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The main idea of this project is to develop “Refrigeration effect from waste heat using thermo electric effects”. we know that complete conversion of heat energy to work is not possible. So the waste heat is effectively used to produce refrigeration effect. The main theme of project is to analyze hermo electric principle as waste heat recovery technology and to apply the hermo electric effect as waste heat recovery to household appliances. In this project we are hoping to build a circuit which involves various components that help in charging the battery from waste heat which in turn the electric energy from battery helps in producing refrigeration effect. The waste heat from radiator is captured by peltier plates and the voltage generated is charged to a 12v battery using charging circuit. The electrical energy from battery is needed to send to a RPS ( ReGULA ING POWeR SUPPLY ) circuit and micro controller motherboard circuit . The RPS circuit sends the required power input and mother board circuit sends the required logical input to the relay circuit, which is the input to refrigeration generation effect. Thermo electric generator directly converts waste heat energy into electric power where it is unnecessary to consider cost of the thermal energy input. The application of this technology can also improve the overall efficiency of energy conversion systems. Even though output is low with available techniques,feasible electricity generation is possible due to waste heat emitted from the automobiles.
AIM AND OBJECTIVE
The primary objective of the project is generating refrigeration effect by waste heat ( radiator heat) using thermo electric effects.
This project would provide an alternative to conventional refrigeration systems which are generally used.While considering the power refrigerator with the use of heat energy which is a non conventional energy ,will be economical without use of any electrical power.
The thermoelectric effect is the conversion of temperature differences to electric voltage and vice versa. A thermoelectric device generate voltage when it’s ends differ in temperatures on either sides. Conversely, when a voltage is applied to it, it generates a temperature difference at its junctions. hermoelectric effect can be used to generate electricity, know temperature or change the temperature of the materials when needed. Because the polarity of the voltage will makes us to know the direction of the cooling and heating, these devices will be used as temperature controllers.
The term “thermoelectric effect” encloses three separately identified effects: the Seebeck effect, Peltier effect, and homson effect, this will be treated as peltier -seebeck effect and its study . The Peltier–Seebeck and homson effects are thermodynamically reversible, whereas Joule heating is not.
A thermocouple is a temperature detecting device consisting of two dissimilar conductors that contact each other at one or more spots. It produces a voltage when the temperature of one of the spots differs from the other spots. Thermocouples are a widely used type of temperature sensors for measuring devices and control instruments,and can also convert a temperature gradient into electricity. Thermo couples are affordable in price and has wide usage, interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures. In addition to most other methods of temperature measurement, thermocouples are self-powered and require no external form of excitation. Any junction of dissimilar metals produce an electric potential related to temperature. Thermocouples for practical measurement of temperature are junctions of specific alloys which have a predictable relation between temperature and voltage. Different alloys are used for different temperature ranges. Properties such as resistance to corrosion is also important when choosing a type of thermocouple. Thermocouples are standardized against a reference temperature of 0 degrees Celsius, practical instruments use electronic methods of cold-junction compensation to adjust for varying temperature at the instrument terminals. electronic instruments can also compensate for the varying characteristics of the thermocouple, and so improve the precision and accuracy of measurements.
The working principle of thermocouple is based on three effects, discovered by Seebeck, Peltier and homson. hey are as follows:
1) Seebeck effect: he Seebeck effect states that when two different or unlike metals are joined together at two junctions, an electromotive force (emf) is generated at the two junctions. he amount of emf generated is different for different combinations of the metals.
2) Peltier effect: As per the Peltier effect, when two dissimilar metals are joined together to form two junctions, emf is generated within the circuit due to the different temperatures of the two junctions of the circuit.
3) Thomson effect: As per the Thomson effect, when two unlike metals are joined together forming two junctions, the potential exists within the circuit due to temperature gradient along the entire length of the conductors within the circuit.
In most of the cases the emf suggested by the Thomson effect is very small and it can be neglected by making proper selection of the metals. The Peltier effect plays a prominent role in the working principle of the thermocouple.
Principle of operation
Fig.3:PRINCIPLe OF OPeRATION
A thermocouple measuring circuit with a heat source, cold junction and a measuring instrument.
In 1821, the Germanestonian physicist Thomas Johann See beck discovered that when any conductor is subjected to a thermal gradient, it will generate a voltage. his is now known as the thermoelectric or See beck effect. Any attempt to measure this voltage necessarily involves connecting another conductor to the “hot” end. This additional conductor will then also experience the temperature gradient, and develop a voltage of its own which will oppose the original. Fortunately, the magnitude of the effect depends on the metal in use. Using a dissimilar metal to complete the circuit creates a circuit in which the two legs generate different voltages, leaving a small difference in voltage available for measurement. hat difference increases with temperature, and is between 1 and 70 microvolts per degree Celsius (µV/°C) for standard metal combinations.
The general circuit for the working of thermocouple is shown in the figure 1 above. It comprises of two dissimilar metals, A and B. These are joined together to form two junctions, p and q, which are maintained at the temperatures 1and 2 respectively. Remember that the thermocouple cannot be formed if there are not two junctions. Since the two junctions are maintained at different temperatures the Peltier emf is generated within the circuit and it is the function of the temperatures of two junctions.
If the temperature of both the junctions is same, equal and opposite emf will be generated at both junctions and the net current flowing through the junction is zero. If the junctions are maintained at different temperatures, the emf’s will not become zero and there will be a net current flowing through the circuit. The total emf flowing through this circuit depends on the metals used within the circuit as well as the temperature of the two junctions. he total emf or the current flowing through the circuit can be measured easily by the suitable device.
The device for measuring the current or emf is connected within the circuit of the thermocouple. It measures the amount of emf flowing through the circuit due to the two junctions of the two dissimilar metals maintained at different temperatures. In figure 2 the two junctions of the thermocouple and the device used for measurement of emf (potentiometer) are shown.
Now, the temperature of the reference junctions is already known, while the temperature of measuring junction is unknown. he output obtained from the thermocouple circuit is calibrated directly against the unknown temperature. Thus the voltage or current output obtained from thermocouple circuit gives the value of unknown temperature directly.
EMBEDDED SYS EM
An embedded system is a special-purpose system in which the computer is completely encapsulated by or dedicated to the device or system it controls. Unlike a general-purpose computer, such as a personal computer, an embedded system performs one or a few predefined tasks, usually with very specific requirements. Since the system is dedicated to specific tasks, design engineers can optimize it, reducing the size and cost of the product. embedded systems are often mass-produced, benefiting from economies of scale.
Personal digital assistants (PDAs) or handheld computers are generally considered embedded devices because of the nature of their hardware design, even though they are more expandable in software terms. his line of definition continues to blur as devices expand. With the introduction of the OQO Model 2 with the Windows XP operating system and ports such as a USB port — both features usually belong to “general purpose computers”, — the line of nomenclature blurs even more.
Physically, embedded systems ranges from portable devices such as digital watches and MP3 players, to large stationary installations like traffic lights, factory controllers, or the systems controlling nuclear power plants.
In terms of complexity embedded systems can range from very simple with a single microcontroller chip, to very complex with multiple units, peripherals and networks mounted inside a large chassis or enclosure.
1.2 examples of embedded Systems:
- Avionics, such as inertial guidance systems, flight control hardware/software and other integrated systems in aircraft and missiles
- Cellular telephones and telephone switches
- engine controllers and antilock brake controllers for automobiles
- Home automation products, such as thermostats, air conditioners, sprinklers, and security monitoring systems
- Handheld calculators
- Handheld computers
- Household appliances, including microwave ovens, washing machines, television sets, DVD players and recorders
- Medical equipment
- Personal digital assistant
- Videogame consoles
- Computer peripherals such as routers and printers.
- Industrial controllers for remote machine operation.
Hard ware implementation
Fig.4:PIN DIAGRAM OF MICROCONTROLLeR
Digital supply voltage.
Port B (PB7:0) X AL1/X AL2/ OSC1/ OSC2
PortB is an 8-bit bi-directional I/O port with internal pull-up resistors(selected for each bit).
The Port B output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up resistors are activated. he 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.
Port C (PC5:0)
Port C is a 7-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). hePC5..0 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. he Port C pins are tri-stated when a reset condition becomes active,even if the clock is not running.
If the RS DISBL 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 RS DISBL Fuse is unprogrammed, PC6 is used as a Reset input. A low level on this pinfor longer than the minimum pulse length will generate a Reset, even if the clock is not running . The minimum pulse length is given in able 29-3 on page 307. Shorter pulses are not guaranteed to generate a Reset.
Port D (PD7:0)
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). he 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. he Port D pins are tri-stated when a reset condition becomes active,even if the clock is not running.
A is the supply voltage pin for the A/D Converter, PC3:0, and ADC7:6. It should be externallyconnected to VCC, even if the ADC is not used. .
through a low-pass filter. Note that PC6..4 use digital supply voltage, VCC
AReF is the analog reference pin for the A/D Converter.
ADC7:6 ( QFP and QFN/MLF package only)
In the QFP 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
The Atmel A mega48/88/168 is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. By executing powerful instructions in a single clock cycle, the A mega48/88/168 achieves throughputs approaching 1 MIPS per MHz allowing the system designer to optimize power consumption versus processing speed.
The AVR core combines a rich instruction set with 32 general purpose working registers. All the32 registers are directly connected to the Arithmetic Logic Unit (ALU), allowing two independent registers to be accessed in one single instruction executed in one clock cycle. he resulting architecture is more code efficient while achieving throughputs up to ten times faster than conventional CISC microcontrollers.
Reliability Qualification results show that the projected data retention failure rate is much less than 1 PPM over 20 years at 85°C or 100 years at 25°C.
Capacitive touch sensing
The Atmel Q ouch Library provides a simple to use solution to realize touch sensitive interfaceson most Atmel AVR microcontrollers. he Q ouch Library includes support for the Q ouch and QMatrix acquisition methods. ouch sensing can be added to any application by linking the appropriate Atmel Q ouch Libraryfor the AVR Microcontroller. his is done by using a simple set of APIs to define the touch channels and sensors, and then calling the touch sensing API’s to retrieve the channel information and determine the touch sensor states.
2.3 Architectural overview
FIG.5:ARCHITeCTURe OF MICROCONTROLLeR
In order to maximize performance and parallelism, the AVR uses a Harvard architecture – with separate memories and buses for program and data. Instructions in the program memory are executed with a single level pipelining. While one instruction is being executed, the next instruction is pre-fetched from the program memory. his concept enables instructions to be executed in every clock cycle. he program memory is In-System Reprogrammable Flash memory.
The fast-access Register File contains 32 × 8-bit general purpose working registers with a singleclock cycle access time. his allows single-cycle Arithmetic Logic Unit (ALU) operation. In a typical ALU operation, two operands are output from the Register File, the operation is executed,and the result is stored back in the Register File – in one clock cycle.
Six of the 32 registers can be used as three 16-bit indirect address register pointers for DataSpace addressing – enabling efficient address calculations. One of the these address pointerscan also be used as an address pointer for look up tables in Flash program memory. heseadded function registers are the 16-bit X-register, Y-register, and Z-register, described later inthis section.
The ALU supports arithmetic and logic operations between registers or between a constant anda register. Single register operations can also be executed in the ALU. After an arithmetic operation, the Status Register is updated to reflect information about the result of the operation. Program flow is provided by conditional and unconditional jump and call instructions, able to directly address the whole address space. Most AVR instructions have a single 16-bit word format. every program memory address contains a 16-bit or 32-bit instruction.
ALU – Arithmetic Logic Unit
The high-performance AVR ALU operates in direct connection with all the 32 general purpose working registers. Within a single clock cycle, arithmetic operations between general purpose registers or between a register and an immediate are executed. hTe ALU operations are divided into three main categories – arithmetic, logical, and bit-functions. Some implementations of the architecture also provide a powerful multiplier supporting both signed/unsigned multiplication and fractional format.
The Status Register contains information about the result of the most recently executed arithmetic instruction. his information can be used for altering program flow in order to perform conditional operations. Note that the Status Register is updated after all ALU operations, as specified in the Instruction Set Reference. his will in many cases remove the need for using the dedicated compare instructions, resulting in faster and more compact code.
The Status Register is not automatically stored when entering an interrupt routine and restored when returning from an interrupt. his must be handled by software.
General purpose register file
The register file is optimized for the AVR enhanced RISC instruction set. In order to achieve the required performance and flexibility, the following input/output schemes are supported.
- One 8-bit output operand and one 8-bit result input
- wo 8-bit output operands and one 8-bit result input
- wo 8-bit output operands and one 16-bit result input
- One 16-bit output operand and one 16-bit result input
Figure 7-2shows the structure of the 32 general purpose working registers in the CPU.
Most of the instructions operating on the register file have direct access to all registers, and most of them are single cycle instructions.
directly into the first 32 locations of the user Data Space. Although not being physically implemented as SRAM locations, this memory organization provides great flexibility in access of the egisters, as the X-, Y- and Z-pointer registers can be set to index any register in the file
The Stack is mainly used for storing temporary data, for storing local variables and for storing return addresses after interrupts and subroutine calls. he Stack Pointer Register always points to the top of the Stack. Note that the Stack is implemented as growing from higher memory locations to lower memory locations. his implies that a Stack PUSH command decreases the Stack Pointer.
he Stack Pointer points to the data SRAM Stack area where the Subroutine and InterruptStacks are located. his Stack space in the data SRAM must be defined by the program before any subroutine calls are executed or interrupts are enabled. he Stack Pointer must be set to point above 0x0100, preferably RAMeND. he Stack Pointer is decremented by one when data is pushed onto the Stack with the PUSH instruction, and it is decremented by two when the return address is pushed onto the Stack with subroutine call or interrupt. he Stack Pointer is incremented by one when data is popped from the Stack with the POP instruction, and it is incremented by two when data is popped from the Stack with return from subroutine Re or return from interrupt Re I.
The AVR Stack Pointer is implemented as two 8-bit registers in the I/O space. he number of bits actually used is implementation dependent. Note that the data space in some implementations of the AVR architecture is so small that only SPL is needed. In this case, the SPH Register will not be present.
Reset and interrupt handling
The AVR provides several different interrupt sources. These interrupts and the separate Reset Vector each have a separate program vector in the program memory space. All interrupts are assigned individual enable bits which must be written logic one together with the Global Interrupt enable bit in the Status Register in order to enable the interrupt. Depending on the Program Counter value, interrupts may be automatically disabled when Boot Lock bits BLB02 or BLB12 are programmed. his feature improves software security. See the section “Memory programming” on page 285 for details.
he lowest addresses in the program memory space are by default defined as the Reset determines the priority levels of the different interrupts. he lower the address the higher is the priority level. ReSe has the highest priority, and next is IN 0 – the external Interrupt Request0. he Interrupt Vectors can be moved to the start of the Boot Flash section by setting the IVSeL bit in the MCU Control Register (MCUCR). Refer to “Interrupts” on page 56for more information.
The Reset Vector can also be moved to the start of the Boot Flash section by programming the BOOTRS Fuse, see “Boot loader support – Read-while-write self-programming, Atmel
A mega88 and Atmel A mega168” on page 269.
When an interrupt occurs, the Global Interrupt enable I-bit is cleared and all interrupts are disabled. he user software can write logic one to the I-bit to enable nested interrupts. All enabled interrupts can then interrupt the current interrupt routine. he I-bit is automatically set when a Return from Interrupt instruction – Re I – is executed.
There are basically two types of interrupts. he first type is triggered by an event that sets the Interrupt Flag. For these interrupts, the Program Counter is vectored to the actual Interrupt Vector in order to execute the interrupt handling routine, and hardware clears the corresponding Interrupt Flag. Interrupt Flags can also be cleared by writing a logic one to the flag bit position(s)to be cleared. If an interrupt condition occurs while the corresponding interrupt enable bit is cleared, the Interrupt Flag will be set and remembered until the interrupt is enabled, or the flag is cleared by software. Similarly, if one or more interrupt conditions occur while the Global Interrupt enable bit is cleared, the corresponding Interrupt Flag(s) will be set and remembered until the Global Interrupt enable bit is set, and will then be executed by order of priority.
The second type of interrupts will trigger as long as the interrupt condition is present. These interrupts do not necessarily have Interrupt Flags. If the interrupt condition disappears before the interrupt is enabled, the interrupt will not be triggered.
When the AVR exits from an interrupt, it will always return to the main program and execute one more instruction before any pending interrupt is served. Note that the Status Register is not automatically stored when entering an interrupt routine, nor restored when returning from an interrupt routine. This must be handled by software. When using the CLI instruction to disable interrupts, the interrupts will be immediately disabled. No interrupt will be executed after the CLI instruction,even if it occurs simultaneously with the CLI instruction. The following example shows how this can be used to avoid interrupts during the timed eePROM write sequence.
Assembly code example
T his documentation contains simple code examples that briefly show how to use various parts of the device. These code examples assume that the part specific header file is included before compilation. Be aware that not all C compiler vendors include bit definitions in the header files and interrupt handling in C is compiler dependent. Please confirm with the C compiler documentation for more details.
For I/O Registers located in extended I/O map, “IN”, “OU ”, “SBIS”, “SBIC”, “CBI”, and “SBI” instructions must be replaced with instructions that allow access to extended I/O. Typically “LDS” and “S S” combined with “SBRS”, “SBRC”, “SBR”, and “CBR”.
in r16, SReG ; store SReG value
cli ; disable interrupts during timed sequence
sbieeCR, eeMPe ; start eePROM write
outSReG, r16 ; restore SReG value (I-bit)
C code example
cSReG = SReG;/* store SReG value */
/* disable interrupts during timed sequence */
eeCR |= (1<<eeMPe); /* start eePROM write */
eeCR |= (1<<eePe);
SReG = cSReG; /* restore SReG value (I-bit) */
Assembly code example
sei ; set Global Interrupt enable
sleep; enter sleep, waiting for interrupt
; note: will enter sleep before any pending interrupt(s)
C code example
__enable_interrupt(); /* set Global Interrupt enable */
__sleep(); /* enter sleep, waiting for interrupt */
/* note: will enter sleep before any pending interrupt(s) */
Interrupt response time
The interrupt execution response for all the enabled AVR interrupts is fourclock cycles minimum. After four clock cycles the program vector address for the actual interrupt handling routine is executed. During this four clock cycle period, the Program Counter is pushed onto the Stack.
The vector is normally a jump to the interrupt routine, and this jump takes three clock cycles. If an interrupt occurs during execution of a multi-cycle instruction, this instruction is completed before the interrupt is served. If an interrupt occurs when the MCU is in sleep mode, the interrupt execution response time is increased by four clock cycles. his increase comes in addition to the start-up time from the selected sleep mode.
A return from an interrupt handling routine takes four clock cycles. During these four clock Cycles, the Program Counter (two bytes) is popped back from the Stack, the Stack Pointer is Incremented by two, and the I-bit in SReG is set.
by enabling the internal Brown-out Detector (BOD). If the detection level of the internal BOD does not match the needed detection level, an external low VCCreset Protection circuit can be used. If a reset occurs while a write operation is in progress, the write operation will be completed provided that the power supply voltage is sufficient.
General purpose I/O registers
The A mega48/88/168 contains three General Purpose I/O Registers. hese registers can be used for storing any information, and they are particularly useful for storing global variables and Status Flags. General Purpose I/O Registers within the address range 0x00 – 0x1F are directly bit-accessible using the SBI, CBI, SBIS, and SBIC instructions.
System clock and clock options
Clock systems and their distribution
need not be active at a given time. In order to reduce power consumption, the clocks to modules not being used can be halted by using different sleep modes, as described in “Power management and sleep modes”
Power management and sleep modes
Sleep modes enable the application to shut down unused modules in the MCU, thereby saving power. he AVR provides various sleep modes allowing the user to tailor the power consumption to the application’s requirements.
When the SM2..0 bits are written to 000, the SLeeP instruction makes the MCU enter Idle mode, stopping the CPU but allowing the SPI, USAR , analog comparator, ADC, 2-wire serial interface, timer/counters, watchdog, and the interrupt system to continue operating. This sleep mode basically halts clkCPU and clkFLASH, while allowing the other clocks to run.
Idle mode enables the MCU to wake up from external triggered interrupts as well as internal ones like the timer overflow and USAR transmit complete interrupts. If wake-up from the analog comparator interrupt is not required, the analog comparator can be powered down by setting the ACD bit in the analog comparator control and status register– ACSR. his will reduce power consumption in Idle mode. If the ADC is enabled, a conversion starts automatically when this mode is entered.
ADC noise reduction mode
When the SM2..0 bits are written to 001, the SLeeP instruction makes the MCU enter ADC Noise Reduction mode, stopping the CPU but allowing the ADC, the external interrupts, the 2-wire Serial Interface address watch, imer/Counter2
This improves the noise environment for the ADC, enabling higher resolution measurements. If the ADC is enabled, a conversion starts automatically when this mode is entered. Apart from the ADC Conversion Complete interrupt, only an external Reset, a Watchdog System Reset, a Watchdog Interrupt, a Brown-out Reset, a 2-wire Serial Interfaceaddress match, a imer/Counter2 interrupt, an SPM/eePROM ready interrupt, an external level interrupt on IN 0 or IN 1 or a pin change interrupt can wake up the MCU from ADC Noise Reduction mode.
When the SM2..0 bits are written to 010, the SLeeP instruction makes the MCU enter powerdown mode. In this mode, the external oscillator is stopped, whilethe external interrupts, the 2-wire serial Interface address watch, and the Watchdog continue operating (if enabled). Only an external reset, a watchdog system reset, a watchdog interrupt, a brown-out reset, a 2-wire serial interface address match, an external level interrupt on IN 0 or IN 1, or a pin change interrupt can wake up the MCU. his sleep mode basically halts all generated clocks, allowing operation of asynchronous modules only.
Note that if a level triggered interrupt is used for wake-up from power-down mode, the changed level must be held for some time to wake up the MCU. Refer to “external interrupts” on page 66 for details.
When waking up from power-down mode, there is a delay from the wake-up condition occurs until the wake-up becomes effective. his allows the clock to restart and become stable after having been stopped. he wake-up period is defined by the same CKSeL fuses that define the reset time-out period, as described in “Clock sources” .
When the SM2..0 bits are written to 011, the SLeeP instruction makes the MCU enter powersave mode. his mode is identical to power-down, with one exception:
If imer/Counter2 is enabled, it will keep running during sleep. he device can wake up from either timer overflow or output compare event from imer/Counter2 if the corresponding imer/Counter2 interrupt enable bits are set in IMSK2, and the global interrupt enable bit in SReG is set.
When the SM2..0 bits are 110 and an external crystal/resonator clock option is selected, the SLeeP instruction makes the MCU enter standby mode. his mode is identical to power-down with the exception that the oscillator is kept running.From standby mode, the device wakes up in six clock cycles
Power reduction register
The power reduction register (PRR), see “PRR – Power reduction register” on page 44, provides a method to stop the clock to individual peripherals to reduce power consumption. The current state of the peripheral is frozen and the I/O registers can not be read or written. Resources used by the peripheral when stopping the clock will remain occupied, hence the peripheral should in most cases be disabled before stopping the clock.Waking up a module, which is done by clearing the bit in PRR, puts the module in the same state as before shutdown.
Module shutdown can be used in Idle mode and Active mode to significantly reduce the overall power consumption. See “Power-down supply current” on page 323for examples. In all other sleep modes, the clock is already stopped.
Minimizing power consumption
There are several possibilities to consider when trying to minimize the power consumption in an AVR controlled system. In general, sleep modes should be used as much as possible, and the sleep mode should be selected so that as few as possible of the device’s functions are operating. All functions not needed should be disabled. In particular, the following modules may need special consideration when trying to achieve the lowest possible power consumption.
Analog to digital converter
If enabled, the ADC will be enabled in all sleepmodes. o save power, the ADC should be disabled before entering any sleep mode. When the ADC is turned off and on again, the next conversion will be an extended conversion. Refer to “Analog-to-digital converter” on page 244 for details on ADC operation.
When entering Idle mode, the analog comparator should be disabled if not used. When entering ADC noise reduction mode, the analog comparator should be disabled. In other sleep modes, the analog comparator is automatically disabled. However, if the analog comparator is set up to use the internal voltage reference as input, the analog comparator should be disabled in all sleep modes. Otherwise, the internal voltage reference will be enabled, independent of sleep mode. Refer to “Analog comparator” on page 241for details on how to configure the analog
On-chip debug system
If the on-chip debug system is enabled by the DWeN Fuse and the chip enters sleep mode, the main clock source is enabled and hence always consumes power. In the deeper sleep modes, this will contribute significantly to the total current consumption.
A relay is an electrical switch that opens and closes under the control of another electrical circuit. In the original form, the switch is operated by an electromagnet to open or close one or many sets of contacts. A relay is able to control an output circuit of higher power than the input circuit, it can be considered to be, in a broad sense, a form of an electrical amplifier. So a relay can be defined as an automatic electromagnetic/electronic switch, which can be used to make or break the circuit.
The relay used in this project work is electromagnetic relay. he electromagnetic relay is basically a switch (or a combination of switches) operated by the magnetic force generated by a current flowing through a coil. essentially, it consists of four parts an electromagnet comprising a coil and a magnetic circuit, a movable armature, a set of contacts, and a frame to mount all these components. However, very wide ranges of relays have been developed to meet the requirements of the industry. This relay is nothing but a switch, which operates electromagnetically. It opens or closes a circuit when current through the coil is started or stopped. When the coil is energized armature is attracted by the electromagnet and the contacts are closed. That is how the power is applied to the signals (indicators). hTe construction of the typical relay contains a code surrounded by a coil of copper wire. he core is mounted on a metal frame . The movable part of the relay is called armature. When a voltage is applied to the coil terminals, the current flowing through the coil produces a magnetic field in the core. In other words, the core acts as an electromagnet and attracts the metal armature. When the armature is attracted to the core, the magnetic path is from the core through armature, through the frame, and back to the core. On removing the voltage the spring attached to the armature returns the armature to its original position. In this position, there is a small air-gap in the magnetic path. Hence, more power is needed to pull in the armature than that needed to keep it held in the attracted position. he detailed description of the relay is provided in the further chapters.
A Light emitting diode (LeD) is essentially a p-n junction diode. When carriers are injected across a forward-biased junction, it emits incoherent light. Most of the commercial LeD’s are realized using a highly doped n and a p Junction. p-n+ Junction under Unbiased and biased conditions. (p-n Junction Devices and Light emitting Diodes by Safa Kasap) To understand the principle, let’s consider an unbiased p-n+junction (Figure1 shows the p-n+ energy band diagram). The depletion region extends mainly into the p-side. here is a potential barrier from econ the n-side to the econ the p-side, called the built-in voltage, V0. This potential barrier prevents the excess free electrons on the n+ side from diffusing into the p side. When a Voltage V is applied across the junction, the built-in potential reduced from V0 to V0– V. This allows the electrons from the n+ side to get injected into the p-side. Since electrons are the minority carriers in the p-side, this process is called minority carrier injection. But the hole injection from the p side to n+ side is very less and so the current is primarily due to the flow of electrons into the p-side.
These electrons injected into the p-side recombine with the holes. This recombination results in spontaneous emission of photons (light). This effect is called injection electro luminescence. These photons should be allowed to escape from the device without being reabsorbed.
The recombination can be classified into the following two kinds
- Direct recombination
- Indirect recombination
In direct band gap materials, the minimum energy of the conduction band lies directly above the maximum energy of the valence band in momentum space energy In this material, free electrons at the bottom of the conduction band can recombine directly with free holes at the top of the valence band, as the momentumof the two particles is the same. his transition from conduction band to valence band involves photon emission (takes care of the principle of energy conservation). his is known as direct recombination. Direct recombination occurs spontaneously. GaAs is an example of a direct band-gap material. Direct Bandgap and Direct Recombination Indirect Recombination: In the indirect band gap materials, the minimum energy in the conduction band is shifted by a k-vector relative to the valence band. he k-vector difference represents a difference in momentum. Due to this difference in momentum, the probabilityof direct electronhole recombination is less. In these materials, additional dopants(impurities) are added which form very shallow donor states. These donor states capture the free electrons locally; provides the necessary momentum shift for recombination. These donor states serve as the recombination centers. his is called Indirect (non-radiative) Recombination. the e-k plot of an indirect band gap material and an example of how Nitrogen serves as a recombination center in GaAsP. In this case it creates a donor state,
WhenSiC is doped with Al, it recombination takes place through an acceptor level. he indirect recombination should satisfy both conservation energy, and momentum. Thus besides a photon emission, phonon emission or absorption has to take place.
GaP is an example of an indirect band-gap material. Indirect Bandgap and NonRadiative recombination he wavelength of the light emitted, and hence the color, depends on the band gap energy of the materials forming the p-n junction. he emitted photon energy is approximately equal to the band gap energy of the semiconductor. he following equation relates the wavelength and the energy band gap.
λ= hc/ eg
Where h is Plank’s constant, c isthe speed of the light and egis the energy band gap hus, a semiconductor with a 2 eV band-gap emits light at about 620 nm, in the red. A 3 eV band-gap material would emit at 414 nm, in the violet. Appendix 4 shows a list of semiconductor materials and the corresponding colors.
Power Supply: As per the power requirement of the hardware of the intelligent traffic light control and monitoring system, supply of +5V w.r.t GND
µA7800 SeRIeS POSITIVE-VOL AGE REGULATORS
3- Terminal Regulators Output Current up to 1.5 A Internal Thermal-Overload Protection High Power-Dissipation Capability Internal Short-Circuit Current Limiting Output Transistor Safe-Area Compensation
Fig.6 :REGULATOR OVERVIEW
description/ordering information his series of fixed-voltage integrated-circuit voltage regulators is designed for a wide range of applications. These applications include on-card regulation for elimination of noise and distribution problems associated with single-point regulation. each of these regulators can deliver up to 1.5 A of output current. The internal current-limiting and thermal-shutdown features of these regulators essentially make them immune to overload.
In addition to use as fixed-voltage regulators, these devices can be used with external components to obtain adjustable output voltages and currents, and also can be used as the power-pass element in precision regulators.
operation with a load common to a voltage of opposite polarity
In many cases, a regulator powers a load that is not connected to ground but, instead, is connected to a voltage source of opposite polarity (e.g., operational amplifiers, level-shifting circuits, etc.). In these cases, a clamp diode should be connected to the regulator output. his protects the regulator from output polarity reversals during startup and short-circuit operation.
For example a 5V regulated supply:
FIG.7:BLOCK DIAGRAM OF MICROCONTROLeR
each of the blocks is described in more detail below:
- Transformer – steps down high voltage AC mains to low voltage AC.
- Rectifier – converts AC to DC, but the DC output is varying.
- Smoothing – smoothes the DC from varying greatly to a small ripple.
- Regulator – eliminates ripple by setting DC output to a fixed voltage.
Power supplies made from these blocks are described below with a circuit diagram and a graph of their output:
- Transformer only
- Transformer + Rectifier
- T ransformer + Rectifier + Smoothing
- Transformer + Rectifier + Smoothing + Regulator
The low voltage AC output is suitable for lamps, heaters and special AC motors. It is not suitable for electronic circuits unless they include a rectifier and a smoothing capacitor.
Transformer + Rectifier:
The varying DC output is suitable for lamps, heaters and standard motors. It is not suitable for electronic circuits unless they include a smoothing capacitor.
Transformer + Rectifier + Smoothing:
T he smooth DC output has a small ripple. It is suitable for most electronic circuits.
Transformer + Rectifier + Smoothing + Regulator:
The regulated DC output is very smooth with no ripple. It is suitable for all electronic circuits.
Fig .8: SCHEMATIC CIRCUIT DIAGRAM
4.1 AVR STUDIO
AVR Studio 4 is a professional Integrated Development environment (IDe) for writing and debugging AVR applications in Windows 9x/N /2000/XP environments. his tutorial assumes that you have installed AVR Studio 4 on your computer. If you do not have AVR Studio yet, you may obtain a copy of AVR Studio 4 from one of 3 places:
- Atmel Corporation: http://www.atmel.com
- AVR Freaks: http://www.avrfreaks.net
- Borrow a CD from your instructor
This will guide you through the steps required for:
- executing the AVR Studio 4 Integrated Development environment (IDe),
- Typing in a program,
- Assembling the program, and
- Simulating a program
Open AVR Studio 4 IDe. You should see the program banner shown below:
Figure : AVR Studio 4 Banner
When IDe opens, you will see the programming and simulator environment as well as adialog box (Figure 3) requesting information: are you starting a new project or opening a saved
Click on the “New Project” button:
In the next dialog box, choose the Atmel AVR Assembler as the project type:
Choose Atmel AVR Assembler
Type in a project name and the initial file name:
Figure: Type Project and Initial File Names
Click on the “Next” button
Choose “AVR Simulator” for the Debug Platform and then scroll down the right window to choose the A mega32 AVR processor. Select in the drop down list.Choose Simulator and A mega32
Click on the “Finish” button. You should then see the IDe
Type in the program as shown in Figure 1. Note the color-coded text. This is done automatically by the IDe and helps you to make corrections as you go.
When you have completed the program save it. It is also good practice to periodically save your program as you type.
Assemble your program. You may do this by selecting “Build” from the “Build Menu” or by striking the [F7] key:
Continue assembling and correcting errors until the program assembles without error (Note the green dot in the lower window and the comment that states: “Assembly complete, 0 errors, 0 warnings”) you are ready to simulate.
Simulate the program. o start the simulator you may choose “Start Debugging” from the “Debug Menu” or you may click on the arrow button as shown below:
A MeGA 8 COMPAILeR AV4-IDe USING:
Atmega8 program dumping from ISP7 using :
Building Projects and Creating a HEX Files
Typical, the tool settings under Options – Target are all you need to start a new application. You may translate all source files and line the application with a click on the Build Target toolbar icon. When you build an application with syntax errors, avr4 will display errors and warning messages in the Output Window – Build page. A double click on a message line opens the source file on the correct location in a AVR4 editor window. Once you have successfully generated your application you can start debugging.
Advantages and Applications
- The recovery process will add to the efficiency of the process and thus it will decrease the fuel costs and consumption of energy needed for that process.
- There will be dramatical reduction in the pollution since most of the energy is recycled.
- Power generation from concentrated solar panels.
- Power generation from house hold appliances like television , microwave oven and washing machine etc which releases heat.
- There will be reduction in the energy fed to the systems like fans, pumps etc.
- Waste heat of different temperatures can be used for the various mechanical applications.
Net Refrigeration effect at the junction is given by
Q1 = α c i -1/2 i2R-U( H– C)
Q1=Net refrigeration effect at the cold junction
α=Relative seebeck co-efficient for given material
C= Heat source temperature
I= Current in Amps
R= Total electric resistance in ohms
1/UA = 1/h1A1+Dx/KA+1/h2A2
Overall Heat transfer co-efficent
h1,h2=Convective heat transfer coefficient of aluminium
K=thermal conductivity of aluminium
Range=205 to 250 w/mk
U = 1/(1/50+1/1000*250+1/50)
Voltage = 12v
Current = 1.3 amps
By ohms law,
12 = 1.3 * R
Resistance, R= 9.2 ohms
U = 25 w/m2k
h = 60+273 = 333k
c = 23+273 = 296k
α = 3.5 for AL
I = 1.3 amps
V = 12 volts
R = 9.2 ohms
NE REFRIGERATION EFFECT
Q1 =α c i -1/2 i2R-U( H– C)
= 3.5*296*1.3 – .5(1.69*9.2) – 25(333-296)
= 1346.8 – 7.774 – 925
= 414.026 w
Power input = α*I*( h– c) + i2R
= 3.5*1.3(333-296) + 1.69(9.2)
= 183.896 w
Coefficient of Performance (Ø) is given by
Ø =Refrigeration effect/power input
Ø = 2.251
RESULTS AND DISCUSSIONS
Fig.9: Final refrigeration effect shown in the fridge
The fridge equipment shown in the fig.9 shows the final output refrigeration effect of the experimental setup of the refrigeration using waste heat using thermo electric effect.
It is constructed as empty box with insulated material for restricting the escape of heat into the box . The refrigeration effect can be felt through hand and can also be measured using thermometer.
Fig.10: Basic circuit built for conversion of waste heat to powergeneration
The experimental setup shown in the above figure demonstrates about the basic circuit designed for conversion of waste heat to refrigeration effect.
It involves charging circuit to the battery from peltier plates of radiator, a 12V battery, RPS (ReGULA eD POWeR SUPPLY) circuit, micro controller motherboard circuit and relay circuit.
Fig.11:Functioning of RPS circuit, controller motherboard circuit and relay circuit shown through glowing LeD’s
The above figures describes the functioning of the circuit through glowing LeD’s .It represents the working of circuit under passing of electrical energy from the battery.
The three glowing LeD’s represent the working of RPS circuit, micro controller motherboard circuit and relay circuit respectively . The LeD in the relay circuit triggers due to regulating effect when energy passes over 5V because power above 5V can burn the peltier plates which are fixed at fridge where the refrigeration effect is seen.
With the increasing concern about environmental issues of emissions, in particular global warming and the limitations of energy sources has resulted in further research to bring in innovative technologies of generating electrical power. In such criteria thermoelectric power generation has become an good innovative technology. In addition to this, large amount of waste heat are discharged into the environment much of it at temperatures which are too low (i.e. low-grade thermal energy) to recover using conventional electrical power generators. Thermoelectric power generation provides a useful technology in the direct conversion of waste-heat energy, into electrical power. In this paper, a background on the basic concepts of thermoelectric power generation is presented . Currently, waste heat powered thermoelectric generators are utilized in large number of useful applications due to their various advantages. These applications can be split into micro-scale and macro-scale applications based on the potential amount of heat waste energy available for conversion into electrical energy using thermoelectric generators.
Here by we conclude that energy cannot be wasted, it will be reused in another way if we go through such innovative techniques with decreased amount of emissions to the environment.
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