IR and Metal senosors Based Product Sorting.docx

CONTENTS
TOPIC
ABSTRACT
LIST OF FIGURES
1. INTRODUCTION
1.1 Introduction of the project
1.2 Objective of Project
2. EMBEDDED SYSTEMS
2.1. Introduction
2.2 Need of Embedded systems
2.3 Explanation of Embedded systems
3. HARDWARE DESCRIPTION
3.1. Regulated Power Supply
3.2 Microcontroller
3.3 DC Motor
3.4 IR sensor

3.5 Mental sensor
3.6 Conveyor belt
3.7 Four bar link mechnism
4. SOFTWARE DESCRIPTION
5. Tools
6. Advantages
7. Applications
8. Conclusion
9. Referance

CHAPTER 1
INTRODUCTION
1.1 ABSTRACT
Now a day’s industrial area requires demand for automation.Due
to automation human efforts are goes on decreasing since last
decade. The object sorting based on colour is difficult task in
recent days.In industry there is rapidly increasing demands for
automation.The Sorting of objects based on colour is very
difficult task. This project gives us an idea about automatic colour
sorting. Here we are designing and implementing an efficient
colour sorting using colour sensor TCS3200 based on Arduino
UNO. This project gives high accuracy and performance. Easy to
operate and construct which reduces human errors. Existing
sorting method uses a set of inductive, capacitive and optical
sensors do differentiate object colour.

CHAPTER 2
EMBEDDED SYSTEM
An embedded system can be defined as a computing device
that does a specific focused job. Appliances such as the air-
conditioner, VCD player, DVD player, printer, fax machine,
mobile phone etc. are examples of embedded systems. Each of
these appliances will have a processor and special hardware to
meet the specific requirement of the application along with the
embedded software that is executed by the processor for meeting
that specific requirement. The embedded software is also called
“firm ware”. The desktop/laptop computer is a general purpose
computer. You can use it for a variety of applications such as
playing games, word processing, accounting, software
development and so on. In contrast, the software in the embedded
systems is always fixed listed below:
· Embedded systems do a very specific task, they cannot be
programmed to do different things. . Embedded systems have
very limited resources, particularly the memory. Generally, they
do not have secondary storage devices such as the CDROM or the
floppy disk. Embedded systems have to work against some

deadlines. A specific job has to be completed within a specific
time. In some embedded systems, called real-time systems, the
deadlines are stringent. Missing a deadline may cause a
catastrophe-loss of life or damage to property. Embedded systems
are constrained for power. As many embedded systems operate
through a battery, the power consumption has to be very low.
· Some embedded systems have to operate in extreme
environmental conditions such as very high temperatures and
humidity.
Application Areas
Nearly 99 per cent of the processors manufactured end up in
embedded systems. The embedded system market is one of the
highest growth areas as these systems are used in very market
segment- consumer electronics, office automation, industrial
automation, biomedical engineering, wireless communication,
data communication, telecommunications, transportation,
military and so on.
Consumer appliances:

At home we use a number of embedded systems which include
digital camera, digital diary, DVD player, electronic toys,
microwave oven, remote controls for TV and air-conditioner,
VCO player, video game consoles, video recorders etc. Today’s
high-tech car has about 20 embedded systems for transmission
control, engine spark control, air-conditioning, navigation etc.
Even wristwatches are now becoming embedded systems. The
palmtops are powerful embedded systems using which we can
carry out many general-purpose tasks such as playing games and
word processing.
Office Automation:
The office automation products using embedded systems are
copying machine, fax machine, key telephone, modem, printer,
scanner etc.
Industrial Automation:
Today a lot of industries use embedded systems for process
control. These include pharmaceutical, cement, sugar, oil
exploration, nuclear energy, electricity generation and
transmission. The embedded systems for industrial use are
designed to carry out specific tasks such as monitoring the

temperature, pressure, humidity, voltage, current etc., and then
take appropriate action based on the monitored levels to control
other devices or to send information to a centralized monitoring
station. In hazardous industrial environment, where human
presence has to be avoided, robots are used, which are
programmed to do specific jobs. The robots are now becoming
very powerful and carry out many interesting and complicated
tasks such as hardware assembly.
Medical Electronics:
Almost every medical equipment in the hospital is an embedded
system. These equipments include diagnostic aids such as ECG,
EEG, blood pressure measuring devices, X-ray scanners;
equipment used in blood analysis, radiation, colonoscopy,
endoscopy etc. Developments in medical electronics have paved
way for more accurate diagnosis of diseases.
Computer Networking:
Computer networking products such as bridges, routers,
Integrated Services Digital Networks (ISDN), Asynchronous
Transfer Mode (ATM), X.25 and frame relay switches are
embedded systems which implement the necessary data

communication protocols. For example, a router interconnects
two networks. The two networks may be running different
protocol stacks. The router’s function is to obtain the data packets
from incoming pores, analyze the packets and send them towards
the destination after doing necessary protocol conversion. Most
networking equipments, other than the end systems (desktop
computers) we use to access the networks, are embedded systems.
Telecommunications:
In the field of telecommunications, the embedded systems can be
categorized as subscriber terminals and network equipment. The
subscriber terminals such as key telephones, ISDN phones,
terminal adapters, web cameras are embedded systems. The
network equipment includes multiplexers, multiple access
systems, Packet Assemblers Dissemblers (PADs), sate11ite
modems etc. IP phone, IP gateway, IP gatekeeper etc. are the
latest embedded systems that provide very low-cost voice
communication over the Internet.
Wireless Technologies:
Advances in mobile communications are paving way for many
interesting applications using embedded systems. The mobile

phone is one of the marvels of the last decade of the 20’h century.
It is a very powerful embedded system that provides voice
communication while we are on the move. The Personal Digital
Assistants and the palmtops can now be used to access
multimedia service over the Internet. Mobile communication
infrastructure such as base station controllers, mobile switching
centers are also powerful embedded systems.
Insemination:
Testing and measurement are the fundamental requirements in all
scientific and engineering activities. The measuring equipment
we use in laboratories to measure parameters such as weight,
temperature, pressure, humidity, voltage, current etc. are all
embedded systems. Test equipment such as oscilloscope,
spectrum analyzer, logic analyzer, protocol analyzer, radio
communication test set etc. are embedded systems built around
powerful processors. Thank to miniaturization, the test and
measuring equipment are now becoming portable facilitating
easy testing and measurement in the field by field-personnel.
Security:

Security of persons and information has always been a major
issue. We need to protect our homes and offices; and also the
information we transmit and store. Developing embedded
systems for security applications is one of the most lucrative
businesses nowadays. Security devices at homes, offices, airports
etc. for authentication and verification are embedded systems.
Encryption devices are nearly 99 per cent of the processors that
are manufactured end up in~ embedded systems. Embedded
systems find applications in every industrial segment- consumer
electronics, transportation, avionics, biomedical engineering,
manufacturing, process control and industrial automation, data
communication, telecommunication, defense, security etc. Used
to encrypt the data/voice being transmitted on communication
links such as telephone lines. Biometric systems using fingerprint
and face recognition are now being extensively used for user
authentication in banking applications as well as for access
control in high security buildings.
Finance:
Financial dealing through cash and cheques are now slowly
paving way for transactions using smart cards and ATM
(Automatic Teller Machine, also expanded as Any Time Money)

machines. Smart card, of the size of a credit card, has a small
micro-controller and memory; and it interacts with the smart card
reader! ATM machine and acts as an electronic wallet. Smart card
technology has the capability of ushering in a cashless society.
Well, the list goes on. It is no exaggeration to say that eyes
wherever you go, you can see, or at least feel, the work of an
embedded system.
Overview of Embedded System Architecture

Every embedded system consists of custom-built hardware built
around a Central Processing Unit (CPU). This hardware also
contains memory chips onto which the software is loaded. The
software residing on the memory chip is also called the
‘firmware’. The embedded system architecture can be represented
as a layered architecture as shown in Fig. The operating system
runs above the hardware, and the application software runs above
the operating system. The same architecture is applicable to any
computer including a desktop computer. However, there are
significant differences. It is not compulsory to have an operating
system in every embedded system. For small appliances such as
remote control units, air conditioners, toys etc., there is no need

for an operating system and you can write only the software
specific to that application. For applications involving complex
processing, it is advisable to have an operating system. In such a
case, you need to integrate the application software with the
operating system and then transfer the entire software on to the
memory chip. Once the software is transferred to the memory
chip, the software will continue to run for a long time you don’t
need to reload new software.
Now, let us see the details of the various building blocks of the
hardware of an embedded system. As shown in Fig. the building
blocks are;
· Central Processing Unit (CPU)
· Memory (Read-only Memory and Random Access Memory)
· Input Devices
· Output devices
· Communication interfaces

· Application-specific circuitry
Central Processing Unit (CPU):
The Central Processing Unit (processor, in short) can be any of
the following: microcontroller, microprocessor or Digital Signal
Processor (DSP). A micro-controller is a low-cost processor. Its
main attraction is that on the chip itself, there will be many other
components such as memory, serial communication interface,
analog-to digital converter etc. So, for small applications, a
micro-controller is the best choice as the number of external
components required will be very less. On the other hand,
microprocessors are more powerful, but you need to use many
external components with them. D5P is used mainly for

applications in which signal processing is involved such as audio
and video processing.
Memory:
The memory is categorized as Random Access 11emory (RAM)
and Read Only Memory (ROM). The contents of the RAM will
be erased if power is switched off to the chip, whereas ROM
retains the contents even if the power is switched off. So, the
firmware is stored in the ROM. When power is switched on, the
processor reads the ROM; the program is program is executed.
Input Devices:
Unlike the desktops, the input devices to an embedded system
have very limited capability. There will be no keyboard or a
mouse, and hence interacting with the embedded system is no
easy task. Many embedded systems will have a small keypad-you
press one key to give a specific command. A keypad may be used
to input only the digits. Many embedded systems used in process
control do not have any input device for user interaction; they take
inputs from sensors or transducers 1’fnd produce electrical signals
that are in turn fed to other systems.

Output Devices:
The output devices of the embedded systems also have very
limited capability. Some embedded systems will have a few Light
Emitting Diodes (LEDs) to indicate the health status of the system
modules, or for visual indication of alarms. A small Liquid
Crystal Display (LCD) may also be used to display some
important parameters.
Communication Interfaces:
The embedded systems may need to, interact with other
embedded systems at they may have to transmit data to a desktop.
To facilitate this, the embedded systems are provided with one or
a few communication interfaces such as RS232, RS422, RS485,
Universal Serial Bus (USB), IEEE 1394, Ethernet etc.
Application-Specific Circuitry:
Sensors, transducers, special processing and control circuitry may
be required fat an embedded system, depending on its application.
This circuitry interacts with the processor to carry out the
necessary work. The entire hardware has to be given power
supply either through the 230 volts main supply or through a

battery. The hardware has to design in such a way that the power
consumption is minimized.

CHAPTER 3
HARDWARE DESCRIPTION
MODULES
1. POWER SUPPLY
The power supply section is the section which provide
+5V for the components to work. IC LM7805 is used for
providing a constant power of +5V.
The ac voltage, typically 220V, is connected to a transformer,
which steps down that ac voltage down to the level of the desired
dc output. A diode rectifier then provides a full-wave rectified
voltage that is initially filtered by a simple capacitor filter to
produce a dc voltage. This resulting dc voltage usually has some
ripple or ac voltage variation.
A regulator circuit removes the ripples and also retains the same
dc value even if the input dc voltage varies, or the load connected
to the output dc voltage changes. This voltage regulation is
usually obtained using one of the popular voltage regulator IC
units.

Block Diagram Of Power Supply
Transformer
Transformers convert AC electricity from one voltage to
another with little loss of power. Transformers work only with
AC and this is one of the reasons why mains electricity is AC.
Step-up transformers increase voltage, step-down transformers
reduce voltage. Most power supplies use a step-down transformer
to reduce the dangerously high mains voltage (230V in India) to
a safer low voltage.
The input coil is called the primary and the output coil is called
the secondary. There is no electrical connection between the two
coils; instead they are linked by an alternating magnetic field
created in the soft-iron core of the transformer. Transformers
waste very little power so the power out is (almost) equal to the

power in. Note that as voltage is stepped down current is stepped
up.
The transformer will step down the power supply voltage (0-
230V) to (0- 6V) level. Then the secondary of the potential
transformer will be connected to the bridge rectifier, which is
constructed with the help of PN junction diodes. The advantages
of using bridge rectifier are it will give peak voltage output as DC.
Rectifier
There are several ways of connecting diodes to make a
rectifier to convert AC to DC. The bridge rectifier is the most
important and it produces full-wave varying DC. A full-wave
rectifier can also be made from just two diodes if a centre-tap
transformer is used, but this method is rarely used now that diodes
are cheaper. A single diode can be used as a rectifier but it only
uses the positive (+) parts of the AC wave to produce half-wave
varying DC
Bridge Rectifier

When four diodes are connected as shown in figure, the
circuit is called as bridge rectifier. The input to the circuit is
applied to the diagonally opposite corners of the network, and the
output is taken from the remaining two corners. Let us assume
that the transformer is working properly and there is a positive
potential, at point A and a negative potential at point B. the
positive potential at point A will forward bias D3 and reverse
bias D4.
Bridge Rectifier
The negative potential at point B will forward bias D1 and reverse
D2. At this time D3 and D1 are forward biased and will allow
current flow to pass through them; D4 and D2 are reverse biased
and will block current flow.

One advantage of a bridge rectifier over a conventional full-wave
rectifier is that with a given transformer the bridge rectifier
produces a voltage output that is nearly twice that of the
conventional full-wave circuit.
i. The main advantage of this bridge circuit is that it does not
require a special centre tapped transformer, thereby reducing its
size and cost.
ii. The single secondary winding is connected to one side of the
diode bridge network and the load to the other side as shown
below.
iii. The result is still a pulsating direct current but with double the
frequency.
Output Waveform Of DC
Smoothing

Smoothing is performed by a large value electrolytic
capacitor connected across the DC supply to act as a reservoir,
supplying current to the output when the varying DC voltage from
the rectifier is falling. The capacitor charges quickly near the peak
of the varying DC, and then discharges as it supplies current to
the output.
Voltage Regulators
Voltage regulators comprise a class of widely used ICs. Regulator
IC units contain the circuitry for reference source, comparator
amplifier, control device, and overload protection all in a single
IC. IC units provide regulation of either a fixed positive voltage,
a fixed negative voltage, or an adjustably set voltage. The
regulators can be selected for operation with load currents from
hundreds of milli amperes to tens of amperes, corresponding to
power ratings from milli watts to
tens of watts.
A fixed three-terminal voltage regulator has an unregulated dc
input voltage, Vi, applied to one input terminal, a regulated dc

output voltage, Vo, from a second terminal, with the third
terminal connected to ground.
The series 78 regulators provide fixed positive regulated voltages
from 5 to 24 volts. Similarly, the series 79 regulators provide
fixed negative regulated voltages from 5 to 24 volts. Voltage
regulator ICs are available with fixed (typically 5, 12 and 15V) or
variable output voltages. They are also rated by the maximum
current they can pass. Negative voltage regulators are available,
mainly for use in dual supplies. Most regulators include some
automatic protection from excessive current ('overload
protection') and overheating ('thermal protection').
Many of the fixed voltage regulator ICs has 3 leads and look like
power transistors, such as the 7805 +5V 1Amp regulator. They
include a hole for attaching a heat sink if necessary.
Regulator

Circuit Diagram Of Power Supply

2. ATMEGA328:
Features
• High Performance, Low Power AVR® 8-Bit Microcontroller
• Advanced RISC Architecture
– 131 Powerful Instructions – Most Single Clock Cycle Execution
– 32 x 8 General Purpose Working Registers
– Fully Static Operation
– Up to 20 MIPS Throughput at 20 MHz
– On-chip 2-cycle Multiplier
• High Endurance Non-volatile Memory Segments
– 4/8/16/32K Bytes of In-System Self-Programmable Flash
progam memory
(ATmega48PA/88PA/168PA/328P)
– 256/512/512/1K Bytes EEPROM

– 512/1K/1K/2K Bytes Internal SRAM
– Write/Erase Cycles: 10,000 Flash/100,000 EEPROM
– Data retention: 20 years at 85°C/100 years at 25°C(1)
– Optional Boot Code Section with Independent Lock Bits
In-System Programming by On-chip Boot Program
True Read-While-Write Operation
– Programming Lock for Software Security
• Peripheral Features
– Two 8-bit Timer/Counters with Separate Prescaler and
Compare Mode
– One 16-bit Timer/Counter with Separate Prescaler, Compare
Mode, and Capture
Mode
– Real Time Counter with Separate Oscillator
– Six PWM Channels
– 8-channel 10-bit ADC in TQFP and QFN/MLF package

Temperature Measurement
– 6-channel 10-bit ADC in PDIP Package
Temperature Measurement
– Programmable Serial USART
– Master/Slave SPI Serial Interface
– Byte-oriented 2-wire Serial Interface (Philips I2C compatible)
– Programmable Watchdog Timer with Separate On-chip
Oscillator
– On-chip Analog Comparator
– Interrupt and Wake-up on Pin Change
• Special Microcontroller Features
– Power-on Reset and Programmable Brown-out Detection
– Internal Calibrated Oscillator
– External and Internal Interrupt Sources
– Six Sleep Modes: Idle, ADC Noise Reduction, Power-save,
Power-down, Standby,

and Extended Standby
• I/O and Packages
– 23 Programmable I/O Lines
– 28-pin PDIP, 32-lead TQFP, 28-pad QFN/MLF and 32-pad
QFN/MLF
• Operating Voltage:
– 1.8 - 5.5V for ATmega48PA/88PA/168PA/328P
• Temperature Range:
– -40°C to 85°C
• Speed Grade:
– 0 - 20 MHz @ 1.8 - 5.5V
• Low Power Consumption at 1 MHz, 1.8V, 25°C for
ATmega48PA/88PA/168PA/328P:
– Active Mode: 0.2 mA
– Power-down Mode: 0.1 μA
– Power-save Mode: 0.75 μA (Including 32 kHz RTC)

1.1.1 VCC Digital supply voltage.
1.1.2 GND Ground.
1.1.3 Port B (PB7:0) XTAL1/XTAL2/TOSC1/TOSC2
Port B is an 8-bit bi-directional I/O port with internal pull-up
resistors (selected for each it). The Port B output buffers have
symmetrical drive characteristics with both high sink and source
capability. As inputs, Port B pins that are externally pulled low
will source current if the pull-up resistors are activated. The Port
B pins are tri-stated when a reset condition becomes active, even
if the clock is not running. Depending on the clock selection fuse
settings, PB6 can be used as input to the inverting Oscillator
amplifier and input to the internal clock operating circuit.
Depending on the clock selection fuse settings, PB7 can be used
as output from the inverting Oscillator amplifier.
If the Internal Calibrated RC Oscillator is used as chip clock
source, PB7..6 is used as TOSC2..1 input for the Asynchronous
Timer/Counter2 if the AS2 bit in ASSR is set. The various special
features of Port B are elaborated in ”Alternate Functions of Port
B” on page 82 and ”System Clock and Clock Options” on page
26.

1.1.4 Port C (PC5:0)
Port C is a 7-bit bi-directional I/O port with internal pull-up
resistors (selected for each it). The PC5..0 output buffers have
capability. As inputs, Port C pins that are externally pulled low
C pins are tri-stated when a reset condition becomes active, even
if the clock is not running.
1.1.5 PC6/RESET
If the RSTDISBL Fuse is programmed, PC6 is used as an I/O pin.
Note that the electrical characteristics of PC6 differ from those
of the other pins of Port C. If the RSTDISBL Fuse is un
programmed, PC6 is used as a Reset input. A low level on this pin
for longer than the minimum pulse length will generate a Reset,
even if the clock is not running.
The minimum pulse length is given in Table 28-3 on page 318.
Shorter pulses are not guaranteed to generate a Reset. The various
special features of Port C are elaborated in ”Alternate Functions
of Port C” on page 85.
1.1.6 Port D (PD7:0)

Port D is an 8-bit bi-directional I/O port with internal pull-up
resistors (selected for each bit). The Port D output buffers have
capability. As inputs, Port D pins that are externally pulled low
D pins are tri-stated when a reset condition becomes active, even
if the clock is not running. The various special features of Port D
are elaborated in ”Alternate Functions of Port D” on page
88.
1.1.7 AVCC
AVCC is the supply voltage pin for the A/D Converter, PC3:0,
and ADC7:6. It should be externally connected to VCC, even if
the ADC is not used. If the ADC is used, it should be connected
to VCC through a low-pass filter. Note that PC6..4 use digital
supply voltage, VCC.
1.1.8 AREF
AREF is the analog reference pin for the A/D Converter.
1.1.9 ADC7:6 (TQFP and QFN/MLF Package Only)

In the TQFP and QFN/MLF package, ADC7:6 serve as analog
inputs to the A/D converter. These pins are powered from the
analog supply and serve as 10-bit ADC channels.
Overview
The ATmega48PA/88PA/168PA/328P is a low-power CMOS 8-
bit microcontroller based on the AVR enhanced RISC
architecture. By executing powerful instructions in a single clock
cycle, the ATmega48PA/88PA/168PA/328P achieves
throughputs approaching 1 MIPS per MHz allowing the system
designer to optimize power consumption versus processing
speed.
2.1 Block Diagram

The AVR core combines a rich instruction set with 32 general
purpose working registers. All the 32 registers are directly
connected to the Arithmetic Logic Unit (ALU), allowing two
independent registers to be accessed in one single instruction
executed in one clock cycle. The resulting architecture is more
code efficient while achieving throughputs up to ten times faster
than conventional CISC microcontrollers.
The ATmega48PA/88PA/168PA/328P provides the following
features: 4K/8K bytes of In-System Programmable Flash with
Read-While-Write capabilities, 256/512/512/1K bytes EEPROM,
512/1K/1K/2K bytes SRAM, 23 general purpose I/O lines, 32
general purpose working registers, three flexible Timer/Counters
with compare modes, internal and external interrupts, a serial
programmable USART, a byte-oriented 2-wire Serial Interface,
an SPI serial port, a 6-channel 10-bit ADC (8 channels in TQFP
and QFN/MLF packages), a programmable Watchdog Timer with
internal Oscillator, and five software selectable power saving
modes. The Idle mode stops the CPU while allowing the SRAM,
Timer/Counters, USART, 2-wire Serial Interface, SPI port, and
interrupt system to continue functioning. The Power-down mode

saves the register contents but freezes the Oscillator, disabling all
other chip functions until the next interrupt or hardware reset.
In Power-save mode, the asynchronous timer continues to run,
allowing the user to maintain a timer base while the rest of the
device is sleeping. The ADC Noise Reduction mode stops the
CPU and all I/O modules except asynchronous timer and ADC,
to minimize switching noise during ADC conversions. In Standby
mode, the crystal/resonator Oscillator is running while the rest of
the device is sleeping. This allows very fast start-up combined
with low power consumption.
The device is manufactured using Atmel’s high density non-
volatile memory technology. The On-chip ISP Flash allows the
program memory to be reprogrammed In-System through an SPI
serial interface, by a conventional non-volatile memory
programmer, or by an On-chip Boot program running on the AVR
core. The Boot program can use any interface to download the
application program in the Application Flash memory. Software
in the Boot Flash section will continue to run while the
Application Flash section is updated, providing true Read-While-
Write operation. By combining an 8-bit RISC CPU with In-
System Self-Programmable Flash on a monolithic chip, the Atmel

ATmega48PA/88PA/168PA/328P is a powerful microcontroller
that provides a highly flexible and cost effective solution to many
embedded control applications.
The ATmega48PA/88PA/168PA/328P AVR is supported with a
full suite of program and system development tools including: C
Compilers, Macro Assemblers, Program Debugger/Simulators,
In-Circuit Emulators, and Evaluation kits.
2.2 Comparison Between ATmega48PA, ATmega88PA,
ATmega168PA and ATmega328P

The ATmega48PA, ATmega88PA, ATmega168PA and
ATmega328P differ only in memory sizes, boot loader support,
and interrupt vector sizes. Table 2-1 summarizes the different
memory and interrupt vector sizes for the three devices.
ATmega88PA, ATmega168PA and ATmega328P support a real
Read-While-Write Self-Programming mechanism. There is a
separate Boot Loader Section, and the SPM instruction can only
execute from there. In ATmega48PA, there is no Read-While-
Write support and no separate Boot Loader Section. The SPM
instruction can execute from the entire Flash.
AVR CPU Core

6.1 Overview
This section discusses the AVR core architecture in general. The
main function of the CPU core is to ensure correct program
execution. The CPU must therefore be able to access memories,
perform calculations, control peripherals, and handle interrupts.

In order to maximize performance and parallelism, the AVR uses
a Harvard architecture – with separate memories and buses for
program and data. Instructions in the program memory are
executed with a single level pipelining. While one instruction is
being executed, the next instruction is pre-fetched from the
program memory. This concept enables instructions to be
executed in every clock cycle. The program memory is In-System
Reprogrammable Flash memory.
The fast-access Register File contains 32 x 8-bit general purpose
working registers with a single clock cycle access time. This
allows single-cycle Arithmetic Logic Unit (ALU) operation. In a
typical ALU operation, two operands are output from the Register
File, the operation is executed, and the result is stored back in the
Register File – in one clock cycle. Six of the 32 registers can be
used as three 16-bit indirect address register pointers for Data
Space addressing – enabling efficient address calculations. One
of the these address pointers can also be used as an address pointer
for look up tables in Flash program memory. These added
function registers are the 16-bit X-, Y-, and Z-register, described
later in this section.

The ALU supports arithmetic and logic operations between
registers or between a constant and a register. Single register
operations can also be executed in the ALU. After an arithmetic
operation, the Status Register is updated to reflect information
about the result of the operation.
Program flow is provided by conditional and unconditional jump
and call instructions, able to directly address the whole address
space. Most AVR instructions have a single 16-bit word format.
Every program memory address contains a 16- or 32-bit
instruction.
Program Flash memory space is divided in two sections, the Boot
Program section and the Application Program section. Both
sections have dedicated Lock bits for write and read/write
protection. The SPM instruction that writes into the Application
Flash memory section must reside in the Boot Program section.
During interrupts and subroutine calls, the return address Program
Counter (PC) is stored on the Stack. The Stack is effectively
allocated in the general data SRAM, and consequently the Stack
size is only limited by the total SRAM size and the usage of the
SRAM. All user programs must initialize the SP in the Reset

routine (before subroutines or interrupts are executed). The Stack
Pointer (SP) is read/write accessible in the I/O space. The data
SRAM can easily be accessed through the five different
addressing modes supported in the AVR architecture.
The memory spaces in the AVR architecture are all linear and
regular memory maps.
A flexible interrupt module has its control registers in the I/O
space with an additional Global Interrupt Enable bit in the Status
Register. All interrupts have a separate Interrupt Vector in the
Interrupt Vector table. The interrupts have priority in accordance
with their Interrupt Vector position.
The lower the Interrupt Vector address, the higher the priority.
The I/O memory space contains 64 addresses for CPU peripheral
functions as Control Registers,
SPI, and other I/O functions. The I/O Memory can be accessed
directly, or as the Data Space locations following those of the
Register File, 0x20 - 0x5F. In addition, the
ATmega48PA/88PA/168PA/328P has Extended I/O space from
0x60 - 0xFF in SRAM where only the ST/STS/STD and
LD/LDS/LDD instructions can be used.

6.2 ALU – Arithmetic Logic Unit
The high-performance AVR ALU operates in direct connection
with all the 32 general purpose working registers. Within a single
clock cycle, arithmetic operations between general purpose
registers or between a register and an immediate are executed.
The ALU operations are divided into three main categories –
arithmetic, logical, and bit-functions. Some implementations of
the architecture also provide a powerful multiplier supporting
both signed/unsigned multiplication and fractional format. See
the “Instruction Set” section for a detailed description.
6.3 Status Register
The Status Register contains information about the result of the
most recently executed arithmetic instruction. This information
can be used for altering program flow in order to perform
conditional operations. Note that the Status Register is updated
after all ALU operations, as specified in the Instruction Set
Reference. This will in many cases remove the need for using the
dedicated compare instructions, resulting in faster and more
compact code. The Status Register is not automatically stored

when entering an interrupt routine and restored when returning
from an interrupt. This must be handled by software.
AVR Memories
7.1 Overview
This section describes the different memories in the
ATmega48PA/88PA/168PA/328P. The AVR architecture has
two main memory spaces, the Data Memory and the Program
Memory space. In addition, the
ATmega48PA/88PA/168PA/328P features an EEPROM
Memory for data storage. All three memory spaces are linear and
regular.
7.2 In-System Reprogrammable Flash Program Memory
The ATmega48PA/88PA/168PA/328P contains 4/8/16/32K
bytes On-chip In-System Reprogrammable Flash memory for
program storage. Since all AVR instructions are 16 or 32 bits
wide, the Flash is organized as 2/4/8/16K x 16. For software
security, the Flash Program memory space is divided into two
sections, Boot Loader Section and Application Program Section

in ATmega88PA and ATmega168PA. See SELFPRGEN
description in section ”SPMCSR – Store Program Memory
Control and Status Register” on page 292 for more details.
The Flash memory has an endurance of at least 10,000 write/erase
cycles. The ATmega48PA/88PA/168PA/328P Program Counter
(PC) is 11/12/13/14 bits wide, thus addressing the 2/4/8/16K
program memory locations. The operation of Boot Program
section and associated Boot Lock bits for software protection are
described in detail in ”Self-Programming the Flash,
ATmega48PA” on page 269 and ”Boot Loader Support – Read-
While-Write Self-Programming, ATmega88PA, ATmega168PA
and ATmega328P” on page 277. ”Memory Programming” on
page 294 contains a detailed description on Flash Programming
in SPI- or Parallel Programming mode.
Constant tables can be allocated within the entire program
memory address space (see the LPM – Load Program Memory
instruction description).
SRAM Data Memory

The ATmega48PA/88PA/168PA/328P is a complex
microcontroller with more peripheral units than can be supported
within the 64 locations reserved in the Opcode for the IN and
OUT instructions. For the Extended I/O space from 0x60 - 0xFF
in SRAM, only the ST/STS/STD and LD/LDS/LDD instructions
can be used. The lower 768/1280/1280/2303 data memory
locations address both the Register File, the I/O memory,
Extended I/O memory, and the internal data SRAM. The first 32
locations address the Register File, the next 64 location the
standard I/O memory, then 160 locations of Extended I/O
memory, and the next 512/1024/1024/2048 locations address the
internal data SRAM.
The five different addressing modes for the data memory cover:
Direct, Indirect with Displacement, Indirect, Indirect with Pre-
decrement, and Indirect with Post-increment. In the Register File,
registers R26 to R31 feature the indirect addressing pointer
registers.
The direct addressing reaches the entire data space. The Indirect
with Displacement mode reaches 63 address locations from the
base address given by the Y- or Z-register.

When using register indirect addressing modes with automatic
pre-decrement and post-increment, the address registers X, Y, and
Z are decremented or incremented. The 32 general purpose
working registers, 64 I/O Registers, 160 Extended I/O Registers,
and the 512/1024/1024/2048 bytes of internal data SRAM in the
ATmega48PA/88PA/168PA/328P are all accessible through all
these addressing modes.
EEPROM Data Memory
The ATmega48PA/88PA/168PA/328P contains 256/512/512/1K
bytes of data EEPROM memory. It is organized as a separate data
space, in which single bytes can be read and written. The
EEPROM has an endurance of at least 100,000 write/erase cycles.
The access between the EEPROM and the CPU is described in
the following, specifying the EEPROM Address Registers, the
EEPROM Data Register, and the EEPROM Control Register.
7.4.1 EEPROM Read/Write Access
The EEPROM Access Registers are accessible in the I/O space.

lets the user software detect when the next byte can be written. If
the user code contains instructions that write the EEPROM, some
precautions must be taken. In heavily filtered power supplies,
VCC is likely to rise or fall slowly on power-up/down. This
causes the device for some period of time to run at a voltage lower
than specified as minimum for the clock frequency used. In order
to prevent unintentional EEPROM writes, a specific write
procedure must be followed. Refer to the description of the
EEPROM Control Register for details on this. When the
EEPROM is read, the CPU is halted for four clock cycles before
the next instruction is executed. When the EEPROM is written,
the CPU is halted for two clock cycles before the next instruction
is executed.
Low Power Crystal Oscillator
Pins XTAL1 and XTAL2 are input and output, respectively, of an
inverting amplifier which can be configured for use as an On-chip
Oscillator, Either a quartz crystal or a ceramic resonator may be
used. This Crystal Oscillator is a low power oscillator, with
reduced voltage swing on the XTAL2 output.

It gives the lowest power consumption, but is not capable of
driving other clock inputs, and may be more susceptible to noise
in noisy environments. C1 and C2 should always be equal for
both crystals and resonators. The optimal value of the capacitors
depends on the crystal or resonator in use, the amount of stray
capacitance, and the electromagnetic noise of the environment.
For ceramic resonators, the capacitor values given by the
manufacturer should be used.
Watchdog Timer
Features

• Clocked from separate On-chip Oscillator
• 3 Operating modes
– Interrupt
– System Reset
– Interrupt and System Reset
• Selectable Time-out period from 16ms to 8s
• Possible Hardware fuse Watchdog always on (WDTON) for
fail-safe mode
Overview
ATmega48PA/88PA/168PA/328P has an Enhanced Watchdog
Timer (WDT). The WDT is a timer counting cycles of a separate
on-chip 128 kHz oscillator. The WDT gives an interrupt or a
system reset when the counter reaches a given time-out value. In
normal operation mode, it is required that the system uses the
WDR - Watchdog Timer Reset - instruction to restart the counter
before the time-out value is reached. If the system doesn't restart
the counter, an interrupt or system reset will be issued.

In Interrupt mode, the WDT gives an interrupt when the timer
expires. This interrupt can be used to wake the device from sleep-
modes, and also as a general system timer. One example is to limit
the maximum time allowed for certain operations, giving an
interrupt when the operation has run longer than expected. In
System Reset mode, the WDT gives a reset when the timer
expires. This is typically used to prevent system hang-up in case
of runaway code. The third mode, Interrupt and System Reset
mode, combines the other two modes by first giving an interrupt
and then switch to System Reset mode. This mode will for
instance allow a safe shutdown by saving critical parameters
before a system reset.
The Watchdog always on (WDTON) fuse, if programmed, will
force the Watchdog Timer to System Reset mode. With the fuse
programmed the System Reset mode bit (WDE) and Interrupt
mode bit (WDIE) are locked to 1 and 0 respectively. To further
ensure program security, alterations to the Watchdog set-up must
follow timed sequences. The sequence for clearing WDE and
changing time-out configuration is as follows:

1. In the same operation, write a logic one to the Watchdog
change enable bit (WDCE) and WDE. A logic one must be
written to WDE regardless of the previous value of the WDE bit.
2. Within the next four clock cycles, write the WDE and
Watchdog prescaler bits (WDP) as desired, but with the WDCE
bit cleared. This must be done in one operation.
The following code example shows one assembly and one C
function for turning off the Watchdog Timer. The example
assumes that interrupts are controlled (e.g. by disabling interrupts
globally) so that no interrupts will occur during the execution of
these functions.
8-bit Timer/Counter0 with PWM
Features
• Two Independent Output Compare Units
• Double Buffered Output Compare Registers
• Clear Timer on Compare Match (Auto Reload)
• Glitch Free, Phase Correct Pulse Width Modulator (PWM)

• Variable PWM Period
• Frequency Generator
• Three Independent Interrupt Sources (TOV0, OCF0A, and
OCF0B)
Overview
Timer/Counter0 is a general purpose 8-bit Timer/Counter
module, with two independent Output Compare Units, and with
PWM support. It allows accurate program execution timing
(event management) and wave generation.
CPU accessible I/O Registers, including I/O bits and I/O pins, are
shown in bold.
Gear DC Motor
Definition:
Gear motor is a type of electrical motor. Like all
electrical motors, it uses the magnetism induced by an electrical current
to rotate a rotor that is connected to a shaft. The energy transferred from
the rotor to the shaft is then used to power a connected device.

In a gear motor, the energy output is used to turn a series
of gears in an integrated gear train. There are a number of
different types of gear motors, but the most common are AC
(alternating current) and DC (direct current).
Function:
In a gear motor, the magnetic current (which can be produced
by either permanent magnets or electromagnets) turns gears that

are either in a gear reduction unit or in an integrated gear box. A
second shaft is connected to these gears. The result is that the
gears greatly increase the amount of torque the motor is capable
of producing while simultaneously slowing down the motor's
output speed. The motor will not need to draw as much current to
function and will move more slowly, but will provide greater
torque.
Gear motors are complete motive force systems consisting of
an electric motor and a reduction gear train integrated into one easy-to-
mount and -configure package. This greatly reduces the complexity and
cost of designing and constructing power tools, machines and

appliances calling for high torque at relatively low shaft speed or RPM.
Gear motors allow the use of economical low-horsepower motors to
provide great motive force at low speed such as in lifts, winches,
medical tables, jacks and robotics. They can be large enough to lift a
building or small enough to drive a tiny clock.
Operation Principle:
Most synchronous AC electric motors have output ranges
of from 1,200 to 3,600 revolutions per minute. They also have
both normal speed and stall-speed torque specifications. The
reduction gear trains used in gear motors are designed to reduce
the output speed while increasing the torque. The increase in
torque is inversely proportional to the reduction in speed.
Reduction gearing allows small electric motors to move large
driven loads, although more slowly than larger electric motors.
Reduction gears consist of a small gear driving a larger gear.
There may be several sets of these reduction gear sets in a
reduction gear box.
Speed Reduction:
Sometimes the goal of using a gear motor is to reduce the
rotating shaft speed of a motor in the device being driven, such as

in a small electric clock where the tiny synchronous motor may
be spinning at 1,200 rpm but is reduced to one rpm to drive the
second hand, and further reduced in the clock mechanism to drive
the minute and hour hands. Here the amount of driving force is
irrelevant as long as it is sufficient to overcome the frictional
effects of the clock mechanism.
Torque Multiplication
Another goal achievable with a gear motor is to use a
small motor to generate a very large force albeit at a low speed.
These applications include the lifting mechanisms on hospital
beds, power recliners, and heavy machine lifts where the great
force at low speed is the goal.
Motor Varieties
Most industrial gear motors are AC-powered, fixed-speed
devices, although there is fixed-gear-ratio, variable-speed motors
that provide a greater degree of control. DC gear motors are used
primarily in automotive applications such as power winches on
trucks, windshield wiper motors and power seat or power window
motors.

Calculate Torque:
Suppose you need to determine how much torque is required to
lift a load, cause a wheel to accelerate or to make a conveyor belt move.
If you know how much force is required at one radius (arm length) of
leverage, you can easily convert the torque requirement for another arm
length. The relevant equation is Torque = Perpendicular Force x Radius
about the center of rotation.

Instructions
1. Draw a diagram of a pulley wheel of radius R with a mass m hanging
off of it. You can translate this example to a range of torque problems,
where the load applies a perpendicular force at radius R from the center
of rotation.
2. Determine the force created by the mass. In this case, use Newton's
second law to get F=ma=mg, where g is the gravitational acceleration
constant, 9.80 meters per second squared.
3. Calculate the torque you'll need to apply to the pulley to keep the
weight from dropping. In other words, FR = mgR is the torque needed.
So if you use a motor to drive a wheel of radius r attached to the same
axle as the pulley, then the motor needs to apply a force of F = mgR/r.

Calculate Rotational Force:
Rotational force, also known as torque or centripetal force, is
the measurement of the force of an object rotating around a central axis
or pivot. For example, using a wrench to turn a bolt creates enough force
to either tighten or remove the bolt. The force that is coming from
turning the wrench is considered the rotational force that is being
created. To find rotational force, a person must know the mass of the
object creating the torque, the velocity that it is being moved, and the
radius of how far away the object is from the axis.
Instructions

1. Take the velocity of the object that is being turned to the second
power. For example, if the velocity of the object is 15 meters per
second, multiply 15 by 15 to get 225.
2. Multiply the mass of the object being used to create torque by the
squared velocity. For example, if the mass of the object is 28 grams,
that would mean you multiply 28 by 225 to get 6300.
3. Divide the answer from Step 2 by the radius that is measured from
the center of the axis to the object that is being used to create the
rotational force. For example, if the radius is 19 meters, that would
mean you divide 6300 by 19 to get 331.58 Newton meters. (Newton
meters are the SI unit used for rotational force.) This is the rotational
force that is being created.
Calculate Moments of Force:
When force is applied to an object at a certain point, it does two
things: push the object, and rotate the object. The amount of that
rotational tendency is described by the moment of force. A moment of
force is a vector: it has both a magnitude (the strength of the rotational
force) and a direction (the axis along which the rotation will take place).
The direction can be determined using the right hand rule: with your

thumb pointed along the moment of force, your fingers curl in the
direction of rotation. Calculating the moment of force is simple vector
math.
Instructions
1. Subtract the position vector of the point of rotation from the position
vector of the point where the force is applied. In other words, calculate
the vector (Rx -- Ax, Ry -- Ay, Rz -- Az). For example, if a force is
applied at coordinates (2, 3, 6) to an object whose center of gravity (and
thus position of rotation) is at coordinates (-2, 8, 0), you would get a
vector of (2 -- (-2), 3 -- 8, 6 -- 0) = (4, -5, 6). This vector points from
the point of rotation to the point of force application.
2 .Find the cross product of the vector from step 1 (which we will
hereafter call B) and the force vector (F), as described in this and the
next two steps. Firstly, find the x component of the cross product by
subtracting the product of the y component of F and the z component of
B from the product of the y component of B and the z component of F.
To put it succinctly, calculate (B X F)x = By*Fz -- Bz*Fy
3. Find the y component of the cross product in a similar fashion,
by subtracting the product of the z component of F and the x
component of B from the product of the z component of B and

the x component of F. In other words, calculate (B X F)y = Bz*Fx
-- Bx*Fz.
4. Find the z component of the cross product by subtracting the product
of the x component of F and the y component of B from the product of
the x component of B and the y component of F. In other words,
calculate (B X F)z = Bx*Fy -- By*Fx.
5.Write the moment of force as the vector with x, y, and z components
as the results of steps 2, 3, and 4, respectively. To put it all into one
formula, the moment M is (By*Fz -- Bz*Fy, Bz*Fx -- Bx*Fz, Bx*Fy -
- By*Fx).
How to Calculate Gear Spur on a DC Motor?
The spur gear is adjacent to the pinion gear, which sits directly
on the motor shaft. The spur gear's relationship to the pinion gear is
significant in that the ratio of one to the other determines the vehicle's
performance. Learn how to calculate the size of the spur gear to better
understand how your vehicle will handle.
Instructions:

1. Mark one of the teeth on the spur gear with the marker to indicate the
first tooth you will consider in your calculation.
2. Open the safety pin, and then press it between the teeth with the
marked tooth underneath it.
3. Rotate the gear counterclockwise while counting the number of clicks
you hear as you pass the safety pin over the teeth.
4. Use the total number of teeth on the spur gear to determine the gear
ratio between the spur gear and the pinion. For example, if the spur gear
has 36 teeth and the pinion gear has 6, then you're running a ratio of 6:1.
This means that for every rotation of the spur gear, the pinion gear turns
6 times.
DC Reduction Gear Motors:
The DC Gear motor, consisting of a DC electric motor and
a gearbox, is at the heart of several electrical and electronic
applications. Precision Micro drives have been designing and
developing such high quality mini DC gear motors in an easy-to-
mount package for a range of products and equipment. Our
miniature gear motor work smoothly and efficiently, supporting
these electrical and electronic applications. These geared motors

have reduction gear trains capable of providing high torque at
relatively low shaft speed or revolutions per minute
(RPM). Precision Micro drives DC geared motors reduce the
complexity and cost of designing and constructing applications
such as industrial equipment, actuators, medical tools, and
robotics.
Precision Micro drives have engineered a range of
planetary and spur gear motors (also known as mini-geared
motors and micro-geared motors) suitable for many future and
existing applications. The main characteristics of these gear
motors are miniature form factors, offering significant strength,
torque, and other technical capabilities that these applications
require. Their linear performance characteristics make them
suitable for many applications requiring a controlled
performance.
Whether you are looking for automotive, medical, or
domestic applications, DC Gear motors from Precision Micro
drives not only offer the variable speed and torque control
required in each of these applications. They also possess quality
characteristics of reliability, ruggedness, and compactness. The

operations performed by Precision Micro drives geared motors
appear simple and effortless. However, they are highly
sophisticated devices, and some units are encapsulated in
housings to prevent exposure to moisture and dust. Precision
Micro drives are the leading supplier of sub Ø60 mm DC Gear
motors in the industry.
DC Gear motors from Precision Micro drives are
designer-friendly, with multiple options available for any
application. We are helping our clients with unrivalled

application support and on-hand technical expertise to develop
stringent quality-controlled, cost-effective and competitive
solutions in their niche. We also provide continually updated data
sheets, web-based help features and technical bulletins to help
clients looking for solutions in their niche. We carry the widest
range in stock and are capable of delivering in order quantities of
any size (1+).
Gear Mechanisam:
All gears, including the output gear, are attached to the shaft
and supported by non-lubricated metal bearings. This type of
mechanism is suitable for medium load applications and continuous
duty cycle operation.
Gears in DC motor increase the torque:
Two differently-sized gears increase or decrease torque
because they have different radii.
If you (or another gear) apply a tangential force at the
edge of a gear (where the teeth are), the torque you create equals
the force multiplied by the radius of the gear.

That means if a gear that's 1 inch wide has 10 foot-pounds of
torque on it, and it's driving a gear that's 4 inches wide, the 4-inch-
wide gear gets 40 foot-pounds of torque, because its radius is 4
times as large as the smaller gear.
Another way to think about it is that the speed of rotation
is inversely proportional to the torque. If you halve the speed, you
double the torque.
What is the difference between a geared and non-geared dc motor?
A: It has a gearbox, usually to gear down to get more torque and lower
speed, usually to drive wheels or a winch. Rarely would one gear up.

Uses:
Gear motors are commonly used in conveyor-belt drives,
home appliances, in handicap and platform lifts, medical and
laboratory equipment, machine tools, packaging machinery and
printing presses.
A special type of gear motor, the servo motor, provides
more power in a compact, precise fashion, and is used when a
motor with a rapid, accurate response is needed.
Many Applications:

What power can openers, garage door openers, stair lifts,
rotisserie motors, timer cycle knobs on washing machines, power
drills, cake mixers and electromechanical clocks have in common
is that they all use various integrations of gear motors to derive a
large force from a relatively small electric motor at a manageable
speed. In industry, gear motor applications in jacks, cranes, lifts,
clamping, robotics, conveyance and mixing are too numerous to
count.
Introduction to Servomotors
Hobby servomotors are a very elegant solution to the problem
of adding a motor to your robot. They are mainly used in hobby RC
airplanes, so they are very compact, powerful, light and power
conservative. Since they have been in production for a long time they
are also very cheap. You can buy a standard hobby servomotor for
under $13. In a very small package you get a DC motor, gearbox, and
feedback control system.

The Futaba S-148 standard servo.
Available from towerhobbies.com or any RC hobby store (Colpar)
Servomotors are designed to operate control surfaces on hobby
RC planes. So they do not rotate continuously. Rather they are
designed to rotate through 180 degrees with precise position control. If
you want to use them as the main drive motor for a mobile robot you
need to modify them so that they will rotate continuously. This is not a
difficult thing to do. I will not cover it here but if you want to do it there
are many sites on the web that cover this. An excellent one is

They do not simply run on a DC voltage like a standard DC
motor. They have 3 wires. Red is power (generally 3V – 12V max),
black is ground and then there is another wire, usually white or yellow
that is the “input signal wire”.
A servomotor is controlled by sending a pulse signal that is
HIGH for a brief time, generally 1 – 2 ms. If you just connect a battery
to power and ground, nothing will happen. You must have a timer
circuit that generates this pulsed signal and by varying the pulse ON
time (or the pulse width) the motor will move to a certain position over
its range of motion and then stop as long as the input pulse width is the
same. Depending on the pulse width, you’ll get a different position.

This diagram shows some control signal pulses for a
typical servo and the position to which it will rotate in response
to the pulse width.

There is another element to the signal that also requires timing
accuracy. The frequency of the signal or its rate of refresh. Not only
do you have to send the pulse, you have to keep sending them as long
as you want the motor to be in that position (or to keep rotating for
modified servos). Generally a frequency of 50 Hz is good. This means
that you send the Hi pulse 50 times every second.
I mentioned earlier that a servo will only rotate through 180
degrees unless you modify it for continuous rotation (you can also buy

them already modified through Acroname and other companies). One
interesting thing that comes out this modification is that you get a speed
control function out of it, though somewhat coarse.
When you make the modification you replace the circuitry in
the motor that tells the motor what position it is in. The mods you make
tell the motor that it is always in the center position. So if you feed a
1.75 ms pulse, it rotates to the 180 degree position, checks the feedback
which tells it that “hey, you haven’t moved yet. You’re still in the
center position, keep going” so it does, checks and sees that it hasn’t
moved yet and keeps doing it. Since it thinks that it is in center position
and it has to move to its right most position it will move at its fastest
rate.
Now suppose you send it a signal that says to rotate to 95
degrees, 5 degrees right of center. The internal control system knows
that it is now to move a very short distance. It also knows that if it
rotates at its fastest speed that it may overshoot this and have to come
back, and overshoot again in the other direction and try again, and so
forth. This is called oscillation and is not a good thing. The advantage
that you get out of this is that the motor will move slower when you
feed a signal that is close to the center position. So you feed it a “go to

95 degree” signal and it will rotate CW at a slow rate. Give it “go to
180 degrees” and it will rotate CW at its fastest rate. And the same for
CCW.
3.9 OBSTACLE SENSOR
This sensor is a short range obstacle detector with no dead zone.
It has a reasonably narrow detection area which can be increased
using the dual version. Range can also be increased by increasing
the power to the IR LEDs or adding more IR LEDs
The photo below shows my test setup with some IR LED's (dark
blue) as a light source and two phototransistors in parallel for the
receiver. You could use one of each but I wanted to spread them
out to cover a wider area. This setup works like a FritsLDR but

with IR. It has a range of about 10-15cm (4-6 inches) with my
hand as the object being detected.
Circuit of obstacle sensors:
Starting from the left you can see my two IR LEDs with a resistor
and transistor in series. The transistor allows the processor to turn
the LEDs on or off. This is necessary to tell the difference
between the ambient IR from daylight and indoor lighting and the
reflected light from the LEDs that indicates the presence of an
object.
Next are my two phototransistors in parallel with a 1M resistor in
series. You could use only one but I wanted to cover a wider area
so my transistors will point in slightly different directions. If
either one detects IR it will allow more current to flow. Since
volts=current x resistance, even a small increase in current will
create a reasonable increase in voltage across the 1M resistor.
Unfortunately the low input impedance of many AD converters
will act like a small resistor in parallel with the 1M resistor and
dramatically reduce the output to the processor. This is where our
BC549 transistor comes in to save the day. In conjunction with
the 1K and 10K resistors it amplifies the signal so that the analog

input on your processor gets a nice strong signal. The BC549 is
not too critical, just about any general purpose signal transistor
should do. My transistor had a hfe of 490 when measured with a
multimeter. You should probably have a hfe of at least 200-300.
This has the advantage that you can flex the leds and transistors
outward to cover a larger area. This is juniors reversing sensor to
prevent him reversing into anything and as such will cover a wide
area. I will make single Led/Phototransistor sensors for front left
and front right. This will allow him to avoid crashing into
obstacles when his rangefinder/object tracker is looking
elsewhere.
Note that the phototransistors are slightly forward of the blue
LEDs. This helps stop stray light from the LEDs being detected
Working of infrared communication:
Various types of infrared based applications are available
in the market. The circuit for infrared based applications is
designed along with the transmitter and receiver sections i.e. we
can’t use it for other application. But the infrared communication
project which we have done here can be used in any application

just by replacing the application at the place of infrared LED in
the circuit diagram of infrared communication. By using this
project we can design infrared based applications easily. The
entire circuit consists of two sections named as
1. Transmitter section and
2. Receiver section
1. Transmitter section:
The transmitter section consists of a 555 timer IC
functioning in astable mode. It is wired as shown in figure. The
output from astable mode is fed to an IR LED via resistor which
limits its operating current. Infrared LED in the transmitter
section emits IR radiation which is focused by a plastic lens
(optics) in to a narrow beam.
2. Receiver section:
The receiver section consists of a silicon phototransistor to
convert the infrared radiation to an electric current. It responds
only to the rapidly pulsing signal created by the transmitter, and
filters out slowly changing infrared radiation from ambient light.

The receiver section comprises an infrared receiver module, and
a led indicator. When the signals are interrupted, the IR Led goes
off after a few seconds depending upon the value of RC
combination.
We can increase the distance between the IR transmitter
and receiver just by placing the lens between them. After
connecting the IR transmitter and receiver circuit, we can get the
output by applying 6V Power supply to the circuit. We can use
this circuit with any application very simply. For example a
buzzer circuit is placed at the output of IR circuit, when the
signals are interrupted, the buzzer produces sound. Both the
transmitter and receiver parts can be mounted on a single bread
board or PCB. The infrared receiver must be placed behind the IR
Led to avoid false indication due to infrared leakage. An object
moving nearby actually reflects the IR rays emitted by the IR Led.
Photo Diodes:
A photodiode is a semiconductor diode that functions as a
photo detector. Photodiodes are packaged with either a window
or optical fiber connection, to let in the light to the sensitive part

of the device. They may also be used without a window to detect
vacuum UV or X-rays.
A phototransistor is in essence nothing more than a
bipolar transistor that is encased in a transparent case so that light
can reach the base-collector junction. The phototransistor works
like a photodiode, but with a much higher responsivity for light,
because the electrons that are generated by photons in the base-
collector junction are injected into the base, and this current is
then amplified by the transistor operation.
Fig (3.13) Photodiode schematic symbol
Principle of operation:
A photodiode is a p-n junction or p-i-n structure.
When a photon of sufficient energy strikes the diode, it excites an
electron thereby creating a mobile electron and a positively

charged electron hole. If the absorption occurs in the junction's
depletion region, or one diffusion length away from it, these
carriers are swept from the junction by the built-in field of the
depletion region, producing a photocurrent.
Photodiodes can be used under either zero bias (photovoltaic
mode) or reverse bias (photoconductive mode). In zero bias, light
falling on the diode causes a current across the device, leading to
forward bias which in turn induces "dark current" in the opposite
direction to the photocurrent. This is called the photovoltaic
effect, and is the basis for solar cells in fact; a solar cell is just a
large number of big photodiodes. Reverse bias induces only little
current (known as saturation or back current) along its direction.
But a more important effect of reverse bias is
widening of the depletion layer (therefore expanding the reaction
volume) and strengthening the photocurrent. Circuits based on
this effect are more sensitive to light than ones based on the
photovoltaic effect and also tend to have lower capacitance,
which improves the speed of their time response. On the other
hand, the photovoltaic mode tends to exhibit less electronic noise.

Avalanche photodiodes have a similar structure, but
they are operated with much higher reverse bias. This allows each
photo-generated carrier to be multiplied by avalanche breakdown,
resulting in internal gain within the photodiode, which increases
the effective responsivity of the device.
Features:
Critical performance parameters of a photodiode include:
1. Responsivity:
The responsivity may also be expressed as quantum
efficiency, or the ratio of the number of photo generated carriers
to incident photons and thus a unit less quantity.
2. Dark current:
The dark current includes photocurrent generated by
background radiation and the saturation current of the
semiconductor junction. Dark current must be accounted for by
calibration if a photodiode is used to make an accurate optical
power measurement, and it is also a source of noise when a
photodiode is used in an optical communication system.

3. Noise-equivalent power:
(NEP) The minimum input optical power to generate
photocurrent, equal to the RMS noise current in a 1 hertz
bandwidth. The related characteristic directivity (D) is the inverse
of NEP, 1/NEPThe NEP is roughly the minimum detectable input
power of a photodiode.
Applications:
1. P-N photodiodes are used in similar applications to other
photo detectors, such as photoconductors, charge-coupled
devices, and photomultiplier tubes.
2. Photodiodes are used in consumer electronics devices
such as compact disc players, smoke detectors, and the
receivers for remote controls in VCRs and televisions.
3. PIN diodes are much faster and more sensitive than
ordinary p-n junction diodes, and hence are often used for
optical communications and in lighting regulation.
P-N vs. P-I-N Photodiodes:

1. Due to the intrinsic layer, a PIN photodiode must be
reverse biased (Vr). The Vr increases the depletion region
allowing a larger volume for electron-hole pair
production, and reduces the capacitance thereby
increasing the bandwidth.
2. The Vr also introduces noise current, which reduces the
S/N ratio. Therefore, a reverse bias is recommended for
higher bandwidth applications and/or applications where
a wide dynamic range is required.
3. A PN photodiode is more suitable for lower light
applications because it allows for unbiased operation.

Features
 Modulated IR transmitter
 Ambient light protected IR receiver
 3 pin easy interface connectors

 Bus powered module
 Indicator LED
 Up to 12 inch range for white object
 Can differentiate between dark and light colors.
Applications
 Proximity Sensor
 Obstacle Detector Sensor
 Line Follower Sensor
 Wall Follower Sensor
APPLICATIONS
 Obstacle sensing robot can be applied at the toys where
small children will play.
 It can used for the army application we can add a cam to
it.
 We can apply number pairs of IR pairs for the safe
direction control of the robot.

Metal Detection Sensor:
A metal detection sensor detects metallic objects which are at a
distance up to 7 cm. The sensor gives an active low output when
detecting a metal and also indicates through a LED.

Operation:
The heart of this sensor is the inductive oscillator circuit which
monitors high frequency current loss in coil. The circuit is designed for
any metallic body detection by detecting the variations in the high

frequency Eddy current losses. With an external tuned circuit they act
as oscillators. Output signal level is altered by an approaching metallic
object.
Output signal is determined by supply current changes.
Independent of supply voltage, this current is high or low according to
the presence or the absence of a close metallic object. If the metal
object is near the searching coil, the output current will flow more. On
the other hand, the current will be decrease when the object is far
from the searching coil.
Specifications
1. Detection range adjustable up to 7 cm
2. Operation range varies according to size of the metallic
object
3. Power Supply: 5V DC Power Consumption: 50mA max.
4. Detection Indicator LED
5. Digital output: Active with logic “0”
6. Dimensions: 53x72 mm
7. Full SMD design

Procedure:
1. Connect regulated DC power supply of 5 Volts.
Black wire is Ground, Next middle wire is Brown which is output and
Red wire is positive supply. These wires are also marked on PCB.
2. When adjusting sensitivity move away from any metal object
3. Turn sensitivity pre-set until the LED is about to light. To set
maximum sensitivity, turn preset until the LED is weakly lit and just
becomes off.
4. To test sensors you only need power the sensor by connect two
wires +5V and GND. 5. You can leave the output wire as it is. When LED
is off the output is at 5V.
Bring the metal object nearby the PCB coil and the LED will lit up and
output becomes 0V.
6. The output is active low and can be given directly to
microcontroller for interfacing applications.

Metal detectors use electromagnetic fields to detect the
presence of metallic objects. They exist in a variety of walk-
through, hand-held, and vehicle-mounted models and are used to
search personnel for hidden metallic objects at entrances to
airports, public schools, courthouses, and other guarded spaces;
to hunt for landmines, archaeological artifacts, and miscellaneous
valuables; and for the detection of hidden or unwanted metallic
objects in industry and construction. Metal detectors detect
metallic objects, but do not image them. An x-ray baggage
scanner, for example, is not classed as a metal detector because it
images metallic objects rather than merely detecting their
presence.
Metal detectors use electromagnetism in two
fundamentally different ways, active and passive. (1) Active
detection methods illuminate some detection space—the opening
of a walk-through portal, for example, or the space directly in
front of a hand-held unit—with a time-varying electromagnetic
field. Energy reflected from or passing through the detection
space is affected by the presence of conductive material in that

space; the detector detects metal by measuring these effects. (2)
Passive detection methods do not illuminate the detection space,
but take advantage of the fact that every unshielded detection
space is already permeated by the Earth's natural magnetic field.
Ferromagnetic objects moving through the detection space cause
temporary, but detectable changes in this natural field.
(Ferromagnetic objects are made of metals, such as iron, that are
capable of being magnetized; many metals, such as aluminum, are
conducting but not ferromagnetic, and cannot be detected by
passive means.)
Types of Metal detection sensors:
1. Walk-through metal detectors

Walk-through or portal detectors are common in airports, public
buildings, and military installations. Their portals are bracketed
with two large coils or loop-type antennae, one a source and the
other a detector. Electromagnetic waves (in this case, low-
frequency radio waves) are emitted by the source coil into the
detection space. When the electromagnetic field of the
transmitted wave impinges on a conducting object, it induces
transient currents on the surface of the object; these currents, in
turn, radiate electromagnetic waves. These secondary waves are
sensed by the detector coil.
2. Hand-carried metal detectors.
Metal detectors small enough to be hand-held are often used at
security checkpoints to localize metal objects whose presence has
been detected by a walk-through system. Some units are designed
to be carried by a pedestrian scanning for metal objects in the
ground (e.g., nails, loose change, landmines). All such devices
operate on variations of the same physical principle as the walk-
through metal detector, that is, they emit time-varying
electromagnetic fields and listen for waves coming back from
conducting objects. Some ground-search models further analyze

the returned fields to distinguish various common metals from
each other. Hand-carried metal detectors have long been used to
search for landmines; however, modern land mines are often
made largely of plastic to avoid this cheap and obvious counter-
measure. New technologies, especially neutron activation
analysis and ground-penetrating radar, are being developed to
search for nonmetallic landmines.
3. Gradiometer metal detectors.
Gradiometer metal detectors are passive systems that exploit the
effect of moving ferromagnetic objects on the earth's magnetic
field. A gradiometer is an instrument that measures a gradient—
the difference in magnitude between two points—in a magnetic
field. When a ferromagnetic object moves through a gradiometer
metal detector's detection space, it causes a temporary disturbance
in the earth's magnetic field, and this disturbance (if large enough)
is detected. Gradiometer metal detectors are usually walk-through
devices, but can also be mounted on a vehicle such as a police car,

with the intent of detecting ferromagnetic weapons (e.g., guns)
borne by persons approaching the vehicle. Gradiometer metal
detectors are limited to the detection of ferromagnetic objects and
so are not suitable for security situations where a would-be evader
of the system is likely to have access to non ferromagnetic
weapons.
4. Magnetic imaging portals
The magnetic imaging portal is a relatively new technology. Like
traditional walk-through metal detectors, it illuminates its
detection space with radio-frequency electromagnetic waves;
however, it does so using a number of small antennas arranged
ring like around its portal, pointing inward. Each of these
antennas transmits in turn to the antennas on the far side of the
array; each antenna acts as a receiver whenever it is not
transmitting. A complete scan of the detection space can take
place in the time it takes a person to walk through the portal.
Using computational techniques adapted from computed axial
tomography (CAT) scanning, a crude image of the person (or
other object) inside the portal is calculated and displayed. The
magnetic imaging portal may for some purposes be classed as a

metal detector rather than as an imaging system because it does
not produce a detailed image of the metal object detected, but only
reveals its location and approximate size.
Advantages of Metal detection sensor:
1. Metal Detectors are designed to safeguard security-sensitive
areas like schools, courtrooms, corrections facilities, sports
events, businesses, nightclubs, bars and other public areas and
events.
2. They are used along with walk-through metal detectors.
Construction crews and woodworkers also use metal detectors to
find dangerous nails or other metallic debris in reclaimed building
materials and trees.

3. A recent study proves that metal detectors are just as accurate
as x-rays in finding coins and other metallic objects swallowed by
children.
4. They are cheaper and radiation-free, are usually lightweight,
highly sensitive and require little maintenance. The special shape
of the sensitive surface makes operation of the device easy, unlike
portable metal detectors with ring transducers. They come with
9V batteries or rechargeable NiMH batteries.
5. Metal detectors are most commonly used for body searches for
weapons in crowd control, and checking parcels and letters.
6. Larger portable metal detectors are used by archaeologists and
treasure hunters to locate metallic items, such as jewelry, coins,
bullets, and other various artifacts buried shallowly underground.

Disadvantages of Metal Detectors
Before you start searching for used metal detectors on sale
however, you may have to consider the pros and cons of having such
a kind. The first advantage that you could get from a used one is
definitely a more affordable price tag. Because it's not anymore brand-
new, it is naturally a cheaper. Thus, you don't have to allot a large
amount for it. Besides this though, there can be no other benefits at
all. It's not something that acquires skills when it gets a bit older. Thus,
you can't expect it to be much better than the new one because it is
old and 'experienced.' The price drop reflects the depreciation of the
item. The depreciation rate may also be the measure of the decrease
in its effectiveness or efficiency.
It is obvious that a brand new metal detector may be more
expensive but this should not be the reason why you should turn your
back on it. Compared to a used detector, you could rest assured that
this is a much better choice when you are after effectiveness and
durability. Thus, you in fact get your money's worth when you buy one
if its price is half higher than the used detector.

Applications
1. Detect presence of any metallic object
2. Locate pipes, cables, metal studs, …
3. Avoid disasters when drilling holes in walls
4. Great project for novices
5. Your own unique application
6. Interface with any microcontroller
Conveyor Belt
The belt conveyor is an endless belt moving over two end pulleys at
fixed positions and used for transporting material horizontally or at
an incline up or down. The main components of a belt conveyor are:
1. The belt that forms the moving and supporting surface on
which the conveyed material rides. It is the tractive element.
The belt should be selected considering the material to be
transported.
2. The idlers, which form the supports for the carrying and
return stands of the belt.
3. The pulleys that support and move the belt and controls its
tension.

4. The drive that imparts power to one or more pulleys to
move the belt and its loads.
5. The structure that supports and maintains the alignments of
the idlers and pulleys and support the driving machinery.
Other components include:
1. Loading chute or feeder chute that organises the flow of material
and directs it on the belt conveyor.
2. Take-up-device which is used to maintain the proper tension of the
belt for effective power transmission.
3. Belt cleaner that keeps the belt free from materials sticking to the
belt.
4. Tramp removal device, which is optionally used in case the
conveyed material bears the chance of having tramp iron mixed
with it and subsequent handling of the material, demands its
removal.
5. Continuous weighing device for constantly measuring the load
being carried by the conveyor belt.
6. Discharge chutes to guide the discharged projectile to subsequent
conveyor or other receiving point.
7. Surge hopper and feeder, which is essential for supplying material
to the conveyor at uniform rate when the supply of material is
intermittent.
8. Tripper arrangement to discharge material at different point or to
other device.

Application
Conveyor belts are widely used in mineral industry. Underground
mine transport, opencast mine transport and processing plants
deploy conveyor belts of different kinds to adopt the specific job
requirements. The main advantages of conveyor belt system are:
1. A wider range of material can be handled which pause problems in
other transportation means. Belt conveyor can be used for
abrasive, wet, dry, sticky or dirty material. The lump size of the
transported material is limited by the width of the belt. Belts up to
2500 mm wide are used in mining industry.
2. Higher capacity can be handled than any other form of conveyor at
a considerably lower cost per tonne kilometre. Conveyor belts with
capacity of 11000t/h and even higher can be deployed to match
with higher capacity mining machinery.
3. Longer distances can be covered more economically than any other
transportation system. A single belt conveyor or a series of belt
conveyors can do this. Belt conveyors can be adopted for cross-
country laying.
4. By the use of many forms of ancillary equipment such as mobile
trippers or spreaders bulk material can be distributed and
deposited whenever required.
5. Many other functions can be performed with the basic conveying
like weighing, sorting, picking, sampling, blending, spraying,
cooling, drying etc.
6. Structurally it is one of the lightest forms of conveying machine. It
is comparatively cheaper and supporting structures can be used for
many otherwise impossible structures such as crossing rivers,
streets and valleys.

7. The belt conveyor can be adopted for special purposes (fire
resistant, wear resistant, corrosion resistant, high angle negotiation
etc.) and can be integrated with other equipment.
8. It can be horizontal, incline or decline or combination of all.
9. Minimum labour is required for the operation and maintenance of
belt conveyor system.
10. In underground mine transport, belt conveyor can be used in thin
seams as it eliminates the rock works that might otherwise be
required to gain haulage height. Moreover, belt conveyor can
provide continuous haulage service from pit bottom to the surface.
The limitations of conveyor belt are:
1. The loading and transfer points need to be properly designed.
2. Numbers of protective devices have to be incorporated to save the
belt from getting damaged by operational problems.
3. The belt needs higher initial tension (40-200% of useful pull).
4. The use of belt is restricted by the lump size. If the maximum
diagonal of a irregular lump is X then the belt width (B) is
approximately given by:
200

 Xa
B
where, B: Belt width, mm
X: Longest diagonal of irregular lump, mm

a: Factor to account for grading. a is taken as 2.5 for graded
material and 3 for un-graded material. However, for particular
material these values must be properly estimated.
5. Conveying of sticky material is associated with problems of cleaning
and discharge causing poor productivity.
6. Higher elongation of the belt (4% elongation may take place at the
working load).
Some of the applications of belt conveyors are shown in Figures
below:
Level or inclined Conveyor receiving material at tail end and
discharging at head end.

Level Conveyor receiving material at any point through travelling
Hopper and discharging at head end.

Level and inclined Conveyor receiving material at and near tail end,
having vertical curve to incline, and discharging at head end.
Level and inclined Conveyor with chute. Material received from bins
too close to elevated head end to permit use of vertical curve.

Inclined and level Conveyor receiving material at tail end and
discharging from level section through a movable Tripper.
Level Conveyor on raised structure with double-wing Tripper forming
storage piles on both sides of Conveyor.

Inclined Conveyor receiving material at tail end and discharging at
several points through a series of fixed Trippers.
Level Conveyor with Stacker or Boom Conveyor mounted on
revolving turntable so as to discharge to both sides of Conveyor.

INFORMATION REQUIRED TO DESIGN A
BELT CONVEYOR
1. Length of conveyor from centre to centre of end pulleys.
2. Inclination-level or inclined. Either degree of inclination, or
distance to be lifted or lowered.
3. Average capacity per hour.
4. Maximum capacity per hour.
5. Material to be conveyed, and weight per cubic foot. 6. Average size
of material.
7. Size of largest pieces and percentage in feed.
8. (a) Nature of material -dry or wet (moisture content).
(b) Abrasive or corrosive?
9. How material is to be fed to the belt and particulars of feed point
or points.
10. How material is to be discharged from the belt i.e. overhead
pulley or by trippers, and particulars of discharge points.
11. General indication of supporting structure.
12. Power available for driving. If by A.C. electric motor, state
voltage, phase and frequency. If D.C. motor state voltage.
Items 1 and 2 determine the suitability of belt conveyors, since
inclination is a limiting factor. Items 1-7 determine the speed and

width of the conveyor belt, the power needed for the drive, the type
of drive, the number of belt plies, size of pulleys, shafts and spacing
of idlers. Items 8-10 determine the quality and thickness of the
rubber cover on the belt.
Description of Components
Belt
The belt consists of a carcass covered from all sides with a filler
material like PVC and neoprene as shown in Figure 1.
Figure 1 Construction of conveyor belt.
Essential Properties
The belt works as a tractive element as well as load-carrying element.
It may be used for different kind of material transportation at a
higher speed ( 6-8 m/s). For this purpose the belt need to have the
following essential properties:
1. Flexibility
Top Cover
Bottom Cover
(Carrying Side)
(Non-Carrying Side)
End Cover
End Cover
Carcass

2. Transverse rigidity
3. Low mass per unit length
4. High strength
5. Simplicity and inexpensive
6. Longer life
7. Should not stretch under normal working stresses ,i.e., low relative
elongation.
8. Wear resistant
9. Fire resistant
Recommended maximum belt speeds are given as shown in Table 1
Speed
(m/sec)
Speed
(fpm)
Width
(mm)
Width
(inches)
Coal, damp clay,
soft ore, fine
crushed stone,
Over burden and
earth
2.032
3.048
4.064
5.08
400
600
800
1000
457.2
609.6-914.4
1066.8-
1524
1828.8-
2413
18
24-36
42-60
72-95
Heavy, hard,
sharp edged ore.
Coarse crushed
stone
1.778
2.54
3.048
350
500
600
457.2
609.6-914.4
over 914.4
18
24-36
over 36
The carcass can absorb the longitudinal tensile stresses and make the
belt rigid transversely. Filler protects carcass against moisture,

mechanical damage, abrasion and combine the carcass into an
integral body forming top cover and bottom cover. The filler can be
synthetic rubber or polymer like PVC with adequate additives for
getting particular expected characteristics. The carcass can be a fabric
type with plies of fabric or steel chord type.
A fabric ply has a longitudinal thread called warp and a transverse
thread called weft. The fabric plies are made of capron, nylon or
lavsan etc. The longitudinal member of the carcass transfers the
tension. Both the warp and weft carry the load via the cover. The
cover while protecting the carcass from external damage bear the
impact and abrasion at the feeding points and wear at the cleaning
points. Figure 2 shows the cross section of the types of conveyor belt.
Figure 2 Cross section of a multi ply conveyor belt.
The belt ends are joined together by mechanical means or by
vulcanising. The belt needs to be protected from damage of its sides
that may occur due to sway of the belt. In case of belt carrying wet
sticky material fixtures for cleaning the belt should be properly
selected. Materials coming on to the return side of the belt needs to
be arrested from coming under the end pulley by adequate scrapers.
Rubber Interply
Top Cover
Bottom Cover

As shown in the Figure 4 belt cleaners are used to clean the return
side of the conveyor belt. These cleaning belt can be of V shape as
well.
Figure 3 Belt scrapers
As shown in the Figure 3(a), the pow blade's 20° leading edge
"spirals" debris off the return-side belt surface. There are specially
designed belt cleaners for the tail pulley, they are engineered to
clean the inside of the belt so rocks, lumps and other debris never get
the chance to damage the pulley, belt, splices or lagging. Normally
plows are easy to install on virtually any conveyor structure, and
come with universal mounting brackets. Though there are suppliers
of such scrapers, these can be fabricated at the mine’s workshop.
The diagonal deflector plow (Figure 3a) is installed on a 45° angle
across the belt to discharge debris to one side of the belt. In such

cleaners the blade is installed in a fixed position, eliminating
bouncing problems associated with some floating style plows.
Twin-bladed plow ( Figure 3b) is designed to clean belt in both
directions of travel. This cleaner discharges material to either side of
the belt. It is installed securely to conveyor structure and can work
on conveyors with severe belt vibration.
CONVEYOR BELT FASTENERS
One of the important components that require attention in
maintaining services of belt conveyor is the conveyor belt fasteners.
Selection of fasteners should consider required performance,
expected life and ease of installation and maintenance so that higher
availability of the belt conveyor is ensured.
There are different types of fasteners. Mechanical fasteners are
commonly used in underground coal mining. The required rating of
the mechanincal fasteners is calculated based on the required belt
tension and it may be upto 263 kN/m of belt width.
One such fastener is Flexco®
SR™ Scalloped Edge™ RAR8 belt
fastener, designed for use on mainline and panel belts with
mechanical fastener ratings up to 1,500 PIW (263kN/m). The 8-rivet
pattern, along with the scalloped edge design, ensures quality
performance in high-tension applications.

Figure 4 Mechanical Belt joint
Fasteners are available with self-setting rivets which allow to install
quickly from the topside of the belt. Most important in belt fastening
is to take care that the plates must be accurately positioned to get
perfect edges and stress distribution should be uniform along the
joints.
Effectiveness of maintenance will be enhanced by provision of
adequate and improved tools for carrying out the job. Management
should encourage innovation of workers for making work tools or
improvement of work environment and safety.
Idlers
In a conveyor belt installation different types of idlers or roller
supports are used. The idlers are required for proper support and
protection of the belt and proper support of the load being
conveyed.Idlers are designed with different diameters and are

provided with antifriction bearings and seals, and are mounted on
shafts. Frictional resistance of idlers influences the belt tension and
consequently the power requirement.
Idlers are mounted on a support frame, which can be shiftable or
permanent. The carrying side of the belt is supported on the carrier
rollers sets. A set of three rollers are arranged to form a trough for
the troughed belt conveyor. The return side of the belt is supported
on straight return idlers. The spacing of the idlers is determined
based on the belt sag between the idlers. The sag depends on the
belt tension, belt width, belt properties and the pay-load per meter
of the belt. The idlers are specified by its length and diameter. These
parameters are selected based on the required belt speed for the
particular width of the belt.
Figure 5 Different types of roller supports

Figure 7 Components of belt conveyor
Self aligning idler set is used infront of the loading point. This set of
idlers can rotate on a horizontal plan depending on the belt sway and
restores true running of the belt. Belt training idlers should be spaced
100 to 150 feet apart and at least one such idlers should be used on
conveyors less thqan 100 feet long. Such idlers are not used in the
areas of belt transition.
Fixed guide rolls placed perpendicular to the edge of the conveyor
belt are not generally recommended as they cause edge wear and
reduce belt life.
Offcentre running of the belt occurs when the belt loading is not
proper. Garland type idlers assist true running of the belt under
difficult loading conditions. In this type of idlers the idlers are
connected to form a string. The connections are through universal
type coupling that allows each idlers to rotate about its own axis

independently. Garland idlers are available as two roll, three roll or
five roll units. Normally two-roll units are used as return idlers and
three-rolls or five-rolls units are used in carrying idlers.
Belt weight, material weight, idler load rating, belt sag, idler life, belt
rating, belt tension and radius in vertical curves determine the
spacing of idlers. Some suggested normal spacing are shown in Table
3.
Pulley
A conveyor belt system uses different types of pulleys like end pulley,
snub pulley, bend pulley etc. as shown in the Figure 3. The end
pulleys are used for driving and sometimes for making tensioning
arrangements. Snub pulleys increase the angle of wrap thereby
increasing the effective tension in the belt. The pulley diameter
depends on the belt width and belt speed.
Pulleys are used for providing the drive to the belt as well as for
maintaining the proper tension to the belt.
Minimum transition distance as shown in Table 4 should be followed
while placing idlers in front of pulleys.
Snub pulleys may be fitted in as shown in the following figures:

Loose Snub Tight Snub
Figure 8
The angle of wrap is increased by using tandem drive as shown in
Figure below:
Figure 9 Tandem drive

Drive
Belt drive is provided normally at the discharge ends, however, it may
be provided through the head end or through intermediate pulley by
coupling the pulley shaft to the reducing gear’s output shaft. The
coupling is selected based on the load characteristics and
applications. Flexible coupling or fluid couplings are often used.
Various drive arrangements are shown in the Figures below:
Take-up
The purposes of take-up are:
1. To allow for stretch and shrinkage of the belt.
2. To ensure that the minimum tension in the belt is sufficient to
prevent undue sag between idlers.
3. To ensure that the tension in the belt in the rear of the drive
pulley is sufficient to permit such pulley to transmit the load.
There are different types of take-up systems as shown in the Figures
below:

Figure 11 Gravity Take up
Conveyor Support
The support of conveyor is normally a structural frame. Depending on
the situation the structure can be mounted on floor or on skid. The
main job of the support is to let the belt run without getting skewed.
Depending on situations the support can be made moving type. In
such cases idler a wheel mounted or crawler mounted platform
keeps the necessary provision to support the idlers on which the
conveyor runs.
4 bar link mechanism
Linkage Mechanisms:
Have you ever wondered what kind of mechanism
causes the wind shield wiper on the front widow of car
to oscillate
Let's make a simple mechanism with similar
behavior. Take some cardboard and make four strips,
Take 4 pins and assemble them

Now, hold the 6in. strip so it can't move and turn
the 3in. strip. You will see that the 4in. strip oscillates
The four bar linkage is the simplest and often
times, the most useful mechanism. As we mentioned
before, a mechanism composed of rigid bodies and
lower pairs is called a linkage (Hunt 78). In planar
mechanisms, there are only two kinds of lower pairs ---
revolute pairs and prismatic pairs.
The simplest closed-loop linkage is the four bar
linkage which has four members, three moving links,

one fixed link and four pin joints. A linkage that has at
least one fixed link is a mechanism. The following
example of a four bar linkage was created in SimDesign
in simdesign/fourbar.sim.
Four bar linkage in SimDesign
This mechanism has three moving links. Two of
the links are pinned to the frame which is not shown in
this picture. In SimDesign, links can be nailed to the
background thereby making them into the frame.
How many DOF does this mechanism have? If we
want it to have just one, we can impose one constraint
on the linkage and it will have a definite motion. The

four bar linkage is the simplest and the most useful
mechanism.
Reminder: A mechanism is composed of rigid
bodies and lower pairs called linkages (Hunt 78). In
planar mechanisms there are only two kinds of lower
pairs: turning pairs and prismatic pairs.
Functions of Linkages
The function of a link mechanism is to produce
rotating, oscillating, or reciprocating motion from the
rotation of a crank or vice versa Stated more specifically
linkages may be used to convert:
1. Continuous rotation into continuous rotation,
with a constant or variable angular velocity ratio.
2. Continuous rotation into oscillation or
reciprocation (or the reverse), with a constant or
variable velocity ratio.

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