Temperature Monitoring Robot

8/3/2019 Temperature Monitoring Robot

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Temperature Monitoring Robot

Abstract

A robot is a mechanical or virtual artificial agent. In practice, it is usually an electro-

mechanical system which, by its appearance or movements, conveys a sense that it

has intent or agency of its own. The word robot can refer to both physical robots

and virtual software agents, but the latter are usually referred to as Robots There is no consensus

on which machines qualify as robots, but there is general agreement among experts and the

public that robots tend to do some or all of the following: move around, operate a mechanical

arm, sense and manipulate their environment, and exhibit intelligent behavior, especially

behavior which mimics humans or animals.

Micro controller controls the robot in this project. This robot can measure the temperature

at various locations. IR sensors are placed at the front for the obstacle detection. LCD is used for

display. L293d is used as a driver IC for controlling the DC Motors.

This prototype project is basically helpful in places like where there is a necessary of

measuring high temperatures like industries, power generators (coal mine), etc.,

The project is built around the AVR micro controller from Atmel. This micro controller providesall the functionality of the display and wireless control.
http://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Virtualhttp://en.wikipedia.org/wiki/Artificialhttp://en.wikipedia.org/wiki/Electromechanicshttp://en.wikipedia.org/wiki/Electromechanicshttp://en.wikipedia.org/wiki/Intentionhttp://en.wiktionary.org/wiki/agencyhttp://en.wikipedia.org/wiki/Virtualhttp://en.wikipedia.org/wiki/Software_agenthttp://en.wikipedia.org/wiki/Internet_bothttp://en.wikipedia.org/wiki/Internet_bothttp://en.wikipedia.org/wiki/Software_agenthttp://en.wikipedia.org/wiki/Virtualhttp://en.wiktionary.org/wiki/agencyhttp://en.wikipedia.org/wiki/Intentionhttp://en.wikipedia.org/wiki/Electromechanicshttp://en.wikipedia.org/wiki/Electromechanicshttp://en.wikipedia.org/wiki/Artificialhttp://en.wikipedia.org/wiki/Virtualhttp://en.wikipedia.org/wiki/Machine


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Block Diagram:

AVR

MICRO

CONTROLLER

LCD

L293D

Battery

Temperature

Sensor

ADC

MOTOR1

MOTOR2


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Schematic Diagram:

PB0/ICP114

PB1/OC1A15

PB2/SS/OC1B16

PB3/MOSI/OC217

PB4/MISO18

PB5/SCK19

PB6/TOSC1/XTAL19

PB7/TOSC2/XTAL210

PC6/RESET1

PD0/RXD2

PD1/TXD3

PD2/INT04

PD3/INT15

PD4/T0/XCK6

PD5/T111

PD6/AIN012

PD7/AIN113

PC0/ADC023

PC1/ADC124

PC2/ADC225

PC3/ADC326

PC4/ADC4/SDA27

PC5/ADC5/SCL28

AREF21

AVCC20

U1

ATMEGA8

D7

14

D6

13

D5

12

D4

11

D3

10

D2

9

D1

8

D0

7

E

6

RW

5

RS

4

VSS

1

VDD

2

VEE

3

LCD1LM016L

27.0

3

1

VOUT2

U2

LM35

IN12

OUT13

OUT26

OUT311

OUT414

IN27

IN310

IN415

EN11

EN29

VS

8

VSS

16

GND GND

U3

L293D

+88.8

+88.8

IR RX IR TX


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Atmega 8:

Features:

High-performance, Low-power AtmelAVR 8-bit Microcontroller

Advanced RISC Architecture

130 Powerful InstructionsMost Single-clock Cycle Execution

32 8 General Purpose Working Registers

Fully Static Operation

Up to 16MIPS Throughput at 16MHz

On-chip 2-cycle Multiplier

High Endurance Non-volatile Memory segments

8Kbytes of In-System Self-programmable Flash program memory

512Bytes EEPROM

1Kbyte Internal SRAM

Write/Erase Cycles: 10,000 Flash/100,000 EEPROM

Data retention: 20 years at 85C/100 years at 25C(1)

Optional Boot Code Section with Independent Lock Bits


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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, one Compare Mode

One 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture Mode

Real Time Counter with Separate Oscillator

Three PWM Channels

8-channel ADC in TQFP and QFN/MLF package Eight Channels 10-bit Accuracy

6-channel ADC in PDIP package

Six Channels 10-bit Accuracy

Byte-oriented Two-wire Serial Interface

Programmable Serial USART

Master/Slave SPI Serial Interface

Programmable Watchdog Timer with Separate On-chip Oscillator

On-chip Analog Comparator

Special Microcontroller Features

Power-on Reset and Programmable Brown-out Detection

Internal Calibrated RC Oscillator

External and Internal Interrupt Sources

Five Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, and Standby

I/O and Packages


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23 Programmable I/O Lines

28-lead PDIP, 32-lead TQFP, and 32-pad QFN/MLF

Operating Voltages

2.7V - 5.5V (ATmega8L)

4.5V - 5.5V (ATmega8)

Speed Grades

0 - 8MHz (ATmega8L)

0 - 16MHz (ATmega8)

Power Consumption at 4Mhz, 3V, 25C

Active: 3.6mA

Idle Mode: 1.0mA

Power-down Mode: 0.5A

Pin Diagram:


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Block Diagram:


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Pin Descriptions:


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VCC Digital supply voltage.

GND Ground.

Port B (PB7..PB0):

XTAL1/XTAL2/TOSC1/TOSC2

Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each

bit). ThePort 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

Port C (PC5..PC0)

Port C is an 7-bit bi-directional I/O port with internal pull-up resistors (selected for each

bit). The Port C output buffers have symmetrical drive characteristics with both high sink and

source capability. As inputs, Port C pins that are externally pulled low will source current if the

pull-up resistors are activated. The Port C pins are tri-stated when a reset condition becomes


PC6/RESET


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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

unprogrammed, 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 15 on page 38. Shorter pulses are not guaranteed to

generate a Reset.

Port D (PD7..PD0)

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 symmetrical drive characteristics with both high sink and

source capability. As inputs, Port D pins that are externally pulled low will source current if the

pull-up resistors are activated. The Port D pins are tri-stated when a reset condition becomes


RESET

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. Shorter pulses are not guaranteed to generate a

reset.

AVCC

AVCC is the supply voltage pin for the A/D Converter, Port C (3..0), and ADC (7..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 Port C (5..4) use digital supply

voltage, VCC.

AREF AREF is the analog reference pin for the A/D Converter.

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.


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AVR Atmega 8 Memories:

In-System Reprogrammable Flash Program Memory

The ATmega8 contains 8Kbytes On-chip In-System Reprogrammable Flash memory forprogram storage. Since all AVR instructions are 16-bits or 32-bits wide, the Flash is organized as

4K 16 bits. For software security, the Flash Program memory space is divided into two

sections, Boot Program section and Application Program section. The Flash memory has an

endurance of at least 10,000 write/erase cycles. The ATmega8 Program Counter (PC) is 12 bits

wide, thus addressing the 4K Program memory locations. Constant tables can be allocated within

the entire Program memory address space.

SRAM Data Memory


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The lower 1120 Data memory locations address the Register File, the I/O Memory, and

the internal data SRAM. The first 96 locations address the Register File and I/O Memory, and

the next 1024 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-register 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, and the 1024 bytes of internal data

SRAM in the ATmega8 are all accessible through all these addressing modes.

Data Memory Access Times


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This section describes the general access timing concepts for internal memory access.

EEPROM Data Memory

The ATmega8 contains 512bytes 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

below, specifying the EEPROM Address Registers, the EEPROM Data Register, and the

EEPROM Control Register.

EEPROM Read/Write Access

The EEPROM Access Registers are accessible in the I/O space. A self-timing function,

however, 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. When the EEPROM is read, the CPU is halted for four clock cycles before the


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next instruction is executed. When the EEPROM is written, the CPU is halted for two clock

cycles before the next instruction is executed.

The EEPROM Address RegisterEEARH and EEARL

Bits 15..9Res: Reserved Bits

These bits are reserved bits in the ATmega8 and will always read as zero.

Bits 8..0 EEAR8..0: EEPROM Address

The EEPROM Address Registers EEARH and EEARLspecify the EEPROM address in the

512bytes EEPROM space. The EEPROM data bytes are addressed linearly between 0 and 511.

The initial value of EEAR is undefined. A proper value must be written before the EEPROM

may be accessed.

The EEPROM Data RegisterEEDR

Bits 7..0EEDR7..0: EEPROM Data


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For the EEPROM write operation, the EEDR Register contains the data to be written to

the EEPROM in the address given by the EEAR Register. For the EEPROM read operation, the

EEDR contains the data read out from the EEPROM at the address given by EEAR.

The EEPROM Control RegisterEECR

Bits 7..4 Res: Reserved Bits

These bits are reserved bits in the AtmelAVR ATmega8 and will always read as zero.

Bit 3 EERIE: EEPROM Ready Interrupt Enable

Writing EERIE to one enables the EEPROM Ready Interrupt if the I bit in SREG is set. Writing

EERIE to zero disables the interrupt. The EEPROM Ready interrupt generates a constant

interrupt when EEWE is cleared.

Bit 2 EEMWE: EEPROM Master Write Enable

The EEMWE bit determines whether setting EEWE to one causes the EEPROM to be written.

When EEMWE is set, setting EEWE within four clock cycles will write data to the EEPROM at

the selected address If EEMWE is zero, setting EEWE will have no effect. When EEMWE has

been written to one by software, hardware clears the bit to zero after four clock cycles.

Bit 1 EEWE: EEPROM Write Enable

The EEPROM Write Enable Signal EEWE is the write strobe to the EEPROM. When address and data

are correctly set up, the EEWE bit must be written to one to write the value into the EEPROM. The

EEMWE bit must be written to one before a logical one is written to EEWE, oth- erwise no EEPROM

write takes place. The following procedure should be followed when writing the EEPROM


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1. Wait until EEWE becomes zero

2. Wait until SPMEN in SPMCR becomes zero

3. Write new EEPROM address to EEAR (optional)

4. Write new EEPROM data to EEDR (optional)

5. Write a logical one to the EEMWE bit while writing a zero to EEWE in EECR

6. Within four clock cycles after setting EEMWE, write a logical one to EEWE

The EEPROM can not be programmed during a CPU write to the Flash memory. The

software must check that the Flash programming is completed before initiating a new EEPROM

write.

Step 2 is only relevant if the software contains a boot loader allowing the CPU to

program the Flash. If the Flash is never being updated by the CPU, step 2 can be omitted. See

Boot Loader Support Read-While-Write Self-Programming on page 202 for details about

boot programming.

Caution: An interrupt between step 5 and step 6 will make the write cycle fail, since the

EEPROM Master Write Enable will time-out. If an interrupt routine accessing the EEPROM is

interrupting another EEPROM access, the EEAR or EEDR Register will be modified, causing

the interrupted EEPROM access to fail. It is recommended to have the Global Interrupt Flag

cleared during all the steps to avoid these problems.

When the write access time has elapsed, the EEWE bit is cleared by hardware. The user

software can poll this bit and wait for a zero before writing the next byte. When EEWE has been

set, the CPU is halted for two cycles before the next instruction is executed.

Bit 0 EERE: EEPROM Read Enable

The EEPROM Read Enable Signal EERE is the read strobe to the EEPROM. When the

correct address is set up in the EEAR Register, the EERE bit must be written to a logic one to

trigger the EEPROM read. The EEPROM read access takes one instruction, and the requested


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data is available immediately. When the EEPROM is read, the CPU is halted for four cycles

before the next instruction is executed.

The user should poll the EEWE bit before starting the read operation. If a write operation

is in progress, it is neither possible to read the EEPROM, nor to change the EEAR Register.

Crystal Oscillator

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. The CKOPT Fuse selects between two different Oscillator amplifier modes. When

CKOPT is programmed, the Oscillator output will oscillate a full rail-torail swing on the output.

This mode is suitable when operating in a very noisy environment or when the output from

XTAL2 drives a second clock buffer. This mode has a wide frequency range. When CKOPT is

unprogrammed, the Oscillator has a smaller output swing. This reduces power consumption

considerably. This mode has a limited frequency range and it cannot be used to drive other clock

buffers.

For resonators, the maximum frequency is 8MHz with CKOPT unprogrammed and

16MHz with CKOPT programmed. 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, theamount of stray capacitance, and the electromagnetic noise of the environment. Some initial

guidelines for choosing capacitors for use with crystals are given in Table 4. For ceramic

resonators, the capacitor values given by the manufacturer should be used.


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Timer/Counter Oscillator

For AVR microcontrollers with Timer/Counter Oscillator pins (TOSC1 and TOSC2), the

crystal is connected directly between the pins. By programming the CKOPT Fuse, the user can

enable internal capacitors on XTAL1 and XTAL2, thereby removing the need for external

capacitors. The Oscillator is optimized for use with a 32.768kHz watch crystal. Applying an

external clock source to TOSC1 is not recommended.

System Control and Reset

Resetting the AVR During Reset, all I/O Registers are set to their initial values, and the program

starts execution from the Reset Vector. If the program never enables an interrupt source, the

Interrupt Vectors are not used, and regular program code can be placed at these locations. This isalso the case if the Reset Vector is in the Application section while the Interrupt Vectors are in

the boot section or vice versa.

The I/O ports of the AVR are immediately reset to their initial state when a reset source

goes active. This does not require any clock source to be running. After all reset sources have

gone inactive, a delay counter is invoked, stretching the internal reset. This allows the power to

reach a stable level before normal operation starts. The time-out period of the delay counter is

defined by the user through the CKSEL Fuses.

Reset Sources

The ATmega8 has four sources of Reset:

Power-on Reset. The MCU is reset when the supply voltage is below the Power-on Reset

threshold (VPOT)

External Reset. The MCU is reset when a low level is present on the RESET pin for longer than

the minimum pulse length

Watchdog Reset. The MCU is reset when the Watchdog Timer period expires and the

Watchdog is enabled


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Brown-out Reset. The MCU is reset when the supply voltage VCC is below the Brown-out

Reset threshold (VBOT) and the Brown-out Detector is enabled

Watchdog Timer

The Watchdog Timer is clocked from a separate On-chip Oscillator which runs at 1MHz.

This isthe typical value at VCC = 5V. See characterization data for typical values at other VCC

levels. By controlling the Watchdog Timer prescaler, the Watchdog Reset interval can be

adjusted as shown in Table 17 on page 44. The WDR Watchdog Resetinstruction resets the

Watchdog Timer. The Watchdog Timer is also reset when it is disabled and when a Chip Reset

occurs.

Eight different clock cycle periods can be selected to determine the reset period. If the reset

period expires without another Watchdog Reset, the ATmega8 resets and executes from the

Reset Vector. To prevent unintentional disabling of the Watchdog, a special turn-off sequence

must be followed when the Watchdog is disabled.


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Interrupt Vectors in ATmega8

VOLTAGE REGULATOR 7805:

Features:

Output Current up to 1A.

Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V.

Thermal Overload Protection.


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Short Circuit Protection.

Output Transistor Safe Operating Area Protection.

Description:

The LM78XX/LM78XXA series of three-terminal positive regulators are available in the

TO-220/D-PAK package and with several fixed output voltages, making them useful in a Wide

range of applications. Each type employs internal current limiting, thermal shutdown and safe

operating area protection, making it essentially indestructible. If adequate heat sinking is

provided, they can deliver over 1A output Current. Although designed primarily as fixed voltage

regulators, these devices can be used with external components to obtain adjustable voltages and

currents.

Internal Block Diagram

FIG: BLOCK DIAGRAM OF VOLTAGE REGULATOR


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Absolute Maximum Ratings:

TABLE: RATINGS OF THE VOLTAGE REGULATOR

Typical Performance Characteristics:


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FIG: PERFORMANCE CHARACTERISTICS OF REGULATOR

CAPACITORS:

A capacitor or condenser is a passive electronic component consisting of a pair of

conductors separated by a dielectric. When a voltage potential difference exists between the

conductors, an electric field is present in the dielectric. This field stores energy and produces a

mechanical force between the plates. The effect is greatest between wide, flat, parallel, narrowly

separated conductors.


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An ideal capacitor is characterized by a single constant value, capacitance, which is

measured in farads. This is the ratio of the electric charge on each conductor to the potential

difference between them. In practice, the dielectric between the plates passes a small amount of

leakage current. The conductors and leads introduce an equivalent series resistance and the

dielectric has an electric field strength limit resulting in a breakdown voltage.

The properties of capacitors in a circuit may determine the resonant frequency and

quality factor of a resonant circuit, power dissipation and operating frequency in a digital logic

circuit, energy capacity in a high-power system, and many other important aspects.

A capacitor (formerly known as condenser) is a device for storing electric charge. The forms of

practical capacitors vary widely, but all contain at least two conductors separated by a non-

conductor. Capacitors used as parts of electrical systems, for example, consist of metal foils

separated by a layer of insulating film.

Capacitors are widely used in electronic circuits for blocking direct current while

allowing alternating current to pass, in filter networks, for smoothing the output of power

supplies, in the resonant circuits that tune radios to particular frequencies and for many other

purposes.
http://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/LC_circuithttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/LC_circuithttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Direct_current


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A capacitor is a passive electronic component consisting of a pair ofconductors separated

by a dielectric (insulator). When there is a potential difference (voltage) across the conductors, a

static electric field develops in the dielectric that stores energy and produces a mechanical force

between the conductors. An ideal capacitor is characterized by a single constant value,

capacitance, measured in farads. This is the ratio of the electric charge on each conductor to the

potential difference between them.

The capacitance is greatest when there is a narrow separation between large areas of

conductor, hence capacitor conductors are often called "plates", referring to an early means of

construction. In practice the dielectric between the plates passes a small amount of leakage

current and also has an electric field strength limit, resulting in a breakdown voltage, while the

conductors and leads introduce an undesired inductance and resistance.

History:

Battery of four Leyden jars in Museum Boerhaave, Leiden, the Netherlands

In October 1745, Ewald Georg von Kleist ofPomerania in Germany found that charge

could be stored by connecting a high voltage electrostatic generator by a wire to a volume of

water in a hand-held glass jar. Von Kleist's hand and the water acted as conductors and the jar as

a dielectric (although details of the mechanism were incorrectly identified at the time). Von

Kleist found, after removing the generator, that touching the wire resulted in a painful spark. In a

letter describing the experiment, he said "I would not take a second shock for the kingdom of
http://en.wikipedia.org/wiki/Passivity_%28engineering%29http://en.wikipedia.org/wiki/Electronic_componenthttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Potential_differencehttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Faradhttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Leakage_%28electronics%29http://en.wikipedia.org/wiki/Leakage_%28electronics%29http://en.wikipedia.org/wiki/Breakdown_voltagehttp://en.wikipedia.org/wiki/Lead_%28electronics%29http://en.wikipedia.org/wiki/Equivalent_series_inductancehttp://en.wikipedia.org/wiki/Equivalent_series_resistancehttp://en.wikipedia.org/wiki/Leyden_jarhttp://en.wikipedia.org/wiki/Museum_Boerhaavehttp://en.wikipedia.org/wiki/Leidenhttp://en.wikipedia.org/wiki/Netherlandshttp://en.wikipedia.org/wiki/Ewald_Georg_von_Kleisthttp://en.wikipedia.org/wiki/Pomeraniahttp://en.wikipedia.org/wiki/Electrostatic_generatorhttp://en.wikipedia.org/wiki/File:Leidse_flessen_Museum_Boerhave_december_2003_2.jpghttp://en.wikipedia.org/wiki/Electrostatic_generatorhttp://en.wikipedia.org/wiki/Pomeraniahttp://en.wikipedia.org/wiki/Ewald_Georg_von_Kleisthttp://en.wikipedia.org/wiki/Netherlandshttp://en.wikipedia.org/wiki/Leidenhttp://en.wikipedia.org/wiki/Museum_Boerhaavehttp://en.wikipedia.org/wiki/Leyden_jarhttp://en.wikipedia.org/wiki/Equivalent_series_resistancehttp://en.wikipedia.org/wiki/Equivalent_series_inductancehttp://en.wikipedia.org/wiki/Lead_%28electronics%29http://en.wikipedia.org/wiki/Breakdown_voltagehttp://en.wikipedia.org/wiki/Leakage_%28electronics%29http://en.wikipedia.org/wiki/Leakage_%28electronics%29http://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Faradhttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Potential_differencehttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electronic_componenthttp://en.wikipedia.org/wiki/Passivity_%28engineering%29


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France." The following year, the Dutch physicist Pieter van Musschenbroek invented a similar

capacitor, which was named the Leyden jar, after the University of Leiden where he worked.

Daniel Gralath was the first to combine several jars in parallel into a "battery" to increase the

charge storage capacity. Benjamin Franklin investigated the Leyden jar and "proved" that the

charge was stored on the glass, not in the water as others had assumed. He also adopted the term

"battery", (denoting the increasing of power with a row of similar units as in a battery of

cannon), subsequently applied to clusters of electrochemical cells. Leyden jars were later made

by coating the inside and outside of jars with metal foil, leaving a space at the mouth to prevent

arcing between the foils. The earliest unit of capacitance was the 'jar', equivalent to about 1

nanofarad.

Leyden jars or more powerful devices employing flat glass plates alternating with foil conductors

were used exclusively up until about 1900, when the invention of wireless (radio) created a

demand for standard capacitors, and the steady move to higher frequencies required capacitors

with lower inductance. A more compact construction began to be used of a flexible dielectric

sheet such as oiled paper sandwiched between sheets of metal foil, rolled or folded into a small

package.

Early capacitors were also known as condensers, a term that is still occasionally used today. The

term was first used for this purpose by Alessandro Volta in 1782, with reference to the device's

ability to store a higher density of electric charge than a normal isolated conductor.

Theory of operation:

Main article: Capacitance
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Charge separation in a parallel-plate capacitor causes an internal electric field. A dielectric

(orange) reduces the field and increases the capacitance.

A simple demonstration of a parallel-plate capacitor

A capacitor consists of two conductors separated by a non-conductive region The non-

conductive region is called the dielectric or sometimes the dielectric medium. In simpler terms,

the dielectric is just an electrical insulator. Examples of dielectric mediums are glass, air, paper,

vacuum, and even a semiconductor depletion region chemically identical to the conductors. A

capacitor is assumed to be self-contained and isolated, with no net electric charge and no

influence from any external electric field. The conductors thus hold equal and opposite charges

on their facing surfaces, and the dielectric develops an electric field. In SI units, a capacitance of

one farad means that one coulomb of charge on each conductor causes a voltage of one voltacross the device. The capacitor is a reasonably general model for electric fields within electric

circuits. An ideal capacitor is wholly characterized by a constant capacitance C, defined as the

ratio of charge Q on each conductor to the voltage V between them:

Sometimes charge build-up affects the capacitor mechanically, causing its capacitance to vary. In

this case, capacitance is defined in terms of incremental changes:
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Energy storage:

Work must be done by an external influence to "move" charge between the conductors in a

capacitor. When the external influence is removed the charge separation persists in the electric

field and energy is stored to be released when the charge is allowed to return to its equilibrium

position. The work done in establishing the electric field, and hence the amount of energy stored,

is given by:[11]

Current-voltage relation

The current i(t) through any component in an electric circuit is defined as the rate of flow of a

charge q(t) passing through it, but actual charges, electrons, cannot pass through the dielectric

layer of a capacitor, rather an electron accumulates on the negative plate for each one that leaves

the positive plate, resulting in an electron depletion and consequent positive charge on one

electrode that is equal and opposite to the accumulated negative charge on the other. Thus the

charge on the electrodes is equal to the integral of the current as well as proportional to the

voltage as discussed above. As with any antiderivative, a constant of integration is added to

represent the initial voltage v (t0). This is the integral form of the capacitor equation,

.

Taking the derivative of this, and multiplying by C, yields the derivative form,

.

The dual of the capacitor is the inductor, which stores energy in the magnetic field rather than the

electric field. Its current-voltage relation is obtained by exchanging current and voltage in the

capacitor equations and replacing C with the inductance L.

DC circuits

See also: RC circuit
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A simple resistor-capacitor circuit demonstrates charging of a capacitor.

A series circuit containing only a resistor, a capacitor, a switch and a constant DC source of

voltage V0 is known as a charging circuit. If the capacitor is initially uncharged while the switch

is open, and the switch is closed at t = 0, it follows from Kirchhoff's voltage law that

Taking the derivative and multiplying by C, gives a first-order differential equation,

At t = 0, the voltage across the capacitor is zero and the voltage across the resistor is V 0. The

initial current is then i (0) =V0 /R. With this assumption, the differential equation yields

where 0 = RC is the time constant of the system.

As the capacitor reaches equilibrium with the source voltage, the voltage across the resistor and

the current through the entire circuit decay exponentially. The case of discharging a charged

capacitor likewise demonstrates exponential decay, but with the initial capacitor voltage

replacing V0 and the final voltage being zero.

AC circuits:

Impedance, the vector sum of reactance and resistance, describes the phase difference and the

ratio of amplitudes between sinusoidally varying voltage and sinusoidally varying current at a

given frequency. Fourier analysis allows any signal to be constructed from a spectrum of
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frequencies, whence the circuit's reaction to the various frequencies may be found. The reactance

and impedance of a capacitor are respectively

where j is the imaginary unit and is the angular velocity of the sinusoidal signal. The - j phase

indicates that the AC voltage V = Z I lags the AC current by 90: the positive current phase

corresponds to increasing voltage as the capacitor charges; zero current corresponds to

instantaneous constant voltage, etc.

Note that impedance decreases with increasing capacitance and increasing frequency. This

implies that a higher-frequency signal or a larger capacitor results in a lower voltage amplitude

per current amplitudean AC "short circuit" or AC coupling. Conversely, for very low

frequencies, the reactance will be high, so that a capacitor is nearly an open circuit in AC

analysisthose frequencies have been "filtered out".

Capacitors are different from resistors and inductors in that the impedance is inversely

proportional to the defining characteristic, i.e. capacitance.

Parallel plate model:

Dielectric is placed between two conducting plates, each of area A and with a separation of d.

The simplest capacitor consists of two parallel conductive plates separated by a dielectric with

permittivity (such as air). The model may also be used to make qualitative predictions for other

device geometries. The plates are considered to extend uniformly over an area A and a charge
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density = Q/A exists on their surface. Assuming that the width of the plates is much greater

than their separation d, the electric field near the centre of the device will be uniform with the

magnitude E = /. The voltage is defined as the line integral of the electric field between the

plates

Solving this for C = Q/V reveals that capacitance increases with area and decreases with

separation

.

The capacitance is therefore greatest in devices made from materials with a high permittivity.

Several capacitors in parallel.

Networks:See also: Series and parallel circuits

For capacitors in parallel

Capacitors in a parallel configuration each have the same applied voltage. Their

capacitances add up. Charge is apportioned among them by size. Using the schematic

diagram to visualize parallel plates, it is apparent that each capacitor contributes to the

total surface area.

For capacitors in series
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Several capacitors in series.

Connected in series, the schematic diagram reveals that the separation distance, not the plate

area, adds up. The capacitors each store instantaneous charge build-up equal to that of every

other capacitor in the series. The total voltage difference from end to end is apportioned to each

capacitor according to the inverse of its capacitance. The entire series acts as a capacitor smaller

than any of its components.

Capacitors are combined in series to achieve a higher working voltage, for example for

smoothing a high voltage power supply. The voltage ratings, which are based on plate

separation, add up. In such an application, several series connections may in turn be connected in

parallel, forming a matrix. The goal is to maximize the energy storage utility of each capacitor

without overloading it.

Series connection is also used to adapt electrolytic capacitors for AC use.

Non-ideal behaviour:

Capacitors deviate from the ideal capacitor equation in a number of ways. Some of these, such as

leakage current and parasitic effects are linear, or can be assumed to be linear, and can be dealt

with by adding virtual components to the equivalent circuit of the capacitor. The usual methods

ofnetwork analysis can then be applied. In other cases, such as with breakdown voltage, theeffect is non-linear and normal (i.e., linear) network analysis cannot be used, the effect must be

dealt with separately. There is yet another group, which may be linear but invalidate the

assumption in the analysis that capacitance is a constant. Such an example is temperature

dependence.

Breakdown voltage:

Above a particular electric field, known as the dielectric strength Eds, the dielectric in a capacitor

becomes conductive. The voltage at which this occurs is called the breakdown voltage of the

device, and is given by the product of the dielectric strength and the separation between the

conductors,

Vbd = Edsd

The maximum energy that can be stored safely in a capacitor is limited by the breakdown

voltage. Due to the scaling of capacitance and breakdown voltage with dielectric thickness, all
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capacitors made with a particular dielectric have approximately equal maximum energy density,

to the extent that the dielectric dominates their volume.

For air dielectric capacitors the breakdown field strength is of the order 2 to 5 MV/m; for mica

the breakdown is 100 to 300 MV/m, for oil 15 to 25 MV/m, and can be much less when other

materials are used for the dielectric. The dielectric is used in very thin layers and so absolute

breakdown voltage of capacitors is limited. Typical ratings for capacitors used for general

electronics applications range from a few volts to 100V or so. As the voltage increases, the

dielectric must be thicker, making high-voltage capacitors larger than those rated for lower

voltages. The breakdown voltage is critically affected by factors such as the geometry of the

capacitor conductive parts; sharp edges or points increase the electric field strength at that point

and can lead to a local breakdown. Once this starts to happen, the breakdown will quickly "track"

through the dielectric till it reaches the opposite plate and cause a short circuit.

The usual breakdown route is that the field strength becomes large enough to pull electrons in the

dielectric from their atoms thus causing conduction. Other scenarios are possible, such as

impurities in the dielectric, and, if the dielectric is of a crystalline nature, imperfections in the

crystal structure can result in an avalanche breakdown as seen in semi-conductor devices.

Breakdown voltage is also affected by pressure, humidity and temperature.

Equivalent circuit

Two different circuit models of a real capacitor

An ideal capacitor only stores and releases electrical energy, without dissipating any. In reality,

all capacitors have imperfections within the capacitor's material that create resistance. This is
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specified as the equivalent series resistance or ESR of a component. This adds a real component

to the impedance:

As frequency approaches infinity, the capacitive impedance (or reactance) approaches zero and

the ESR becomes significant. As the reactance becomes negligible, power dissipation approaches

PRMS = VRMS /RESR.

Similarly to ESR, the capacitor's leads add equivalent series inductance or ESL to the

component. This is usually significant only at relatively high frequencies. As inductive reactance

is positive and increases with frequency, above a certain frequency capacitance will be canceled

by inductance. High-frequency engineering involves accounting for the inductance of all

connections and components.

If the conductors are separated by a material with a small conductivity rather than a perfect

dielectric, then a small leakage current flows directly between them. The capacitor therefore has

a finite parallel resistance, and slowly discharges over time (time may vary greatly depending on

the capacitor material and quality).

L293D:

Features:

Featuring Unitrode L293 and L293D Products Now From Texas Instruments Wide Supply-Voltage Range: 4.5 V to 36 V Separate Input-Logic Supply Internal ESD Protection Thermal Shutdown High-Noise-Immunity Inputs Functional Replacements for SGS L293 and SGS L293D Output Current 1 A Per Channel (600 mA for L293D) Peak Output Current 2 A Per Channel
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(1.2 A for L293D) Output Clamp Diodes for Inductive Transient Suppression (L293D)

Pin Diagram:

Description:

The L293 and L293D are quadruple high-current half-H drivers. The L293 is designed to

provide bidirectional drive currents of up to 1 A at voltage from 4.5 V to 36 V. The L293D is

designed to provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to 36 V.

Both devices are designed to drive inductive loads such as relays, solenoids, dc and bipolar

stepping motors, as well as other high-current/high-voltage loads in positive-supply applications.

All inputs are TTL compatible. Each output is a complete totem-pole drive circuit, with a

Darlington transistor sink and a pseudo-Darlington source. Drivers are enabled in pairs, with

drivers 1 and 2 enabled by 1,2EN and drivers 3 and 4 enabled by 3,4EN. When an enable input is

high, the associated drivers are enabled and their outputs are active and in phase with their

inputs. When the enable input is low, those drivers are disabled and their outputs are off and in

the high-impedance state. With the proper data inputs, each pair of drivers forms a full-H (or

bridge) reversible drive suitable for solenoid or motor applications. On the L293, external high-

speed output clamp diodes should be used for inductive transient suppression. A VCC1 terminal,

separate from VCC2, is provided for the logic inputs to minimize device power dissipation. The

L293and L293D are characterized for operation from 0C to 70C.


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Block diagram:

Logic Diagram:


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DC Motors

A direct current (DC) motor is a fairly simple electric motor that uses electricity and a magneticfield to produce torque, which turns the motor. At its most simple, a DC motor requires two

magnets of opposite polarity and an electric coil, which acts as an electromagnet. The repellent

and attractive electromagnetic forces of the magnets provide the torque that causes the DC motor

to turn.

Whenever a robotics hobbyist talk about making a robot, the first thing comes to his mind is

making the robot move on the ground. And there are always two options in front of the designer

whether to use a DC motor or a stepper motor. When it comes to speed, weight, size, cost... DC

motors are always preferred over stepper motors. There are many things which you can do with

your DC motor when interfaced with a microcontroller. For example you can control the speed

of motor, you can control the direction of rotation, you can also do encoding of the rotation made

by DC motor i.e. keeping track of how many turns are made by your motors etc. So you can see

DC motors are no less than a stepper motor.

How to interface a DC motor with a microcontroller? Usually H-bridge is preferred way of

interfacing a DC motor. These days many IC manufacturers have H-bridge motor drivers

available in the market like L293D is most used H-Bridge driver IC. H-bridge can also be made

with the help of transistors and MOSFETs etc. rather of being cheap, they only increase the size

of the design board, which is sometimes not required so using a small 16 pin IC is preferred for

this purpose.

Working Theory of H-Bridge:

The name "H-Bridge" is derived from the actual shape of the switching circuit which control the

motion of the motor. It is also known as "Full Bridge". Basically there are four switching

elements in the H-Bridge as shown in the figure below.


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As you can see in the figure above there are four switching elements named as "High side left",

"High side right", "Low side right", "Low side left". When these switches are turned on in pairs

motor changes its direction accordingly. Like, if we switch on High side left and Low side right

then motor rotate in forward direction, as current flows from Power supply through the motor

coil goes to ground via switch low side right. This is shown in the figure below.


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Similarly, when you switch on low side left and high side right, the current flows in opposite

direction and motor rotates in backward direction. This is the basic working of H-Bridge. We can

also make a small truth table according to the switching of H-Bridge explained above.

Truth Table

High Left High Right Low Left Low Right Description

On Off Off On Motor runs clockwise

Off On On Off Motor runs anti-clockwise

On On Off Off Motor stops

Off Off On On Motor stops

As already said, H-bridge can be made with the help of transistors as well as MOSFETs, the only

thing is the power handling capacity of the circuit. If motors are needed to run with high current

then lot of dissipation is there. So head sinks are needed to cool the circuit.

Now you might be thinking why we did not discuss the cases like High side left on and Low side

left on or high side right on and low side right on. Clearly seen in the diagram, we don't want to

burn our power supply by shorting them. So that is why those combinations are not discussed in

the truth table.

So we have seen that using simple switching elements we can make our own H-Bridge, or other

option we have is using an IC based H-bridge driver.

LM35 Temperature Sensor:

The LM35 is a popular and low cost temperature sensor. It has three pins. The Vcc can be from

4V to 20V as specified by the datasheet. To use the sensor simply connect the Vcc to +5V ,GND

to ground and the OUT to one of the ADC (analog to digital converter) channel. The output

linearly varies with temperature. The output is


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10 mV per degree centigrade

So if the output is 310 mV then temperature is 31 degree C.

IR Sensors:

Object Detection using IR light

It is the same principle in ALL Infra-Red proximity sensors. The basic idea is to send infra red

light through IR-LEDs, which is then reflected by any object in front of the sensor.

For detecting the reflected IR light, we are

going to use a very original technique: we

are going to use another IR-LED, to detect

the IR light that was emitted from another led

of the exact same type!

This is an electrical property of Light Emitting

Diodes (LEDs) which is the fact that a led

Produce a voltage difference across its leads

when it is subjected to light. As if it was a

photo-cell, but with much lower output current.

In other words, the voltage generated by the

leds can't be - in any way - used to generate

electrical power from light, It can barely be

detected.


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LCD:

Liquid Crystal Display also called as LCD is very helpful in providing user interface as

well as for debugging purpose. The most commonly used Character based LCDs are based on

Hitachi's HD44780 controller or other which are compatible with HD44580. The most

commonly used LCDs found in the market today are 1 Line, 2 Line or 4 Line LCDs which have

only 1 controller and support at most of 80 characters, whereas LCDs supporting more than 80

characters make use of 2 HD44780 controllers.

Pin Description

Pin No. Name Description

1 VSS Power supply (GND)

2 VCC Power supply (+5V)

3 VEE Contrast adjust

4 RS0 = Instruction input

1 = Data input

5 R/W

0 = Write to LCD module

1 = Read from LCD module

6 EN Enable signal

7 D0 Data bus line 0 (LSB)

8 D1 Data bus line 1


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14 D7 Data bus line 7 (MSB)

15 LED+ Back Light VCC

16 LED- Back Light GND

DDRAM - Display Data RAM

Display data RAM (DDRAM) stores display data represented in 8-bit character codes. Itsextended capacity is 80 X 8 bits, or 80 characters. The area in display data RAM (DDRAM) that

is not used for display can be used as general data RAM. So whatever you send on the DDRAM

is actually displayed on the LCD. For LCDs like 1x16, only 16 characters are visible, so

whatever you write after 16 chars is written in DDRAM but is not visible to the user.

CGROM - Character Generator ROM

Now you might be thinking that when you send an ASCII value to DDRAM, how the character

is displayed on LCD? So the answer is CGROM. The character generator ROM generates 5 x 8

dot or 5 x 10 dot character patterns from 8-bit character codes. It can generate 208 5 x 8 dot

character patterns and 32 5 x 10 dot character patterns.

CGRAM - Character Generator RAM

As clear from the name, CGRAM area is used to create custom characters in LCD. In the

character generator RAM, the user can rewrite character patterns by program. For 5 x 8 dots,

eight character patterns can be written, and for 5 x 10 dots, four character patterns can be written.

BF - Busy Flag

Busy Flag is a status indicator flag for LCD. When we send a command or data to the LCD for

processing, this flag is set (i.e. BF =1) and as soon as the instruction is executed successfully this


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flag is cleared (BF = 0). This is helpful in producing and exact amount of delay for the LCD

processing.

To read Busy Flag, the condition RS = 0 and R/W = 1 must be met and The MSB of the LCD

data bus (D7) act as busy flag. When BF = 1 means LCD is busy and will not accept next

command or data and BF = 0 means LCD is ready for the next command or data to process.

Instruction Register (IR) and Data Register (DR)

There are two 8-bit registers in HD44780 controller Instruction and Data register. Instruction

register corresponds to the register where you send commands to LCD e.g. LCD shift command,

LCD clear, LCD address etc. and Data register is used for storing data which is to be displayed

on LCD. When send the enable signal of the LCD is asserted, the data on the pins is latched in tothe data register and data is then moved automatically to the DDRAM and hence is displayed on

the LCD. Data Register is not only used for sending data to DDRAM but also for CGRAM, the

address where you want to send the data, is decided by the instruction you send to LCD.

Commands and Instruction set

Only the instruction register (IR) and the data register (DR) of the LCD can be controlled by the

MCU. Before starting the internal operation of the LCD, control information is temporarily

stored into these registers to allow interfacing with various MCUs, which operate at different

speeds, or various peripheral control devices. The internal operation of the LCD is determined by

signals sent from the MCU. These signals, which include register selection signal (RS),

read/write signal (R/W), and the data bus (DB0 to DB7), make up the LCD instructions (Table

3). There are four categories of instructions that:

Designate LCD functions, such as display format, data length, etc. Set internal RAM addresses Perform data transfer with internal RAM


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Perform miscellaneous functions


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Although looking at the table you can make your own commands and test them. Below is a brief

list of useful commands which are used frequently while working on the LCD.

No. Instruction Hex Decimal

1 Function Set: 8-bit, 1 Line, 5x7 Dots 0x30 48




5 Entry Mode 0x06 6

6

Display off Cursor off

(clearing display without clearing DDRAM

content)

0x08 8

7 Display on Cursor on 0x0E 14

8 Display on Cursor off 0x0C 12

9 Display on Cursor blinking 0x0F 15

10 Shift entire display left 0x18 24

12 Shift entire display right 0x1C 30

13 Move cursor left by one character 0x10 16

14 Move cursor right by one character 0x14 20

15 Clear Display (also clear DDRAM content) 0x01 1

16Set DDRAM address or cursor position on

display0x80+add 128+add

17Set CGRAM address or set pointer to CGRAM

location

0x40+add 64+add


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Sending Commands to LCD

To send commands we simply need to select the command register. Everything is same as we

have done in the initialization routine. But we will summarize the common steps and put them in

a single subroutine. Following are the steps:

move data to LCD port select command register select write operation send enable signal wait for LCD to process the command

Sending Data to LCD

To send data we simply need to select the data register. Everything is same as the command

routine. Following are the steps:

move data to LCD port select data register select write operation send enable signal wait for LCD to process the data

Working with AVR Studio:

AVR studio is an Integrated Development Environment (IDE) by ATMEL for developing

applications based on 8-bit AVR microcontroller. Prior to installation of AVR Studio you have

to install the compiler WinAVR. This will allow AVR Studio to detect the compiler.
http://www.engineersgarage.com/articles/avr-microcontrollerhttp://www.engineersgarage.com/articles/avr-microcontroller


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Step 1:

Step 2:

Click on new project


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Step 3:

Click on AVR GCC

Write the project name

Select your project location.

Click on Next>>


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Step 4:

Click on AVR Simulator in left block and then select your controller (e.g.: ATmega16).

Click on finish button
http://www.engineersgarage.com/atmega16-avr-microcontrollerhttp://www.engineersgarage.com/atmega16-avr-microcontroller


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Step5:

Write the code in main body area.

Save the project file.


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Step6:

Go to PROJECT -> Configuration Options


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Step 7:

Write the crystal frequency if you are using external crystal.

Check the checkbox corresponding to Create Hex File and then click on OK.

Save the project again.


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Step 8:

Go to BUILD -> Compile.

This will compile your code and generate error if any.


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For the first time it will generate two errors, ignore them.

Step 9:


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Again go to BUILD and click on Build.

This will generate hex file of the code.

Use that Hex file to burn your microcontroller.

Where you will find Hex file?

Just go to the location which you selected at the starting. Open that folder you will find one more

folder named Default. This is the default location of where the hex file is generated.

While working in real time if you want to change the code, make changes and build the file

again. This will automatically update the previous hex file.


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Documents

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