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Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
Remote sensing and control of an irrigation system using a distributed wireless sensor network
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Remote sensing and control of an irrigation system using a distributed wireless sensor network

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  • 1. Remote sensing and control of an irrigation system using a distributed wireless sensor networkUNIT-1INTRODUCTION The project report describes the design Development and Fabrication of One demo unitof the project work “ Remote sensing and control of an irrigation system using a distributedwireless sensor network” using embedded systems. The purpose of this project is Efficient energy yield is a major concern in photovoltaicsystems in solar energy supply. Smart photovoltaic modules offer a potential solution toallow solar generators to maximize their productivity. And this paper describes details of the design and instrumentation of smartphotovoltaic modules, a wireless sensor network, and software for real-time sensing andcontrol of a photovoltaic system with maximum power point tracking at module level. Now a day, with the advancement technology, particularly in the field ofMicrocontrollers, all the activities in our daily living have become a part of Informationtechnology and we find microcontrollers in each and every application. Thus, trend is directingtowards Microcontrollers based project works. However, in this project the data is communicatedby using GSM. The microcontroller block is playing a major role in this project work. The microcontroller chip used in this project work is PIC 16F877A and this is like heart of the project. ThePIC 16F877A microcontroller is a 40-pin IC.1.1 RELATED WORK: To complete our project we studied about embedded systems basics and system designcycle to know how to develop the Microcontroller and Microprocessor based projects. Furtherwe analyzed some of latest controllers’ architecture available in the market. Finally we selectedPIC 16f877A controller because of its features (it is discussed in hardware requirements). Forour successful completion of this project obviously we utilized howstuffworks.com,www.microchip.com, www.google.com, en.wikipedia.org.VCET 1|Page
  • 2. Remote sensing and control of an irrigation system using a distributed wireless sensor network1.2 SCOPE OF THE PROJECT: The scope of the project is the Efficient energy yield is a major concern inphotovoltaic systems in solar energy supply. Smart photovoltaic modules offer a potentialsolution to allow solar generators to maximize their productivity. And this paper describesdetails of the design and instrumentation of smart photovoltaic modules, a wireless sensornetwork, and software for real-time sensing and control of a photovoltaic system withmaximum power point tracking at module level.VCET 2|Page
  • 3. Remote sensing and control of an irrigation system using a distributed wireless sensor networkUNIT-2INTRODUCTION TO EMBEDDED SYSTEMS2.1 EMBEDDED SYSTEM: Embedded System is a combination of hardware and software used to achieve a singlespecific task. An embedded system is a microcontroller-based, software driven, reliable, real-time control system, autonomous, or human or network interactive, operating on diverse physicalvariables and in diverse environments and sold into a competitive and cost conscious market. An embedded system is not a computer system that is used primarily for processing, nota software system on PC or UNIX, not a traditional business or scientific application. High-endembedded & lower end embedded systems. High-end embedded system - Generally 32, 64 BitControllers used with OS. Examples Personal Digital Assistant and Mobile phones etc .Lowerend embedded systems - Generally 8,16 Bit Controllers used with an minimal operating systemsand hardware layout designed for the specific purpose. Examples Small controllers and devicesin our everyday life like Washing Machine, Microwave Ovens, where they are embedded in.VCET 3|Page
  • 4. Remote sensing and control of an irrigation system using a distributed wireless sensor networkSYSTEM DESIGN CALLS:2.1.1 EMBEDDED SYSTEM DESIGN CYCLEVCET 4|Page
  • 5. Remote sensing and control of an irrigation system using a distributed wireless sensor network “V Diagram” In this place we need to discuss the role of simulation software, real-time systems anddata acquisition in dynamic test applications. Traditional testing is referred to as “static” testingwhere functionality of components is tested by providing known inputs and measuring outputs.Today there is more pressure to get products to market faster and reduce design cycle times.This has led to a need for “dynamic” testing where components are tested while in use with theentire system – either real or simulated. Because of cost and safety concerns, simulating the restof the system with real-time hardware is preferred to testing components in the actual realsystem. The diagram shown on this slide is the “V Diagram” that is often used to describe thedevelopment cycle. Originally developed to encapsulate the design process of softwareapplications, many different versions of this diagram can be found to describe different productdesign cycles. Here we have shown one example of such a diagram representing the designcycle of embedded control applications common to automotive, aerospace and defenseapplications. In this diagram the general progression in time of the development stages is shown fromleft to right. Note however that this is often an iterative process and the actual development willnot proceed linearly through these steps. The goal of rapid development is to make this cycle asefficient as possible by minimizing the iterations required for a design. If the x-axis of theVCET 5|Page
  • 6. Remote sensing and control of an irrigation system using a distributed wireless sensor networkdiagram is thought of as time, the goal is to narrow the “V” as much as possible and therebyreduce development time. The y-axis of this diagram can be thought of as the level at which the system componentsare considered. Early on in the development, the requirements of the overall system must beconsidered. As the system is divided into sub-systems and components, the process becomesvery low-level down to the point of loading code onto individual processors. Afterwardscomponents are integrated and tested together until such time that the entire system can enterfinal production testing. Therefore the top of the diagram represents the high-level system viewand the bottom of the diagram represents a very low-level view.Notes: • V diagram describes lots of applications—derived from software development. • Reason for shape, every phase of design requires a complimentary test phase. High-level to low-level view of application. • This is a simplified version. • Loop Back/Iterative process, X-axis is time (sum up).2.1.2 CHARACTERISTICS OF EMBEDDED SYSTEM • An embedded system is any computer system hidden inside a product other than a computer. • There will encounter a number of difficulties when writing embedded system software in addition to those we encounter when we write applications – Throughput – Our system may need to handle a lot of data in a short period of time. – Response–Our system may need to react to events quickly – Testability–Setting up equipment to test embedded software can be difficult – Debugability–Without a screen or a keyboard, finding out what the software is doing wrong (other than not working) is a troublesome problem – Reliability – embedded systems must be able to handle any situation without human interventionVCET 6|Page
  • 7. Remote sensing and control of an irrigation system using a distributed wireless sensor network – Memory space – Memory is limited on embedded systems, and you must make the software and the data fit into whatever memory exists – Program installation – you will need special tools to get your software into embedded systems – Power consumption – Portable systems must run on battery power, and the software in these systems must conserve power – Processor hogs – computing that requires large amounts of CPU time can complicate the response problem – Cost – Reducing the cost of the hardware is a concern in many embedded system projects; software often operates on hardware that is barely adequate for the job. • Embedded systems have a microprocessor/ microcontroller and a memory. Some have a serial port or a network connection. They usually do not have keyboards, screens or disk drives.2.2 APPLICATIONS 1. MILITARY AND AEROSPACE EMBEDDED SOFTWARE APPLICATIONS 2. COMMUNICATION APPLICATIONS 3. INDUSTRIAL AUTOMATION AND PROCESS CONTROL SOFTWARE2.3 CLASSIFICATION 1. Real Time Systems. 2. RTS is one which has to respond to events within a specified deadline. 3. A right answer after the dead line is a wrong answer2.3.1 RTS CLASSIFICATION 1. Hard Real Time Systems 2. Soft Real Time System2.3.1.1 HARD REAL TIME SYSTEM • "Hard" real-time systems have very narrow response time. • Example: Nuclear power system, Cardiac pacemaker.VCET 7|Page
  • 8. Remote sensing and control of an irrigation system using a distributed wireless sensor network2.3.1.2 SOFT REAL TIME SYSTEM • "Soft" real-time systems have reduced constrains on "lateness" but still must operate very quickly and repeatable. • Example: Railway reservation system – takes a few extra seconds the data remains valid.LANGUAGES USED • C • C++ • Java • Linux • Ada • Assembly2.4 MPLAB FEATURES MPLAB Integrated Development Environment (IDE) is a free, integrated toolset for thedevelopment of embedded applications employing Microchips PIC® and dsPIC®microcontrollers. MPLAB Integrated Development Environment (IDE) is a free, integrated toolset for thedevelopment of embedded applications employing Microchips PIC® and dsPIC®microcontrollers. MPLAB IDE runs as a 32-bit application on MS Windows®, is easy to use and includesa host of free software components for fast application development and super-chargeddebugging. MPLAB IDE also serves as a single, unified graphical user interface for additionalMicrochip and third party software and hardware development tools. Moving between tools is asnap, and upgrading from the free software simulator to hardware debug and programming toolsis done in a flash because MPLAB IDE has the same user interface for all tools.VCET 8|Page
  • 9. Remote sensing and control of an irrigation system using a distributed wireless sensor network MPLAB IDE’s SIM, high speed software simulator for PIC and dsPIC (Digital SignalProcessing PIC Microcontroller) devices with peripheral simulation, complex stimulus injectionand register loggingUNIT-3BLOCK DIAGRAM3.1 TRANSMITTER: PIC RF Tx 16F877A LCD KEYPADVCET 9|Page
  • 10. Remote sensing and control of an irrigation system using a distributed wireless sensor network3.2 RECEIVER: SOLAR BATTERY PANEL UNIT UNIT RELAY PIC UNIT WITH DRIVER CONTROLLER SOLINOID VALVE WATER RF Rx TANKVCET 10 | P a g e
  • 11. Remote sensing and control of an irrigation system using a distributed wireless sensor network3.3 DESCRIPTION OF THE BLOCK DIAGRAM The major components of this project are PIC micro controller and Power supply, Relay& driver unit, RF MODULE, Motor, Sensor, Inverter circuit. Field condition is monitored by voltage, current, irradiance, and temperaturesensors distributed across the photovoltaic field. The sensory data are periodically sampledand transmitted to a base station. The power point is controlled by a integrated DC-DCconverter. The output voltage in the converter is regulated by a digital controller. Thereference voltage is calculated based on a neural network model, which is used to identifymaximum power point. The communication data for remote monitoring and distributed controlare successfully transmitted using a low-cost RF MODULE wireless network. The web-basedsoftware developed in this paper offers stable remote access to field conditions and real-timecontrol of the power points in the smart photovoltaic system.Power supply: The Entire Project (both TX and RX side) needs power for its operation. However, fromthe study of this project it comes to know that we supposed to design 5v and 12v dc powersupply. So by utilizing the following power supply components required power has been gained.(230/12v (1A and 500mA) – Step down transformers, Bridge rectifier to converter ac to dc,booster capacitor and +5v (7805) and +12v (7812) regulator to maintain constant 5v & 12 supplyfor the controller circuit and driver circuit).VCET 11 | P a g e
  • 12. Remote sensing and control of an irrigation system using a distributed wireless sensor networkUNIT-4PIC MICROCONTROLLER The major heart of this project is PIC16F877A microcontroller, the reasons why weselected this in our project?, it has more features like 16bit timer, 10-bit ADC, USART, SPI, I2C,256 bytes of EEPROM memory, and 8kbytes of flash program memory, then at last its speed ofprogram execution is about to 1 microsecond or 10 MIPS (10 Million Instructions per second),etc. However, compare to other microcontroller it is fast and very ease to program in C languagebecause of huge support can gain from the manufacturer (Microchip Corporation)forprogramming. The special IDE offered by the manufacture, it is named as MPLAB IDE for itcode generation purpose. Then one more thing is several cheapest programming tools to dumpthe coding in to the controller are available, for example: Pro PIC, PIC Flash, Pro MATE, andPro Universal.4.1 CIRCUIT DIAGRAMVCET 12 | P a g e
  • 13. Remote sensing and control of an irrigation system using a distributed wireless sensor network4.1.1 RECEIVER SECTIONVCET 13 | P a g e
  • 14. Remote sensing and control of an irrigation system using a distributed wireless sensor network4.1.2 TRANSMITTER SECTION4.2 CIRCUIT DESCRIPTIONPOWER SUPPLY: Power supply unit consists of Step down transformer, Rectifier, Input filter, Regulatorunit, Output filter.VCET 14 | P a g e
  • 15. Remote sensing and control of an irrigation system using a distributed wireless sensor network The Step down Transformer is used to step down the main supply voltage from 230V ACto lower value. This 230 AC voltage cannot be used directly, thus it is stepped down. TheTransformer consists of primary and secondary coils. To reduce or step down the voltage, thetransformer is designed to contain less number of turns in its secondary core. The output fromthe secondary coil is also AC waveform. Thus the conversion from AC to DC is essential. Thisconversion is achieved by using the Rectifier Circuit/Unit. The Rectifier circuit is used to convert the AC voltage into its corresponding DC voltage.There are Half-Wave, Full-Wave and bridge Rectifiers available for this specific function. Themost important and simple device used in Rectifier circuit is the diode. The simple function ofthe diode is to conduct when forward biased and not to conduct in reverse bias. Capacitors are used as filter. The ripples from the DC voltage are removed and pure DCvoltage is obtained. And also these capacitors are used to reduce the harmonics of the inputvoltage. The primary action performed by capacitor is charging and discharging. It charges inpositive half cycle of the AC voltage and it will discharge in negative half cycle. Here we used1000µF capacitor. So it allows only AC voltage and does not allow the DC voltage. This filter isfixed before the regulator. Thus the output is free from ripples. Regulator regulates the output voltage to be always constant. The output voltage ismaintained irrespective of the fluctuations in the input AC voltage. As and then the AC voltagechanges, the DC voltage also changes. Thus to avoid this Regulators are used. Also when theinternal resistance of the power supply is greater than 30 ohms, the output gets affected. Thusthis can be successfully reduced here. The regulators are mainly classified for low voltage andfor high voltage. Here we used 7805 & 7812 positive regulators. 7805 it reduces the 12V dcvoltage to 5V dc Voltage and 7812 it will maintain constant 12. The Filter circuit is often fixed after the Regulator circuit. Capacitor is most oftenused as filter. The principle of the capacitor is to charge and discharge. It charges during thepositive half cycle of the AC voltage and discharges during the negative half cycle. So it allowsonly AC voltage and does not allow the DC voltage. This filter is fixed after the Regulator circuitto filter any of the possibly found ripples in the output received finally. Here we used 0.1µFcapacitor.MICCONTROLLER CIRCUIT:VCET 15 | P a g e
  • 16. Remote sensing and control of an irrigation system using a distributed wireless sensor network The PIC 16f877A microcontroller is a 40-pin IC. The first pin of the controller is MCLRpin and the 5V dc supply is given to this pin through 10KΩ resistor. This supply is also given to11th pin directly. The 12th pin of the controller is grounded. A tank circuit consists of a 4 MHZcrystal oscillator and two 22pf capacitors are connected to 13th and 14th pins of the PIC.4.3 SENSORS A sensor (also called detectors) is a converter that measures a physical quantity andconverts it into a signal which can be read by an observer or by an (today mostly electronic)instrument. For example, a mercury-in-glass thermometer converts the measured temperatureinto expansion and contraction of a liquid which can be read on a calibrated glass tube. A thermocouple converts temperature to an output voltage which can be read by a voltmeter. Foraccuracy, most sensors are calibrated against known standards.Sensors are used in everyday objects such as touch-sensitive elevator buttons (tactile sensor) andlamps which dim or brighten by touching the base. There are also innumerable applications forsensors of which most people are never aware. Applications include cars, machines, aerospace,medicine, manufacturing and robotics.4.3.1 TEMPERATURE SENSOR: Temperature Sensor converts the sensed temperature quantity into an easilymeasurable quantity such as Voltage or Current. Big difference exist between differenttemperature sensor or temperature measurement device types. Using one perspective, they can besimply classified into two groups, contact and non-contact. Contact temperature sensors measure their own temperature. One infers the temperatureof the object to which the sensor is in contact by assuming or knowing that the two are in thermalequilibrium, that is, there is no heat flow between them. Examples: Thermo couples,Thermistors. Most commercial and scientific noncontact temperature sensors measure thethermal radiant power of the Infrared or Optical radiation that they receive from a known orVCET 16 | P a g e
  • 17. Remote sensing and control of an irrigation system using a distributed wireless sensor networkcalculated area on its surface, or a known or calculated volume within it. Examples: RadiationThermometers, Fiber optic temperature sensors. Temperature sensor is an equipment used to sense the temperature of the particulararea. Thermometer is the simple temperature sensor which is used to measure the temperature ofa human being in medical field.There are different types of temperature sensors. some of them are • Clinical thermometer one used to determine the temperature of the human body. • Oral thermometer a clinical thermometer that is placed under the tongue. • Recording thermometer a temperature-sensitive instrument by which the temperature to which it is exposed is continuously recorded.Rectal thermometer a clinical thermometer that is inserted into the rectum.4.3.2 HUMIDITY SENSOR: Humidity sensors detect the relative humidity of the immediate environments in which they are placed. They measure both the moisture and temperature in the air and express relative humidity as a percentage of the ratio of moisture in the air to the maximum amount that can be held in the air at the current temperature. As air becomes hotter, it holds more moisture, so the relative humidity changes with the temperature. Most humidity sensors use capacitive measurement to determine the amount of moisture in the air. This type of measurement relies on two electrical conductors with a non- conductive polymer film laying between them to create an electrical field between them. Moisture from the air collects on the film and causes changes in the voltage levels between the two plates. This change is then converted into a digital measurement of the air’s relative humidity after taking the air temperature into account.VCET 17 | P a g e
  • 18. Remote sensing and control of an irrigation system using a distributed wireless sensor networkUNIT-5RF MODULE RF MODULE is the only standards-based wireless technology designed to address theunique needs of low-cost, low-power wireless sensor and control networks in just about anymarket. Since RF MODULE can be used almost anywhere, is easy to implement and needs littlepower to operate, the opportunity for growth into new markets, as well as innovation in existingmarkets, is limitless. Here are some facts about RF MODULE:  With hundreds of members around the globe, RF MODULE uses the 2.4 GHz radio frequency to deliver a variety of reliable and easy-to-use standards anywhere in the world.  Consumer, business, government and industrial users rely on a variety of smart and easy- to-use RF MODULE standards to gain greater control of everyday activities.  With reliable wireless performance and battery operation, RF MODULE gives you the freedom and flexibility to do more.  RF MODULE offers a variety of innovative standards smartly designed to help you be green and save money.5.1 RELAY: A relay is usually an electromechanical device that is actuated by an electrical current.The current flowing in one circuit causes the opening or closing of another circuit. Relays arelike remote control switches and are used in many applications because of their relativeVCET 18 | P a g e
  • 19. Remote sensing and control of an irrigation system using a distributed wireless sensor networksimplicity, long life, and proven high reliability. Relays are used in a wide variety of applicationsthroughout industry, such as in telephone exchanges, digital computers and automation systems.Highly sophisticated relays are utilized to protect electric power systems against trouble andpower blackouts as well as to regulate and control the generation and distribution of power. Inthe home, relays are used in refrigerators, washing machines and dishwashers, and heating andair-conditioning controls. Although relays are generally associated with electrical circuitry, thereare many other types, such as pneumatic and hydraulic. Input may be electrical and outputdirectly mechanical, or vice versa. All relays contain a sensing unit, the electric coil, which is powered by AC or DCcurrent. When the applied current or voltage exceeds a threshold value, the coil activates thearmature, which operates either to close the open contacts or to open the closed contacts. When apower is supplied to the coil, it generates a magnetic force that actuates the switch mechanism.The magnetic force is, in effect, relaying the action from one circuit to another. The first circuitis called the control circuit; the second is called the load circuit. On/Off Control: Example: Air conditioning control, used to limit and control a “highpower” load, such as a compressor Limit Control:Example: Motor Speed Control, used to disconnect a motor if it runs slower or faster than thedesired speed Logic Operation: Example: Test Equipment, used to connect the instrument to a numberof testing points on the device under test.Electromechanical Relays: In our project we will be using an electromechanical relay, which will be a 5 pin relayand the working of the relay will be like as. The general-purpose relay is rated by the amount ofcurrent its switch contacts can handle. Most versions of the general-purpose relay have one toeight poles and can be single or double throw. These are found in computers, copy machines, andother consumer electronic equipment and appliances.VCET 19 | P a g e
  • 20. Remote sensing and control of an irrigation system using a distributed wireless sensor networkLoad Types:Load parameters include the maximum permissible voltage and the maximum permissiblecurrent. The relay can handle both volts and amps. Both the size of the load and its type areimportant. There are four types of loads:1.) Resistive, 2.) Inductive, 3.) AC or DC, and 4.) High or Low Inrush.1.) Resistive Load is one that primarily offers resistance to the flow of current. Examples ofresistive loads include electric heaters, ranges and ovens, toasters and irons.2.) Inductive Loads include power drills, electric mixers, fans, sewing machines and vacuumcleaners. Relays that are going to be subjected to high-inrush inductive loads, such as an ACmotor, will often be rated in horsepower, rather than in volts and amps. This rating reflects theamount of power the relay contacts can handle at the moment the device is turned on (orswitched).3.) AC or DC – This affects the contacts circuit of the relay (due to EMF) and the timingsequencing. And may result in performance issues in the switching capacity of the relay fordifferent load types (I.e. resistive, inductive, etc.).4.) High or Low Inrush - Some load types draw significantly higher amounts of current(amperage) when first turned then they do when the circuit later stabilizes (loads may alsopulsate as the circuit continues operating, thus increasing and decreasing the current). AnVCET 20 | P a g e
  • 21. Remote sensing and control of an irrigation system using a distributed wireless sensor networkexample of a high inrush load is a light bulb, which may draw 10 or more times its normaloperating current when first turned on (some manufacturers refer to this as lamp load).5.2 INTERNAL OPERATION OF MECHANICAL RELAYSStandard: Single Side Stable with any of the following three different methods for closingcontacts:1. Flexure Type: The armature actuates the contact spring directly, and the contact is driven intoa stationary contact, closing the circuit.2. Lift-off Type: The moveable piece is energized by the armature, and the contact closes3. Plunger Type: The lever action caused by the energization of the armature produces a longstroke action. Reed: A Single Side Stable Contact that involves low contact pressure and asimple contact point.4. Polarized: Can be either a single side stable or dual-winding. A permanent magnet is used toeither attract or repel the armature that controls the contact. A definite polarity (+ or -) is requiredBy the relay coil. The latching option makes a polarized relay dual-winding, meaning it remainsin the current state after the coil is de-energized.5.3 RELAY DRIVER (ULN2003): The ULN2001A, ULN2002A, ULN2003 and ULN2004Aare high Voltage, high currentDarlington arrays each containing seven open collector Darlington pairs with common emitters.Each channel rated at 500mAand can withstand peak currents of 600mA.Suppressiondiodesareincluded for inductive load driving and the inputs are pinned opposite the outputs to simplifyboard layout. These versatile devices are useful for driving a wide range of loads including solenoids,relays DC motors; LED displays filament lamps, thermal printheads and high power buffers. TheULN2001A/2002A/2003A and 2004A are supplied in 16 pin plastic DIP packages with a copperlead frame to reduce thermal resistance. They are available also in small outline package (SO-16)as ULN2001D/2002D/2003D/2004D.VCET 21 | P a g e
  • 22. Remote sensing and control of an irrigation system using a distributed wireless sensor networkFEATURES OF DRIVER: • SEVENDARLINGTONS PER PACKAGE. • OUTPUT CURRENT 500mA PER DRIVER (600mA PEAK) • OUTPUT VOLTAGE 50V. • INTEGRATED SUPPRESSION DIODES FOR INDUCTIVE LOADS. • OUTPUTS CAN BE PARALLELED FOR HIGHER CURRENT. • TTL/CMOS/PMOS/DTLCOMPATIBLE INPUTS. • INPUTS PINNED OPPOSITE OUTPUTS TO SIMPLIFY LAYOUTPIN CONNECTION:5.4 SERIAL COMMUNICATION A serial port sends and receives data one bit at a time over one wire. While it takes eighttimes as long as to transfer each byte of data this way, only a few wires are required. In fact,VCET 22 | P a g e
  • 23. Remote sensing and control of an irrigation system using a distributed wireless sensor networktwo-way (full duplex) communications is possible with only three separate wires- one to send,one to receive, and a common signal ground wire.  Bi-directional communications  Communicating by wires  The Parity Bit  Cable lengths  MAX-232C  DCE And DTE devices  Synchronous and Asynchronous Communications5.4.1 Bi-directional Communications The serial port on your PC is a full-duplex device meaning that it can send and receivedata at the same time. In order to be able to do this, it uses separate lines for transmitting andreceiving data. Some types of serial devices support only one-way communications andtherefore use only two-wires in the cable – the transmit line and the signal ground.5.4.2 Communicating by bits Once the start bit has been sent, the transmitter sends the actual data bits. There mayeither be 5, 6, 7 or 8 data bits, depending on the number you have selected. Both receiver andthe transmitter must agree on the number of data bits, as well as the baud rate. Almost alldevices transmit data using either 7 or 8 data bits. Notice that when only 7 data bits areemployed, you cannot send ASCII values greater than 127. Likewise, using 5 bits limits thehighest possible value to 31. After the data has been transmitted, a stop bit is sent. A stop bithas a value of 1- or a mark state- and it can be detected correctly even if the previous data bitalso had a value of 1. This is accomplished by the stop bit’s duration.5.4.3 The Parity Bit Besides the synchronization provided by the use of start and stop bits, an additional bitcalled a parity bit may optionally be transmitted along with the data. A parity bit affords aVCET 23 | P a g e
  • 24. Remote sensing and control of an irrigation system using a distributed wireless sensor networksmall amount of error checking, to help detect data corruption that might occur duringtransmission.5.4.4 Cable Lengths The MAX-232 standard imposes a cable length limit of 50 feet. You can usually ignorethis “standard”, since a cable can be as long as 10000 feet at baud rates up to 19200 if you usea high quality, well shielded cable. The external environment has a large effect on lengths forunshielded cables.5.4.5 MAX232 (Voltage Converter) Since the RS232 is not compatible with today microprocessors and micro controller,we need line driver to convert the RS232 signals to TTL voltage levels that will be acceptableto the 8051’s TXD and RXD pins. One example of such a converter is MAX 232 from maximcorp. The MAX 232 converts from RS232 voltage levels to TTL voltage levels, and vice versa.One advantage of MAX232 chip is that it uses a +5V power source, which is the same as thesource voltage for the at89s52 micro controller. In other words, with a single +5v power supplywe can power both the PIC and MAX 232, with no need of for the dual power supplies that arecommon in many older systems. The MAX 232 requires four capacitors ranging from 1 to 22microfarad. The most widely used value for this capacitor is 22microfarad. The MAX232 is a dual driver/receiver that includes a capacitive voltage generator tosupply TIA/EIA-232-Fvoltage levels from a single 5-V supply. Each receiver convertsTIA/EIA-232-F inputs to 5-V TTL/CMOS levels. These receivers have a typical threshold of1.3 V, a typical hysterias is of 0.5 V, and can accept ±30-V inputs. Each driver convertsTTL/CMOS input levels into TIA/EIA-232-F levels.PIN DIAGRAM OF MAX232VCET 24 | P a g e
  • 25. Remote sensing and control of an irrigation system using a distributed wireless sensor network Fig 4.5 max232 pin diagram5.4.6 DCE and DTE devices Two terms you should be familiar with are DTE and DCE. DTE stands for DataTerminal Equipment, and DCE stands for Data Communication Equipment. These terms areused to indicate the pin-out for the connectors on a device and the direction of the signals onthe pins. Your computer is a DTE device, while most other devices are usually DCE devices. Ifyou have trouble keeping the two straight then replace the term “DTE device” with your PCand the term DCE device with “remote Device” in the following discussion. The RS-232standard states that DTE devices use a 25-pin male connector, and DCE devices use a 25-pinfemale connector. You can therefore connect a DTE device to a DCE using a straight pin-for-pin connection. However, to connect two like devices, you must instead use a null modemcable. Null modem cables cross the transmit and receive lines in the cable. The DTE device puts this line in a mark condition to tell the remote device that it isready and able to receive data. If the DTE device is not able to receive data (typically becauseits receive buffer is almost full), it will put this line in the space condition as a signal to theDCE to stop sending data. When the DTE device is ready to receive more data it will place thisline back in the mark condition. The complement of the RTS wire is CTS, which stands forClear to Send. The DCE device puts this line in a mark condition to tell the DTE device that itis ready to receive the data. Likewise, if the DCE device is unable to receive data, it will placethis line in the space condition. Together, these two lines make up what is called RTS/CTS or“hardware” flow control. The software wedge supports this type of flow control as well asVCET 25 | P a g e
  • 26. Remote sensing and control of an irrigation system using a distributed wireless sensor networkXon/Xoff or “software” flow control. Software flow control uses special control characterstransmitted from one device to another to tell the other device to stop or start sending data.With software flow control the RTS and CTS lines are not used. DTR stands for Data Terminal Ready. Its intended function is very similar to theRTS line. DSR (Data Set Ready) is the companion to DTR in the same way that CTS is toRTS. Some serial devices use DTR and DSR as signals to simplify confirm that a device isconnected and turned on. The software wedge sets DTR to the mark state when the serial portis opened and leaves it in that state until the port is closed. The DTR and DSR lines wereoriginally designed to provide an alternate method of hardware handshaking. It would bepointless to use both RTS/CTS and DTR/DSR for flow control signals at the same time.Because of this DTR and DSR are rarely used for flow control.5.4.7 Synchronous and Asynchronous Communications There are two basic types of serial communications, synchronous and asynchronous.With synchronous communications, the two devices initially synchronize themselves to eachother, and then continually send characters to stay in sync. Even when the data is not reallybeing sent, a constant flow of bits allows each device to know where the other is at any giventime. That is, each character that is sent is either actual data or an idle character. Synchronouscommunications allows faster data transfer rates than asynchronous methods, becauseadditional bits to mark the beginning and end of each data byte are not required. The serialports on IBM style PCs are asynchronous devices and therefore only support asynchronousserial communications. Asynchronous means no “synchronization”, and thus does not requiresending and receiving idle characters. However, the beginning and end of each byte of datamust be identified by start and stop bits. The start bit indicates when the data byte is about tobegin and the stop bit signals when it ends.VCET 26 | P a g e
  • 27. Remote sensing and control of an irrigation system using a distributed wireless sensor networkUNIT-6HARDWARE REQUIREMENTS6.1 MICROCONTROLLERIntroduction to microcontroller: A computer-on-a-chip is a variation of a microprocessor which combines the processorcore (CPU), some memory, and I/O (input/output) lines, all on one chip. The computer-on-a-chipis called the microcomputer whose proper meaning is a computer using a (number of)microprocessor(s) as its CPUs, while the concept of the microcomputer is known to be amicrocontroller. A microcontroller can be viewed as a set of digital logic circuits integrated on asingle silicon chip. This chip is used for only specific applications. Most microcontrollers do not require a substantial amount of time to learn how toefficiently program them, although many of them, which have quirks, which you will have tounderstand before you, attempt to develop your first application.VCET 27 | P a g e
  • 28. Remote sensing and control of an irrigation system using a distributed wireless sensor network Along with microcontrollers getting faster, smaller and more power efficient they are alsogetting more and more features. Often, the first version of microcontroller will just have memoryand digital I/O, but as the device family matures, more and more pat numbers with varyingfeatures will be available. In this project we used PIC 16f877A microcontroller. For most applications, we will beable to find a device within the family that meets our specifications with a minimum of externaldevices, or an external but which will make attaching external devices easier, both in terms ofwiring and programming. For many microcontrollers, programmers can built very cheaply, or even built in to thefinal application circuit eliminating the need for a separate circuit. Also simplifying thisrequirement is the availability of micro-controllers wit SRAM and EEPROM for control store,which will allow program development without having to remove the micro controller fro theapplication circuit.6.2 PIC MICROCONTROLLER CORE FEATURES: • High-performance RISC CPU. • Only 35 single word instructions to learn. • All single cycle instructions except for program branches which are two cycle. • Operating speed: DC - 20 MHz clock input DC - 200 ns instruction cycle. • Up to 8K x 14 words of FLASH Program Memory, Up to 368 x 8 bytes of Data Memory (RAM) Up to 256 x 8 bytes of EEPROM data memory. • Pin out compatible to the PIC16C73B/74B/76/77 • Interrupt capability (up to 14 sources) • Eight level deep hardware stack • Direct, indirect and relative addressing modes. • Power-on Reset (POR).VCET 28 | P a g e
  • 29. Remote sensing and control of an irrigation system using a distributed wireless sensor network • Power-up Timer (PWRT) and Oscillator Start-up Timer (OST). • Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation. • Programmable code-protection. • Power saving SLEEP mode. • Selectable oscillator options. • Low-power, high-speed CMOS FLASH/EEPROM technology. • Fully static design. • In-Circuit Serial Programming (ICSP) . • Single 5V In-Circuit Serial Programming capability. • In-Circuit Debugging via two pins. • Processor read/write access to program memory. • Wide operating voltage range: 2.0V to 5.5V. • High Sink/Source Current: 25 mA. • Commercial and Industrial temperature ranges. • Low-power consumption. In this project we used PIC 16f877A microcontroller. PIC means Peripheral InterfaceController. The PIC family having different series. The series are 12- Series, 14- Series, 16-Series, 18- Series, and 24- Series. We used 16 Series PIC microcontrollers.6.3 ADVANTAGES OF USING A MICROCONTROLLER OVER MICROPROCESSOR: A designer will use a Microcontroller to • Gather input from various sensors • Process this input into a set of actions • Use the output mechanisms on the Microcontroller to do something useful • RAM and ROM are inbuilt in the MC. • Cheap compared to MP. • Multi machine control is possible simultaneously.Examples 8051 (ATMEL), PIC (Microchip), Motorola (Motorola), ARM Processor.VCET 29 | P a g e
  • 30. Remote sensing and control of an irrigation system using a distributed wireless sensor networkAPPLICATIONS: • Cell phones. • Computers. • Robots. • Interfacing to two PC’s.6.4 PIN DIAGRAM PIC 16 F874A/877A:VCET 30 | P a g e
  • 31. Remote sensing and control of an irrigation system using a distributed wireless sensor network6.5 FUNCTIONAL BLOCK DIAGRAM OF PIC 16F877A:VCET 31 | P a g e
  • 32. Remote sensing and control of an irrigation system using a distributed wireless sensor networkPIN DESCRIPTION:VCET 32 | P a g e
  • 33. Remote sensing and control of an irrigation system using a distributed wireless sensor networkOSC1/CLKI: Oscillator crystal or external clock input. Oscillator crystal input or external clock sourceinput. ST buffer when configured in RC mode; otherwise CMOS. External clock source input.Always associated with pin function OSC1 (see OSC1/CLKI, OSC2/CLKO pins).OSC2/CLKO: Oscillator crystal or clock output. Oscillator crystal output. Connects to The crystal orresonator in Crystal Oscillator mode. In RC mode, OSC2 pin outputs CLKO, which has 1/4 thefrequency of OSC1 and denotes the instruction cycle rate.MCLR/VPP: Master Clear (input) or programming voltage (output). Master Clear (Reset) input. Thispin is an active low Reset to the device. Programming voltage input. • RA0/AN0. • RA1/AN1. • RA2/AN2/VREF-/CVREF. • VREFCVREF. • RA3/AN3/VREF+. • VREF+. • RA4/T0CKI/C1OUT. • T0CKI. • C1OUT. • RA5/AN4/SS/C2OUT/SS/C2OUT.I/O PORTS: Some pins for these I/O ports are multiplexed with an alternate function for the peripheralfeatures on the device. In general, when a peripheral is enabled, that pin may not be used as ageneral purpose I/O pin.PORT A AND TRIS A REGISTER:VCET 33 | P a g e
  • 34. Remote sensing and control of an irrigation system using a distributed wireless sensor network PORT A is a 6-bit wide, bidirectional port. The corresponding data direction register isTRIS A. Setting a TRIS A bit (= 1) will make the corresponding PORT A pin an input (i.e., putthe corresponding output driver in a High – Impedance mode). Clearing a TRIS A bit (= 0) willmake the corresponding PORT A pin an output (i.e., put the contents of the output latch on theselected pin). Reading the PORT A register reads the status of the pins, whereas writing to it willwrite to the port latch. All write operations are read-modify-write operations. Therefore, a writeto a port implies that the port pins are read; the value is modified and then written to the port datalatch. Pin RA4 is multiplexed with the Timer0 module clock input to become the RA4/T0CKIpin. The RA4/T0CKI pin is a Schmitt Trigger input and an open-drain output. All other PORT Apins have TTL input levels and full CMOS output drivers. Other PORT A pins are multiplexedwith analog inputs and the analog VREF input for both the A/D converters and the comparators.The operation of each pin is selected by clearing/setting the appropriate control bits in theADCON1 and/or CMCON registers. The TRIS A register controls the direction of the port pinseven when they are being used as analog inputs. The user must ensure the bits in the TRIS Aregister are maintained set when using them as analog inputs.Note: On a Power-on Reset, these pins are configured as analog inputs and read as ‘0’. Thecomparators are in the off (digital).PORT B AND TRIS B REGISTER: PORT B is an 8-bit wide, bidirectional port. The corresponding data direction register isTRIS B. Setting a TRIS B bit (= 1) will make the corresponding PORT B pin an input (i.e., putthe corresponding output driver in a High-Impedance mode). Clearing a TRIS B bit (= 0) willmake the corresponding PORT B pin an output (i.e., put the contents of the output latch on theselected pin). Three pins of PORT B are multiplexed with the In-Circuit Debugger and Low-Voltage Programming function: RB3/PGM, RB6/PGC and RB7/PGD. Four of the PORT B pins, RB7:RB4, have an interruption- change feature. Only pinsconfigured as inputs can cause this interrupt to occur (i.e., any RB7:RB4 pin configured as anoutput is excluded from the interruption- change comparison). The input pins (of RB7:RB4) arecompared with the old value latched on the last read of PORTB. The “mismatch” outputs ofVCET 34 | P a g e
  • 35. Remote sensing and control of an irrigation system using a distributed wireless sensor networkRB7:RB4 are OR’ed together to generate the RB port change interrupt with flag bit RBIF(INTCON<0>). This interrupt can wake the device from Sleep. The user, in the Interrupt ServiceRoutine, can clear the interrupt in the following manner:a) Any read or write of PORT B. This will end the mismatch condition.b) Clear flag bit RBIF. A mismatch condition will continue to set flag bit RBIF. Reading PORT B will endthe mismatch condition and allow flag bit RBIF to be cleared. The interrupt-on-change feature isrecommended for wake-up on key depression operation and operations where PORT B is onlyused for the interrupt-on-change feature. Polling of PORT B is not recommended while using theinterrupt-on- change feature. This interrupt-on-mismatch feature, together with softwareconfigurable pull-ups on these four pins, allow easy interface to a keypad and make it possiblefor wake-up on key depression.PORT C AND TRIS C REGISTER: PORT C is an 8-bit wide, bidirectional port. The corresponding data direction register isTRIS C. Setting a TRIS C bit (= 1) will make the corresponding PORT C pin an input (i.e., putthe corresponding output driver in a High- Impedance mode). Clearing a TRIS C bit (= 0) willmake the corresponding PORT C pin an output (i.e., put the contents of the output latch on theselected pin). PORT C is multiplexed with several peripheral functions (Table 4-5). PORT Cpins have Schmitt Trigger input buffers. When the I2C module is enabled, the PORT C<4:3>pins can be configured with normal I2C levels, or with SMBus levels, by using the CKE bit(SSPSTAT<6>). When enabling peripheral functions, care should be taken in defining TRIS bitsfor each PORT C pin. Some peripherals override the TRIS bit to make a pin an output, whileother peripherals override the TRIS bit to make a pin an input. Since the TRIS bit override is ineffect while the peripheral is enabled, read-modify write instructions (BSF, BCF, XORWF) withTRIS C as the destination, should be avoided. The user should refer to the correspondingperipheral section for the correct TRIS bit settings.PORT D AND TRIS D REGISTERS:VCET 35 | P a g e
  • 36. Remote sensing and control of an irrigation system using a distributed wireless sensor network PORT D is an 8-bit port with Schmitt Trigger input buffers. Each pin is individuallyconfigurable as an input or output. PORT D can be configured as an 8-bit wide microprocessorport (Parallel Slave Port) by setting control bit, PSP MODE (TRISE<4>). In this mode, the inputbuffers are TTL.PORT E AND TRIS E REGISTER: PORT E has three pins (RE0/RD/AN5, RE1/WR/AN6 and RE2/CS/AN7) which areindividually configurable as inputs or outputs. These pins have Schmitt Trigger input buffers.The PORT E pins become the I/O control inputs for the microprocessor port when bitPSPMODE (TRISE<4>) is set. In this mode, the user must make certain that the TRIS E<2:0>bits are set and that the pins are configured as digital inputs. Also, ensure that ADCON1 isconfigured for digital I/O. In this mode, the input buffers are TTL. Register 4-1 shows the TRISE register which also controls the Parallel Slave Port operation. PORT E pins are multiplexedwith analog inputs. When selected for analog input, these pins will read as ‘0’s. TRIS E controls. Thedirection of the RE pins, even when they are being used as analog inputs. The user must makesure to keep the pins configured as inputs when using them as analog inputs.MEMORY ORGANIZATION: There are three memory blocks in each of the PIC16F87XA devices. The programmemory and data memory have separate buses so that concurrent access can occur and isdetailed in this section. The EEPROM data memory block is detailed in.PROGRAM MEMORY ORGANIZATION: The PIC16F87XA devices have a 13-bit program counter capable of addressing an 8Kword x 14 bit program memory space. The PIC16F876A/877A devices have 8K words x 14 bitsof Flash program memory, while PIC16F873A/874A devices have 4K words x 14 bits.Accessing a location above the physically implemented address will cause a wraparound. TheReset vector is at 0000h and the interrupt vector is at 0004h.VCET 36 | P a g e
  • 37. Remote sensing and control of an irrigation system using a distributed wireless sensor network The data memory is partitioned into multiple banks which contain the General PurposeRegisters and the Special Function Registers. Bits RP1 (Status<6>) and RP0 (Status<5>) are thebank select bits. Each bank extends up to 7Fh (128 bytes). The lower locations of each bank arereserved for the Special Function Registers. Above the Special Function Registers are GeneralPurpose Registers, implemented as static RAM. All implemented banks contain Special FunctionRegisters. Some frequently used Special Function Registers from one bank may be mirrored inanother bank for code reduction and quicker access.TIMER0 MODULE:The Timer0 module timer/counter has the following features:• 8-bit timer/counter• Readable and writable• 8-bit software programmable prescaler• Internal or external clock select• Interrupt on overflow from FFh to 00h• Edge select for external clockTimer mode is selected by clearing bit T0CS (OPTION_REG<5>). In Timer mode, the Timer0module will increment every instruction cycle (without prescaler). If the TMR0 register iswritten, the increment is inhibited for the following two instruction cycles. The user can workaround this by writing an adjusted value to the TMR0 register.TIMER0 INTERRUPT: The TMR0 interrupt is generated when the TMR0 register overflows from FFh to 00h.This overflow sets bit TMR0IF (INTCON<2>). The interrupt can be masked by clearing bitTMR0IE (INTCON<5>). Bit TMR0IF must be cleared in software by the Timer0 moduleInterrupt Service Routine before re-enabling this interrupt. The TMR0 interrupt cannot awakenthe processor from Sleep since the timer is shut-off during Sleep.TIMER1 MODULE:VCET 37 | P a g e
  • 38. Remote sensing and control of an irrigation system using a distributed wireless sensor networkThe Timer1 module is a 16-bit timer/counter consisting of two 8-bit registers (TMR1H andTMR1L) which are readable and writable. The TMR1 register pair (TMR1H:TMR1L)increments from 0000h to FFFFh and rolls over to 0000h. The TMR1 interrupt, if enabled, isgenerated on overflow which is latched in interrupt flag bit, TMR1IF (PIR1<0>). This interruptcan be enabled/disabled by setting or clearing TMR1 interrupt enable bit, TMR1IE (PIE1<0>).Timer1 can operate in one of two modes:• As a Timer• As a CounterThe operating mode is determined by the clock select bit, TMR1CS (T1CON<1>).In Timer mode, Timer1 increments every instruction cycle. In Counter mode, it increments onevery rising edge of the external clock input. Timer1 can be enabled/disabled by setting/clearingcontrol bit, TMR1ON (T1CON<0>).Timer1 also has an internal “Reset input”. This Reset can begenerated by either of the two CCP modules. Shows the Timer1 Control register. When the Timer1 oscillator is enabled (T1OSCEN is set), the RC1/T1OSI/CCP2 andRC0/T1OSO/T1CKI pins become inputs. That is, the TRISC<1:0> value is ignored and thesepins read as ‘0’.TIMER2 MODULE: Timer2 is an 8-bit timer with a pre scaler and a post scaler. It can be used as the PWMtime base for the PWM mode of the CCP module(s). The TMR2 register is readable and writableand is cleared on any device Reset. The input clock (FOSC/4) has a prescale option of 1:1, 1:4 or1:16, selected by control bits T2CKPS1:T2CKPS0 (T2CON<1:0>). The Timer2 module has an8-bit period register, PR2. Timer2 increments from 00h until it matches PR2 and then resets to00h on the next increment cycle. PR2 is a readable and writable register. The PR2 register isinitialized to FFh upon Reset. The match output of TMR2 goes through a 4-bit postscaler (whichgives a 1:1 to 1:16 scaling inclusive) to generate a TMR2 interrupt (latched in flag bit, TMR2IF(PIR1<1>)). Timer2 can be shut-off by clearing control bit, TMR2ON (T2CON<2>), tominimize power consumption.IN-CIRCUIT DEBUGGER:VCET 38 | P a g e
  • 39. Remote sensing and control of an irrigation system using a distributed wireless sensor network PIC16F87XA devices have a Watchdog Timer which can be shut-off only throughconfiguration bits. It runs off its own RC oscillator for added reliability. There are two timersthat offer necessary delays on power-up. One is the Oscillator Start-up Timer (OST), intended tokeep the chip in Reset until the crystal oscillator is stable. The other is the Power-up Timer(PWRT), which provides a fixed delay of 72 ms (nominal) on power-up only. It is designed tokeep the part in Reset while the power supply stabilizes. With these two timers on-chip, mostapplications need no external Reset circuitry. Sleep mode is designed to offer a very low currentpower-down mode. The user can wake-up from Sleep through external Reset, Watchdog Timerwake-up or through an interrupt. Several oscillator options are also made available to allow thepart to fit the application. The RC oscillator option saves system cost while the LP crystal optionsaves power. A set of configuration bits is used to select various options.VCET 39 | P a g e
  • 40. Remote sensing and control of an irrigation system using a distributed wireless sensor networkUNIT-7POWER SUPPLY UNITPower supply unit consists of following units: 1) Step down transformer 2) Rectifier unit 3) Input filter 4) Regulator unit 5) Output filter7.1 STEPDOWN TRANSFORMER: The Step down Transformer is used to step down the main supply voltage from 230V ACto lower value. This 230 AC voltage cannot be used directly, thus it is stepped down. TheTransformer consists of primary and secondary coils. To reduce or step down the voltage, thetransformer is designed to contain less number of turns in its secondary core. The output fromthe secondary coil is also AC waveform. Thus the conversion from AC to DC is essential. Thisconversion is achieved by using the Rectifier Circuit/Unit. Step down transformers can step down incoming voltage, which enables you to have thecorrect voltage input for your electrical needs. For example, if our equipment has been specifiedfor input voltage of 12 volts, and the main power supply is 230 volts, we will need a step downtransformer, which decreases the incoming electrical voltage to be compatible with your 12 voltequipment.VCET 40 | P a g e
  • 41. Remote sensing and control of an irrigation system using a distributed wireless sensor network7.2 RECTIFIER UNIT: The Rectifier circuit is used to convert the AC voltage into its corresponding DC voltage.The most important and simple device used in Rectifier circuit is the diode. The simple functionof the diode is to conduct when forward biased and not to conduct in reverse bias. Now we areusing three types of rectifiers. They are 1. Half-wave rectifier 2. Full-wave rectifier 3. Bridge rectifierVCET 41 | P a g e
  • 42. 7.2.1 Half-wave rectifier: In half wave rectification, either the positive or negative half of theAC wave is passed, while the other half is blocked. Because only one half of the input waveformRemote sensing and control of an irrigation system using a distributed wireless sensor networkreaches the output, it is very inefficient if used for power transfer. Half-wave rectification can beachieved with a single diode in a one phase supply, or with three diodes in a three-phase supply.7.2.2 Full-wave rectifier: A full-wave rectifier converts the whole of the input waveform to oneof constant polarity (positive or negative) at its output. Full-wave rectification converts bothpolarities of the input waveform to DC (direct current), and is more efficient. However, in acircuit with a non-center tapped transformer, four diodes are required instead of the one neededfor half-wave rectification. A full-wave rectifier uses a diode bridge, made of four diodes, likethisAt first, this may look just as confusing as the one-way streets of Boston. The thing to realize isthat the diodes work in pairs. As the voltage of the signal flips back and forth, the diodes shepardthe current to always flow in the same direction for the output.Heres what the circuit looks like to the signal as it alternates:So, if we feed our AC signal into a full wave rectifier, well see both halves of the wave above 0Volts. Since the signal passes through two diodes, the voltage out will be lower by two diodedrops, or 1.2 Volts.VCET 42 | P a g e
  • 43. Remote sensing and control of an irrigation system using a distributed wireless sensor network7.2.3 Bridge rectifier: A bridge rectifier makes use of four diodes in a bridge arrangement toachieve full-wave rectification. This is a widely used configuration, both with individual diodeswired as shown and with single component bridges where the diode bridge is wired internally.A diode bridge or bridge rectifier is an arrangement of four diodes in a bridge configurationthat provides the same polarity of output voltage for either polarity of input voltage. When usedin its most common application, for conversion of alternating current (AC) input into directcurrent (DC) output, it is known as a bridge rectifier. A bridge rectifier provides full-waverectification from a two-wire AC input, resulting in lower cost and weight as compared to acenter-tapped transformer design. The Forward Bias is achieved by connecting the diode’s positive with positive of thebattery and negative with battery’s negative. The efficient circuit used is the Full wave Bridgerectifier circuit. The output voltage of the rectifier is in rippled form, the ripples from theobtained DC voltage are removed using other circuits available. The circuit used for removingthe ripples is called Filter circuit.7.3 INPUT FILTER Capacitors are used as filter. The ripples from the DC voltage are removed and pure DCvoltage is obtained. And also these capacitors are used to reduce the harmonics of the inputvoltage. The primary action performed by capacitor is charging and discharging. It charges inpositive half cycle of the AC voltage and it will discharge in negative half cycle. So it allowsonly AC voltage and does not allow the DC voltage. This filter is fixed before the regulator.Thus the output is free from ripples.VCET 43 | P a g e
  • 44. Remote sensing and control of an irrigation system using a distributed wireless sensor networkThere are two types of filters. They are 1. Low pass filter 2. High pass filter7.3.1 Low pass filter: One simple electrical circuit that will serve as a low-pass filter consists of a resistor inseries with a load, and a capacitor in parallel with the load. The capacitor exhibits reactance, andblocks low-frequency signals, causing them to go through the load instead. At higher frequenciesthe reactance drops, and the capacitor effectively functions as a short circuit. The combination ofresistance and capacitance gives you the time constant of the filter τ = RC (represented by theGreek letter tau). The break frequency, also called the turnover frequency or cutoff frequency (inhertz), is determined by the time constant: or equivalently (in radians per second): One way to understand this circuit is to focus on the time the capacitor takes to charge. Ittakes time to charge or discharge the capacitor through that resistor: • At low frequencies, there is plenty of time for the capacitor to charge up topractically the same voltage as the input voltage. • At high frequencies, the capacitor only has time to charge up a small amountbefore the input switches direction. The output goes up and down only a small fraction of theamount the input goes up and down. At double the frequency, theres only time for it to chargeup half the amount.VCET 44 | P a g e
  • 45. Remote sensing and control of an irrigation system using a distributed wireless sensor network Another way to understand this circuit is with the idea of reactance at a particularfrequency: • Since DC cannot flow through the capacitor, DC input must "flow out" the pathmarked Vout (analogous to removing the capacitor). • Since AC flows very well through the capacitor — almost as well as it flowsthrough solid wire — AC input "flows out" through the capacitor, effectively short circuiting toground (analogous to replacing the capacitor with just a wire).It should be noted that the capacitor is not an "on/off" object (like the block or pass fluidicexplanation above). The capacitor will variably act between these two extremes. It is the Bodeplot and frequency response that show this variability.7.3.2 High pass filter:The above circuit diagram illustrates a simple RC high-pass filter. we should find that the circuitpasses high frequencies fairly well, but attenuates low frequencies. Hence it is useful as a filterto block any unwanted low frequency components of a complex signal whilst passing higherfrequencies. Circuits like this are used quite a lot in electronics as a D.C. Block - i.e. to pass a.c.signals but prevent any D.C. voltages from getting through.VCET 45 | P a g e
  • 46. Remote sensing and control of an irrigation system using a distributed wireless sensor networkThe basic quantities which describe this circuit are similar to those used for the Low Pass Filter.In effect, this circuit is just a simple low-pass filter with the components swapped over.The action of the circuit can also be described in terms of a related quantity, the Turn overFrequency, f0, which has a valueAs with the low-pass filter, the circuits behavior we can be understood as arising due to the timetaken to change the capacitors charge when we alter the applied input voltage. It always takes afinite (i.e. non-zero) time to change the amount of charge stored by the capacitor. Hence it takestime to change the potential difference across the capacitor. As a result, any sudden change in theinput voltage produces a similar sudden change on the other side of the capacitor. This producesa voltage across the resistor and causes a current to flow thorough it, charging the capacitor untilall the voltage falls across it instead of the resistor. The result is that steady (or slowly varying)voltages appear mostly across the capacitor and quick changes appear mostly across the resistor.Since were using the voltage across the resistor as out output the main properties of the circuitareThereforeThe Voltage Gain:The Phase Delay:Try using the above experimental system to collect results and plot a graph of how the voltagegain, Av, (and the phase change) depend upon the input frequency and if we check result agreesVCET 46 | P a g e
  • 47. Remote sensing and control of an irrigation system using a distributed wireless sensor networkwith the above formulae. Compare this with a low-pass filter that uses the same componentvalues and you should see that they give opposite results. In the high-pass filter, the outputwaveform leads the input waveform - i.e. it peaks before the input.7.4 REGULATOR UNIT 7805 Regulator Regulator regulates the output voltage to be always constant. The output voltage ismaintained irrespective of the fluctuations in the input AC voltage. As and then the AC voltagechanges, the DC voltage also changes. Thus to avoid this Regulators are used. Also when theinternal resistance of the power supply is greater than 30 ohms, the output gets affected. Thusthis can be successfully reduced here. The regulators are mainly classified for low voltage andfor high voltage. Further they can also be classified as: i) Positive regulator 1---> input pin 2---> ground pin 3---> output pin It regulates the positive voltage. ii) Negative regulator 1---> ground pin 2---> input pin 3---> output pin It regulates the negative voltage.VCET 47 | P a g e
  • 48. Remote sensing and control of an irrigation system using a distributed wireless sensor networkFixed regulators An assortment of 78xx series ICs"Fixed" three-terminal linear regulators are commonly available to generate fixed voltages ofplus 3 V, and plus or minus 5 V, 9 V, 12 V, or 15 V when the load is less than about 7 amperes.7805 VOLTAGE REGULATOR: The 7805 provides circuit designers with an easy way to regulate DC voltages to 5v.Encapsulated in a single chip/package (IC), the 7805 is a positive voltage DC regulator that hasonly 3 terminals. They are: Input voltage, Ground, Output Voltage.General Features: • Output Current up to 1A • Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V • Thermal Overload Protection • Short Circuit Protection • Output Transistor Safe Operating Area Protection7812 12V Integrated Circuit3-Terminal Positive Voltage Regulator: • The 7812 fixed voltage regulator is a monolithic integrated circuit in a TO220 type package designed for use in a wide variety of applications including local, onboard regulation. This regulator employs internal current limiting, thermal shutdown, and safe area compensation.VCET 48 | P a g e
  • 49. Remote sensing and control of an irrigation system using a distributed wireless sensor network • With adequate heat-sinking it can deliver output currents in excess of 1.0 ampere. Although designed primarily as a fixed voltage regulator, this device can be used with external components to obtain adjustable voltages and currents.7.5 OUTPUT FILTER The Filter circuit is often fixed after the Regulator circuit. Capacitor is most often usedas filter. The principle of the capacitor is to charge and discharge. It charges during the positivehalf cycle of the AC voltage and discharges during the negative half cycle. So it allows only ACvoltage and does not allow the DC voltage. This filter is fixed after the Regulator circuit to filterany of the possibly found ripples in the output received finally. Here we used 0.1µF capacitor.The output at this stage is 5V and is given to the Microcontroller. The output voltage overshootswhen the load is removed or a short clears. When the load is removing from a switching modepower supply with a LC low-pass output filter, the only thing the control loop can do is stop theswitching action so no more energy is taken from the source. The energy that is stored in theoutput filter inductor is dumped into the output capacitor causing a voltage overshoot.The magnitude of the overshoot is the vector sum of two orthogonal voltages, the output voltagebefore the load is removed and the current through the inductor times the characteristicimpedance of the output filter, Zo = (L/C)^1/2. This can be derived from conservation of energyconsiderations.The initial energy, Ei, is: Ei = 1/2*(L*Ii^2 + C*Vi^2)The final energy, Ef, is: Ef = 1/2*(L*If^2 = C*Vf^2)The two energies are equal when the load is removed, since the load is no longer taking energyfrom the system. Equating the two energies, substituting zero current for the final inductorcurrent, then the solution for the final voltage Vf is:VCET 49 | P a g e
  • 50. Remote sensing and control of an irrigation system using a distributed wireless sensor network Vf = (Vi^2 + (Ii*Zo)^2)^1/2This is the orthogonal vector sum of the output voltage and the load current times thecharacteristic impedance and is illustrated in Figure 1. Figure 1: Overshoot Voltage as Vector SumThe problem becomes worse if the current in the inductor is established by a short circuit on theoutput and the short circuit clears. In this case, the initial voltage is zero (short circuit) and theovershoot is I*Zo, where I can be very large, resulting in a ruinous overshooot7.6 RF MODULESThe relay subsystem is an electrically-operated switch. Itrequires a separate electrical supply to provide power toan output device. It is often used for reversing motors. Like ordinary switches, relay switches are available as single-pole single-throw (SPST), single- pole double-throw (SPDT), and double-pole double-throw (DPDT). The circuit diagram showsVCET 50 | P a g e
  • 51. Remote sensing and control of an irrigation system using a distributed wireless sensor network a DPDT relay. The switching is done by a coil of wire (an electromagnet) that creates a magnetic field when a current passes through it. The switch contacts in the relay change over due to the force from the magnetic field when a current passes through the coil. The reverse biased diode is included because, when relays are switched off, they can generate a ‘back e.m.f.’ that can damage the driver. When the relay is switched off the diode conducts current and prevents the damage. The driver subsystem that provides the input signal to the relay must be able to supply enough current for the coil. A DPDT relay has three pairs of connections known as common (CO), normally open (NO) and normally closed (NC).VCET 51 | P a g e
  • 52. Remote sensing and control of an irrigation system using a distributed wireless sensor network A DPDT relay is often used to reverse a motor. The circuit diagram on the left shows how the motor is connected to the relay. Relay circuit for reversing a motor When the input signal to the relay is high there is no current in the relay coil (as on the left), the positive side of the battery B1 is connected to the right-hand terminal of the motor, so the current in the motor flows from right to left. When the input signal to the relay is low there is current in the relay coil (as on the left) and the switch contacts change over. So now the positive side of the battery is connected to the left-hand terminal of the motor, the current in the motor flows from left to right and so the direction of rotation of the motor reverses. The circuit diagram shows the basic principles. If it is necessary to stop and start the motor this can be done with a separate driver or a SPST relay.VCET 52 | P a g e
  • 53. Remote sensing and control of an irrigation system using a distributed wireless sensor network A few relays need relatively low currents and can be driven directly from a PIC, 555Timer IC or LM324 op-amp. In these cases the relay coil is connected to the input signal and to0V.Possible applications • Reversing a motor • Providing electrical isolation between a noisy output device (such as a motor) and the processing electronics. • Controlling a low voltage a.c. output device, e.g. a low voltage halogen bulb (hotlink to bulb data sheet, section that refers to halogen bulb)Making:Pins of the Rapid 60-0100 DPDT relayThe diagram shows the pin arrangements and numbering for the Rapid 60-0100 DPDT relay.Note the unusual pin labelling system. The PCB shows the basic circuit. The separate powersupply and output device would be connected to the six upper pins.Build and test the driver unit that will provide the input signal before building the relay.Use a 16-pin Dual In Line (DIL) socket for the relay. Before inserting the relay, connect thepower supply and use a voltmeter to check that: • the voltage on pin ‘b’ is high (the supply voltage); • the voltage on pin ‘a’ (the blue PCB track) goes high and low in response to the driver unit that provides the input signal.VCET 53 | P a g e
  • 54. Remote sensing and control of an irrigation system using a distributed wireless sensor networkInsert the relay the right way round.7.7 TESTING Use a multimeter to test the resistance between the switch contacts and make sure thattheir resistance changes from high to low when the coil is switched on and off.Fault findingIf there is a fault, check that: • The voltage on pin ‘b’ is high • The relay has been correctly insertedIf there is a fault, check the tracks and solder joints.Alternatives • Pair of SPDT relays can be used to provide forward, reverse, stop and start for a motor – this has the advantage of providing a better ‘brake’ for a motor but is more expensive. • A L293D IC can also be used to provide forward, reverse, stop and start for two motors – this has the advantage of providing a better ‘brake’ for a motor, but is more expensive. • If the relay is being used to provide electrical isolation from noise, an alternative is the opto-isolator.HUMIDITY SENSOR:VCET 54 | P a g e
  • 55. Remote sensing and control of an irrigation system using a distributed wireless sensor networkHumidity sensitive resistor is used a new type of organic polymer materials, the humiditysensing element, with a sense of wet-range, fast response, strong anti-pollution, no heat cleaningand performance is stable and reliable long-term use and many other features. Humidity Sensor:Our professional agents of the product, the series is complete, fast delivery. This product iswidely used in: air conditioning, refrigerator, water heater, radio clock, electronic calendar,microwave ovens, cars, granaries, medical equipment, fire alarm devices, small appliances andother fields.Sensor type: humidity sensorOperating temperature: 0...60°CMeasuring range: 20%...95% RHOutput configuration: analogue voltageTolerance: ±5% RHFeatures:- Highly marketable product - Small and light- Long history - Mass productionApplicationWeather station, Humidifier & dehumidifier, Air-conditioner, Refrigerator and so onVCET 55 | P a g e
  • 56. Remote sensing and control of an irrigation system using a distributed wireless sensor networkVCET 56 | P a g e
  • 57. Remote sensing and control of an irrigation system using a distributed wireless sensor network A humidity sensor also called a hygrometer, measures and regularly reports the relativehumidity in the air. They may be used in homes for people with illnesses affected by humidity;as part of home heating, ventilating, and air conditioning (HVAC) systems; and in humidors orwine cellars. Humidity sensors can also be used in cars, office and industrial HVAC systems, andin meteorology stations to report and predict weather. A humidity sensor senses relative humidity. This means that it measures both airtemperature and moisture. Relative humidity, expressed as a percent, is the ratio of actualmoisture in the air to the highest amount of moisture air at that temperature can hold. Thewarmer the air is, the more moisture it can hold, so relative humidity changes with fluctuations intemperature. The most common type of humidity sensor uses what is called “capacitive measurement.”This system relies on electrical capacitance, or the ability of two nearby electrical conductors tocreate an electrical field between them. The sensor itself is composed of two metal plates with anon-conductive polymer film between them. The film collects moisture from the air, and themoisture causes minute changes in the voltage between the two plates. The changes in voltageare converted into digital readings showing the amount of moisture in the air.VCET 57 | P a g e
  • 58. Remote sensing and control of an irrigation system using a distributed wireless sensor network7.8 INVETER: So how can an inverter give us a high voltage alternating current from a low voltage direct current? Lets first consider how an alternator produces an alternating current. In its simplest form, an alternator would have a coil of wire with a rotating magnet close to it. As one pole of the magnet approaches the coil, a current will be produced in the coil. This current will grow to a maximum as the magnet passes close to the coil, dying down as the magnetic pole moves further away. However when the opposite pole of the magnet approaches the coil, the current induced in the coil will flow in the opposite direction. As this process is repeated by the continual rotation of the magnet, an alternating current is produced. Now let’s consider what a transformer does. A transformer also causes an electric current to be induced in a coil, but this time, the changing magnetic field is produced by another coil having an alternating current flowing through it. Any coil with an electric current flowing through it will act like a magnet and produce a magnetic field. If the direction of the current changes then the polarity of the field changes. Now, the handy thing about a transformer is that, the voltage produced in the secondary coil is not necessarily the same as that applied to the primary coil. If the secondary coil is twice the size (has twice the number of turns) of the primary coil, the secondary voltage will be twice that of the voltage applied to the primary coil. We can effectively produce whatever voltage weVCET 58 | P a g e
  • 59. Remote sensing and control of an irrigation system using a distributed wireless sensor network want by varying the size of the coils. If we connected a direct current from a battery to the primary coil it would not induce a current in the secondary as the magnetic field would not be changing. However, if we can make that direct current effectively change direction repeatedly, then we have a very basic inverter. This inverter would produce a square wave output as the current would be changing direction suddenly. This type of inverter might have been used in early car radios that needed to take 12 volts available in the car and produce the higher voltages required to run radio valves (known as tubes in America) in the days before transistors were widely used.100Watt Inverter 24VDC to 220VAC IIVCET 59 | P a g e
  • 60. Remote sensing and control of an irrigation system using a distributed wireless sensor networkThis is another 100watt inverter circuit diagram. Built based on IC CD4047 and Mosfet IRF540,this inverter have ability to supply electronic device -which require 220VAC- up to 100w from2-3A transformer..VCET 60 | P a g e
  • 61. Remote sensing and control of an irrigation system using a distributed wireless sensor networkUNIT-8SOFTWARE REQUIREMENTS8.1 SOFTWARE TOOLS • Development tool – MPLAB IDE v7.42 • Hardware Compiler - HI-Tech PIC C • Programmer - PIC Flash • Hardware Simulation tool - Proteus v7.6Sp08.2 INTRODUCTION TO EMBEDDED ‘C’: Ex: Hitec – c, Keil – c HI-TECH Software makes industrial-strength software development tools and Ccompilers that help software developers write compact, efficient embedded processor code. For over two decades HI-TECH Software has delivered the industrys most reliableembedded software development tools and compilers for writing efficient and compact code torun on the most popular embedded processors. Used by tens of thousands of customers includingGeneral Motors, Whirlpool, Qualcomm, John Deere and many others, HI-TECHs reliabledevelopment tools and C compilers, combined with world-class support have helped seriousembedded software programmers to create hundreds of breakthrough new solutions. Whichever embedded processor family you are targeting with your software, whether it isthe ARM, PICC or 8051 series, HI-TECH tools and C compilers can help you write better codeand bring it to market faster. HI-TECH PICC is a high-performance C compiler for the Microchip PIC micro10/12/14/16/17 series of microcontrollers. HI-TECH PICC is an industrial-strength ANSI CVCET 61 | P a g e
  • 62. Remote sensing and control of an irrigation system using a distributed wireless sensor networkcompiler - not a subset implementation like some other PIC compilers. The PICC compilerimplements full ISO/ANSI C, with the exception of recursion. All data types are supportedincluding 24 and 32 bit IEEE standard floating point. HI-TECH PICC makes full use of specificPIC features and using an intelligent optimizer, can generate high-quality code easily rivalinghand-written assembler. Automatic handling of page and bank selection frees the programmerfrom the trivial details of assembler code.8.3 EMBEDDED “C” COMPILER • ANSIC - full featured and portable • Reliable - mature, field-proven technology • Multiple C optimization levels • An optimizing assembler • Full linker, with overlaying of local variables to minimize RAM usage • Comprehensive C library with all source code provided • Includes support for 24-bit and 32-bit IEEE floating point and 32-bit long data types • Mixed C and assembler programming • Unlimited number of source files • Listings showing generated assembler • Compatible - integrates into the MPLAB IDE, MPLAB ICD and most 3rd-party development tools • Runs on multiple platforms: Windows, Linux, UNIX, Mac OS X, Solaris8.4 MPLAB INTEGRATION MPLAB Integrated Development Environment (IDE) is a free, integrated toolset for the development of embedded applications employing Microchips PIC micro and dsPIC microcontrollers. MPLAB IDE runs as a 32-bit application on MS Windows, is easy to use and includes a host of free software components for fast application development and super- charged debugging. MPLAB IDE also serves as a single, unified graphical user interface for additional Microchip and third party software and hardware development tools. MovingVCET 62 | P a g e

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