Gps based vehicle monitoring system copy

A
PROJECT REPORT
ON

GPS BASED VEHICLE MONITORING SYSTEM
Submitted By:
SUMIT VARSHNEY

Submitted to the Department of Electronics & Communication
in the partial fulfillment of the requirements
for the degree of
Bachelor of Technology
in
Electronics & Communication

GAUTAM BUDDHA TECHNICAL UNIVERSITY, LUCKNOW
JUNE, 2011

TABLE OF CONTENTS
Page No.
CERTIFICATE
DECLARATION
ACKNOWLEDGEMENT

ABSTRACT
LIST OF FIGURES
LIST OF TABLES
CHAPTER 1. INTRODUCTION
CHAPTER 3. BLOCK DIAGRAM
3.1 GPS SECTION
3.2 COLLISION AVOIDANCE SECTION
CHAPTER 4 CIRCUIT DIAGRAM
4.1 INTERFACING WITH MICROCONTROLLER
4.2 IR TRANSMITTER/RECEIVER SECTION
CHAPTER5. COMPONENT LIST
CHAPTER 6. DETAILS OF COMPONENTS
6.1 POWER SUPPLY
6.2 MICROCONTROLLER AT89C51
6.3 IC MAX 232
6.4 IC HT12D
6.5 IC HT12E
6.6 VOLTAGE REGULATOR FOR +5V (7805)
6.7 BC547 NPN TRANSISTOR
6.8 RESISTOR
6.9 CAPACITOR
6.10 LCD DISPLAY
6.11 RF TRANSCEIVER
6.12 GPS MODULE
6.13 IC L293D
6.14 TSOP 1738
6.15 IR TRANSMITTER/RECEIVER
6.16 DC MOTOR
6.17 LED
CHAPTER 7. HARDWARE DESIGN
CHAPTER 8. SOFTWARE DESIGN
8.1 PROGRAMMING
8.2 WORKING WITH µVISION KEIL

2

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90
92
94
96
98
100
102
104

CHAPTER 9 TESTING
CHAPTER 10. PROBLEMS FACED
CHAPTER 11. ADVANTAGES
CHAPTER12. LIMITATIONS
CHAPTER13. APPLICATIONS
CHAPTER14. FUTURE ASPECTS
CHAPTER 15. CONCLUSION
CHAPTER 16. REFERENCES
CHAPTER 17. APPENDIX
17.1 ESTIMATED COST
17.2 DATASHEET

106
107

3

CERTIFICATE

This is to certify that Project Report entitled “GPS Based Vehicle
Monitoring System” which is submitted by Sumit Varshney in partial
fulfillment of the requirement for the award of degree B. Tech. in
Department of Electronics & Communication from JSS ACADEMY
OF TECHNICAL EDUCATION of Engineering & Technology,
Muzaffarnagar of U.P. Technical University, is a record of the
candidate own work carried out by him under my supervision. The
matter embodied in this thesis is original and has not been submitted
for the award of any other degree.

Er. Amit Kumar Chauhan

Prof. N.K. Sharma

(Project Guide)

(H.O.D., Deptt. Of ECE)

External Examiner

Dr. S. N. Chauhan
(Director)

4

DECLARATION

We hereby declare that this submission is our own work and that, to the best of our
knowledge and belief, it contains no material previously published or written by another
person nor material which to a substantial extent has been accepted for the award of any
other degree or diploma of the university or other institute of higher learning, except
where due acknowledgment has been made in the text.

Signature

:

Name
Date

:
:

Sumit Varshney

5

ACKNOWLEDGEMENT
It gives us a great sense of pleasure to present the report of the B. Tech Project
“GPS Based Vehicle Monitoring System” undertaken during B. Tech. Final Year.
We owe special debt of gratitude to Mr. Amit Kumar Chauhan (A.P., Department
of Electronics & Communication Engineering, JSS Academy of Technical
Education NOIDA) for his constant support and guidance throughout the course of
our work. His sincerity, thoroughness and perseverance have been a constant
source of inspiration for us. It is only his cognizant efforts that our endeavors have
seen light of the day.
We also take the opportunity to acknowledge the contribution of Prof. N. K.
Sharma (Head, Department of Electronics & Communication, JSS Academy of
Technical Education NOIDA) for their full support and assistance during the
development of the project.
From the core of my heart, I would also like to express my profound gratitude to
reverend
Dr. S.N. Chauhan (Executive Director, S.D.C.E.T.) and respected Dr.
A.K. Gautam (Principal, S.D.C.E.T.) for providing us the necessary facilities and
such a blooming environment to work upon this project.
We also do not like to miss the opportunity to acknowledge the contribution of all
faculty members of the department for their kind assistance and cooperation during
the development of our project. Last but not the least, we acknowledge our friends
for their contribution in the completion of the project.
Signature
Name
Date

:
:
:

Sumit Varshney

6

ABSTRACT
This project present an automotive localization system using GPS. The system
permits localization of robot and display of the position on the LCD in the form of
latitude and longitude. Vehicle can be operated in both autonomous and manual mode.
We can store the position of vehicle by using remote control. Later this stored
information can be viewed by connecting it to PC. For collision avoidance it uses IR
sensors to detect obstacles and make a decision to avoid them.
The conventional mobile robot have used front-steering and rear- wheel driving
mechanism to response all needed robot obvious motions, but the motion restriction is a
major problem in the use of such mechanism. The omnidirectional configuration is a
most suggested mechanism for mobile robot, which to have the capability of changing
directions within the limited space in the indoor environment.

8

LIST OF FIGURES
Page No.
17
Fig.1 Block Diagram of GPS based vehicle monitoring
system
Fig.2 Block Diagram of collision avoidance system
Fig.3 Circuit Diagram of interfacing with AT89C51
Fig.4 Circuit Diagram of receiver for collision avoidance
Fig.5 Circuit Diagram of transmitter for collision avoidance
Fig.6 Pin diagram of AT89C51
Fig.7 Program Memory of AT89C5
Fig.8 Program Memory of AT89C52
Fig.9A Data Memory of AT89C51
Fig.9B Data Memory of AT89C52
Fig.10 128 Bytes of Directly and Indirectly Addressable
RAM
Fig.11 Pin Diagram of MAX232 DIP Package
Fig.12 Pin Diagram of HT12D
Fig.13 Pin Diagram of HT12E
Fig.14 Pin Diagram of IC7805
Fig.15 BC547 Transistor
Fig.16 Internal Block diagram of LCD Display
Fig.17 Pin Configuration of LCD Display
Fig.18 Pin Configuration of RF Transmitter/Receiver
Fig.19 Different components of GPS
Fig.20 GPS Receiver communication with satellite and sending
information through the wireless mobile phone
Fig.21 GPS modem device
Fig.22 Pin Diagram of L293D
Fig.23 Pin Diagram of TSOP
Fig.24 Working of LED
Fig.25 Soldering Procedure
9

18
23
24
24
30
34
35
35
36
38
44
46
47
49
50
53
53
54
58

60
61
63
64
66
70

LIST OF TABLES
Page No.
31
39
41
45
46
48
49
53
54
55

Table1. PIN Description of AT89C51
Table2. SFRs of AT89C51
Table3. SFRs of AT89C51
Table4. PIN Description of IC MAX232
Table5. PIN Description of IC HT12D
Table6. PIN Description of IC HT12E
Table7. PIN Description of IC 7805
Table8. Ratings of LCD Display
Table9. PIN Description of RF Transmitter
Table10. PIN Description of RF Receiver

10

1. INTRODUCTION
In general, we have no correct mechanism to know the parameters like the route
in which a vehicle has travelled, where was it at a particular instant of time, with what
speed did it travel at that place and time and did it go to the desired place or not, we
don’t have a option rather than to believe the driver. The problem arises when the driver
doesn’t give us the exact authentic information.
If we want vehicle to go to certain place, via certain route later when we access
the information about the journey, we have to simply depend up on the driver for the
information of the vehicle and the driver may not give us the exact information about the
journey and could use the (vehicle) for his personal use.
The GPS BASED VEHICLE MONITORING SYSTEM answers to all the
problems raised above. We can know the parameters like latitude and longitude; route
adopted by the driver without being dependent on him.
We make use of a GPS modem, Micro controller and a wireless network (RF
transceiver) and PC.
Data from GPS receiver is sent to the LCD. We can store the position of vehicle
by using remote control. Later this stored information can be viewed by connecting it to
PC.

12

2. PRINCIPLE OF OPERATION
The vehicle monitoring system deals with the latitude and longitude of vehicle
which is obtained from GPS receiver and display the data on the LCD.
As it involves the identification of the vehicle it requires a Global Processing
System (GPS) to know the position of the vehicle. There are 24 satellites revolving
around the earth’s orbit, at least 3 satellites are required for the GPS receiver. When the
GPS receiver is exposed to at least 3 satellites it receives the data from the satellites i.e.
latitude, longitude, distance, speed, time, altitude. The receiver continuously gives the
data until it is switched off. A 5V external power supply is given to the GPS receiver.
The baud rate of the GPS receiver is 4800 bits/sec.
The GPS receiver is interfaced with a Microcontroller (AT 89C51). The 5V
power supply is needed for the micro controller. The GPS receiver is interfaced with the
Microcontroller using a RS-232 protocol.
The data from the GPS RECEIVER is transferred to the PC using a wireless
network i.e. RF transceiver. There are two RF transceivers, one is connected to PC and
other is connected to Microcontroller. The data is presented in the Google Earth map
graphically. For collision avoidance it uses IR sensor to sense the obstacle and send
signal to embedded controller. The embedded controller receives these obstacle
detecting signals and then send signal to motors for taking direction to avoid obstacle.
The project uses µc 80C51 as the controlling element. It uses 3 IR (Infra Red) sensors
and 3 IR transmitting circuitry. When the obstacle comes in path of robot IR beam is
reflected from the obstacle then sensor gives +5V voltage to µc. This +5V voltage is
detected then µc decides to avoid the obstacle by taking left or right turn. If the sensor

14

gives zero to µc that means there is no obstacle present in its path so it goes straight until
any obstacle is detected.
The three IR transmitter circuits are fitted on front, right and left side of robot.
The three IR sensors are placed near to transmitters’ IR LEDs. The connections can be
given from main circuit to sensors using simple twisted pair cables. Two motors namely
right motor and left motor are connected to driver IC (L293D). L293D is interface with
µc. Micro-controller sends logic 0 & logic 1 as per the programming to driver IC which
moves motors forward or reverse direction

15

3. Block Diagram:
3.1 GPS Section:

17

Fig 1: G.P.S Based Vehicle Monitoring System

3.2 Collision Avoidance Section:

Fig 2: Collision Avoidance System

18

The Major Building blocks of this Project
1. Microcontroller (AT89C51)
2. Motor driver IC (L293D)
3. DC Motors
4. GPS Receiver
5. RF Transceiver
6. Power supply
7. R.S 232
8. LCD
9. IR Sensors

BLOCK DIAGRAM EXPLANATION:
Overview of each block is given below:

1. Microcontroller
This is the most important block of the system. Microcontroller is the decision
making logical device which has its own memory, I/O ports, CPU and Clock circuit
embedded on a single chip.

2. Driver
L293D is used as driver IC. Motors are connected to this IC. According to
program in µc it drives the left and right motor.

3. Motor

19

We have used two D.C motors to give motion to the ROBOT. Motors are
connected to L293D IC. According to the program in microcontroller, the left and right
motor drives.

4. GPS
GPS is the only fully functional GNSS in the world. GPS uses the constellation
of between 24 and 32 Medium Earth Orbit satellites that transmit precise microwave
signals, which enable GPS receivers to determine their current location, the time, and
their velocity. Its official name is NAVSTAR GPS.

5. RF Transceiver:
5.1 Transmitter in RF Transceiver:
The base stations and subscriber units include radio frequency transmitters and
RF receivers; together they're called "RF transceivers." RF transceivers service the
wireless links between the base stations and subscriber units.
The RF transmitter receives a base band signal from a base band processor,
converts the base band signal to an RF signal, and couples the RF signal to an antenna
for transmission.

5.2 Receiver in RF Transceiver:
The function of the receiver is to detect signals in the presence of noise and
interference, and provide amplification, down conversion and demodulation of the
detected the signal such that it can be displayed or used in a data processor.

6. Power Supply:
20

The power supply unit is used to provide a constant 5V supply to different IC’s.
This is a circuit in which external 12VDC Battery is connected to fixed 3-pin voltage
regulator. Diode is added in series to avoid Reverse voltage.

7. RS 232:
Two allow compatibility among the data communication equipment made by
various manufacturers; an interfacing standard called RS232, was set by the electronics
industries association (EIA) in 1960. RS 232 is the standard defined for the connection
of "Data Terminal Equipment" (DTE) to "Data Communications Equipment" (DCE).

8. LCD:
A liquid crystal display (LCD) is a flat panel display, electronic visual display,
or video display that uses the light modulating properties of liquid crystals (LCs). LCs
does not emit light directly.

9. IR Transmitter & Receiver
The IR Transmitter block mainly used to generate IR signal. It uses timer IC555
in astable multivibrator mode to generate square wave which have continuous pulses of
50% duty cycle of frequency 38 KHz. This transmitter is so arranged that the IR rays are
focused on the sensor.
IR sensor (TSOP 1738) which gives normally zero volt at output of it. After
receiving infrared light at output of sensor we get +5V

21

CIRCUIT DIAGRAM:
4.1 Interfacing With Microcontroller:

Fig3: Interfacing with 89C51

23

4.2

Collision

Avoidance

Section:

Fig 4: Receiver Circuit

24

Fig 5: Transmitter Circuit

COmPONENTS LIST
25

COMPONENTS LIST

S. No.
1
2
3
4
5
6
7
8
1
2

COMPONENTS
QUANTITY
Semiconductors
IC-AT89C51 Microcontroller
1
IC-HT12D Decoder
1
IC-HT12E Encoder
1
IC-MAX232 Driver/Receiver
1
IC-7805, 5V Regulator
2
NPN Transistor
3
IC- L293D
1
TSOP 1738
1
Resistors
R1, R2- 4.7 kΩ
3
R3- 1 kΩ
6

26

3
1
2
3
4
5
6
7
8
1
2
3
4

VR1- 10 kΩ preset
Miscellaneous
XTAL- 12MHz Crystal
S1- Push-to-On Switch
TX1- 38 kHz IR Transmitter
RX1- 38 kHz IR Receiver
RF Module
GPS Module
LCD Display
DC Motors
Capacitors
C1, C2- 3.3 nF Ceramic Disk
C4-10μF, 16V Electrolytic
C- 1μF, Electrolytic
0.01μF, Polyster

27

7
1
1
3
3
1
1
1
2
2
1
4
6

DETAILS OF
COmPONENTS

6.1

POWER SUPPLY
Power supply is the major concern for every electronic device. The power supply

unit is used to provide a constant 5V supply to different IC’s. This is a circuit in which
external 12VDC Battery is connected to fixed 3-pin voltage regulator. Diode is added in
series to avoid Reverse voltage.
Since the controller and other devices used are low power devices there is a need
to regulate the output to convert the output to a +5V constant dc. It is accomplished by
using following components.
28

Voltage Regulator:
The voltage regulator is used for the voltage regulation purpose. We use IC 7805
voltage regulator. The IC number has a specific significance. The number 78 represents
the series while 05 represents the output voltage generated by the IC
Light Emitting Diode:
We employ a light emitting diode for testing the functionality of the power
supply circuit. LED’s are also employed in other areas for many purposes. The following
are the advantages of using LED’s.
•

It helps us while troubleshooting the device i.e. when the device is

malfunctioning it would be easy to detect where the actual problem arised.
•

LED employed with microcontroller verifies whether data is being transmitted

29

6.2 MICROCONTROLLER (AT89C51)
The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer
with 4K bytes of Flash programmable and erasable read only memory (PEROM). The
device is manufactured using Atmel’s high-density nonvolatile memory technology and
is compatible with the industry-standard MCS-51 instruction set and pinot. The on-chip
Flash allows the program memory to be reprogrammed in-system or by a conventional
nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a
monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a
highly-flexible and cost-effective solution to many embedded control applications.

Features:
• Compatible with MCS-51™ Products
• 4K Bytes of In-System Reprogrammable Flash Memory
– Endurance: 1,000 Write/Erase Cycles
• Fully Static Operation: 0 Hz to 24 MHz
• Three-level Program Memory Lock
• 128 x 8-bit Internal RAM
• 32 Programmable I/O Lines
• Two 16-bit Timer/Counters
• Six Interrupt Sources
• Programmable Serial Channel
• Low-power Idle and Power-down Modes

30

Description of Microcontroller (AT89C51):

Fig 6: Pin Diagram of Microcontroller AT89C51

31

Pin Description
Pin Description
Pin Number

Description

1-8

P1.0 - P1.7 - Port 1

9

RST - Reset

10 - 17

P3.0 - P3.7 - Port 3

18

XTAL2 - Crystal

19

XTAL1 - Crystal

20

GND - Ground

21 - 28

P2.0 - P2.7 - Port 2

29

PSEN - Program Store Enable

30

ALE - Address Latch Enable

31

EA - External Access Enable

32 - 39

P0.7 - P0.1 - Port 0

40

Vic - Positive Power Supply

TABLE 1
Pin Description:
VCC: Supply voltage.
GND: Ground.
Port 0:
Port 0 is an 8-bit open-drain bi-directional 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 may 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. External
pull-ups are required during program verification.
32

Port 1:
Port 1 is an 8-bit bi-directional 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.
Port 1 also receives the low-order address bytes during Flash programming and
verification.
Port 2:
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, it 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:
externally being pulled low will source current (IIL) because of the pull-ups. Port 3 also
serves the functions of various special features of the AT89C51 as listed below:
P3.0 -RXD (serial input port)
P3.1- TXD (serial output port)
P3.2 -INT0 (external interrupt 0)

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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).
Port 3 also receives some control signals for Flash programming and verification.
RST: Reset input. A high on this pin for two machine cycles while the oscillator is
running resets the device.
ALE/PROG: Address Latch Enable 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 is the read strobe to external program memory. When the
AT89C51 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. 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,
for parts that require12-volt VPP.

34

XTAL1: input to the inverting oscillator amplifier and input to the internal clock
operating circuit.
XTAL2: Output from the inverting oscillator amplifier.

Memory Organization: Memory Organization
Program Memory
The AT89C Microcontroller has separate address spaces for program memory
and data memory. The program memory can be up to 64K bytes long. The lower
addresses may reside on-chip. Figure 8 shows a map of the AT89C51 program memory,
and Figure 9 shows a map of the AT89C52 program memory. The AT89C1051/2051
does not have off-board memory expansion.

Figure 7. AT89C51 Program Memory

35

Figure 8. AT89C52 Program Memory
B) Data Memory:
The AT89C can directly address up to 64K bytes of data memory external to the
chip. The MOVX instruction accesses the external data memory. (Refer to the
Instruction Set section in this chapter for a detailed description of instructions).
The AT89C51 has 128 bytes of on-chip RAM (256 bytes in the AT89C52) plus a
number of Special Function Registers (SFRs). The lower 128 bytes of RAM can be
accessed either by direct addressing (MOV data addr) or by indirect addressing (MOV
@Ri). Figure 10 shows the AT89C51 and the AT89C52 data memory organization.

36

Figure 9A: The AT89C51 Data Memory

Figure 9B: The AT89C52 Data Memory

Indirect Address Area In Figure 3b, the SFRs and the indirect address RAM
have the same addresses (80H through 0FFH). Nevertheless, they are two separate areas
and are accessed in two different ways. For example, the following instruction writes
0AAH to Port0, which is one of the SFRs. MOV 80H, # 0AAH
The following instruction writes 0BBH in location 80H of the data RAM.
MOVR0, # 80H
MOV@ R0, # 0BBH
37

Thus, after executing both of these instructions, Port 0 contains 0AAH, and
location 80H of the RAM contains 0BBH.The stack operations are examples of indirect
addressing, so the upper 128 bytes of data RAM are available as stack space in devices
that implement 256 bytes of internal RAM.
Direct and Indirect Address Area
The 128 bytes of RAM that can be accessed by both direct and indirect
addressing can be divided into 3 segments as described in this section and as shown in
Figure11.

1. Register Banks 0-3: Locations 0 through 1FH (32bytes). Reset default is to register
bank 0. To use the other register banks, the user must select them in the software.

Each register bank contains eight 1-byte registers, 0 through 7. Reset initializes
the Stack Pointer to location 07H. The Stack Pointer is then incremented once to start
from location 08H, which is the first register (R0) of the second register bank. Thus, in
order to use more than one register bank, the SP should be initialized to a different
location of the RAM that is not used for data storage (that is, a higher part of the RAM).
2. Bit Addressable Area: 16 bytes have been assigned for this segment, 20H through
2FH. Each of the 128 bits of this segment can be directly addressed (0 through 7FH).
These bits can be referred to in two ways. One way is to refer to their addresses, that is,
0 to 7FH. The other way is with reference to bytes 20H to 2FH. Thus, bits 0 through 7
can also be referred to as bits 20.0 through 20.7 and bits 8 through FH are the same as
21.0 through 21.7, and so on. Each of the 16 bytes in this segment can also be addressed
as a byte.

38

3. Scratch Pad Area: Bytes 30H through 7FH are available to the user as data RAM.
However, if the stack pointer has been initialized to this area, enough bytes should be
left aside to prevent SP data destruction.

Special Function Registers
Table 2 contains a list of all the SFRs and their addresses.

40

TABLE 2
PSW: Program Status Word (Bit Addressable)
CY

AC

F0

RS1

RS1

RS0

OV

−

P

CY PSW.7 Carry flag.
AC PSW.6 Auxiliary carry flag.
F0

PSW.5 Flag 0 available to the user for general purpose.

RS1 PSW.4 Register Bank selector bit 1.(1)
RS0 PSW.3 Register Bank selector bit 0. (1)
OV PSW.2 Overflow flag.
—

PSW.1 User definable flag.

P

PSW.0 Parity flag. Set/cleared by hardware each instruction cycle to indicate an

odd/even number of 1’s bit in the accumulator.
RS1 RS0 Register Bank
0
0
0
0
1
1
1
0
2
1
1
3

Address
00H-07H
08H-0FH
10H-17H
18H-1FH

PCON: Power Control Register (Not Bit Addressable)
SMOD

−

−

−

GF1

GF0

PD

IDL

SMOD Double baud rate bi
t. If Timer 1 is used to generate baud rate and SMOD = 1, the baud rate is doubled when
the Serial Port is used in modes 1, 2, or 3.
41

— Not implemented, reserved for future use.(1)
— Not implemented, reserved for future use.(1)
— Not implemented, reserved for future use. (1)
GF1 General purpose flag bit.
GF0 General purpose flag bit.
PD Power Down bit. Setting this bit activates Power Down operation in the AT89C51.
IDL Idle Mode bit. Setting this bit activates Idle Mode operation in the AT89C51.
If 1s are written to PD and IDL at the same time, PD takes precedence.
Interrupts
In order to use any of the interrupts in the Flash microcontroller, take the following three
steps.
1. Set the EA (enable all) bit in the IE register to 1.
2. Set the corresponding individual interrupt enable bit in the IE register to 1.
3. Begin the interrupt service routine at the corresponding Vector Address of that
interrupt. See the following table 3.
Interrupt Source Vector
Address
IE0
0003H
TF0
000BH
IE1
0013H
TF1
001BH
R1 and T1
0023H
(1)
TF2 and EXF2
002BH

TABLE 3

IE: Interrupt Enable Register (Bit Addressable)
If the bit is 0, the corresponding interrupt is disabled. If the bit is 1, the corresponding
interrupt is enabled.
EA

−

ET2

ES

ET1
42

EX1

ET0

EX0

EA IE.7 Disables all interrupts. If EA = 0, no interrupt is acknowledged. If EA = 1,
each interrupt source is individually enabled or disabled by setting or clearing its enable
bit.
— IE.6

Not implemented, reserved for future use.(1)

ET2 IE.5 Enables or disables the Timer 2 overflow or capture interrupt (AT89C52
only).
ES IE.4 Enables or disables the serial port interrupt.
ET1 IE.3 Enables or disables the Timer 1 overflow interrupt.
EX1 IE.2 Enables or disables External Interrupt 1.
ET0 IE. 1 Enables or disables the Timer 0 overflow interrupt.
EX0 IE.0 Enables or disables External Interrupt 0.
Assigning Higher Priority to One or More Interrupts
In order to assign higher priority to an interrupt the corresponding bit in the IP register
must be set to 1.While an interrupt service is in progress, it cannot be interrupted by an
interrupt of the same or lower priority.
Priority Within Level
The only purpose of priority within a level is to resolve simultaneous requests of the
same priority level. From high to low, interrupt sources are listed below.
IE0
TF0
IE1
TF1
RI or TI
TF2 or EXF2
IP: Interrupt Priority Register (Bit Addressable)
If the bit is 0, the corresponding interrupt has a lower priority. If the bit is 1, the
corresponding interrupt has a higher priority.

43

−

−

PT2

PS

PT1

PX1

— IP. 7

PX0


—

PT0


IP. 6

PT2 IP. 5

Defines the Timer 2 interrupt priority level (AT89C52 only).

PS

Defines the Serial Port interrupt priority level.

IP. 4

PT1 IP. 3

Defines the Timer 1 interrupt priority level.

PX1 IP. 2

Defines External Interrupt 1 priority level.

PT0 IP. 1

Defines the Timer 0 interrupt priority level.

PX0 IP. 0

Defines the External Interrupt 0 priority level.

TCON: Timer/Counter Control Register (Bit Addressable)
TF1

TF1 TCON. 7

TR1

TF0

TR0

IE1

IT1

IE0

IT0

Timer 1 overflow flag. Set by hardware when the Timer/Counter 1

overflows. Cleared by hardware as the processor vectors to the interrupt service routine.
TR1 TCON. 6 Timer 1 run control bit. Set/cleared by software to turn Timer/Counter 1
ON/OFF.
TF0 TCON. 5

Timer 0 overflow flag. Set by hardware when the Timer/Counter 0

overflows. Cleared by hardware as the processor vectors to the service routine.
TR0 TCON. 4 Timer 0 run control bit. Set/cleared by software to turn Timer/Counter 0
ON/OFF.
IE1 TCON. 3 External Interrupt 1 edge flag. Set by hardware when the External
Interrupt edge is detected.
Cleared by hardware when the interrupt is processed.

44

IT1 TCON. 2 Interrupt 1 type control bit. Set/cleared by software to specify falling
edge/low level triggered.
External Interrupt.
IE0 TCON. 1 External Interrupt 0 edge flag. Set by hardware when External Interrupt
edge detected. Cleared by hardware when interrupt is processed.
IT0 TCON. 0

Interrupt 0 type control bit. Set/cleared by software to specify falling

edge/low level triggered.

6.3 IC MAX 232
The MAX232 from Maxim was the first IC which in one package contains the
necessary drivers (two) and receivers (also two), to adapt the RS-232 signal voltage
levels to TTL logic. It became popular, because it just needs one voltage (+5V) and
generates the necessary RS-232 voltage levels (approx. -10V and +10V) internally.

Fig12: MAX232 DIP Package

45

MAX232 DIP PACKAGE LAYOUT
Nbr
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

Name
C1+
V+
C1C2+
C2VT2out
R2in
R2out
T2in
T1in
R1out
R1in
T1out
GND
VCC

Purpose
+Connector for Capacitor C1
Output of Voltage Pump
-Connector for Capacitor C1
+Connector for Capacitor C2
-Connector for Capacitor C2
Output of Voltage Pump/Inverter
Driver 2 Output
Receiver 2 Input
Receiver 2 Output
Driver 2 Input
Driver 1 Input
Receiver 1 Output
Receiver 1 Intput
Driver 1 Output
Ground
Power Supply

TABLE 4

6.4 IC HT12D
Features:
•

Operating voltage: 2.4V~12V

•

Low power and high noise immunity CMOS technology

•

Low standby current

•

Capable of decoding 12 bits of information

•

Binary address setting

•

Received codes are checked 3 times

46

Fig12: PIN Assignment of HT12D

PIN DESCRIPTION
Pin
Name
A0~A11

I/O

D8 ~D11
DIN
VT
OSC1
OSC2
VSS
VDD

O
I
O
I
O
I
I

I

Internal connection
NMOS
TRANSMISSION
GATE
CMOS OUT
CMOS IN
CMOS OUT
OSCILLATOR
OSCILLATOR
−
−

Description
Input pins for address A0 ~ A11 setting
They can be externally set to VDD or
VSS.
Output Data Pins
Serial Data Input Pin
Valid Transmission ON, Active High
Oscillator Input Pin
Oscillator Output Pin
Negative Power Supply
Positive Power Supply

TABLE 5

47

6.5 IC HT12E
Features
•

Operating voltage

•

2.4V~5V for the HT12A

•

2.4V~12V for the HT12E

•


•

Low standby current: 0.1_A (typ.) at VDD=5V

•

HT12A with a 38kHz carrier for infrared

Fig13: PIN Assignment of HT12E

48

PIN Description
Pin Name
A0 ~ A7

I/O
I

AD8 ~ AD11

I

D8 – D11

I

DOUT
L/MB

Internal Connection
CMOS-IN
Pull-High
(HT12A)
NMOS TRANSMISSION
GATE
PROTECTION DIODE
(HT12E)
NMOS TRANSMISSION
GATE
PROTECTION DIODE
(HT12E)
CMOS IN
Pull High

O
I

CMOS OUT
CMOS IN
Pull High

Description
Input pins for address A0 ~ A7 setting
These pins can be externally set to V or left
open.

Input pins for address/data AD8 ~ AD11 setting
These pins can be externally set to V or left
open.
Input pins for data D8 ~ D11 setting and
transmission enable, active low
These pins should be externally set to V or left
open.
Encoder data serial transmission output
Latch/Momentary transmission format
selection
pin:
Latch: Floating or VDD
Momentary: VSS

TABLE 6

6.6 IC 7805
Features
• Output Current up to 1A
• Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V
• Thermal Overload Protection
• Short Circuit Protection
• Output Transistor Safe Operating Area Protection

49

Fig 14: PIN Description

Pin No.
Function
1
Input Voltage (5V-18V)
2
Ground (0V)
3
Regulated Output; 5V (4.8V-5.2V)

50

Name
Input
Ground
Output

TABLE 7

6.7 BC 547 TRANSISTOR
BC547 is an NPN bi-polar junction transistor. A transistor, stands for transfer of
resistance, is commonly used to amplify current. A small current at its base controls a
larger current at collector & emitter terminals.
BC547 is mainly used for amplification and switching purposes. It has a
maximum current gain of 800. Its equivalent transistors are BC548 and BC549.
For amplification applications, the transistor is biased such that it is partly on for
all input conditions. The input signal at base is amplified and taken at the emitter. BC547
is used in common emitter configuration for amplifiers.

Fig15: BC 547 Transistor

6.8 RESISTOR
6.8.1 RESISTOR:

51

A

resistor is

a passive

two-terminal

electrical

component

that

implements electrical resistance as a circuit element. The current through a resistor is
in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the
voltage applied across a resistor's terminals to the intensity of current through the circuit
is called resistance. This relation is represented by Ohm's law :

where I is the current through the conductor in units of amperes, V is the potential
difference measured across the conductor in units of volts, and R is the resistance of the
conductor in units of ohms. Practical resistors have a series inductance and a small
parallel capacitance; these specifications can be important in high-frequency
applications. The ohm (symbol: Ω) is the SI unit of electrical resistance, named
after Georg Simon Ohm. An ohm is equivalent to a volt per ampere. Since resistors are
specified and manufactured over a very large range of values, the derived units of
milliohm (1 mΩ = 10−3 Ω), kilohm (1 kΩ = 103Ω), and megaohm (1 MΩ = 106 Ω) are
also in common usage.
The symbol used for a resistor in a circuit diagram varies from standard to
standard and country to country.
6.8.2 POTENTIOMETER: A common element in electronic devices is a threeterminal resistor with a continuously adjustable tapping point controlled by rotation of a
shaft or knob. These variable resistors are known as potentiometers when all three
terminals are present, since they act as a continuously adjustable voltage divider. A
common example is a volume control for a radio receiver.
Accurate, high-resolution panel-mounted potentiometers (or "pots") have
resistance elements typically wirewound on a helical mandrel, although some include a
conductive-plastic resistance coating over the wire to improve resolution. These
52

typically offer ten turns of their shafts to cover their full range. They are usually set with
dials that include a simple turns counter and a graduated dial. Electronic analog
computers used them in quantity for setting coefficients, and delayed-sweep
oscilloscopes of recent decades included one on their panels.

6.9 CAPACITOR
The function of the capacitor is to store electric charge or in effect electrical
energy. It is very useful as a filter, and for passing AC and blocking DC.
It consists of two metal plates separated by a dielectric in between. The symbol is-

1

ELECTROLYTIC CAPACITORS
The important characteristic of electrolytic capacitors is that they have polarity. They
have a positive and a negative electrode. Aluminum is used for the electrodes by using
thin oxidization membrane. Electrolytic capacitors range in value from about 1μF to
thousands of μF. Mainly this type of capacitor is used as a ripple filter in a power supply
circuit, or as a filter to bypass low frequency signals, etc.
POLYESTER FILM CAPACITORS

53

This capacitor uses thin polyester film as the dielectric. They are not high in tolerance,
but they are cheap and handy. Their tolerance is about ±5% to ±10%.

6.10 LCD JHD 162A
A liquid crystal display (LCD) is a flat panel display, electronic visual display,
or video display that uses the light modulating properties of liquid crystals (LCs). LCs
do not emit light directly.

Fig 16: Internal Block Diagram

RATINGS:
Parameter

Symbol

Testing Criteria

Supply Voltage
Input High Voltage
Input Low Voltage
Output High Voltage
Output Low Voltage
Operating Voltage

VD0 –VSS
VIH
VIL
VOH
VOL
IDD

−
−
−
-IOH=0.2mA
IOL =1.2 mA
VDD =5.0V

Standard Values
Min. Typ. Max.
4.5
5.0
5.5
2.2
−
VDD
-0.3
−
0.6
2.4
−
−
−
−
0.4
−
1.5
3.0

Unit
V
V
V
V
V
mA

TABLE 8
1
2
VSS VCC

3
VEE

4
5
RS R/W

6
E

7
DB0

8
DB1

54

9
DB2

10
DB3

11
DB4

12
DB5

13
14
15
DB6 DB7 LED+

16
LED-

Fig 17: Pin Configuration
6.11 RF TRANSECEIVER
The RF module, as the name suggests, operates at Radio Frequency. The corresponding
frequency range varies between 30 kHz & 300 GHz. In this RF system, the digital data is
represented as variations in the amplitude of carrier wave. This kind of modulation is
known as Amplitude Shift Keying (ASK).
Transmission through RF is better than IR (infrared) because of many reasons. Firstly,
signals through RF can travel through larger distances making it suitable for long range
applications. Also, while IR mostly operates in line-of-sight mode, RF signals can travel
even when there is an obstruction between transmitter & receiver. Next, RF transmission
is more strong and reliable than IR transmission. RF communication uses a specific
frequency unlike IR signals which are affected by other IR emitting sources.
This RF module comprises of an RF Transmitter and an RF Receiver. The
transmitter/receiver (Tx/Rx) pair operates at a frequency of 434 MHz. An RF transmitter
receives serial data and transmits it wirelessly through RF through its antenna connected
at pin4. The transmission occurs at the rate of 1Kbps - 10Kbps.The transmitted data is
received by an RF receiver operating at the same frequency as that of the transmitter.
The RF module is often used alongwith a pair of encoder/decoder. The encoder is used
for encoding parallel data for transmission feed while reception is decoded by a
decoder.

55

Fig 18 : Pin Configuration
Pin Description
Pin
No
1
2
3
4

Function

Name

Ground (0V)
Serial data input pin
Supply voltage; 5V
Antenna output pin

Ground
Data
Vcc
ANT

TABLE 9 : RF Transmitter
Pin
No
1
2
3
4
5
6
7
8

Function

Name

Ground (0V)
Serial data output pin
Linear output pin; not connected
Supply voltage; 5V
Supply voltage; 5V
Ground (0V)
Ground (0V)
Antenna input pin

Ground
Data
NC
Vcc
Vcc
Ground
Ground
ANT

TABLE 10 : RF Receiver

6.12 GPS MODULE

6.12.1 Global Positioning System (GPS):
The Global Positioning System (GPS) is a burgeoning technology, which
provides unequalled accuracy and flexibility of positioning for navigation, surveying and
GIS data capture. The GPS NAVSTAR (Navigation Satellite timing and Ranging Global
Positioning System) is a satellite-based navigation, timing and positioning system. The
GPS provides continuous three-dimensional positioning 24 hrs a day throughout the

56

world. The technology seems to be beneficiary to the GPS user community in terms of
obtaining accurate data up to about100 meters for navigation, meter-level for mapping,
and down to millimeter level for geodetic positioning. The GPS technology has
tremendous amount of applications in GIS data collection, surveying, and mapping.
The Global Positioning System (GPS) is a U.S. space-based radio navigation
system that provides reliable positioning, navigation, and timing services to civilian
users on a continuous worldwide basis -- freely available to all. For anyone with a GPS
receiver, the system will provide location with time. GPS provides accurate location and
time information for an unlimited number of people in all weather, day and night,
anywhere in the world.
The Global Positioning System (GPS) is a satellite-based navigation system
made up of a network of 24 satellites placed into orbit by the U.S. Department of
Defense. GPS was originally intended for military applications, but in the 1980s, the
government made the system available for civilian use. GPS works in any weather
conditions, anywhere in the world, 24 hours a day. There are no subscription fees or
setup charges to use GPS.
The GPS is made up of three parts: satellites orbiting the Earth; control and
monitoring stations on Earth; and the GPS receivers owned by users. GPS satellites
broadcast signals from space that are picked up and identified by GPS receivers. Each
GPS receiver then provides three-dimensional location (latitude, longitude, and altitude)
plus the time.

6.12.2 Geo positioning -- Basic Concepts:
By positioning we can understand the determination of stationary or moving
objects. These can be determined as follows:
1. In relation to a well-defined coordinate system, usually by three coordinate values and
2. In relation to other point, taking one point as the origin of a local coordinate system.

57

The first mode of positioning is known as point positioning, the second as
relative positioning. If the object to be positioned is stationary, we can term it as static
positioning. When the object is moving, we call it kinematics positioning. Usually, the
static positioning is used in surveying and the kinematics position in navigation.

GPS Basic Facts:
The GPS uses satellites and computers to compute positions anywhere on earth.
The GPS is based on satellite ranging. That means the position on the earth is
determined by measuring the distance from a group of satellites in space. The basic
principles behind GPS are really simple, even though the system employs some of the
high-tech equipment ever developed. In order to understand GPS basics, the system can
be categorized into 5 Logical steps .
They are listed below:
1. Triangulation from the satellite is the basis of the system.
2. To triangulate, the GPS measures the distance using the travel time of the radio
message.
3. To measure travel time, the GPS need a very accurate clock.
4. Once the distance to a satellite is known, then we need to know where the satellite is
in space.
5. As the GPS signal travels through the ionosphere and the earth's atmosphere, the
signal is delayed.
6. To compute a position in the three dimensions, we need to have four satellite
measurements. The GPS uses a trigonometric approach to calculate the positions,
The GPS satellites are so high up that their orbits are very predictable and each of the
satellites is equipped with a very accurate atomic clock.

58

6.12.3 Components of a GPS:
The GPS is divided into three major components:

Fig 19 : Different Components Of GPS
A)

The Control Segment:

59

The DOD monitoring stations track all GPS signals for use in controlling the
satellites and predicting their orbits. Meteorological data also are collected at the
monitoring stations, permitting the most accurate evaluation of tropospheric delays
of GPS signals. Satellite tracking data from the monitoring stations are transmitted to
the master control station for processing. This processing involves the computation
of satellite ephemerides and satellite clock corrections. The master station controls
orbital corrections, when any satellite strays too far from its assigned position, and
necessary repositioning to compensate for unhealthy (not fully functioning)
satellites.
B)

The Space Segment:
The Space Segment consists of the Constellation of NAVASTAR earth orbiting

satellites. The current Defense Department plan calls for a full constellation of 24 Block
II satellites (21 operational and 3 in-orbit spares). The satellites are arrayed in 6 orbital
planes, inclined 55 degrees to the equator. They orbit at altitudes of about 12000, miles
each, with orbital periods of 12 sidereal hours (i.e., determined by or from the stars), or
approximately one half of the earth's periods, approximately 12 hours of 3-D position
fixes. The next block of satellites is called Block IIR, and they will provide improved
reliability and have a capacity of ranging between satellites, which will increase the
orbital accuracy. Each satellite contains four precise atomic clocks (Rubidium and
Cesium standards) and has a microprocessor on board for limited self-monitoring and
data processing. The satellites are equipped with thrusters which can be used to maintain
or modify their orbits.
C)

The User Segment:
The user segment is a total user and supplier community, both civilian and

military. It consists of all earth-based GPS receivers. Receivers vary greatly in size and
complexity, though the basic design is rather simple. The typical receiver is composed of
an antenna and preamplifier, radio signal microprocessor, control and display device,
data recording unit, and power supply. The GPS receiver decodes the timing signals
from the 'visible' satellites (four or more) and, having calculated their distances,
60

computes its own latitude, longitude, elevation, and time. This is a continuous process
and generally the position is updated on a second-by-second basis, output to the receiver
display device and, if the receiver display device and, if the receiver provides data
capture capabilities, stored by the receiver-logging unit.

6.12.4 How it works:
GPS satellites circle the earth twice a day in a very precise orbit and transmit
signal information to earth. GPS receivers take this information and use triangulation to
calculate the user's exact location. Essentially, the GPS receiver compares the time a
signal was transmitted by a satellite with the time it was received. The time difference
tells the GPS receiver how far away the satellite is. Now, with distance measurements
from a few more satellites, the receiver can determine the user's position and display it
on the unit's electronic map.
GPS receiver must be locked on to the signal of at least three satellites to
calculate a 2D position (latitude and longitude) and track movement. With four or more
satellites in view, the receiver can determine the user's 3D position (latitude, longitude
and altitude). Once the user's position has been determined, the GPS unit can calculate
other information, such as speed, bearing, track, trip distance, distance to destination,
sunrise and sunset time and more.

61

Fig 20: G.P.S receiver communicating with the satellite and sending
information through the wireless mobile phone
6.12.5 G.P.S receiver

Fig 21 : GPS Modem Device(MR-87)
62

Features:
•

Low cost

•

Compact (25. 4 x 25. 4 x 7 mm)

•

32 Channel Receiver

•

Low Power Consumption

•

Built-in Antenna

•

Standard NMEA protocol USB or Serial

•

Available baud rate :4800/9600/14400/19200/38400/57600/115200

•

Frequency :1575. 42 MHz

•

Power Supply :3. 3 ~ 5Vdc

•

Maximum Altitude :18,000 meter

•

Maximum Velocity :515 meter/second

6.12.6 GPS Applications:
There are countless GPS applications, a few important ones are covered in the
following passage.

Science:
•

Archaeology

•

Environmental

Transportation:
•

Aviation

•

Space

Military:
63

•

Intelligence and Target Location

•

Navigation

•

Weapon aiming and Guidance

Industry:
•

Mapping

•

Public safety

•

Surveying

•

Telecommunications

6.13 IC L293D
Features:
•

600mA OUTPUT CURRENT CAPABILITY

•

1.2A PEAK OUTPUT CURRENT

•

ENABLE FACILITY

•

OVER TEMPERATURE PROTECTION

•

LOGICAL ”0” INPUT VOLTAGE UP TO 1.5 V (HIGH NOISE IMMUNITY)

•

INTERNAL CLAMP DIODES

64

Fig 22 : Pin Diagram

6.14 TSOP 1738
The TSOP 1738 is a member of IR remote control receiver series. This IR sensor
module consists of a PIN diode and a pre amplifier which are embedded into a single
package. The output of TSOP is active low and it gives +5V in off state. When IR
waves, from a source, with a centre frequency of 38 kHz incident on it, its output goes
low.
Features:
• Photo detector and preamplifier in one package
• Internal filter for PCM frequency
• Improved shielding against electrical field disturbance
• TTL and CMOS compatibility

65

• Output active low
• Low power consumption
• High immunity against ambient light
• Continuous data transmission possible (up to 2400 bps)

Fig 23: Pin Diagram

6.15 IR Transmitter/Receiver
It consists of 5mm 940 nanometer wave length high power IR LED and
photodiode having peak sensitivity at 940 nanometer wavelength.

Specifications:
•

IR TX RX size: 5mm diameter package

•

IR LED current rating: 30mA nominal, 600mA pulse loading at 1% duty cycle

•

IR LED wavelength: 940Nm

66

•

Photodiode peak response wavelength: 940nMAn IR LED, also known as IR
transmitter, is a special purpose LED that transmits infrared rays in the range of 760
nm wavelength. Such LEDs are usually made of gallium arsenide or aluminium
gallium arsenide. They, along with IR receivers, are commonly used as sensors.

6.16 DC Motor

A DC motor is an electric motor that runs on direct current (DC) electricity. DC
motors were used to run machinery, often eliminating the need for a local steam engine
or internal combustion engine. DC motors can operate directly from rechargeable
batteries, providing the motive power for the first electric vehicles. Today DC motors are
still found in applications as small as toys and disk drives, or in large sizes to operate
steel rolling mills and paper machines. Modern DC motors are nearly always operated in
conjunction with power electronic devices.
Two important performance parameters of DC motors are the motor constants
Kv and Km.

6.17 LED
A light-emitting

diode (LED)

is

a semiconductor light source.

When a light emitting diode is

forward-biased

on), electrons are

(switched

67

able

to

recombine with electron holes within the device, releasing energy in the form
of photons.
This effect is called electroluminescence and the color of the light (corresponding to the
energy of the photon) is determined by the energy gap of the semiconductor. The LED
consists of a chip of semiconducting material doped with impurities to create a p-n
junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side,
or cathode, but not in the reverse direction. Charge-carriers—electrons and holes—flow
into the junction from electrodes with different voltages. When an electron meets a hole,
it falls into a lower energy level, and releases energy in the form of a photon.
The wavelength of the light emitted, and thus its color depends on the band
gap energy of the materials forming the p-n junction. In silicon or germanium diodes, the
electrons and holes recombine by a non-radioactive transition, which produces no
optical emission, because these are indirect band gap materials. The materials used for
the LED have a direct band gap with energies corresponding to near-infrared, visible, or
near-ultraviolet light.
LED development began with infrared and red devices made with gallium
arsenide. Advances in materials science have enabled making devices with ever-shorter
wavelengths, emitting light in a variety of colors.

Fig 24: Working of LED
The symbol of LED is:

68

HARDWARE DESIGN:
Firstly, circuit is drawn on multipurpose pub then at appropriate place
components are soldered by following process.
Soldering is a process in which two or more metal items are joined together
by melting and flowing a filler metal (solder) into the joint, the filler metal having a
lower melting point than the work piece.

Step 1

SOLDERING PROCEDURE
Check that your soldering iron tip is suitable for the Project. (No larger than
the diameter of the pad).
Check the tip is clean and shiny. If not, tin it by adding a small amount of

Step 2

solder to the tip.
Adjust the temperature of the soldering station to 3500 C (degrees Celsius )

Step 3

Ensure the solder sponge is damp. A dry sponge will not clean the tip
effectively, and one that is too wet will lower the temperature of the tip
making for an ineffective solder joint.

Step 4

Carefully wipe the tip on the damp sponge until clean. Continually wipe the
tip while soldering a circuit board.

Step 5

Bend the lead of the component
using fine pliers so that it easily
slides into the holes of the printed
circuit pad.

Step 5

Insert the component to be soldered into the circuit board and bend the leads

Step 6
Step 7

protruding from the bottom of the circuit board at an angle of approx 450.
Cut the leads of the component close to the outer edge of the solder pad.
When ready, hold the soldering iron at a 45° angle, and heat both the lead and
the pad simultaneously. Touch the solder wire in the space between the iron
tip and the lead.

71

Fig 25: Soldering Procedure

Step 8

Keep the soldering iron tip still while moving the solder around the joint as it
melts.

Step 9

Remove the solder tip first and the solder wire next, (prevents spiking).

Step 10

Allow to the joint to cool naturally and undisturbed, do not blow on the solder
joint to cool it.

Step 11

When you have completed all solder joints thoroughly clean your board,
using Isopropyl Alcohol, and a bristle brush, to remove the flux residue and
other contaminants.

Step 12

Wipe or pat dry with a lint free tissue to remove traces of residue.

Step 13

Inspect for a good solder connection. The solder joint should be clean,
smooth and shiny.
Figure a) the amount of solder applied is minimal and may result in a poor
electrical connection over time.
Figure b) is the ideal solder joint.
Figure c) indicates an excessive amount of solder has been applied to the
connection. This may damage the solder pad due to excessive heat applied.

72

Step 13

Leave a large blob of solder on the tip when switching the iron off as this will
protect the tip from oxidation and contamination.

73

8.1 PROGRAMMING
GPS SECTION
* Basic program to show latitude and longitude on LCD extracted from GPGGA
statement */
#include<reg51.h>
#define port2 P2
sbit rs = P1^0;
sbit rw = P1^1;
sbit e = P1^2;
char info[70];
char test[6]={"$GPGGA"};
char comma_position[15];
unsigned int check=0,i;
unsigned char a;
void receive_data();
void lcd_latitude();
void lcd_longitude();
//DELAY FUNCTION
void delay(unsigned int msec)
{
int i,j
for(i=0;i<msec;i++)
for(j=0;j<1275;j++);

75

}
// LCD COMMAND SENDING FUNCTION
void lcd_cmd(unsigned char item)
{
port2 = item;
rs= 0;
rw=0;
e=1;
delay(1);
e=0;
return;
}
// LCD DATA SENDING FUNCTION
void lcd_data(unsigned char item)
{
port2 = item;
rs= 1;
rw=0;
e=1;
delay(1);
e=0;
return;
}
76

// LCD STRING SENDING FUNCTION
void lcd_string(unsigned char *str)
{
int i=0;
while(str[i]!='0')
{
lcd_data(str[i]);
i++;
delay(10);
}
return;
}
// SERIAL PORT SETTING
void serial()
{
TMOD=0x20;
TH1=0xfa;
SCON=0x50 ;
BIT , RECEIVING ON
TR1=1;

//MODE=2
// 4800 BAUD
// SERIAL MODE 1 ,8- BIT DATA ,1 STOP BIT ,1 START
//TIMER START

}
void find_comma()
{

77

unsigned int i,count=0;
for(i=0;i<70;i++)
{
if(info[i]==',')
{
comma_position[count++]=i;
}
}
}
void compare()
{
IE=0x00;

//Interrupt disable

find_comma();
lcd_latitude();

//Function to detect position of comma in the string
//Function to show Latitude

lcd_longitude(); //Function to show Longitude
check=0;
IE=0x90;

//Interrupt enable

}
void receive_data()

interrupt 4

{
info[check++]=SBUF;
if(check<7)

//Read SBUF
//Condition to check the required data

78

{
if(info[check-1]!=test[check-1])
check=0;
}
RI=0;
}
void lcd_shape()

//Function to create shape of degree

{
lcd_cmd(64);
lcd_data(10);
lcd_data(17);
lcd_data(17);
lcd_data(10);
lcd_data(0);
lcd_data(0);
lcd_data(0);
lcd_data(0);
}
void lcd_latitude()

//Function to display Latitude

{
unsigned int c2=comma_position[1]; //Position of second comma
lcd_shape();
lcd_cmd(0x01);

// Clear LCD display
79

lcd_cmd(0x84);

//Move cursor to position 6 of line 1

lcd_string("LATITUDE");

//Showing Latitude

lcd_cmd(0xC0);

//Beginning of second line

lcd_data(info[c2+1]);
lcd_data(0);

//Degree symbol

lcd_data(0x27);

//ASCII of minute sign(')

delay(250);
}
void lcd_longitude()
{
unsigned int c4=comma_position[3];
lcd_cmd(0x01);

//Clear LCD display

80

lcd_cmd(0x84);

//Move cursor to position 4 of line 1

lcd_string("LONGITUDE");

//Showing Longitude

lcd_cmd(0xC0);

//Begining of second line

lcd_data(0);
lcd_data(0x27);

//ASCII of minute sign(')

delay(250);
}
void main()
{
serial();
lcd_cmd(0x38);

//2 LINE, 5X7 MATRIX

81

lcd_cmd(0x0e);

//DISPLAY ON, CURSOR BLINKING

IE=0x90;
while(1)
{
if(check==69)
compare();
}
}

COLLISION AVOIDANCE SECTION:
ALGORITHM-:
1) Start
2) Initialize the input port & output port.
3) Read data from pin 2.0,pin 2.1,pin 2.2.
4) If pin2.0=1, turn right.
Else goto step 5.
5) If pin2.1=1, turn right.
Else goto step 6.
6) If pin2.2=1, turn left.
Else goto step 7.
7) If pin2.0&pin2.1=1, turn right
Else goto step 8.
8) If pin2.2&pin2.1=1, turn left
Else goto step 9.
9) If pin2.0&pin2.2=1,move forward
Else goto step 10.
10) If pin2.0&pin2.1&pin2.2=1, move backward
Else goto step 11.
11) Again go to step 3.

82

12) Stop.
PROGRAMMING
#$mod51
org 00h
mov p2,#0ffh
ag: mov a,p2
anl a,#07h
cjne a,#01h,la1
mov p1,#02h
sjmp ag
la1:
mov a,p2
anl a,#07h
cjne a,#02h,la2
mov p1,#02h
sjmp ag
la2:
mov a,p2
anl a,#07h
cjne a,#04h,la3
mov p1,#02h
sjmp ag
la3:
mov a,p2
anl a,#07h
cjne a,#00h,la4
mov p1,#00010100b
sjmp ag
la4:
mov a,p2
anl a,#07h
83

cjne a,#07h,la5
mov p1,#0ah
sjmp ag
la5:
mov a,p2
anl a,#07h
cjne a,#03h,la6
mov p1,#00001100b
sjmp ag
la6:
mov a,p2
anl a,#07h
cjne a,#06h,ag
mov p1,#00010010b
sjmp ag
end

84

8.2 SOFTWARE DESCRIPTION
µVision Keil: µVision Keil provides IDE for 8051 programming & is very easy to
use. When starting a new project, simply select the microcontroller you use from the
Device Database and the µVision IDE sets all Compiler, Assembler, Linker, and
Memory options. It’s device database is large which supports many ICs of the 8051
family. A HEX file can be created with the help of Keil which is required for burning
onto chip. It has a powerful debugging tool which detects most of the errors in the
program.

Working with µVision Keil :
To open keil software click on start menu then program and then select keil2.
Following window will appear on your screen.
You can see three different windows in this screen.
1) Project work space window
2) Editing window

85

3) Output window
Project workspace window is for showing all the related files connected with your
project.
Editing window is the place where you will edit the code.
Output window will show the output when you compile or build or run your project.
Creating new project in d:keil2myprojectsfirst as shown in figure.

•

Give the name of project as "test". By default it will be saved as *.v2 extension.

•

Now you will be asked to choose your target device for which you want to write the
program. Scroll down the cursor and select generic from list. Expand the list and
select 8051 (all variants).

86

•

When you click OK, you will be asked to add startup code and file to your

project

folder. Click yes. Now on your screen expand target1 list fully. You will see
following window:

•

Now click on file menu and select new file. Editor window will open. Now you

can start writing your code.
•

As you start writing program in C, same way here also you have to first include
the header file. Because our target is 8051 our header file will be "reg51.h".

•

After including this file. Just right click on the file and select open document
<reg51.h>. The following window will appear:

87

•

If you scroll down cursor you will see that all the SFRs like P0-P3, TCON, TMOD,
ACC, bit registers and byte registers are already defined in this header file. So one
can directly use these register names in coding.

•

Now you can write your program same as c language starting with void main().

•

After completing the code save the file in project folder with ".c" extension.

•

Now right click on "source group 1" in project workspace window. Select "add
files to source gorup 1".

•

Select the C file you have created and click add button.
88

•

You will see that the c file has been added in source group.

•

Now to compile the program from project menu select "build target". In the
output window you will see the progress.

•

If there is any compilation error then target will not be created. Remove all the
errors and again build the target till you find "0 Error(s)".

•

Now you are ready to run your program. From debug menu select "start/stop debug
session".

•

You will see your project workspace window now shows most of the SFRs as well
as GPRs r0-r7. Also one more window is now opened named "watches". In this
window you can see different variable values.

•

To add variable in watch window goto "watch#1" tab. Then type F2 to edit and
type the name of your variable.

•

If you want to see the output on ports go to peripheral menu and select I/O ports.
Select the desire port. You can give input to port pins by checking or unchecking
any check box. Here the check mark means digit 1 and no check mark means 0.
The output on the pin will be shown in same manner.

•

To run the program you can use any of the option provided "go", "step by step",
"step forward", "step ove" etc.

89

•

Now after testing your program you need to down load this program on your target
board that is 8051. For this you have to create hex file.

•

To create hex file first stop debug session. Again you will be diverted to project
workspace window.

•

Right click on "target 1" and select "option for target 1". Following window will
appear.

•
•

Select output tag and check "create hex file" box.
Now when you again build your program, you will see the message in output

window "hex file is created".
•

In your project folder you can see the hex file with same name of your project as
"test.hex".

•

This file you can directly load in 8051 target board and run the application on
actual environment.

90

TESTING:1.Continuity test:First of all we checked the PCB that all the tracks are as per the design of PCB and
showing continuity with the help of multimeter and PCB layout.

2. Short circuit test:Then we checked the PCB for any unwanted short circuits with the help of
multimeter and PCB layout.

3. Soldering:In the next step, we soldered the required components. And then checked that
there are no any unwanted shorts occurred due to soldering without putting IC's and
keeping power supply off.

4. Power supply test:In the next step, we put power supply on and checked whether required voltage is
appearing at the required voltage is appearing at the required points i.e. +Vcc and GND
at the respective points. We took care of not connecting IC's in the circuit while
performing this test.

5. Microcontroller test:For testing the microcontroller, we wrote the square wave generation program for
generating square wave on each port pin. Then we fed the program in microcontroller
and checked the output with the help of CRO by connecting the microcontroller in the
circuit. We took care of not connecting any other IC in the circuit.

92

PROBLEMS FACED:

Although the concept & design of the project seemed perfect, there were some
problems faced while actual implementation:
1) Generation of exact 38 KHz Frequency from IC 555 at Transmitter circuit.
Solution: Use variable resistor pot in astable multivibrator. Connect IC 555’s output
pin to C.R.O. & measure frequency pulses generated by IC 555. By varying the resistor
pot we can adjust the frequency of output.

2) Propagation Effects
Solution: The working area for the project should be open and wide so that the
signals can propagate smoothly with least interference.

94

•
•

Low cost.
Since there is no requirement for a GSM modem it does not involve any data
transfer charges.

•

Finds applications in different areas like Tourism, Navigation etc.

•

It does not contain, or need, a qualified operator on board.

•

It can enter environments that are dangerous to human life.

•

Chances of collisions are minimized.

96

1) It is not powered by battery which can be discharged in short duration of
operation.
2) Low speed.
3) Software flexibilities difficult to achieve.
4) Incapable of handling user’s command.
Many new applications can be added to it in the future to make it more advance and
accurate.

98

Applications:
• Latitude and longitude displayed can be used for location identification.
• Vehicle travel record management.
• Wild life researches.
• In every field to monitoring easily.
• Collision Avoidance logic has been specially designed for vaccum-cleaner. By
using heavy rating motors , strong mechanical structure and using highly sensitive
obstacle sensors, it efficiently work as vaccum-cleaner.

100

Future Scope:
1. With the use of high end micro controllers and graphical LCD displays we can
expect the data of the micro controller to be used dynamically during the journey
itself to find our position instead of positioning in the Google earths map.
2. Camera can be added to aid the purpose of surveillance.

102

CONCULSION:
Thus vehicle position logging system using GPS is constructed.
Firstly, integrating features of all the hardware components used. Presence of every
module has been reasoned out and placed carefully thus contributing to the best
working of the unit.
Secondly, using advanced components such as GPS and wireless network with the
help of the growing technology, the project has been successfully implemented.
In this project an effort has been made to study monitoring of the vehicle and to
implement it.

104

REFERENCES:

1. Global positioning systems inertial navigation, and integration Mohinders, Grewal,
Lawrence, R Weil, Angus p Andrews
2. GPS for DUMMIES BY Joel Mc Namara
3. Torsten Baumbach's web site: http://pandora.inf.uni-jena.de/ttbb/
4. 8051 Microcontroller and Embedded Systems by M. A. Mazidi, Janice Gillispie
Mazidi and Rolin D. McKinlay

Web References:


http://en.wikipedia.org/wiki/GPS128*64



http://en.wikipedia.org/wiki/Category:MMC



http://www.microchip.com/wwwproducts/Devices.aspx?
dDocName=en01026



http://www.howstuffworks.com



http://www.8051projects.com



http://www.alldatasheet.com/



http://www.datasheet4u.com/

106

17.1 ESTIMATED COST
S. No.
1
2
3
4
5
6
7
8
1
2
3
1
2
3
4
5
6
7
8
1
2
3
4

COMPONENTS
Semiconductors
IC-AT89C51 Microcontroller
IC-HT12D Decoder
IC-HT12E Encoder
IC-MAX232 Driver/Receiver
IC-7805, 5V Regulator
NPN Transistor
IC- L293D
TSOP 1738
Resistors
R1, R2- 4.7 kΩ
R3- 1 kΩ
VR1- 10 kΩ preset
Miscellaneous
XTAL- 12MHz Crystal
S1- Push-to-On Switch
TX1- 38 kHz IR Transmitter
RX1- 38 kHz IR Receiver
RF Module
GPS Module
LCD Display
DC Motors
Capacitors
C1, C2- 3.3 nF Ceramic Disk
C4-10μF, 16V Electrolytic
C- 1μF, Electrolytic
0.01μF, Polyster
TOTAL COST

108

COST (Rs.)

65
70
70
25
8 for each
2 for each
95
20
1 for each
1 for each
2 for each
10
15
6 for each
6 for each
140
2250
150
175 for each
1 for each
1 for each
2 for each
2 for each
3388

17.2 DATA SHEETS
1. HT12D
Features
•

Operating voltage: 2.4V~12V

•


•

Low standby current

•

Capable of decoding 12 bits of information

•

Binary address setting

•

Received codes are checked 3 times

•

Address/Data number combination

•

HT12D: 8 address bits and 4 data bits

•

Built-in oscillator needs only5% resistor

•

Valid transmission indicator

•

Easy interface with an RF or an infrared transmission medium

•

Minimal external components

Applications
•

Burglar alarm system

•

Smoke and fire alarm system

•

Garage door controllers

•

Car door controllers

•

Car alarm system

•

Security system
109

•

Cordless telephones

•

Other remote control systems

General Description
For proper operation, a pair of encoder/decoder with the same number of
addresses and data format should be chosen. They compare the serial input data three
times continuously with their local addresses. If no error or unmatched codes are found,
the input data codes are decoded and then transferred to the output pins. The VT pin also
goes high to indicate a valid transmission. Of this series, the HT12D is arranged to
provide 8 address bits and 4 data bits, and HT12F is used to decode 12 bits of address
information.
SELECTION TABLE
Address No.
8

Data
VT
No. Type
4
L
√

Oscillator

Trigger

Package

RC Oscillator

DIN Active ″Hi″

18DIP/20SOP

Data type: L stands for latch type data output.
VT can be used as a momentary data output.

110

Note: The address/data pins are available in various combinations (see the
address/data table).
PIN DESCRIPTION
Pin
Name
A0~A11

I/O

D8 ~D11
DIN
VT
OSC1
OSC2
VSS
VDD

O
I
O
I
O
I
I

I

Internal connection
NMOS
TRANSMISSION
GATE
CMOS OUT
CMOS IN
CMOS OUT
OSCILLATOR
OSCILLATOR
−
−

Description
Input Pins for address A0 ~ A11 setting
They can be externally set to VDD or
VSS.
Output Data Pins
Serial Data Input Pin
Valid Transmission ON, Active High
Oscillator Input Pin
Oscillator Output Pin
Negative Power Supply
Positive Power Supply

ELECTRICAL CHARACTERISTICS
Symbol

Parameter

VDD
ISTB

Operating Voltage
Standby Current

IDD

Operating Current

I0

Data Output Source
Current (D8-D11)
VT Output Source Current
VT Output Sink Current
″H″ Input Voltage
″L″ Input Voltage
Oscillator Frequency

IVT
V1H
V1L
fOSC

Test Conditions
VDD Conditions
−
−
5V Oscillator
12V stops
5V No Load
F=150 kHz
5V VOH=4.5V

2.4
−
−
−

5
0.1
2
200

12
1
4
400

V
µA
µA
µA

-1

-1.6

−

mA

5V
5V
5V
5V
5V

-1
1
3.5
0
−

-1.6
1.6
−
−
150

−
−

mA
mA
V
V
kHz

Functional Description
Operation
112

VOH=4.5V
VOL=4.5V
−
−
ROSC=51kΩ

Min Typ Max Unit

5
1
−

The series of 212 decoders provides various combinations of addresses and data
pins in different packages so as to pair with the same series of encoders.
The decoders receive data that are transmitted by an encoder and interpret the
first N bits of code period as addresses and the last 12-N bits as data, where N is the
address code number. A signal on the DIN pin activates the oscillator which in turn
decodes the incoming address and data. The decoders will then check the received
address three times continuously. If the received address codes all match the contents of
the decoder’s local address, the 12-N bits o f data are decoded to activate the output pins
and the VT pin is set high to indicate a valid transmission. This will last unless the
address is incorrect or no signal is received. The output of the VT pin is high only when
the transmission is valid. Otherwise it is always low.

Output type
Of the 212 series of decoders, the HT12F has no data output pin but its VT pin can
be used as a momentary data output. The HT12D, on the other hand, provides 4 latch
type data pins whose data remain unchanged until new data are received.

Part No.

Data Pins

Address Pins

Output Type

Operating Voltage

HT12D

4

8

Latch

2.4V~12V

HT12F

0

12

−

2.4V~12V

Flowchart
113

The oscillator is disabled in the standby state and activated when a logic “high”
signal applies to the DIN pin. That is to say, the D IN should be kept low if there is no
signal input.

114

2. L293D
Features
•

600mA OUTPUT CURRENT CAPABILITY PER CHANNEL

•

1.2A PEAK OUTPUT CURRENT (non repetitive) PER CHANNEL

•

OVERTEMPERATURE PROTECTION

•

ENABLE FACILITY

•

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. The L293D is assembled in a 16 lead plastic
package which has 4 center pins connected together and used for heat sinking.

116

ABSOLUTE M AXIMUM RATINGS
Symbol
VS
VSS
Vi
Ven
I0
Ptot
Tstg, Tj

Parameter
Supply Voltage
Logic Supply Voltage
Input Voltage
Enable Voltage
Peak Output Current (100 μs non repeatitive)
Total Power Dissipation at T=90 oC
Storage and Junction Temperature

117

Value
36
36
7
7
1.2
4
-40 to 150

Unit
V
V
V
V
A
W
o
C

ELECTRICAL CHARACTERISTICS: (for each channel, VS =24V, VSS =5V,
T amb=25 oC, unless otherwise specified)
Symbol
Parameter
VS
Supply Voltage
VSS
Logic Supply Voltage
IS
Total Quiscent Supply
Current (PIN 10)
ISS

VIL
VIH
IL
IH
Ven L
Ven H
Ien L
Ien H
VCE(Sat)H
VCE(sat)L
VF
tr
tf
ton
toff

Total Quiscent Logic
Supply
Current (PIN 20)
Input Low Voltage
(PIN 2,9,12,19)
Input High Voltage
(PIN 2,9,12,19)
Low Voltage Input
Current
(PIN 2,9,12,19)
High Voltage Input
Current
(PIN 2,9,12,19)
Enable Low Voltage
(PIN 1,11)
Enable High Voltage
(PIN 1,11)
Low Voltage Enable
Current
(PIN 1,11)
High Voltage Enable
Current
(PIN 1,11)
Source Output Saturation
Voltage (PINS 3,8,13,18)
Source Output Saturation
Voltage (PINS 3,8,13,18)
Clamp Diode Forward
Voltage
Rise-time
Fall-time
Turn-on Delay
Turn-off Delay

Test Conditions
V1=L:I0=0:Ven=H
V1=H:I0=0:Ven=H
Ven=L
V1=L:I0=0:Ven=H

Min. Typ. Max.
VSS
36
4.5
36
2
6
16
24
4
44
60

V1=H:I0=0:Ven=H
Ven=L

16
16

Unit
V
V
mA
mA
mA
mA

22
24
1.5

mA
mA
V

VSS
7
-10

V
V
μA

100

μA

-0.3

1.5

V

2.3
2.3

VSS
7
-100

V
V
μA

 10

μA

-0.3
VSS≤7V
VSS>7V
V1L=1.5V

2.3
2.3

2.3V≤V1H≤VSS0.6V

VSS≤7V
VSS>7V
VenL=1.5V

30

-30

2.3V≤VenH≤V0.6V
I=-0.6A

1.4

1.8

V

I=+0.6A

1.2

1.8

V

I=600 μA

1.3

V

0.1 to 0.9V0
0.9 to 0.1V0
0.5V1 to 0.5V0
0.5V1 to 0.5V0

250
250
750
200

ns
ns
ns
ns

118

3. MAX232
The MAX232 from Maxim was the first IC which in one package contains the
necessary drivers (two) and receivers (also two), to adapt the RS-232 signal voltage
levels to TTL logic. It became popular, because it just needs one voltage (+5V) and
generates the necessary RS-232 voltage levels (approx. -10V and +10V) internally.
This greatly simplified the design of circuitry. Circuitry designers no longer need to
design and build a power supply with three voltages (e.g. -12V, +5V, and +12V), but
could just provide one +5V power supply, e.g. with the help of a simple 78x05 voltage
regulator.
The MAX232 has a successor, the MAX232A. The ICs are almost identical,
however, the MAX232A is much more often used (and easier to get) than the original
MAX232, and the MAX232A only needs external capacitors 1/10th the capacity of
what the original MAX232 needs.
It should be noted that the MAX232(A) is just a driver/receiver. All it does is to
convert signal voltage levels. Generating serial data with the right timing and
decoding serial data has to be done by additional circuitry, e.g. by a 16550 UART or
one of these small micro controllers (e.g. Atmel AVR, Microchip PIC) getting more
and more popular.
The MAX232 and MAX232A were once rather expensive ICs, but today they are
cheap.

119

MAX232 DIP Package PIN Layout
Nbr Name
1

C1+

2

V+

3

C1-

4

C2+

5

C2-

6.

V-

7
8
9
10
11
12
13
14
15

T2out
R2in
R2out
T2in
T1in
R1out
R1in
T1out
GND

16

VCC

Purpose

Signal Voltage

+Connector for Capacitor
C1
Output of Voltage Pump

Driver 2 Output
Receiver 2 Input
Receiver 2 Output
Driver 2 Input
Driver 1 Input
Receiver 1 Output
Receiver 1 Intput
Driver 1 Output
Ground

Capacitor should stand
atleast 16V
+10V, Capacitor should
stand
atleast 16V
atleast 16V
atleast 16V
atleast 16V
-10V, Capacitor should
stand
atleast 16V
RS-232
RS-232
TTL
TTL
TTL
TTL
RS-232
RS-232
0V

Power Supply

Capacitor
Value
MAX232

+5V

-Connector for Capacitor
C1
+Connector for Capacitor
C2
-Connector for Capacitor
C2
Output of Voltage
Pump/Inverter

1μF
1 μF to
Vcc
1 μF
1 μF
1 μF
1 μF to
GND

1 μF to
Vcc

V+(2) is also connected to VCC via a capacitor (C3). V-(6) is connected to GND via a
capacitor (C4). And GND(15) and VCC(16) are also connected by a capacitor (C5), as
close as possible to the pins.

120

Application
The MAX232(A) has two receivers (converts from RS-232 to TTL voltage
levels) and two drivers (converts from TTL logic to RS-232 voltage levels). This means
only two of the RS-232 signals can be converted in each direction. The old
MC1488/1498 combo provided four drivers and receivers.
Typically a pair of a driver/receiver of the MAX232 is used for


TX and RX

and the second one for


CTS and RTS.

There are not enough drivers/receivers in the MAX232 to also connect the DTR, DSR,
and DCD signals. Usually these signals can be omitted when e.g. communicating with a
PC's serial interface. If the DTE really requires these signals either a second MAX232 is
needed, or some other IC from the MAX232 family can be used (if it can be found in
consumer electronic shops at all).

MAX232 DIP Package
121

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