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Int. J. Elec&Electr.Eng&Telecoms. 2015 M S Steffi et al., 2015

AUTOMATIC IRRIGATION SYSTEM USINGPROGRAMMABLE LOGIC CONTROLLER

M S Steffi1*, P Visitha1 and C Kamal1

*Corresponding Author: M S Steffi, [email protected]

This paper presents a design of a programmable logic controller based system to control anautomatic irrigation system. The system is composed of three modules: the programmablelogic circuits, sensor system and the SCADA monitoring. The irrigation system composes ofthree samples, simulating three different agriculture fields. The Humidity of each field is differentfrom that of other fields according to the requirement of different plantation. It is controlled by twosensors for minimum and maximum humidity respectively. Each sample is irrigated by a separatevalve. The valves are controlled by the PLC. If the maximum humidity is reached, the PLC turnsoff the concerned valve feeding the concerned sample. When all samples have reached theirrespective maximum humidity, the PLC turns off the main pump. The system has been designed,built and tested successfully. This project is proposed to overcome difficulties faced by thefarmers in gaining more profit by increasing the productivity and reducing the consumption ofwater and electricity by using a renewable source of energy. Farmers will be able to monitor andcontrol the irrigation system from one place with the help of software called SCADA (supervisorycontrol and data acquisition) which does the controlling action through PLC (ProgrammableLogic Controller).

Keywords: SCADA, Programmable logic controller, Data register, Master Terminal Unit (MTU),Human Machine Interface (HMI)

INTRODUCTIONIn recent years, global water problems areattracting increasing attention. India is a bigagricultural country with a serious watershortage. At present, 70% of India’s totalannual water consumption, about 550 billioncubic meters, is agricultural water, of which90% is irrigation water. On one hand, India’s

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Int. J. Elec&Electr.Eng&Telecoms. 2015

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agricultural irrigation water shortage is about300 billion cubic meters, and an averageannual the drought stricken area is about 300million mus. These are led to reduce foodproduction from 15 billion to 30 billionkilograms. On the other hand, due to thebackward irrigation technology, the Indianeffective utilization ratio of irrigation water is

Research Paper

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only 40%, only about half of the developed.Grain production capacity is only about 0.87kilograms per cubic meter, much lower thanthe developed for more than 2 kilograms. If theutilization ratio of irrigation water increasesform 10% to 15%, savings of water per yearare about 60 billion to 80 billion cubic meters.Therefore, development of water-savingirrigation technology is urgently needed.

Nowadays, with the increasingly shortageof the water resources, promote water-savingirrigation has become the inevitable choice toease the water crisis. Meeting the crop waterdemand is the trend of current water-savingagriculture. The irrigation is PLC based, usingsensing technology to collect the soilinformation, and achieved intelligent control bycontrol engineering algorithms. Indianresearch in water saving irrigation is not muchcompared with the developed. A lot of irrigationin rural areas was operated by the artificial,even the same in the greenhouse cultivation.Against the situation of India, we hasdeveloped PLC based intelligent water-savingirrigation device (a patented product). Theproduct has been preliminarily completed theindustrial transformation.

The main parts of the irrigation device area battery, sensors (electric probes),Programmable logic controller (Omron CP1E),solenoid valves, and etc. It controls theelectromagnetic valve with low-powertechnologies to open by using electroniccircuits.

The use of this controller in the field Withoutcommercial power and routing, micro-powervalve’s opening or closing can be achievedby an integrate technology of solar power,

Nano-materials, electro-hydraulic drivetechnology, and, etc. This intelligent water-saving irrigation can be implementedaccording to the plant’s needs by the sensingunit detecting soil moisture. Here the sensingunit acts as a conducting switch, when thewater reaches both the probes the circuitconducts and this is detected by PLC andoutput is given the respective solenoid valvesupplies water to that particular sensing unit.

The controlling unit is a Programmable logiccontroller (OMRON-CP1E), which is a typicalcontroller that requires CX-programmer CP1Esoftware for downloading program into thecontroller and OMRON HOST LINK is the I\Odriver that is used to communicate thecontroller with the SCADA.

Supervisory Control and Data Acquisition(SCADA) is the remote monitoring and controlunit that helps the user to monitor as well ascontrol the irrigation system through PersonalComputer from a stationary area. Itcommunicates with PLC with the help of theI\O driver named OMRON HOST LINK. Thecommunication takes place via the accessname that was given in the SCADA and theconfigure setting in the OMRON HOST LINKdriver. Both the name should be similar.

BASIC OPERATION OF A PLCThe figure shows the basic operation cycle ofa PLC. All PLCs have four basic stages ofoperations that are repeated many times persecond. Initially when turned on the first time itwill check its own hardware and software forfaults. If there are no problems it will copy allthe input and copy their values into memory,this is called the input scan. Using only thememory copy of the inputs the ladder logic

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program will be solved once, this is called thelogic scan. While solving the ladder logic theoutput values are only changed in temporarymemory. When the ladder scan is done theoutputs will be updated using the temporaryvalues in memory, this is called the output scan.The PLC now restarts the process by startinga self check for faults. This process typicallyrepeats 10 to 100 times per second. That isthe PLC does

• Self test

• Input scan

• Logic solve

• Output scan

Self TestChecks to see if all cards error free, resetwatch-dog timer, etc. (A watchdog timer willcause an error, and shut down the PLC if notreset within a short period of time this wouldindicate that the ladder logic is not beingscanned normally).

Input ScanReads input values from the chips in the inputcards, and copies their values to memory. Thismakes the PLC operation faster, and avoidscases where an input changes from the startto the end of the program (e.g., an emergencystop). There are special PLC functions thatread the inputs directly, and avoid the inputtables. LOGIC SOLVE/SCAN - Based on theinput table in memory, the program is executed1 step at a time, and outputs are updated. Thisis the focus of the later sections.

Ooutput ScanThe output table is copied from memory to theoutput chips. These chips then drive the output

devices. Input scan takes a snapshot of theinputs, and solves the logic. This preventspotential problems that might occur if an inputthat is used in multiple places in the ladderlogic program changed while half way througha ladder scans. Thus changing the behaviorsof half of the ladder logic program. Thisproblem could have severe effects on complexprograms that are developed later in the book.

One side effect of the input scan is that if achange in input is too short in duration, it mightfall between input scans and be missed. Whenthe PLC is initially turned on the normal outputswill be turned off. This does not affect the valuesof the inputs.

Figure 1: Block Diagram

OMRON-CP1EIn this project PLC is used to control theprocess, SCADA to monitor the process andmoisture sensors ensure optimum usage ofwater for irrigation. Since renewableresources of energies are not dependable inthese days, we implemented solar energy forproducing power supply for our system.

The PLC we used in our system is OMRON-CP1E. OMRON PLC-based Process Controlsystem is based on the SYSMAC CS/CJ PLC

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Series. By adding PLC-based ProcessControl units to the basic system configuration,PLC process control functions can be simplyadded on to the basic functions alreadyinstalled in the PLC. Thus it can be used fordevices that it is compatible with such processcontrol system in which was used before ordevices in which several controllers were usedcombined. With the PLC Installation System,analog processing is carried out by the loopcontrol section or the loop control unit/board(hereafter “loop controller”), and ladderprocessing is handled by the CPU.Communication between the two sections ismade using bits of memory. Since the analogprocessing and ladder processing can becompletely separated and the program issimpler than a ladder only program, theengineering process to construct the systemis facilitated. The PLC Unit utilizes a variety ofdifferent data including user programs, I/OMemory data and comments, CPU Unit andSpecial I/O units, Parameters and RegisteredI/O Table information etc. All of this data that isused by the PLC is stored in the memory areawithin the CPU unit.

The I/O memory area is accessed bycommand operands. It records informationsuch as the CIO, Internal I/O Area, holding area,auxiliary area, DM Area, EM Area, TimerCompletion Flags/Present Value, CompletionFlag/Present Value, Task Flags, IndexRegister, Data Register, Condition Flags,Clock Pulse, etc. The data in the I/O MemoryArea locates in or is in areas in which thecontents are cleared every time the power isturned back on, and areas in which priorinformation is retained. (In some areas you canselect whether to clear or retain).

The parameter area contains all of theinformation regarding initial parameters usedby the PLC. It records information such as thePLC System Parameters, Registered I/OTable, Routing Table, and PLC Setup for CPUBus unit.

SCADA SYSTEMARCHITECTURESpecific terminology is associated with thecomponents of SCADA systems. TheseSCADA elements are defined as follows:

Figure 2: Model of OMRAN PLC-CP1E

Figure 3: SCADA Simulation

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OperatorHuman Operator Who Monitors the SCADASystem and Performs Supervisory controlfunctions for the remote plant operation.

Human Machine Interface (HMI)Presents data to the operator and providesfor Control inputs in a variety of formats,including graphics, schematics, windows, pulldown menus, touch-screens, and so on.

Master Terminal Unit (MTU)Equivalent to a master unit in a master/slavearchitecture. The MTU presents data to theoperator through the HMI, gathers data fromthe distant site, and transmits control signalsto the remote site. The transmission rate ofdata between the MTU and the remote site isrelatively low and the control method is usuallyopen loop because of possible time delays ordata flow interruptions communication methodbetween the MTU and remote controllers.Communication can be through the Internet,wireless or wired networks, or the switchedpublic telephone network.

Remote Terminal Unit (RTU)Functions as a slave in the master/slavearchitecture. Sends control signals to thedevice under control, acquires data from thesedevices, and transmits the data to the MTU.An RTU may be a PLC. The data rate betweenthe RTU and controlled device is relatively highand the control method is usually closed loop.As discussed previously, a SCADAarchitecture comprises two levels: a masteror client level at the supervisory control centerand a slave or data server level that interactswith the processes under control. In additionto the hardware, the software components ofthe SCADA architecture are important.

Moisture SensorsIt helps us to detect the soil moisture so that toensure the optimum usage of water. Type ofirrigation used here is drip irrigation. Moisturesensors are immersed in different part of thefield so that it will continuously monitor the watercontent of the soil. The output from the moisturesensor is compared with the set point andaccordingly water to that area is either limitedor provided.

In our proposed system, a moistureparameter is pre set and the output from themoisture sensor is detected and the waterrequired is given to the area. Since we areusing drip irrigation, solenoid valves are usedat the start point of water pipe.If the outputgiven by the moisture sensor in a particulararea is lesser than the set point parameter thenplc gives signal to the solenoid valve of thatparticular area and its open, if its vice versavalve will be closed or the flow will becontrolled. Effective use of SCADA in oursystem reduces manpower and tiresome infarming job. With help of SCADA one canmonitor and control the whole irrigation landfrom a control room.

The valves used here is the solenoid valve.The specifications of the valves are givenbelow.

• Source needed: 24 v dc.

• Terminals: Two terminals

• I/O: Water in, and Water out

• Description: The input valve will allow theinput water to pass through it when a signalis applied to its terminals. After the signalis disconnected, the valve will return to itsnormal operation (prevent water to pass).

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We needed five valves in this model: Oneis major to guarantee that the pump worksonly when the water level in the tank issuitable that we maintain the pump, andincrease its hypothetical age. There arefurther four secondary valves distributed onthe agricultural areas for the favor of controlon the irrigation process though opening,and closing those valves according to thesoil’s need to water.

ULN2803-RELAY DRIVERA ULN2803 is an Integrated Circuit (IC) chipwith a High Voltage/High Current Darlington

Transistor Array. It allows you to interface TTLsignals with higher voltage/current loads. InEnglish, the chip takes low level signals (TLL,CMOS, PMOS, NMOS—which operate at lowvoltages and low currents) and acts as a relayof sorts itself, switching on or off a higher levelsignal on the opposite side.

A TTL signal operates from 0-5 V, witheverything between 0.0 and 0.8V considered“low” or off, and 2.2 to 5.0 V being considered“high” or on. The maximum power availableon a TTL signal depends on the type, butgenerally does not exceed 25 mW (~5 mA @5 V), so it is not useful for providing power tosomething like a relay coil. Computers andother electronic devices frequently generateTTL signals. On the output side the ULN2803is generally rated at 50V/500mA, so it canoperate small loads directly. Alternatively, itis frequently used to power the coil of one ormore relays, which in turn allow even highervoltages/currents to be controlled by the lowlevel signal. In electrical terms, the ULN2803uses the low level (TTL) signal to switch on/turn off the higher voltage/current signal onthe output side.

Figure 4: Solenoid Valves

Figure 5: ULN2803 Relay Driver

Figure 5: Schematic Diagram of Driver

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The ULN2803 comes in an 18-pin ICconfiguration and includes eight (8) transistors.Pins 1-8 receive the low level signals; pin 9 isgrounded (for the low level signal reference).Pin 10 is the common on the high side andwould generally be connected to the positiveof the voltage you are applying to the relay coil.Pins 11-18 are the outputs (Pin 1 drives Pin18, Pin 2 drives 17, etc.).

CONCLUSION:In the near future resources like water andelectricity will be vanished unless or until weuse renewable energy and the moderntechnology to save water and increase theproductivity of food. This project has atremendous scope for future in saving waterand electricity.

PLC and SCADA are the latesttechnologies that have to be implemented inapplication like industrial automation, robotics,power plants, and agricultural irrigation. Theperson can monitor and control the irrigationsystem through personal computer with thehelp of supervisory control and dataacquisition unit.

Figure 6: ULN2803 ICFuture enhancement of the project is to

replace personal computer by mobile phone.Developing an android application like SCADAwhich will communication through internet orGSM. This will facilitate the farmer to controlthe irrigation system from anywhere bymonitoring.

REFERENCES1. Liu Xiaochu (2002a), “The Intelligent

Water Controller”, Chinese Patent, No.01266763.

2. Liu Xiaochu (2002b), “The Solar-PoweredIntelligent Water Controller”, ChinesePatent, No. 01266948.

3. Liu Xiaochu and Ye Bangyan (2003),“Expect of Technology of Water-SavingIrrigation Device”, Journal of Universityof Electronic Science and Technology.

4. Ouyang Lie (2005), “Some Measures toEnsure the Engineering ConstructionQuality of Greening Project”, Journal ofGuangdong Landscape Architecture,Supplement.

5. Zhang Fuyuan (1998), “PipelineConstruction Technology of Water-SavingIrrigation [J]”, Xinjiang Farmland ScienceTechnology.

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