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CHAPTER- 1
INTRODUCTION & PROBLEM BACKGROUND
1.1 HISTORY
Embedded Systems and Robotics are two interesting fields where every engineer can
display his creative and technical skills. Pleasing aspect of robotics is that anyone can
make a robot indigenously. In this competitive world there is need for every
enthusiastic, from amateur to professional, to make a simple robot having innovated
applications and with robust control.
Mobile phones today became an essential entity for all and so, for any mobile-based
application there is great reception. In this scenario, making a mobile phone operated
land rover is a good idea. Conventionally wireless controlled robots utilize RF
circuits, which had limitations as if limited range limited frequency ranges and
controls. However, a mobile phone controlled DTMF based DC Fan Controller can
hold up these limitations.
Although the appearance and capabilities of robots vary vastly, all robots share the
features of a mechanical, movable structure under some form of control.
This control of robot involves three distinct phases- perception, processing and action.
1.2 GENERAL CONCEPTS
FEATURES OF 8051 ARCHITECTURE
Optimized 8 bit CPU for control applications and extensive Boolean
processing capabilities.
64KB Program Memory address space.
64KB Data Memory address space.
128 bytes of on chip Data Memory.
Thirty-Two Bi-directional and individually addressable I/O lines.
Two 16-bit timer/counters.
Full Duplex UART.
6-source / 5-vector interrupt structure with priority levels.
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On chip clock oscillator.
Now we may be wondering about the non-mentioning of memory space meant for the
program storage, the most important part of any embedded controller. Originally, this
8051 architecture was introduced with on-chip, ‘one time programmable’ version of
Program Memory of size 4K × 8. Intel delivered all these microcontrollers (8051)
with user’s program fused inside the device. The memory portion was mapped at the
lower end of the Program Memory area. However, after getting devices, customers
could not change anything in their program code, which was already made available
inside during device fabrication.
1.3 PROBLEM STATEMENT
In this project, the DC Fan is controlled by a mobile phone that makes a call to the
mobile phone attached to the device. In the course of a call, if any button is pressed, a
tone corresponding to the button pressed is heard at the other end of the call. This tone
is called ‘dual-tone multiple-frequency’ (DTMF) tone. The mobile that makes a call
to the mobile phone stacked in the DTMF based DC Fan Controller acts as a remote.
The main achievement of this project is to control the DC Fan attached with the
DTMF Based DC Fan Controller through the wireless link. The normal wireless link
has the limitation of the limited range as well as the high susceptibility of the
interfaces. To remove the problem of limited range and the possibility of the
interfaces we are going to use the GSM i.e. global system of mobile.
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CHAPTER- 2
DETAILS OF TECHNOLOGY USED
2.1 EMBEDDED SYSTEM DESIGN
Embedded system employs a combination of software & hardware to perform
a specific function. It is a part of a larger system, which may not be a “computer”,
works in a reactive & time constrained environment.
Figure 2.1: Outline of an Embedded System
Any electronic system that uses a CPU chip, but that is not a general-purpose
workstation, desktop or laptop computer is known as embedded system. Such systems
generally use microprocessors; microcontroller or they may use custom-designed
chips or both. They are used in automobiles, planes, trains, space vehicles, machine
tools, cameras, consumer and office appliances, cell phones, PDAs and other
handhelds as well as robots and toys. The uses are endless, and billions of
microprocessors are shipped every year for a myriad of applications.
In embedded systems, the software is permanently set into a read-only
memory such as a ROM or flash memory chip, in contrast to a general-purpose
computer that loads its programs into RAM each time. Sometimes, single board and
rack mounted general-purpose computers are called "embedded computers" if used to
control. We are living in the Embedded World. You are surrounded with many
embedded products and your daily life largely depends on the proper functioning of
these gadgets. Television, Radio, CD player of your living room, Washing Machine or
Microwave Oven in your kitchen, Card readers, Access Controllers, Palm devices of
your work space enable you to do many of your tasks very effectively. Apart from all
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these, many controllers embedded in your car take care of car operations between the
bumpers and most of the times you tend to ignore all these controllers.
In recent days, you are showered with variety of information about these
embedded controllers in many places. All kinds of magazines and journals regularly
dish out details about latest technologies, new devices, fast applications which make
you believe that your basic survival is controlled by these embedded products.
The computer you use to compose your mails, or create a document or analyze the
database is known as the standard desktop computer. These desktop computers are
manufactured to serve many purposes and applications.
You need to install the relevant software to get the required processing
facility. Therefore, these desktop computers can do many things. In contrast,
embedded controllers carryout a specific work for which they are designed. Most of
the time, engineers design these embedded controllers with a specific goal in mind. So
these controllers cannot be used in any other place.
Theoretically, an embedded controller is a combination of a piece of
microprocessor-based hardware and the suitable software to undertake a specific task.
These days designers have many choices in microprocessors/microcontrollers.
Especially, in 8 bit and 32 bit, the available variety really may overwhelm even an
experienced designer. Selecting a right microprocessor may turn out as a most
difficult first step and it is getting complicated as new devices continue to pop-up very
often.
2.2 EMBEDDED APPLICATIONS
AUTOMOBILES: Fuel Injection control (for fuel efficiency), Air bags and
Automatic braking (for safety), and car entertainment systems.
MEDICAL ELECTRONICS: Many sophisticated medical instruments (Body
Scanners, Heart rate monitors, Pacemaker etc.) Industrial Control: such as CNC-
machines are examples of embedded systems.
BUSINESS APPLICATIONS: Vending machines, scanners, printers.
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CONSUMER ELECTRONICS: Cameras, Toys, Cellular Phones, Washing
Machines
AVIONICS: Airplanes, Satellite Stations
Figure 2.2 Embedded Applications
2.3 DUAL-TONE MULTI-FREQUENCY (DTMF)
Dual-tone multi-frequency (DTMF) signaling is used for telecommunication
signaling over analog telephone lines in the voice-frequency band between telephone
handsets and other communications devices and the switching center. The version of
DTMF used for telephone tone dialing is known by the trademarked term Touch-Tone
(canceled March 13, 1984), and is standardized by ITU-T Recommendation Q.23. It is
also known in the UK as MF4. Other multi-frequency systems are used for signaling
internal to the telephone network. As a method of in-band signaling, DTMF tones
were also used by cable television broadcasters to indicate the start and stop times of
local commercial insertion points during station breaks for the benefit of cable
companies. Until better out-of-band signaling equipment was developed in the1990s,
fast, unacknowledged, and loud DTMF tone sequences could be heard during the
commercial breaks of cable channels in the United States and elsewhere.
2.4 TELEPHONE KEYPAD
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The contemporary keypad is laid out in a 3×4 grid, although the original
DTMF keypad had an additional column for four now-defunct menu selector keys.
When used to dial a telephone number, pressing a single key will produce a pitch
consisting of two simultaneous pure tone sinusoidal frequencies. The row in which
the key appears determines the low frequency, and the column determines the high
frequency. For example, pressing the '1' key will result in a sound composed of both a
697 and a 1209-hertz (Hz) tone. The original keypads had levers inside, so each
button activated two contacts.
Figure 2.3 DTMF telephone keypad
Figure 2.4 DTMF keypad frequencies (with sound clips)
Figure 2.5 DTMF Event Frequencies
TONES #, *, A, B, C, AND D
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The engineers had envisioned phones being used to access computers, and
surveyed a number of companies to see what they would need for this role. This led to
the addition of the number sign (#, sometimes called' octothorpe' in this context) and
asterisk or "star" (*) keys as well as a group of keys for menu selection: A, B, C and
D. In the end, the lettered keys were dropped from most phones, and it was many
years before these keys became widely used for vertical service codes such as *67 in
the United States and Canada to suppress caller ID. The U.S. military also used the
letters, relabeled, in their now defunct Autovon phone system. Here they were used
before dialing the phone in order to give some calls priority, cutting in over existing
calls if need be. The idea was to allow important traffic to get through every time.
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CHAPTER- 3
WORKING
3.1 BLOCK DIAGRAM
Fig 3.1: The Block Diagram of The Mobile Operated Land Rover
In this project, the DC Fan is controlled by a mobile phone that makes a call to
the mobile phone attached to the project. In the course of a call, if any button is
pressed, a tone corresponding to the button pressed is heard at the other end of the
call. This tone is called ‘dual-tone multiple-frequency’ (DTMF) tone. The mobile that
makes a call to the mobile phone stacked in the project acts as a remote.
3.2 WORKING
The user in order to control the DC Fan should make a call to the cell phone
attached in the project, from any phone, which can send DTMF tunes on pressing the
numeric buttons. The cell phone in the project will be kept in auto answer mode. So,
after a ring the cell phone accepts the call. Now the user may press any button on his
mobile. The DTMF tones thus produced are received by the cell phone in the project.
These tones are fed to the circuit by head set of the cell phone. MT8870 decodes the
received tone and sends equivalent binary number to the micro controller.
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As explained previously, the motor driver L293D can drive a DC motor with
an enable and two control inputs. So, inputs at 1A (2), 2A (7) and enable at 1, 2 EN
(1) can drive a DC motor connected at 1Y (3) and 2Y (6). The PD0 (14), PD1 (15)
and PD7 (21) pins port D of microcontroller are connected to 1A, 2A and 1,2EN pins
respectively. Therefore, with 1, 2EN pin enabled and if 1A, 2A pins are provided with
1, 0 as input respectively, the motor rotates in a direction and 0, 1 input makes the
motor to run in vice versa. And the input 1, 1 causes electrical brake. The
microcontroller is programmed in such a way that when the user presses (for ex.) ‘2’
button, both the drivers will be activated to make their motors to make a forward
motion. A detailed table is given below, delineating every step in data transfer when a
digit is pressed DTMF assigns a specific frequency (consisting of two separate tones)
to each key so that the electronic circuit can easily identify it. The signal generated by
the DTMF encoder is a direct algebraic summation, in real time, of the amplitudes of
two sine (cosine) waves of different frequencies, i.e., pressing ‘5’ will send a tone
made by adding 1336 Hz and 770 Hz to the other end of the line.
3.3 FLOW CHART
Fig 3.2 Flow Chart
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CHAPTER- 4
HARDWARE IMPLEMENTATION
4.1 CIRCUIT DIAGRAM
Figure 4.1 shows the circuit diagram of the microcontroller-based mobile
phone operated land rover. The important components of this rover are a DTMF
decoder, microcontroller and motor driver.
Fig 4.1 Circuit Diagram
An MT8870 series DTMF decoder is used here. All types of the MT8870
series use digital counting techniques to detect and decode all the 16 DTMF tone pairs
into a 4-bit code output. The built-in dial tone rejection circuit eliminates the need for
pre-filtering. When the input signal given at pin 2 (IN-) in single-ended input
configuration is recognized to be effective, the correct 4-bit decode signal of the
DTMF tone is transferred to Q1 (pin 11) through Q4 (pin 14) outputs.
Table II shows the DTMF data output table of MT8870. Q1 through Q4 outputs of the
DTMF decoder (IC1) are connected to port pins PA0 through PA3 of ATmega16
microcontroller (IC2) after inversion by N1 through N4, respectively.
We can divide complete circuit into three major blocks
1. DTMF decoder
2. Micro controller
3. DC motor driver
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DTMF decoder circuit: -
As shown in figure, it is made up form readily available MT8870 chip that is widely
used for DTMF based application. It receives DTMF tones and generates 4-bit digital
output corresponding to received DTMF signal of digits 0 - 9 and other signals (like *,
# etc.) also. It receives input form cell phone to its pin no 2. It amplifies it through
internal op-amp amplifier. If it receives valid DTMF tone, it will produce pulse output
on StD (pin no 15).
Fig 4.2 Pin Diagram of MT8870
Fig 4.3 MT8870 Circuit
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This is indicated by green LED connected as shown. The 4-bit digital output is
latched on pins 11 - 14 and that is given to micro controller. The StD output is also
given to interrupt pin of micro controller through transistor that will generate negative
pulse every time when DTMF signal is received. This negative pulse will generate an
interrupt. Cell phone digit switches 1 to 8 control all the movements of robotic arm.
The 4-bit digital output corresponding to these switches form MT8870 are as given
here.
Fig 4.4 Output of MT8870
Micro-controller Circuit Part: -
As shown in figure a 40 pin, 8-bit micro controller 89C51 is used for controlling
purpose. It receives 4-bit digital output from DTMF decoder on its port P1 pins P1.0 -
P1.3. In addition, interrupt signal is given to P3.3 (external interrupt 1) pin. It drives
two DC motors through port P2 pins P2.0 - P2.3. A 12 MHz crystal with two 33pf
capacitors is connected to crystal pins (18 & 19) to provide basic clock signal to
micro controller. One push button switch (RST) in parallel with 100nF capacitor
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forms power on reset circuit to reset the micro controller. it will control the motion of
land rover depending upon the code it receives from DTMF decoder as given in table.
Fig 4.5 Microcontroller Circuit Part
DC Motor Driver Circuit: -
Fig 4.6 L293D Pin Diagram
As shown in figure L293D is quadruple H-Bridge driver chip that is widely used for
DC motor and stepper motor driver applications. It receives inputs from micro
controller as shown on its input pins 2,7,10 & 15 and rotates two DC motors in either
direction as per given table. Therefore, to move the land rover forward or backward -
left or right one has to send following data on port.
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Fig 4.7 L293D Circuit Part
4.2 COMPONENTS LIST
SR NO. COMPONENTS QUANTITY
1 ATMEL 89S52 (MICROCONTROLLER) 1
2 LCD 16X21 1
3 M8870(DTMF) 1
4 L293(H-BRIDGE) 1
5 L7805 (5 VOLT REGULATOR) 1
6 CRYSTAL 11.0592MHZ 1
7 CRYSTAL 3.579545MHZ 1
8 LED 5
9 RESISTOR PACK 1
10 BERG STRIP 1
11 VARIABLE RESISTOR(50K) 2
12 CERAMIC CAPACITOR (104) 4
13 330R RESISTOR 1
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14 330K, 100K RESISTORS 3
15 2 PIN CONNECTORS 3
16 DC Fans 2
4.3 Description of Components
4.3.1 AT89S52
FEATURES
Compatible with MCS®-51 Products
8KB of In-System Programmable (ISP) Flash Memory – Endurance: 10,000
Write/Erase Cycles
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
Thirty-Two 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
Power-off Flag
Fast Programming Time
Flexible ISP Programming (Byte and Page Mode)
Green (Pb/Halide-free) Packaging Option
PIN DIAGRAM
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Fig 4.8 Pin Diagram
PIN Description of 8051
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 Indus-try-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 pro-grammar. By combining a versatile 8-bit CPU with in-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.
VCC - Supply voltage. This pin is required to act as main supply voltage pin. Usually
+5V voltage is applied to this pin. This pin is internally connected to the transistors
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inside the integrated circuit to provide them necessary supply voltage. The IC cannot
function properly if proper supply voltage is not provided to this pin.
GND – Ground. This pin is required for return path for the currents in the circuit.
Various transistors in the integrated circuit need ground connections which is
necessary for their operation. This pin will act as a common ground for all the
transistors in the integrated circuit to provide return path for various currents.
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 dur-ing 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.
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 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.
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
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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.
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.
XTAL1- Input to the inverting oscillator amplifier and input to the internal clock
operating circuit.
XTAL2- Output from the inverting oscillator amplifier.
4.3.2 16 × 2 CHARACTER LCD
FEATURES
Intelligent, with built-in Hitachi HD44780 compatible LCD controller and
RAM providing simple interfacing
61 x 15.8 mm viewing area
5 x 7 dot matrix format for 2.96 x 5.56 mm characters, plus cursor line
Can display 224 different symbols
Low power consumption (1 mA typical)
Powerful command set and user-produced characters
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TTL and CMOS compatible
Connector for standard 0.1-pitch pin headers
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. 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.
Fig 4.9 16x2 Character LCD
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.
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Fig 4.10 LCD Pin Diagram
Fig 4.11 Description of Pin Diagram
4.3.3 MT8870 DTMF RECEIVERFEATURES
Low power consumption
Adjustable acquisition and release times
Central office quality and performance
Power-down and inhibit modes (-02 only)
Inexpensive 3.58 MHz time base
Single 5 volt power supply
Dial tone suppression
Applications include telephone switch equipment, remote data entry, paging
systems, personal computers, credit card systems.
Manufactured using CMOS process technology, the M-8870 offers low power
consumption (35 mW max) and precise data handling. Its filter section uses switched
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capacitor technology for both the high and low group filters and for dial tone
rejection. Its decoder uses digital counting techniques to detect and decode all 16
DTMF tone pairs into a 4-bit code. External component count is minimized by
provision of an on-chip differential input amplifier, clock generator, and latched tri-
state interface bus.
Fig 4.12 Pin Diagram of MT8870
PIN Description of MT8870
IN+ (Non-inverting input) - Connections to the front-end differential amplifier.
IN-(Inverting input) - Connections to the front-end differential amplifier.
GS (Gain select - Gives access to output of front-end amplifier for connection of
feedback resistor.
VREF (Reference voltage output)- May be used to bias the inputs at mid-rail.
INH*- Inhibits detection of tones representing keys A, B, C, and D.
PD* -Power down. Logic high powers down the device and inhibits the oscillator.
Internal pull down.
OSC1 (Clock input)- 3.579545 MHz crystal connected between these pins completes
the internal oscillator.
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OSC2 (Clock output)- 3.579545 MHz crystal connected between these pins
completes the internal oscillator.
VSS -Negative power supply (normally connected to 0 V).
TOE- Tri-state-able output enable (input). Logic high enables the outputs Q1 - Q4.
Internal pull up.
Q1, Q2, Q3, Q4 (Pins 11 – 14) -Tri-statable data outputs. When enabled by OE,
provides the code corresponding to the last valid tone pair received
StD (Delayed steering output.) - Presents a logic high when a received tone pair has
been registered and the output latch is updated. Returns to logic low when the voltage
on St/GT falls below VTSt.
ESt( Early steering output.) -Presents a logic high immediately when the digital
algorithm detects a recognizable tone pair (signal condition). Any momentary loss of
signal condition will cause ESt to return to a logic low.
St/GT (Steering input/guard time output (bidirectional)-. A voltage greater than VTSt
detected at St causes the device to register the detected tone pair and update the output
latch. A voltage less than VT St frees the device to accept a new tone pair. The GT
output acts to reset the external steering time constant, and its state is a function of
ESt and the voltage on St.
VDD -Positive power supply. (Normally connected to +5V.)
4.3.4 L293D DUAL H‐BRIDGE MOTOR DRIVER
Features
Separate Input-Logic Supply
Internal ESD Protection
Thermal Shutdown
High-Noise-Immunity Inputs
Functionally Similar to SGS L293 and SGS L293D
Output Current 1A per Channel (600mA for L293D)
Peak Output Current 2A per Channel (1.2A for L293D)
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Output Clamp Diodes for Inductive Transient Suppression (L293D)
Fig 4.13 L293d Dual H‐Bridge Motor Driver
L293D contains two inbuilt H-bridge driver circuits. In its common mode of
operation, two DC motors can be driven simultaneously, both in forward and reverse
direction. The motor operations of two motors can be controlled by input logic at pins
2 & 7 and 10 & 15. Input logic 00 or 11 will stop the corresponding motor. Logic 01
and 10 will rotate it in clockwise and anticlockwise directions, respectively.
Pin No Function Name
1 Enable pin for Motor 1; active high Enable 1,2
2 Input 1 for Motor 1 Input 1
3 Output 1 for Motor 1 Output 1
4 Ground (0V) Ground
5 Ground (0V) Ground
6 Output 2 for Motor 1 Output 2
7 Input 2 for Motor 1 Input 2
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8 Supply voltage for Motors; 9-12V (up to 36V) Vcc 2
9 Enable pin for Motor 2; active high Enable 3,4
10 Input 1 for Motor 1 Input 3
11 Output 1 for Motor 1 Output 3
12 Ground (0V) Ground
13 Ground (0V) Ground
14 Output 2 for Motor 1 Output 4
15 Input2 for Motor 1 Input 4
16 Supply voltage; 5V (up to 36V) Vcc 1
Table 4.1 Description of L293d Dual H‐Bridge Motor Driver
4.3.5 LM7805 VOLTAGE REGULATOR
FEATURES
Output current up to 1A
Fixed output voltage of 3.3V, 4.7V, 5V, 6V, 7V, 8V, 9V, 10V, 12V, 15V, 18V
and 24V available.
Thermal overload shutdown protection
Short circuit current limiting
Output transistor SOA protection
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Fig 4.14 LM7805 Voltage Regulator
DESCRIPTION
The 7805 is a VOLTAGE REGULATOR. It looks like a transistor but it is actually an
integrated circuit with 3 legs and it turns the input voltage into a nice, smooth 5 volts
DC. You need to feed it at least 8 volts and no more than 30 volts to do this. It can
handle around .5 to .75 amps, but it gets hot. Use a heat sink Use it to power circuits
than need to use or run off of 5 volts.
4.3.6 CRYSTAL OSCILLATOR
This application note addresses issues commonly raised during the selection of the
reference crystal, typically 14.318 MHz, for Chrontel's product line.
A simplified schematic of the oscillator circuit used in Chrontel products is shown in
Figure. Note that the typical 2-pin crystal has been replaced by its equivalent circuit
model.
Co is the pin-to-pin capacitance. Its value is associated with the crystal electrode
design and the crystal holder.
Rs is the motion resistance. The crystal manufacturer specifies its value.
Cs is the motion capacitance and Ls is the motion inductance, which are not specified,
and are functions of the crystal frequency.
Rbias is a feedback resistor, implemented on-chip in Chrontel products, which
provides DC bias to the inverting amplifier.
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C1 and C2 are total capacitance-to-ground at the input and output nodes of the
amplifier, respectively. If external capacitance is not added, the values of the internal
capacitance C1 and C2, including pin parasitic capacitance, are each approximately
15pF to 20pF.
Fig 4.15 Crystal Oscillator
Crystal Specifications
The reference frequencies for Chrontel's products are derived from an on-chip Pierce
oscillator with an external crystal. The oscillator has been designed to function
reliably with crystals that conform to the following specifications:
Fig 4.16 Crystal Specifications
4.3.7 LED (LIGHT EMITTING DIODE)
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Light emitting diodes (LEDs) are semiconductor light sources. The light emitted from
LEDs varies from visible to infrared and ultraviolet regions. They operate on low
voltage and power. LEDs are one of the most common electronic components and are
mostly used as indicators in circuits. They are also used for luminance and
optoelectronic applications.
Fig 4.17 LED
Based on semiconductor diode, LEDs emit photons when electrons recombine with
holes on forward biasing. The two terminals of LEDs are anode (+) and cathode (-)
and can be identified by their size. The longer leg is the positive terminal or anode
and shorter one is negative terminal.
The forward voltage of LED (1.7V-2.2V) is lower than the voltage supplied (5V) to
drive it in a circuit. Using an LED as such would burn it because a high current would
destroy its p-n gate. Therefore, a current limiting resistor is used in series with LED.
Without this resistor, either low input voltage (equal to forward voltage) or PWM
(pulse width modulation) is used to drive the LED.
4.3.8 RESISTORSMany resistors are so small that it would be difficult to print their value and
percentage tolerance on their body in digits. To overcome this, a coding system based
on bands of distinctive colors was developed to assist in identification. Learning this
color code. is not as necessary as it used to be (thanks to accurate, low cost digital
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multi meters!), but it’s not hard to learn and it’s quite useful knowledge anyway. The
first thing to know is that in each decade of resistance. i.e., from 10 - 100W, 100 -
1kW, 1k - 10kW, etc. There are only a finite number of different nominal values
allowed.
Most common resistors have values in the E12 series, which only has 12
allowed values per decade. Normalized these are 1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9,
4.7, 5.6, 6.8 and 8.2. Multiples of these values are simply repeated in each decade.
e.g., 10, 12, 15, 18 and so on. Note that the steps between these values are always
very close to 20%, because the E12 series dates from the days of resistors with ± 10%
tolerance. To allow greater accuracy in circuit design, modern 1% tolerance resistors
are made in a larger range of values: the E24 series, which has 12 additional allowed
values per decade as shown in the table. As before, these nominal values are simply
repeated in each decade.
The table at right shows both the E12 and E24 allowed values for comparison.
The next thing to know is that there are two different resistor color-coding systems in
use: one using four-color bands, and the other five. The 5-band system is generally
used for 2% and closer tolerance resistors, even though the 4-band system is quite
capable of handling any resistors with E12 or E24 values. Both systems use the same
band colors to represent the various digits; the main difference is that 5-band resistors
have an additional third band, which is usually BLACK to represent a third digit of
zero.
Here how both systems work in practice: 4-band resistors will usually have
values in the E12 series, while 5-band resistors can have any value in the E24 series?
This is worth remembering, because depending on the resistor’s body color, some of
the band colors may not be easy to distinguish. Blue (6) and grey (8) sometimes look
very similar, as do red (2), brown (1) and orange (3). So if you are in doubt, check the
apparent coded value against the allowed E12 or E24 values to see if its legal or check
with a digital multi meter, just to make sure.
Page | 28
Fig 4.18 Resistors
4.3.9 CAPACITORS
Virtually all of the capacitors stocked by Jaycar have their electrical values
printed directly on their body, in digits and letters. However, there is often still a
coding system, which can make it a bit tricky to work out the capacitance, voltage
rating, and tolerance and so on until you know how it works. This is explained below.
Incidentally, so-called green caps (which can actually be brown, dark red or even
blue!) are one type of metalized polyester film capacitor, like the MKT type, which
tends to be smaller, and in a more tightly controlled rectangular package. Similarly,
the monolithic type is a type of multilayer ceramic capacitor, designed to combine
high capacitance with very low self-inductance
Ceramic & Monolithic Capacitors
Page | 29
Most of these types have their nominal value either printed directly on them or
use the EIA coding system, which is a bit like resistor color coding, but in digits: the
first two digits followed by a multiplier showing the number of zeroes. With this
code, the value is generally given in pico-farads (pF), which you will need to divide
by either one million or one thousand (respectively) if you want the value in
microfarads (mF) or nano farads (nF).
Fig 4.19 Capacitors
4.3.10 DC GEAR MOTOR
Here slow speed dc motor with gearbox to reduce the speed of the platform.
This type of gear motor is getting from the second hand machine. Supply voltage of
this dc motor is 6 to 9 volt dc. As we vary the voltage speed is also vary. Current
consumption of dc motor is 200 mA. It is also possible to use a stepper motor. If we
use stepper motor then we require a high current supply.
Normal stepper motors require a minimum 1A power supply. Brushless DC
motors use a rotating permanent magnet in the rotor, and stationary electrical magnets
on the motor housing. A motor controller converts DC to AC. This design is simpler
than that of brushed motors because it eliminates the complication of transferring
power from outside the motor to the spinning rotor. Advantages of brushless motors
include long life span, little or no maintenance, and high efficiency. Disadvantages
include high initial cost, and more complicated motor speed controllers.
Page | 30
CHAPTER- 5
SOFTWARE IMPLEMENTATION
5.1 SIMULATION DIAGRAM
The simulated diagram of DTMF land rover as shown in figure below.
Fig 5.1 Simulation Diagram
Fig. 5.1 shows the block diagram of the microcontroller-based mobile phone operated
land rover. The important components of this rover are a DTMF decoder,
microcontroller and motor driver.
An MT8870 series DTMF decoder is used here. All types of the MT8870
series use digital counting techniques to detect and decode all the 16 DTMF tone pairs
into a 4-bit code output. The built-in dial tone rejection circuit eliminates the need for
pre-filtering. When the input signal given at pin 2 (IN-) in single-ended input
configuration is recognized to be effective, the correct4-bit decode signal of the
DTMF tone is transferred to Q1 (pin 11) through Q4 (pin 14) outputs.
Page | 32
Table II shows the DTMF data output table of MT8870. Q1 through Q4
outputs of the DTMF decoder (IC1) are connected to port pins PA0 through PA3 of
ATmega16 microcontroller (IC2) after inversion by N1 through N4, respectively. The
ATmega16 is a low-power, 8-bit, CMOS microcontroller based on the AVR enhanced
RISC architecture. It provides the following Features: 16kB of in-system
programmable Flash program memory with read-while-write capabilities, 512 bytes
of EEPROM, 1kB SRAM, 32 general-purpose input/output (I/O) lines and 32 general-
purpose working registers. All the 32 registers are directly connected to the arithmetic
logic unit, allowing two independent registers to be accessed in one single instruction
executed in one clock cycle. The resulting architecture is more code-efficient. Outputs
from port pins PD0 through PD3 and PD7 of the microcontroller are fed to inputs IN1
through IN4 and enable pins (EN1 and EN2) of motor driver L293D, respectively, to
drive two geared DC motors. Switch S1 is used for manual reset. The microcontroller
output is not sufficient to drive the DC motors, so current drivers are required for
motor rotation. The L293D is a quad, high current, half-H River designed to provide
bidirectional drive currents of up to 600 mA at voltages from 4.5V to36V. It makes it
easier to drive the DC motors. The L293D consists of four drivers. Pins IN1 through
IN4 and OUT1 through OUT4 are input and output pins, respectively, of driver 1
through driver 4. Drivers 1 and 2, and drivers 3 and 4 are enabled by enable pin 1
(EN1) and pin 9 (EN2), respectively. When enable input EN1 (pin 1) is high, drivers 1
and 2 are enabled and the outputs corresponding to their inputs are active.
5.2 HOW TO USE KEIL’s µVISION SOFTWARE
Fig 5.2: Keil iVision Logo
The Keil development tools for the 8051 offer numerous features and advantages that
help you quickly and successfully develop embedded applications. They are easy to
use and are guaranteed to help you achieve your design goals.
µVision2 IDE is Windows-based software development platforms that combines a
robust editor, project manager, and make facility. µVision2 supports all of the Keil
Page | 33
tools for the 8051 including the C compiler, macro assembler, linker/locator, and
object-HEX converter. µVision2 helps expedite the development process of your
embedded applications by providing the following:
Full-featured source code editor,
Device database for configuring the development tool setting,
Project manager for creating and maintaining your projects,
Integrated make facility for assembling, compiling, and linking your
embedded applications,
Dialogs for all development tool settings,
True integrated source-level Debugger with high-speed CPU and peripheral
simulator,
Advanced GDI interface for software debugging in the target hardware and for
connection to Monitor-51,
Links to development tools manuals, device datasheets & user’s guides.
STEPS TO ACCESS µVISION:
Double Click on the icon present on the desktop. The following window will be
popped-up.
Fig 5.3: Keil uVision Opening Window
Page | 34
Then click on “project” and select “new project”
Figure 5.4: Project Tab
You can create a new folder of your project name. Then type in the name of the
project.
Then select “New” from “File” menu and save the file as “file_name.c” i.e. save file
with “.c” extension.
Fig 5.5: Creating a New Project
Page | 35
Select the desired device for target by clicking on Flash as shown in figure below.
Fig 5.6: Selecting the target
Configure Device and select clock 11.0592MHZ by clicking on configure from flash
menu, as shown in the figure below,
Page | 36
Fig 5.7: Altering the frequency
Also move to the output tab and click the check box “Create HEX. File”, this is
important.
Fig 5.8: Checking “Create Hex File”
Press right click on the file editor menu and select “INSERT #include<REGF51.H>”,
this will put the required header file for the device that you have selected as target
previously.
Type the application code and don’t forget to include the .c file in the project by right
clicking on the source group and select “Add new file” and then browse for the file
and add it to the project. Then after compiling, hex file will be created and all you
have to do now is to burn it into controller using a bootloader.
5.3 PROGRAMING
#include <REGX52.H>
#define lcd P2
sbit rs = P0^6;
sbit e = P0^7;
Page | 37
sbit sel1 = P1^0;
sbit sel2 = P1^1;
sbit sel3 = P1^2;
sbit sel4 = P1^3;
sbit sel5 = P1^4;
sbit en1 = P1^5;
sbit in1 = P1^6;
sbit in2 = P1^7;
sbit en2 = P3^0;
sbit in3 = P3^1;
sbit in4 = P3^2;
unsigned char cmd[4]={0x38,0x01,0x06,0x0c};
unsigned char msg1[15]={'S','T','O','P',' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' '};
unsigned char msg2[15]={'M','O','V','I','N','G',' ','F','O','R','W','A','R','D',' '};
unsigned char msg3[15]={'M','O','V','I','N','G',' ','B','A','C','K','W','A','R','D'} ;
unsigned char msg4[15]={'M','O','V','I','N','G',' ','L','E','F','T',' ',' ',' ',' '};
unsigned char msg5[15]={'M','O','V','I','N','G',' ','R','I','G','H','T',' ',' ',' '} ;
unsigned char index;
unsigned int a;
void main(void)
{
for(index=0;index<=3;index++)
{
Page | 38
lcd=cmd[index];
rs=0; e=1;
for(a=0;a<5000;a++);
e=0;
}
en1=0; en2=0;
in1=0; in2=0;
in3=0; in4=0;
lcd=0x80;
rs=0; e=1;
for(a=0;a<5000;a++);
e=0;
for(index=0;index<=14;index++)
{
lcd=msg1[index];
rs=1; e=1;
for(a=0;a<5000;a++);
e=0;
}
while(1)
{
if(!sel4 && !sel3 && sel2 && !sel1)
{
Page | 39
en1=1; en2=1;
in1=1; in2=0;
in3=1; in4=0;
lcd=0x80;
rs=0; e=1;
for(a=0;a<5000;a++);
e=0;
for(index=0;index<=14;index++)
{
lcd=msg2[index];
rs=1; e=1;
for(a=0;a<5000;a++);
e=0;
}
}
if(sel4 && !sel3 && !sel2 && !sel1)
{
en1=1; en2=1;
in1=0; in2=1;
in3=0; in4=1;
lcd=0x80;
rs=0; e=1;
for(a=0;a<5000;a++);
Page | 40
e=0;
for(index=0;index<=14;index++)
{
lcd=msg3[index];
rs=1; e=1;
for(a=0;a<5000;a++);
e=0;
}
}
if(!sel4 && sel3 && sel2 && !sel1)
{
en1=1; en2=1;
in1=1; in2=0;
in3=0; in4=1;
lcd=0x80;
rs=0; e=1;
for(a=0;a<5000;a++);
e=0;
for(index=0;index<=14;index++)
{
lcd=msg5[index];
rs=1; e=1;
for(a=0;a<5000;a++);
Page | 41
e=0;
}
}
if(!sel4 && sel3 && !sel2 && !sel1)
{
en1=1; en2=1;
in1=0; in2=1;
in3=1; in4=0;
lcd=0x80;
rs=0; e=1;
for(a=0;a<5000;a++);
e=0;
for(index=0;index<=14;index++)
{
lcd=msg4[index];
rs=1; e=1;
for(a=0;a<5000;a++);
e=0;
}
}
if(!sel4 && sel3 && !sel2 && sel1)
{
en1=0; en2=0;
Page | 42
in1=0; in2=0;
in3=0; in4=0;
lcd=0x80;
rs=0; e=1;
for(a=0;a<5000;a++);
e=0;
for(index=0;index<=14;index++)
{
lcd=msg1[index];
rs=1; e=1;
for(a=0;a<5000;a++);
e=0;
}//for-loop ends here
}//if-statement ends here
}//while-loop ends here
}//main function ends here
5.4 SOFTWARE DESIGN
SOFTWARE USED: PROTEUS 7.7
ISIS & ARES Core Applications:
Fully integrated Shape Based Auto-Router replaces the previous, grid based router.
Users of PCB Design at Level 2 and above can drive the router interactively with the
ability to route selected nets. All uses can run a pre-configured routing schedule
automatically. Per net 'strategies' are replaced by 'net 'classes', and the management of
Page | 43
these is incorporated into the Design Rule Manager. Improved for device
replacement in ISIS.
Proteus VSM Additions: Added syntax highlighting for EASYHDL scriptable
generators. Interactive configuration of the trace diagnostics that is you can enable or
disable particular diagnostics whilst the simulation is running.
Page | 44
CHAPTER 6
PCB CONSTRUCTION
Layout of desired circuit diagram and preparation is first and most important
operation in any printed circuit board manufacturing process. First layout of
component side is to be made in accordance with available component dimensions.
The following points are to be observed while forming the layout of PCB.
Between two components, sufficient space should be maintained.
High wattage/max. Dissipated components should be mounted at a sufficient
distance from semiconductor and electrolytic capacitors.
The single sided PCB is used for general-purpose application where the cost is
to be low and the layout is simple.
6.1 PCB Layout for the project
Fig 6.1 PCB Layout of the project
Page | 45
6.2 THE MAKING OF A PCB
A PCB is nothing but an epoxy or phenolic board that contains all connections of a
circuit in the form of copper tracks. What an average beginner needs is a simple and
low cost way of making and fabricating PCB’s. There are two methods of making
PCB’s: -
(a) Photographic exposure method
(b) Etch resistant applicative method
The first method needs many costly apparatus along with a darkroom, equipped with
moving platforms and several costly chemicals and is rather cumbersome. The
second, on the other hand, is easy to follow and cost-effective and can be used when
the requirement are not very large say one to a few pieces at a time. Therefore, we
give brief guidelines that will enable you to develop high quality PCB’s at low cost,
using the second method.
The few things that are needed in making PCB’s are listed below:
Enamel Paint: The normal black paint used on you doors and windows. PCB
transfers can well be used instead.
A set of thin brushes: The type used for water and oil paintings and are available
from most pen shops. These are not needed if transfers are used.
Petrol or spirit: Used for cleaning and removing paint.
Ferric Chloride (Fecl2): This brownish powder is available from most chemists and
chemical stores in packing of 500 grams each at cost of about Rs. 30.
Tools of cutting, filing and drilling: A hacksaw, a file and a cheap hand drill with a
few types of bits. Buy the bits in this order:-
1 mm for IC’s
3 mm for screws
1.5 mm for diodes and power transistors
8 mm for switches and pots
5 mm for larger screws and heatsinks
Page | 46
Transferring the pattern
Two types of PC board laminates are in common use nowadays. These are: -
Phenolic board
Glass epoxy board
For general use, the phenolic board, which is much cheaper that the glass epoxy
board, may be used.
The copper side if the PCB should be thoroughly cleaned with the help of alcoholic
spirit or petrol, and must be made completely free from dust and other contaminants,
commercially available sprays may be used for this purpose.
The pattern must be carbon copied onto the laminate with the help of a sharp ballpoint
pen and a carbon paper. The position of holes should be marked with care.
The complete pattern may now be made etch-resistant with the help of an enamel
paint ad thin brush. Ordinary nail enamel may be used for quick jobs. The board
should be dried for at least six hours before developing.
The entire pattern can be further simplified by using dry pattern transfers. In this case
the appropriate patters may simply be scratched onto the PCB and no drying is
required. The available varieties are shown in fig ()
In this step, all excessive is removed from the board, and the printed pattern is left
behind. About 100 ml of tap water should be heated to 850C and 30-50 grams of
ferric chloride (Fecl2) added to it. The mixture should be thoroughly stirred, and a
few drops of hydrochloric acid (HCL) may be added optionally to speed up the
process.
The board, with its copper side facing upwards, should be placed in a flat-bottomed
plastic tray and the aqueous solution of EeCl2 poured in. The etching process would
take 25-60 minutes to complete, depending upon the size of the PCB. After etching,
the board should be clearly visible. If not, allow it to stand in the solution for some
more time. The paint should be removed with the help of alcohol or petrol. The
etching solution may be preserved for later use until its color turns green.
After the etching is complete, holes of suitable diameter should be drilled using a
power or had drill, 1 mm bit should be used for IC holes, 1.25 mm for resistors and
Page | 47
capacitors, 1.5 mm for diodes, 3 mm or 5 mm for mountings nuts, and 8 mm for
potentiometers, switches and neons.
Now the PCB should be scrubbed clean until a shiny finish is obtained. The PCB may
be tin-plated using an ordinary 35-watt soldering rod along with solder core. The
position of the components should be marked on the reverse side of the PCB using
any marker. If the copper is not tinned, then it should be given a coat of varnish in
order to prevent oxidation.
The PCB is now ready.
6.3 SOLDERING
Soldering is the process of joining two metallic conductors, the joint where the two
metallic conductors are to be joined or fused is heated with a device called soldering
iron and then an alloy of tin and lead called solder is applied which melts and cover
the joint. The solder cools and solidifies quickly to ensure a good and durable
connection between the joined metals. Covering the joint with solder prevents
oxidation. Just as badly tailored clothes can give way at an unexpected moment, in the
same way the life and reliability of any and all circuits lies in your hands, which wield
this magical rod. Good soldering is a major step towards successful circuit building
and…This is an art, which, once mastered, is rarely forgotten.
Soldering is more of an art than a technique, often, due to the fear of destroying costly
semiconductors or IC’s, constructor opts for a costly IC socket, which increases the
overall circuit cost tremendously.
A dry or shoddy solder joint is often the cause of the failure of a complete system.
Keeping the tips given here in mind, even a layman should be able to construct a
circuit perfectly, without harming the most delicate semi-conductor devices.
6.3.1 Perfect Soldering
Certain conditions are necessary for perfect soldering. These are -
Clean Surfaces: The two surfaces to be soldered must be soldered must be free from
dust particles, grease, oil, etc. If a PCB is used, it must be cleaned thoroughly with
petrol.
Page | 48
A Clean Bit: The tip of the soldering iron must be shining clean and smooth. An
unclean tip may cause loose joints. The tip should be cleaned with a file and tinned
occasionally.
Operating tip temperature: The soldering of tip operates at the specified
temperature or it will lead to dry and unstable joints, whereas temperatures exceeding
the specified value can lead to over heating and eventually the destruction of the
device. For stabilizing the temperature of the tip of the soldering iron, a power
controller may be utilized.
Warm Component Leads: If the leads of the components are cold, the solder cannot
flow properly, and this may lead to loose and unstable solder joints. Thus, component
leads must be warmed sufficiently so that the solder can flow easily. However,
extreme care should be taken while warming the leads of the heat-sensitive semi-
conductors like IC’s. A hot air blower or a soldering iron may be used for warming up
the component leads.
Proper soldering alloy (core): Soldering core is basically an alloy of tin and lead.
The two soldering alloys most commonly used contain tin and lead in a ratio if 60/40
and 40/60, respectively. These two soldering alloys have low melting points and are
sufficient for most electronic work. The core containing 40 percent tin and 60 percent
lead should be used for the soldering of electronic devices that tend to dissipate heat.
The soldering core containing 60 percent tin and 40 percent lead should be used for
general work such as that of low power transistors or IC’s on PCB’s.
Soldering Procedure: A perfect solder joint can be obtained by following this
procedure. Clean the two surfaces to be soldered thoroughly. Remove all dust
particles, stains of grease or chemicals etc. Apply small amount of flux on the
surfaces to be soldered. Heat up the component/surface to be soldered slightly, and
apply the soldering core directly onto the component and not to the tip of the
soldering iron. The flux should remain liquid as long as the joint is being made.
The joint should give shiny bead-like appearance. If not, apply a little more
flux/solder and heat the joint. Now extra lengths of components leads may be cut off.
Fig shows the correct way of soldering. The commercial grade soldering cores dot not
usually melt at temperatures below1800C. So, while soldering the components whose
Page | 49
lead soldering temperature as specified by the manufacturer, is below the temperature
of the soldering core, the soldering may be reduced correspondingly. Soldering of the
IC’s should always be carried out insteps of two to four pins at a time. This reduces
the chances of the destruction of an IC due to overheating, while soldering.
Care for them: Besides lead soldering temperatures, some general precautions
should be kept in mind while soldering a device to prevent any kind of damage. While
soldering IC’s, it is advisable to keep the lead lengths maximum possible (at least 2.5
mm). A small heat sink made of 1 mm aluminium may be fixed temporarily over the
IC pins while soldering to help in dissipating excessive heat. The general precautions
given below must be observed while soldering various electronic components.
Resistors: While soldering resistors, the lead soldering temperatures may go as high
as 3000C. The soldering time should be kept less than 15 seconds. However, while
soldering light dependent resistors, the temperatures should not exceed 2500C.
Soldering core of 60/40 type should be used for soldering low wattage resistors and
40/60 type soldering core should be used for high wattage resistors, or resistors which
tend to dissipate heat during operation.
Capacitors: While soldering electrolytic capacitors, it is advisable to keep the lead
soldering temperature below 2250 C, soldering time being 5 seconds. While soldering
low voltage ceramic capacitors, the soldering temperatures should not exceed 2000C
and soldering time should be kept even less than 5 seconds.
Diodes: While soldering general-purpose silicon/selenium diodes, the lead
temperatures should not exceed 3000c, soldering time being 5 seconds. While
soldering germanium diodes the lead soldering temperature should be kept below
2200C. While soldering LED’s the soldering temperature should be kept below
2000C. The soldering time being 10 seconds. While soldering a diode on a PCB,
length of lead from the PCB surface should be kept at least 2.5 mm in order to prevent
damage to the device.
Power Transistors: They are sturdy devices, which cannot be easily damaged by the
heat generated during soldering. Power transistors in TO-3 package like 2N 3055 and
2N6253 may be soldered at temperatures as high as 2750 C. The 40/60-type core may
be used for this purpose. While soldering transistors in TO-1 and T0-39 packages like
Page | 50
AC188 and SL100 respectively, soldering temperatures should be kept below 2550C.
For soldering transistors in TO-200 package, soldering temperatures should be kept
around 2500C. A small heat sink may be attached temporarily to the tub of the
transistor, in order to prevent overheating.
Low Power Transistors: While soldering transistors in plastic package (BC545,
BC548 etc), TO-18 package (BC179, BC178 etc.), TO-91 package, the lead soldering
temperature should be kept between 150-2000C . The lead length, while soldering on
a PCB, should be kept at least 3mm. Heat sink may be attached to the metallic case of
the device to prevent overheating. A crocodile clip can also be used for this purpose.
The 60/40 type-soldering core may be used.
General-Purpose (Linear) ICs: The lead soldering temperatures of most linear ICs
as specified by majority of manufacturers is 3300C, the soldering time 10 seconds.
But in practice the lead soldering temperatures of such IC’s should be limited to about
2400C, the soldering time 10 seconds. While soldering the ICs having SII type pin
configuration, small heatsink may be attached to its tab to help in dissipating heat
generated during soldering. The 60/40 type of soldering core should be used for
soldering of ICs.
54/70 Series TTL ICs: These ICs are very sensitive to heat, so lead soldering
temperature should be kept around 1750C, soldering time being 10 seconds.
CMOS ICs: The lead soldering temperature of most of the CMOS ICs like 4001,
4027 etc, as specified by most manufacturers is 2650C, the soldering time being 10
seconds. But practically, the lead soldering temperature should be limited to about
220-2400C. Most of CMOS ICs can be damaged easily by electrostatic discharges so,
as a precaution all the pins of the IC must be short circuited with the help of a metallic
foil, until soldering is complete. The tip of the soldering iron used must be grounded.
However, it is not advisable to solder memory ICs like 2716 and 2764,
microprocessors and the other LSI chips.
6.4 EQUIPMENTS REQUIRED
The various tools and equipment required for construction of a PCB are given below -
Solder kit consist of:
Page | 51
Soldering iron.
Soldering wire.
Flux.
Combination pliers.
Tweezers
Long nose pliers
Pen knife
Brushes.
Screw drivers.
Small files.
Cutter
Clipper
Breadboard.
Multi-meter (Measuring instrument.)
6.5 PRECAUTIONS FOR PRACTICAL
The quantity of soldering of component on PCB should be good quantity.
The component fitted on the PCB should loosely fit.
Do not touch the PCB layer with hands and for fitting component use long
nose liers only.
Use 25 w pencil bit soldering iron only.
Use ferric chloride safely.
Add ferric chloride to the water, not water to the ferric chloride.
Page | 52
CHAPTER- 7
RESULT & CONCLUSION
7.1 RESULT
The project “DTMF Based DC Fan Controller” works as expected. For instance if we
call on the mobile attached with the project and dial various keys, we can see the
response in the LCD and the DC Fans run accordingly. The result thus obtained was
the objective of the project entitled “DTMF Based DC Fan Controller”.
7.2 CONCLUSION
In this project, the DC Fan is controlled by a mobile phone that makes a call to the
mobile phone attached to the project. In the course of a call, if any button is pressed, a
tone corresponding to the button pressed is heard at the other end of the call. This tone
is called DTMF(dual-tone-multiple-frequency).The STMF Based Fan Controller
perceives this DTMF tone with the help of the phone stacked in the robot.
The (AT89S52) microcontroller with the help of DTMF decoder MT8870 processes
the received tone. The decoder decodes the DTMF tone into its equivalent binary digit
and this binary number is sent to the microcontroller. The microcontroller is
programmed to take a decision for any given input and outputs its decision to motor
drivers in order to drive the motors in forward direction or backward direction or turn.
The mobile phone that makes a call to mobile phone stacked in the project act as a
remote. Therefore, this robotic project does not require the construction of receiver
and transmitter units
Page | 53
CHAPTER - 8
FUTURE SCOPE & LIMITATIONS
8.1 FUTURE SCOPE
1. Cell Phone Controlled Robot
The DTMF Based DC Fan Controller can be turned into a cell phone controller robot,
by replacing the fans with motors that can control the movements of a robot. ULN
2003 Current Driver IC can be used to generate enough current for those motors.
2. IR Sensors:
IR sensors can be used to automatically detect & avoid obstacles if the robot goes
beyond line of sight. This avoids damage to the vehicle if we are maneuvering it from
a distant place.
3. Password Protection:
Project can be modified in order to password protect the robot so that it can be
operated only if correct password is entered. Either cell phone should be password
protected or necessary modification should be made in the assembly language code.
This introduces conditioned access &increases security to a great extent.
4. Alarm Phone Dialer:
By replacing DTMF Decoder IC CM8870 by a 'DTMF Transceiver IC’ CM8880,
DTMF tones can be generated from the robot. So, a project called 'Alarm Phone
Dialer' can be built which will generate necessary alarms for something that is desired
to be monitored (usually by triggering a relay). For example, a high water alarm, low
temperature alarm, opening of back window, garage door, etc. When the system is
activated it will call a number of programmed numbers to let the user know the alarm
has been activated. This would be great to get alerts of alarm conditions from home
when user is at work.
5. Adding a camera
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If the current project is interfaced with a camera (e.g. a Webcam), robot can be driven
beyond line-of-sight &range becomes practically unlimited as GSM networks have a
very large range.
8.2 LIMITATIONS
Cell phone bill.
Mobile batteries drain out early so charging problem.
Cost of project if Cell phone cost included.
Not flexible with all cell phones as only a particular cell phone whose earpiece
is attached can only be used.
Jamming of system is also a limitation.
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REFRENCES
Schenker, L (1960), "Pushbutton Calling with a Two- Group Voice -Frequency
Code", The Bell system technical journal 39(1): 235–255, ISSN 0005-8580.
“DTMF Tester”, ‘Electronics For You’ Magazine, Edition (June 2003)
http://www.alldatasheet.com/
http://www.datasheet4u.com/
http://www.datasheetcatalog.com/
http://www.8051projects.info/
http://www.instructables.com/
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BIBLIOGRAPHY
BOOKS
The 8051 microcontroller by James W. Stewart, Kai X. Miao
The 8051 microcontroller and embedded system by Muhammad Ali Mazidi,
Janice Gillespie Mazidi.
Embedded Microprocessor Systems by Stuart R. Ball.
The 8051 Microcontroller Architecture, Programming, and Applications By
Ayala.
Electronics for you Magazine.
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APPENDIX – A
AT89S52 DATASHEET
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APPENDIX – B
MT8870 DATASHEET
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APPENDIX – C
L293D DATASHEET
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