View
230
Download
0
Category
Preview:
Citation preview
8/3/2019 Temperature Monitoring Robot
1/56
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/Machine8/3/2019 Temperature Monitoring Robot
2/56
Block Diagram:
AVR
MICRO
CONTROLLER
LCD
L293D
Battery
Temperature
Sensor
ADC
MOTOR1
MOTOR2
8/3/2019 Temperature Monitoring Robot
3/56
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
8/3/2019 Temperature Monitoring Robot
4/56
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
8/3/2019 Temperature Monitoring Robot
5/56
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
8/3/2019 Temperature Monitoring Robot
6/56
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:
8/3/2019 Temperature Monitoring Robot
7/56
Block Diagram:
8/3/2019 Temperature Monitoring Robot
8/56
Pin Descriptions:
8/3/2019 Temperature Monitoring Robot
9/56
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
active, even if the clock is not running.
PC6/RESET
8/3/2019 Temperature Monitoring Robot
10/56
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
active, even if the clock is not running.
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.
8/3/2019 Temperature Monitoring Robot
11/56
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
8/3/2019 Temperature Monitoring Robot
12/56
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
8/3/2019 Temperature Monitoring Robot
13/56
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
8/3/2019 Temperature Monitoring Robot
14/56
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
8/3/2019 Temperature Monitoring Robot
15/56
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
8/3/2019 Temperature Monitoring Robot
16/56
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
8/3/2019 Temperature Monitoring Robot
17/56
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.
8/3/2019 Temperature Monitoring Robot
18/56
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
8/3/2019 Temperature Monitoring Robot
19/56
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.
8/3/2019 Temperature Monitoring Robot
20/56
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.
8/3/2019 Temperature Monitoring Robot
21/56
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
8/3/2019 Temperature Monitoring Robot
22/56
Absolute Maximum Ratings:
TABLE: RATINGS OF THE VOLTAGE REGULATOR
Typical Performance Characteristics:
8/3/2019 Temperature Monitoring Robot
23/56
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.
8/3/2019 Temperature Monitoring Robot
24/56
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_current8/3/2019 Temperature Monitoring Robot
25/56
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%298/3/2019 Temperature Monitoring Robot
26/56
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
http://en.wikipedia.org/wiki/Pieter_van_Musschenbroekhttp://en.wikipedia.org/wiki/Leyden_jarhttp://en.wikipedia.org/wiki/Leiden_Universityhttp://en.wikipedia.org/wiki/Daniel_Gralathhttp://en.wikipedia.org/wiki/Benjamin_Franklinhttp://en.wikipedia.org/wiki/Leyden_jarhttp://en.wikipedia.org/wiki/Artillery_batteryhttp://en.wikipedia.org/wiki/Artillery_batteryhttp://en.wikipedia.org/wiki/Battery_%28electricity%29http://en.wikipedia.org/wiki/Faradhttp://en.wikipedia.org/wiki/Wireless_telegraphyhttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Alessandro_Voltahttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/File:Capacitor_schematic_with_dielectric.svghttp://en.wikipedia.org/wiki/File:Capacitor_schematic_with_dielectric.svghttp://en.wikipedia.org/wiki/File:Capacitor_schematic_with_dielectric.svghttp://en.wikipedia.org/wiki/File:Capacitor_schematic_with_dielectric.svghttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Alessandro_Voltahttp://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Wireless_telegraphyhttp://en.wikipedia.org/wiki/Faradhttp://en.wikipedia.org/wiki/Battery_%28electricity%29http://en.wikipedia.org/wiki/Artillery_batteryhttp://en.wikipedia.org/wiki/Artillery_batteryhttp://en.wikipedia.org/wiki/Leyden_jarhttp://en.wikipedia.org/wiki/Benjamin_Franklinhttp://en.wikipedia.org/wiki/Daniel_Gralathhttp://en.wikipedia.org/wiki/Leiden_Universityhttp://en.wikipedia.org/wiki/Leyden_jarhttp://en.wikipedia.org/wiki/Pieter_van_Musschenbroek8/3/2019 Temperature Monitoring Robot
27/56
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:
http://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Dielectric_mediumhttp://en.wikipedia.org/wiki/Insulator_%28electrical%29http://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Depletion_regionhttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/SIhttp://en.wikipedia.org/wiki/Faradhttp://en.wikipedia.org/wiki/Coulombhttp://en.wikipedia.org/wiki/Volthttp://en.wikipedia.org/wiki/File:Plattenkondensator_hg.jpghttp://en.wikipedia.org/wiki/File:Plattenkondensator_hg.jpghttp://en.wikipedia.org/wiki/File:Plattenkondensator_hg.jpghttp://en.wikipedia.org/wiki/File:Plattenkondensator_hg.jpghttp://en.wikipedia.org/wiki/File:Plattenkondensator_hg.jpghttp://en.wikipedia.org/wiki/File:Plattenkondensator_hg.jpghttp://en.wikipedia.org/wiki/File:Plattenkondensator_hg.jpghttp://en.wikipedia.org/wiki/File:Plattenkondensator_hg.jpghttp://en.wikipedia.org/wiki/Volthttp://en.wikipedia.org/wiki/Coulombhttp://en.wikipedia.org/wiki/Faradhttp://en.wikipedia.org/wiki/SIhttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Depletion_regionhttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Insulator_%28electrical%29http://en.wikipedia.org/wiki/Dielectric_mediumhttp://en.wikipedia.org/wiki/Electrical_conductor8/3/2019 Temperature Monitoring Robot
28/56
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
http://en.wikipedia.org/wiki/Work_%28thermodynamics%29http://en.wikipedia.org/wiki/Equilibriumhttp://en.wikipedia.org/wiki/Capacitor#cite_note-10http://en.wikipedia.org/wiki/Capacitor#cite_note-10http://en.wikipedia.org/wiki/Capacitor#cite_note-10http://en.wikipedia.org/wiki/Integralhttp://en.wikipedia.org/wiki/Antiderivativehttp://en.wikipedia.org/wiki/Constant_of_integrationhttp://en.wikipedia.org/wiki/Duality_%28electrical_circuits%29http://en.wikipedia.org/wiki/Inductorhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/RC_circuithttp://en.wikipedia.org/wiki/RC_circuithttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Inductorhttp://en.wikipedia.org/wiki/Duality_%28electrical_circuits%29http://en.wikipedia.org/wiki/Constant_of_integrationhttp://en.wikipedia.org/wiki/Antiderivativehttp://en.wikipedia.org/wiki/Integralhttp://en.wikipedia.org/wiki/Capacitor#cite_note-10http://en.wikipedia.org/wiki/Equilibriumhttp://en.wikipedia.org/wiki/Work_%28thermodynamics%298/3/2019 Temperature Monitoring Robot
29/56
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
http://en.wikipedia.org/wiki/RC_circuithttp://en.wikipedia.org/wiki/RC_circuithttp://en.wikipedia.org/wiki/RC_circuithttp://en.wikipedia.org/wiki/Resistorhttp://en.wikipedia.org/wiki/Kirchhoff%27s_voltage_lawhttp://en.wikipedia.org/wiki/First-order_differential_equationhttp://en.wikipedia.org/wiki/Time_constanthttp://en.wikipedia.org/wiki/Exponential_decayhttp://en.wikipedia.org/wiki/Electrical_impedancehttp://en.wikipedia.org/wiki/Electrical_reactancehttp://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Fourier_analysishttp://en.wikipedia.org/wiki/Spectrumhttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/Spectrumhttp://en.wikipedia.org/wiki/Fourier_analysishttp://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Electrical_reactancehttp://en.wikipedia.org/wiki/Electrical_impedancehttp://en.wikipedia.org/wiki/Exponential_decayhttp://en.wikipedia.org/wiki/Time_constanthttp://en.wikipedia.org/wiki/First-order_differential_equationhttp://en.wikipedia.org/wiki/Kirchhoff%27s_voltage_lawhttp://en.wikipedia.org/wiki/Resistor8/3/2019 Temperature Monitoring Robot
30/56
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
http://en.wikipedia.org/wiki/Imaginary_unithttp://en.wikipedia.org/wiki/Angular_velocityhttp://en.wikipedia.org/wiki/AC_couplinghttp://en.wikipedia.org/wiki/Permittivityhttp://en.wikipedia.org/wiki/File:Parallel_plate_capacitor.svghttp://en.wikipedia.org/wiki/File:Parallel_plate_capacitor.svghttp://en.wikipedia.org/wiki/File:Parallel_plate_capacitor.svghttp://en.wikipedia.org/wiki/File:Parallel_plate_capacitor.svghttp://en.wikipedia.org/wiki/File:Parallel_plate_capacitor.svghttp://en.wikipedia.org/wiki/File:Parallel_plate_capacitor.svghttp://en.wikipedia.org/wiki/File:Parallel_plate_capacitor.svghttp://en.wikipedia.org/wiki/File:Parallel_plate_capacitor.svghttp://en.wikipedia.org/wiki/Permittivityhttp://en.wikipedia.org/wiki/AC_couplinghttp://en.wikipedia.org/wiki/Angular_velocityhttp://en.wikipedia.org/wiki/Imaginary_unit8/3/2019 Temperature Monitoring Robot
31/56
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
http://en.wikipedia.org/wiki/Line_integralhttp://en.wikipedia.org/wiki/Series_and_parallel_circuitshttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_series.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/File:Capacitors_in_parallel.svghttp://en.wikipedia.org/wiki/Series_and_parallel_circuitshttp://en.wikipedia.org/wiki/Line_integral8/3/2019 Temperature Monitoring Robot
32/56
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
http://en.wikipedia.org/wiki/Electrolytic_capacitorhttp://en.wikipedia.org/wiki/Equivalent_circuithttp://en.wikipedia.org/wiki/Network_analysis_%28electrical_circuits%29http://en.wikipedia.org/wiki/Network_analysis_%28electrical_circuits%29http://en.wikipedia.org/wiki/Equivalent_circuithttp://en.wikipedia.org/wiki/Electrolytic_capacitor8/3/2019 Temperature Monitoring Robot
33/56
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
http://en.wikipedia.org/wiki/Energy_densityhttp://en.wikipedia.org/wiki/Micahttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Avalanche_breakdownhttp://en.wikipedia.org/wiki/File:CircuitosEquivalentesCondensador.pnghttp://en.wikipedia.org/wiki/File:CircuitosEquivalentesCondensador.pnghttp://en.wikipedia.org/wiki/File:CircuitosEquivalentesCondensador.pnghttp://en.wikipedia.org/wiki/File:CircuitosEquivalentesCondensador.pnghttp://en.wikipedia.org/wiki/Avalanche_breakdownhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Micahttp://en.wikipedia.org/wiki/Energy_density8/3/2019 Temperature Monitoring Robot
34/56
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
http://en.wikipedia.org/wiki/Equivalent_series_inductancehttp://en.wikipedia.org/wiki/Equivalent_series_inductance8/3/2019 Temperature Monitoring Robot
35/56
(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.
8/3/2019 Temperature Monitoring Robot
36/56
Block diagram:
Logic Diagram:
8/3/2019 Temperature Monitoring Robot
37/56
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.
8/3/2019 Temperature Monitoring Robot
38/56
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.
8/3/2019 Temperature Monitoring Robot
39/56
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
8/3/2019 Temperature Monitoring Robot
40/56
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.
8/3/2019 Temperature Monitoring Robot
41/56
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
8/3/2019 Temperature Monitoring Robot
42/56
9 D2 Data bus line 2
10 D3 Data bus line 3
11 D4 Data bus line 4
12 D5 Data bus line 5
13 D6 Data bus line 6
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
8/3/2019 Temperature Monitoring Robot
43/56
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
8/3/2019 Temperature Monitoring Robot
44/56
Perform miscellaneous functions
8/3/2019 Temperature Monitoring Robot
45/56
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
2 Function Set: 8-bit, 2 Line, 5x7 Dots 0x38 56
3 Function Set: 4-bit, 1 Line, 5x7 Dots 0x20 32
4 Function Set: 4-bit, 2 Line, 5x7 Dots 0x28 40
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
8/3/2019 Temperature Monitoring Robot
46/56
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-microcontroller8/3/2019 Temperature Monitoring Robot
47/56
Step 1:
Step 2:
Click on new project
8/3/2019 Temperature Monitoring Robot
48/56
Step 3:
Click on AVR GCC
Write the project name
Select your project location.
Click on Next>>
8/3/2019 Temperature Monitoring Robot
49/56
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-microcontroller8/3/2019 Temperature Monitoring Robot
50/56
Step5:
Write the code in main body area.
Save the project file.
8/3/2019 Temperature Monitoring Robot
51/56
Step6:
Go to PROJECT -> Configuration Options
8/3/2019 Temperature Monitoring Robot
52/56
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.
8/3/2019 Temperature Monitoring Robot
53/56
Step 8:
Go to BUILD -> Compile.
This will compile your code and generate error if any.
8/3/2019 Temperature Monitoring Robot
54/56
For the first time it will generate two errors, ignore them.
Step 9:
8/3/2019 Temperature Monitoring Robot
55/56
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.
8/3/2019 Temperature Monitoring Robot
56/56
Recommended