and promoting this critical inputWater for making Indian agriculture toConservation in the meet the International challenges ofField Farming productivity and cost of production. This also helps in(K.Rakesh Reddy) development of country.ABSTRACT CONCEPT:INTRODUCTION: We know the lack and improper power in indiaespically remoteFarm mechanization helps ineffective utilization of inputs to areas where farmeris facing manyincrease the problems.these helps in following:productivity of land and labour. first farmer has to estimateBesides it helps in reducing thedrudgery in farm the time that takes to wetoperations. This modern motor the area and setdevice performs following the timing in the timeroperation: provided in the motor. Automatic irrigation system. He has to switch on the Water management. motor, at that time current Time management. may or may not be there.if Better yield in crops & profit. current is there it flows the Wide scope for modern time period mentioned over agricultural system. there in motor.And if power is lost in betweenThis paper reviews the easy & time after resuming from powersavingfarming for an the motor runs foragriculturalist, including the remaining time period andaspects of problems facing by the gets turnoff.farmer espically in remote villageswhere modern agriculture is notbeing used .These also can beimplemented of their adoption andthe role of different public andprivate Institutions in supporting Advantages:
Helps the farmer for easy bucket or conductance type probes to farming. measure rainfall. Wireless and wired Farmer can do multiple versions both use similar mechanisms to works at the same time. temporarily suspend watering by the Helps in providing the irrigation controller — specifically they are better yielding of crops connected to the irrigation controllers The circuit comprises of sensor terminals, or are installed in series moisture with the solenoid valve common circuit sensors.microcontroller. The such that they prevent the opening of any moisture sensor gives output as valves when rain has been sensed. voltage. If the output voltage from the moisture sensor is Some irrigation rain sensors also contain below the threshold value, it a freeze sensor to keep the system from will be considered that the soil operating in freezing temperatures is dry and plants should be (typically freeze sensors are employed in watered. Using microcontroller regions where irrigation systems are not and relays, we drive the motor "blown-out" for the winter, yet there is for watering the plants/soil. sometimes a chance of overnight frosts,The first is a water conservation device such as Florida, New Jersey, Minnesota,connected to an automatic irrigation system and Connecticut mandate the use of a rainthat causes the system to shut down in theevent of rainfall sensor in all new lawn sprinkler systems. A new trend in "smart" sensors (like the Virtual Rain Sensor) are using recentIrrigation sensors weather observation data (rainfall, sunlight, temperature, humidity, andRain sensors for irrigation systems are pressure) toavailable in both wireless and hard-wired calculate evapotranspiration of water.versions, most employing hygroscopic Used in conjunction with forecast rain anddisks that swell in the presence of rain and temperatures data these can direct homeshrink back down again as they dry out — automation hardware at variable intervalsan electrical switch is in turn depressed or and durations to optimize water savings.released by the hygroscopic disk stack,and the rate of drying is typically adjustedby controlling the ventilation reaching thestack. However, some electrical typesensors are also marketed that use tipping
A DSP based conversion stages, online UPSs have been the most complex and expensive type of On-Line UPS systems. Today’s low cost, high performance Digital Signal Processors(DSPs) provide an improved and cost- effective solution foronline UPSdesign, making them(K.Rakesh Reddy &D.Praveen) software controllable, adding some facilities like remote configuration and monitoring and other network management facilities. This paper presents the basic design and merits of using real time digital signal processing (DSP) control of UPS systems. ABSTRACT Many facilities such as patienthealth care centers, data processingsystems, critical telecommunication links,LAN servers, offices etc rely onuninterruptible power supplies (UPS) tomaintain a continuous supply of power incase of line outage. In addition to requiringcontinuous power, many critical nonlinearloads are sensitive to the incoming linetransients and input harmonic voltagedistortion. Conventional UPS systems INTRODUCTION:operate to protect against suchdisturbances using complex filteringschemes, often employing large passive Un-interruptible power supplies (UPS) play an important role in interfacingcomponents. Among the various UPS critical loads such as computers, tele-systems online UPS provides maximum communication links,data-processingprotection to such loads against any power systems, life supporting systems andproblems. Because of multiple power industrial controls,e.t.c to the power grid
.Among the various UPS topologies, on – 6. Frequency instability: defined asline UPSs provides maximum protection to temporary changes in the mainssuch loads against any utility power frequency.problem, as it protects against power 7. Harmonic distortion: defined as ablackout.However,because of multiple departure from the idealpower conversion stages, on-line UPSs have sinusoidalwaveform expected onbeen most complex and expensive type of the line.systems. Typical On-Line UPS: A typical UPS consists of a rectifierToday’s low cost, high performance supplied battery bank & a static inverter-Digital Signal Processors (DSPs) filter system to convert a dc voltage to aprovide an improved and cost- sinusoidal ac output. Modern UPS systemseffective solution for online UPS minimize the harmonic content of the inverter output voltage through the use ofdesign. complex filtering schemes employing large passive components.Common power problemsThe primary role of any UPS is to provideshort-term power when the input powersource fails. However, most UPS units arealso capable in varying degrees ofcorrecting common utility power problems: 1. Power failure: defined as a total Need for Pulse Width Modulation: loss of input voltage. 2. Surge: defined as a momentary or PWM is nothing but the control of sustained increase in the main UPS inverter switching, under feedback voltage. control to realize the desired output 3. Sag: defined as a momentary or waveform and also to minimize the sustained reduction in input harmonic content of the output voltage. voltage. Pulses are generated whenever a carrier 4. Spikes, defined as a brief high signal & modulating signal crosses voltage excursion. eachother.These pulses are given to 5. Noise, defined as a high frequency thyristors and pulsating output is transient or oscillation, usually generated. Depending on the number of injected into the line by nearby output pulses generated, switching equipment. frequency of inverter is determined. Width of the pulses is proportional to magnitude
of the output sine wave and if the numberof pulses per half cycle is more, lower orderharmonics will be eliminated.General PWM techniques for UPS:1. Using Analog devices: Analog PWM uses natural sampling Then, Why DSP?technique, which compares a sinusoidal Most of the Microprocessor –modulating wave form with a triangular aided UPS systems continue to depend onwave (from a time-base generator) to the analog op-amp controls and they lackgenerate pulses. speed required for high frequency inverter control. Therefore, harmonics are not eliminated in the output wave form, insisting on the large output LC-filter circuit. With the availability of low cost- high performance DSP chips characterised by the execution of most instructions in one instruction cycle, complicated control algorithms can be executed with speed, making very high2. Using Microprocessors: sampling rate possible for digitally A digital PWM signal generator is controlled inverters. High speed DSPsinterfaced with a microprocessor. It are now capable of executing over 30calculates the pulse width at every sampling million instructions per second (MIPS).instant. According to this calculated width,the pulse generator generates the pulseswith a constant switching frequency. More reasons for using DSPs:
No analog circuitry. Thus no offsets( i.e. installation & maintenance cost saved) High speed DSP control allows for real time harmonic cancellation. Flexible configuration for many power sizes. Sophisticated switching algorithm saving overall system costs. Features may be upgraded in the Thus, the application of advanced signal same hardware, to fulfill different processing using a DSP operates to provide incoming needs. sinusoidal load voltages even under varying load situations, while eliminating the need DSP control of UPS systems: of large passive filters. Most electronic loads served The figure shown gives the basicby UPS systems are non-linear and thus block diagram of DSP control withgenerate harmonic currents that must be PWM inverter control circuit:filtered at the inverter output to reduce thedistortion to acceptable levels. The DSPcontrolled UPS systems employs softwarecontrolled harmonic conditioners with theability to dynamically adopt to changingload conditions for compensating loadharmonics without manual intervention. The functional block diagram is asshown below: Description: The output of the UPS PWM inverter is sampled and converted to an
rmsvoltage that is processed in a negative order to detect the real and imaginaryfeedback loop. The actual inverter output is values of the 5th harmonic. This function cancompared to a software rms reference be written for phase ‘a’ as,value to determine the error voltage. Theerror voltage is then passed through aproportional integral (PI) control toeliminate any steady state errors present.The result is the necessary errorcompensation signal.A harmonic distortion Where va (n) is the outputcorrection signal is then subtracted from voltage of phase a for sometime n.the error compensation signal and the The distortion signal may be representedresult is applied to the input of PWM more simply asinverter. The above mentioned harmonicdistortion correction signal is generated inthe negative feedback loop. The DigitalSignal Processor detects the harmonicdistortion signal within the output voltage Where λa5r is the real component of Aa5, andwaveform and determines the amplitude of λa5i is the imaginary component of Aa5.real and imaginary parts of the harmonic Once the harmonic distortion signalcomponents. This process will be described (Aa5, Ab5 and Ac5) is detected by the signalfor the cancellation of the 5th harmonic, correlation function, the amplitudes of thehowever, any harmonic whose frequency is real and imaginary components of the 5thbelow half the sampling frequency can be harmonic are computed by averaging thecancelled in the same manner. amplitude components of the three phases Each frame of the converted digital as shown below.output from the A/D converter passes to areal and imaginary component harmonicdetectors for phases a,b and c. For example,the harmonic distortion waveform (Aa5) isprocessed by a signal correlation function in
The amplitude components are thenapplied to a PI compensator to generate theharmonic distortion correction signalnecessary to cancel harmonic distortionfrom the output voltage. The resultingharmonic distortion correction signal is thensubtracted from the error compensationsignal and applied to the input of the PWMinverter to produce an output voltagewaveform free of harmonic distortion. Thesame technique can be applied to eliminate Hence, the DSP controlled inverterstill higher harmonics like 7th, 9thetc, and harmonic conditioners operate below figure shows the operation of to provideUPS without harmonic conditioner Sinusoidal load voltages even under varying non-linear load conditions while preventing higher operating temperatures due to additional harmonic currents. Advantages of using DSP in UPSs: High reliability and lowBut with all-harmonic conditioners dimensions:with the DSP, theenabled, the output voltage wave is number of electronic components islike below: halved, thereby reducing processing time and failure probability and increasing reliability and eliminating the use of redundant current and voltage sensors. Precision: the DSP controls the electrical values directly,
guaranteeing extreme precision and The conventional methods of UPS stability of output voltage and control and with using DSP, how the UPS avoidance of noise due to distorting control can be made more users friendly, its loads. advantages are discussed in the paper. Interactive communication: DSP No doubt, DSPs are going to lead controls the UPS in its entirety and the market of control inverters in near outputs on a serial interface all the future and already big players in the market supervision reports, for automatic like Texas Instruments, Eaton group, Intel shutdown of servers, for etc are in the arena to make use the communication on a LAN network, technology in a full swing. the Internet and Intranet and for IT maintenance which is carried out Bibliography: without switching the equipment (1)”DSP control of high-power UPS systems off. feeding nonlinear loads” by Annette Von Knowing the history: The control Jouanne and Prasad N.Enjetisen.IEEE software provides users with member, from IEEE transactions on operating and historical data in the Industrial Electronics,Vol 43,no.1,Feb,1996. form of clear read-out monitors, aiding them in taking any decisions. (2)”Digital signal processing based online Moreover the control system UPS” manual by www.cranessoftware.comupgrade can be implemented in software, (3) “Power Electronics Analysis Designmaking the latest features available to any &Apllications” by Ned Mohan,Torecompatible UPS without changes to the M.Undeland, William P. Robbinshardware. (4)”Interfacing DSPs with high performance analog converters” Jim Ryan, Raheen Industrial estate, Ireland. (5)WEMPEC-25th anniversary review meeting, R&D dept.innovation center EatonConclusion: Corporation.
VLSI DesignVLSI chiefly comprises of Front End Design and Back End design these days. While front end designincludes digital design using HDL, design verification through simulation and other verification techniques,the design from gates and design for testability, backend design comprises of CMOS library design andits characterization. It also covers the physical design and fault simulation.While Simple logic gates might be considered as SSI devices and multiplexers and parity encoders asMSI, the world of VLSI is much more diverse. Generally, the entire design procedure follows a step bystep approach in which each design step is followed by simulation before actually being put onto thehardware or moving on to the next step. The major design steps are different levels of abstractions of thedevice as a whole:1. Problem Specification: It is more of a high level representation of the system. The majorparameters considered at this level are performance, functionality, physical dimensions, fabricationtechnology and design techniques. It has to be a tradeoff between market requirements, the availabletechnology and the economical viability of the design. The end specifications include the size, speed,power and functionality of the VLSI system.2. Architecture Definition: Basic specifications like Floating point units, which system to use, like RISC(Reduced Instruction Set Computer) or CISC (Complex Instruction Set Computer), number of ALU’scache size etc.3. Functional Design: Defines the major functional units of the system and hence facilitates theidentification of interconnect requirements between units, the physical and electrical specifications ofeach unit. A sort of block diagram is decided upon with the number of inputs, outputs and timing decidedupon without any details of the internal structure.
4. Logic Design: The actual logic is developed at this level. Boolean expressions, control flow, word width, register allocation etc. are developed and the outcome is called a Register Transfer Level (RTL) description. This part is implemented either with Hardware Descriptive Languages like VHDL and/or Verilog. Gate minimization techniques are employed to find the simplest, or rather the smallest most effective implementation of the logic. 5. Circuit Design: While the logic design gives the simplified implementation of the logic,the realization of the circuit in the form of a netlist is done in this step. Gates, transistors and interconnects are put in place to make a netlist. This again is a software step and the outcome is checked via simulation. 6. Physical Design: The conversion of the netlist into its geometrical representation is done in this step and the result is called a layout. This step follows some predefined fixed rules like the lambda rules which provide the exact details of the size, ratio and spacing between components. This step is further divided into sub-steps which are:6.1 Circuit Partitioning: Because of the huge number of transistors involved, it is not possible to handle the entire circuit all at once due to limitations on computational capabilities and memory requirements. Hence the whole circuit is broken down into blocks which are interconnected.6.2 Floor Planning and Placement: Choosing the best layout for each block from partitioning step and the overall chip, considering the interconnect area between the blocks, the exact positioning on the chip in order to minimize the area arrangement while meeting the performance constraints through iterative approach are the major design steps taken care of in this step.6.3 Routing: The quality of placement becomes evident only after this step is completed. Routing involves the completion of the interconnections between modules. This is completed in two steps. First connections are completed between blocks without taking into consideration the exact geometric details of each wire and pin. Then, a detailed routing step completes point to point connections between pins on the blocks.6.4 Layout Compaction: The smaller the chip size can get, the better it is. The compression of the layout from all directions to minimize the chip area thereby reducing wire lengths, signal delays and overall cost takes place in this design step.
6.5 Extraction and Verification: The circuit is extracted from the layout for comparison with the original netlist, performance verification, and reliability verification and to check the correctness of the layout is done before the final step of packaging. 7. Packaging: The chips are put together on a Printed Circuit Board or a Multi Chip Module to obtain the final finished product. Initially, design can be done with three different methodologies which provide different levels of freedom of customization to the programmers. The design methods, in increasing order of customization support, which also means increased amount of overhead on the part of the programmer, are FPGA and PLDs, Standard Cell (Semi Custom) and Full Custom Design. While FPGAs have inbuilt libraries and a board already built with interconnections and blocks already in place; Semi Custom design can allow the placement of blocks in user defined custom fashion with some independence, while most libraries are still available for program development. Full Custom Design adopts a start from scratch approach where the programmer is required to write the whole set of libraries and also has full control over the block development, placement and routing. This also is the same sequence from entry level designing to professional designing.