG) during Flash

programming. In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator

frequency and may be used for external timing or clocking purposes. Note, however, that one

ALE pulse is skipped during each access to external data memory. If desired, ALE operation can

be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a

MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit

has no effect if the microcontroller is in external execution mode.

PSEN

Program Store Enable (PSEN) is the read strobe to external program memory. When the

AT89S52 is executing code from external program memory, PSEN is activated twice each

machine cycle, except that two PSEN activations are skipped during each access to external

data memory.

EA/VPP

External Access Enable. EA must be strapped to GND in order to enable the device to fetch code

from external program memory locations starting at 0000H up to FFFFH. Note, however, that if

lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC

for internal program executions. This pin also receives the 12-volt programming enable voltage

(VPP) during Flash programming.

XTAL1

Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2

Output from the inverting oscillator amplifier.

2.4.2.2 Features of AT80S52

• Compatible with MCS®-51 Products

• 8K Bytes of In-System Programmable (ISP) Flash Memory

• 4.0V to 5.5V Operating Range

• Fully Static Operation: 0 Hz to 33 MHz

• Three-level Program Memory Lock

• 256 x 8-bit Internal RAM

• 32 Programmable I/O Lines

• Three 16-bit Timer/Counters

• Eight Interrupt Sources

• Full Duplex UART Serial Channel

• Low-power Idle and Power-down Modes

• Interrupt Recovery from Power-down Mode

• Watchdog Timer

• Dual Data Pointer

2.4.3 IC7805

7805 is a voltage regulator integrated circuit. It is a member of 78xx series of fixed linear

voltage regulator ICs. The voltage source in a circuit may have fluctuations and would not give

the fixed voltage output. The voltage regulator IC maintains the output voltage at a constant

value. The xx in 78xx indicates the fixed output voltage it is designed to provide. 7805 provides

+5V regulated power supply. Capacitors of suitable values can be connected at input and

output pins depending upon the respective voltage levels.

Fig 2.7 PIN Diagram of IC7805

Table 2.2: Pin Description of IC7805

Pin No Function Name

1 Input voltage (5V-18V) Input

2 Ground (0V) Ground

3 Regulated output; 5V (4.8V-5.2V) Output

2.4.4 EL1602 LCD

LCD (Liquid Crystal Display) screen is an electronic display module and find a wide range of

applications. A 16x2 LCD display is very basic module and is very commonly used in various

devices and circuits. These modules are preferred over seven segments and other multi

segment LEDs. The reasons being: LCDs are economical; easily programmable; have no

limitation of displaying special & even custom characters (unlike in seven segments),

animations and so on.

Fig 2.8 Pin Diagram of EL1602 LCD

A 16x2 LCD means it can display 16 characters per line and there are 2 such lines. In this LCD

each character is displayed in 5x7 pixel matrix. This LCD has two registers, namely, Command

and Data.

The command register stores the command instructions given to the LCD. A command is an

instruction given to LCD to do a predefined task like initializing it, clearing its screen, setting the

cursor position, controlling display etc. The data register stores the data to be displayed on the

LCD. The data is the ASCII value of the character to be displayed on the LCD. Click to learn more

about internal structure of a LCD.

Table 2.3 Pin Description of EL1602 LCD

Pin No. Symbol Level Description

1 Vss 0V Ground

2 Vdd 5.0V Supply Voltage for logic (option +3V)

3 Vo (Variable) Operating voltage for LCD

4 RS H/L H:DATA, L:Instruction code

5 R/W H/L H:Read(MPU->Module)L:Write(MPU->Module)

6 E H,H->L Chip enable signal

7 DB0 H/L Data bit 0

8 DB1 H/L Data bit 1

9 DB2 H/L Data bit 2

10 DB3 H/L Data bit 3

11 DB4 H/L Data bit 4

12 DB5 H/L Data bit 5

13 DB6 H/L Data bit 6

14 DB7 H/L Data bit 7

15 A/ Vee - Power supply for LED backlight ( + ) /Negative voltage

output

16 K - Power supply for LED backlight (GND )

2.4.5 KEYPAD

A low profile 3 x 4 keypad of compact size suitable for use on hand held and other small

equipment. A single rectangular cut is required to fit the keypad through the front panel and four

mounting holes are required for the retention of the keypad. The conductive rubber contacts

require a low operating force, but have a positive action to give the operator feedback.

Connections are terminated to solder pads on the PCB at the lower edge of the switch.

Fig 2.9 Circuit Diagram of keypad

Table 2.4 KEYPAD OUTPUT ARRANGEMENT

Output pin no. Symbols

1 -

2 Col. 2

3 Row 1

4 Col. 1

5 Row 4

6 Col. 3

7 Row 3

8 Row 2

9 -

10 -

Chapter 3 : Software

3.1. FLOWCHART

Start

Enter password

Turn on relay

Check speed

<=speed limit

Turn off relayTurn on relay

Enter no.

1.Drive

2.setting

Turn on relay

End

1.New password

2. New limit

New password New limit

Display speed

Display speedDisplay speed

No

Yes

False True

1 2

1 2

Fig 2.10 Flowchart

3.2. PROGRAM

#include<stdio.h>

#include<conio.h>

void main()

{

int a=1234,b,c,g,e,f,sl,ch,ca;

// char ch,ca;

clrscr();

printf("Enter the password : ");

scanf("%d",&b);

if(a==b)

{

printf("1. Main menu ");

printf("\n2. Drive menu");

printf("\nEnter your choice : ");

scanf("%d",&ch);

switch (ch)

{

case 1:

printf("\n 1. Change Password ");

printf("\n 2. Change Speed limite ");

printf("\nEnter your choice : ");

scanf("%d",&ca);

switch (ca)

{

case 1:

printf("Enter your current password : ");

scanf("%d",&c);

if (a==c)

{

printf("\nEnter your new password : ");

scanf("%d",g);

printf("\nRe-enetr the password : ");

scanf("%d",e);

if (g==e)

{

printf("\nYour password changed

successfully.");

}

else

{

printf("\nPassword do not

match...");

}

}

else

{

printf("\nYou enter the wrong

password...");

}

break;

case 2:

printf("\nEnter your password : ");

scanf("%d",&f);

if(a==f)

{

printf("\nEnter your new speed limit : ");

scanf("%d",&sl);

printf("Your speed limit changed

successfully.. ");

}

else

{

printf("You entered the wrong

password...");

}

break;

default:

printf("\n Incorrect choice");

break;

}

break;

case 2:

printf("\n Do you want to over drive?");

printf("\n 1. Yes");

printf("\n 2. No");

printf("\n Enter your choice : ");

break;

default:

printf("\n Incorrect choice");

break;

}

}

else

printf("Incorrect passwrd");

getch();

}

Chapter 4 : Application and Merits/demerits

4.1 APPLICATION

In vehicles to display speed

In vehicles as speed protector

It can be used to control the speed of heavy motor and drive speed

4.2 MERITS

Easy user interface

Speed is easy to read due to back lighted LCD

Prevent accidents at high speed

Consumption of fuel is less

Password protection

4.3 DEMERITS

If microcontroller fails than we can’ t start the vehicle

Time consuming

4.4 CONCLUSION

By this digital speedometer we can control the over speed of vehicle and also protect it from

theft. By it we observe that consumption of fuel will decreases.

REFERENCES

[1]. Muhammad ali mazidi, “ The 8051 microcontroller & embedded systems” , Pearson, 2nd

edition.

[2]. www.howstuffworks.com

[3]. www.wikipedia.org

[4]. www.engineersgarage.com

APPENDIX