ADAMA UNIVERSITY SCHOOL OF ENGINEERING AND INFORMATION TECHNOLOGY DEPARTMENT OF ELECTRICAL ENGINEERING SENIOR PROJECT REPORT FOR BSc THESIS ON PLC BASED IRRIGATION SYSTEM CONTROL SUBMITTED TO: ATO KEMAL IBRAHIM PREPARED BY GROUP # 1 1. ADUGNA BEKELE 2. DULLA MEKONNEN 3. EMEBET TADESE 4. MESKEREM TADESE 5. NEWAY MOGES
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ADAMA UNIVERSITYSCHOOL OF ENGINEERING AND INFORMATION TECHNOLOGY
DEPARTMENT OF ELECTRICAL ENGINEERING
SENIOR PROJECT REPORT FOR BSc THESIS ON PLC BASED IRRIGATION SYSTEM CONTROL
SUBMITTED TO: ATO KEMAL IBRAHIM
PREPARED BY GROUP # 1
1. ADUGNA BEKELE
2. DULLA MEKONNEN
3. EMEBET TADESE
4. MESKEREM TADESE
5. NEWAY MOGES
AUGUST, 2010
Abstract
New irrigation electrical control technologies could improve irrigation efficiency, promoting
water conservation and reducing the environmental impacts. The objectives of this project were
to avoid wastage of water and increase irrigation efficiency by using a PLC based irrigation
system with the help of soil moisture sensor. It also improves the traditional irrigation system in
Ethiopia enabling the irrigation system to have high efficiency and low water usage.The existing
irrigation system being tedious, time consuming and very wasteful in water usage. The PLC
based sprinkler irrigation system gives the best feature than the traditional one.
Acknowledgements
In order to successfully accomplish our senior project on PLC based
automation of irrigation system with case study on ADAMA UNIVERSITY garden
watering system the help of many people was very important and unforgettable.
So our kind and deep appreciation and thanks goes to our adviser Ato KEMAL
IBRAHIM for his advice, spending his golden time, knowledge and bringing materials
from different concerned bodies for the success of this project. Our next thanks goes to
M/r WOLFGANG, chief of GTZ/ECBP further training section, and all his subordinates
for their endless support and attempt to help us with any regards in their disposal. We
would like to tank AU water supply section and wood work sections for their kindly
cooperation and patience. Finally we would like to thanks all the teachers in ELT
department
Table of contents Page
Acknowledgement
Abstract
1. Introduction……………………………………………………………………….1.1Background of the project….………………………………………………….1.2Statement of the problem………………………………………………………1.3Objective of the Project……………………………………………………….1.4Scope of the Project……………………………………………………………
2.1.1 History of PLC…………………………………………………………2.1.2 Basic functional sections of PLC……………………………………….2.1.3 Expansion module………………………………………………………2.1.4 Programming a PLC……………………………………………………2.1.5 PLC scan cycle………………………………………………………….2.1.6 Advantage of PLC……………………………………………………..
2.2Solenoid valve…………………………………………………………………..2.2.1 Definition……………………………………………………………….2.2.2 Function…………………………………………………………………2.2.3 Operation principle……………………………………………………....2.2.4 Types of solenoid valve………………………………………………….
2.3Soil moisture sensor……………………………………………………………...2.3.1 Types of soil moisture sensor……………………………………………
2.5.1 Definition………………………………………………………………..2.5.2 Types of level sensor……………………………………………………2.5.3 Application of level sensor………………………………………………
2.6Description of the project………………………………………………………2.6.1 Design …………………………………………………………………..2.6.2 Implementation…………………………………………………………2.6.3 Test………………………………………………………………………
Irrigation in Ethiopia has lasted for decades. Ethiopia covers 12 river basins with an
annual runoff volume of 122 billion m3 of water with an estimated 2.6 billion m3 of ground
water potential. This amounts to 1743 m3 of water per person per year: a relatively large
volume. But due to lack of water storage capacity and large spatial and temporal
variations in rainfall, there is not enough water for most farmers to produce more than
one crop per year with frequent crop failures due to dry spells and droughts. Moreover,
there is significant erosion, reducing the productivity of farmland. [Awulachew] So
irrigation being compulsory for Ethiopia; the government has recognized Ethiopia’s
irrigation potential and has identified the important role of irrigation development for
reducing vulnerability to inconsistent rain fall distribution and poverty reduction of the
people.
Traditional irrigation is very old in Ethiopia. The traditional small-scale schemes
are, in general, simple river diversions. The diversion structures are elementary and
subject to frequent damage by flood.
'Modern' irrigation was started at the beginning of the 1960s by private investors in
the middle Awash valley where big sugar estates, fruit and cotton farms are found. With
the 1975 rural land proclamation, the large irrigated farms were placed under the
responsibility of the Ministry of State Farms. Almost all small-scale irrigation schemes
built after 1975 were made into Producers' Cooperatives. [www.fao.org]
Ethiopia has an estimated irrigation potential of 3.5 up to 4 million hectares
(Awulachew et al. 2007b). During 2005/2006 the total estimated area of irrigated
agriculture in the country was 625,819 ha, which, in total, constitutes about 18% of the
potential (MoWR 2006); of which traditional irrigation accounts for 479,049 hectares
while 124,569 hectares of land was developed through medium and large scale
irrigation schemes ( MoFED, 2007).
According to the Ministry of Water Resource (2002), there are four broad
categories of irrigation systems in Ethiopia, namely; (i) traditional irrigation schemes; (ii)
modern small-scale irrigation schemes, (iii) medium- to large-sc irrigation schemes, and
(iv) large scale irrigation schemes.
About 75 percent of the developed irrigation is small-scale, about three-quarters of
which is traditional, and is mostly based on local practices and indigenous knowledge.
Given that the overwhelming majority of farming activities in Ethiopia is small-scale,
there could be a unique opportunity for positive interventions to stimulate agricultural
production, especially if certain fundamental conditions are met. Experience in many
parts of SSA has shown that with adequate community involvement in planning, design
and management, SSIs can be more viable and sustainable than conventional large-
scale schemes from a number of perspectives (Merry et al., 2002).
Sprinkler Irrigation is a method of supplying water for irrigation in a method similar
to rainfall. Water is distributed through a network of pipes spread out on a field. The
water from these pipes into the air and so irrigates the entire soil surface through many
sprinkler heads. Sprinklers provide better coverage for small to large areas and are
suitable for use on all types of fields. Total area to be irrigated is divided into small
segments called irrigation blocks or zones and these zones are irrigated in sequence
according to the flow of water. It is also adaptable nearly to all irrigable soils since
sprinklers are available in a wide range of discharge capacity. It is suitable for almost all
fields, crops as well as Vegetables and gardens: Residential, Industrial, Hotel, Resorts,
Public & Government Enterprises, Golf Links, Race Courses.
Water is a valuable resource and therefore its usage should be in an efficient manner.
Also, water scarcity is one of the most important factors driving growth in agriculture-
based industries in our country Ethiopia. For efficient use of water for irrigation, labor
cost, etc., drives the need for highly efficient automated sprinkler irrigation systems.
Automated sprinkler system has the following categories
(a)Time based system.
Time based automatic sprinkler systems is better to avoid being bothered with the
routine work of lawn watering, but tend to “set them and forget them”. This method of
watering accomplishes the task of keeping the lawn green, but over the growing season
uses significantly more water than the grass requires. This problem contribute to water
waste and are not often fixed because the lawn is unnoticed moist most of the time.
(b) Quantity based system.
In volume based system, the preset amount of water can be applied in the field
segments by using automatic volume controlled metering valves. Sequencing of
metering values can also be done automatically. Even though the amount of water
applied can be excess because the discharging of the moisture may vary in time.
(c) Moisture sensor based system
In the moisture sensing system the operation of irrigation valves are controlled by
a controller get values from the moisture sensors placed directly in to the root zone. If
there is sufficient moisture, then the sensor will prevent the sprinkler system from
activating and applying water. However, if it senses that the soil is dry, it allows irrigation
to take place.
Automatic sprinkler systems have the potential to save water if they are well
designed, installed and maintained and it will give a great advantage for the owners and
workers.[ Brent Q. Mecham] So, our project is a PLC based sprinkler irrigation system
using moisture sensor which can give the best feature in giving effective watering and
intense satisfaction of job well-done to bring an irrigation development in our country
Ethiopia.
1.2 Statement of the problem
Irrigation system has lasted years in Ethiopia which is traditional. Farmers are
traditionally accustomed to directing flood (surface) water for supplementing their crops
(spate irrigation).These irrigation systems have many drawbacks like wastage of water,
high labor cost, timing problem, uniformity of water supply, so that each plant will not get
the amount of water it needs, either too much or too little. Since the system is
uncontrolled the soil is soaked too much .These systems have low requirements for
infrastructure and technical equipment but need high labor inputs . So our project
comes up with a remedy to solve the above problem with high efficiency and low water
usage.
1.3 Objective of the Project
The general objective of the project is to design automated control system sprinkler
irrigation for the development of irrigation in our country.
Specific objective of the study are:
1. To design and implement a control system of sprinkler system for a
Garden of Adama University
2. To minimize human intervention in agricultural irrigation industry .
3. To improve automation, control, and distribution technology in irrigation system.
4. To increase irrigation water utilization efficiency.
5. To enhance the transfer of irrigation technologies and management alternatives
emphasizing economic and environmental benefits.
1.4. Scope of the project
Sprinkler irrigation system in this project takes water from Adama University of the existing garden water tap to irrigate a garden by automated control system and the principle can be extended to a higher to large scale farms and small scale ETHIOPIAN farmers land irrigation for farmers specially who live in a place where water is very scares and water can be stored in well and/or there is another water body like lake, river, ….etc but not suitable to surface irrigation system with the same control philosophy but pump- motor assembly instead of water tap with solenoid valve.
2. Project description
In working principle of automatic irrigation system there are three in put parameters to the controller:
1. Soil moisture sensor signal.2. Water balancing tank level signal.
3. Four push button signal.
The controller is programmable logic controller and the controlled variable in this system is electrically controlled solenoid valve mounted on tap end. The final elements are the PVC pipes and the sprinkler heads.
State of the valve is controlled and determined by statuses of the three PLC inputs,
1. The two moisture sensors are installed at two different depths under the plant root. The shallow moisture sensor is installed at 1/3 of the rooting depth to sense the moisture at 1/3 of the depth .The second moisture sensor installed at 2/3 of the rooting depth of the plant to senses wetness. When the system starts the irrigation the shallow moisture sensor senses first and irrigation continued until the second moisture senses. At this point the controller takes an action and the main valve will be closed.
2. The second input is a water level sensor in the balancing water tanker. When defective sprinkler head or any other problem clog the irrigation pipe network develops high pressure. The pressurized water is stored as a relief inside a balancing water tanker placed at elevated palace and its water level is detected by the level sensor to take action by the controller to avoid the over flow of water. So when the water in the balancing tank reaches at a pre determined set point it closes or opens solenoid valve accordingly.
3. Other inputs are start, stop, emergency stop and test buttons which send command according to programmed parameters. These input parameters to the controller sets high whenever the user want to start, stop and test the irrigation system irrespective of the status of the level sensor in the balancing tank and status of moisture sensors in the root zone of the plant.
Programmable logic controllers (PLC)
A PROGRAMMABLE LOGIC CONTROLLER is a solid state control system that
continuously monitors the status of devices connected as inputs. Based upon a user
written program, stored in memory, it controls the status of devices connected as
outputs.
History of PLC
The development of the industrial society led each manufacturing process to
become larger in scale, and more advanced and complex, requiring many different
forms of control systems. Up to now, control systems for automation were connected to
related electronic components, such as relay, contractor, timer, counter, etc, depending
on the circuit layout, which led to problems such as difficulty in the lining process and
the amount of space for sequence control, and the slow of operation.
Recognizing these problems, in 1968, General Motors, the American automobile
manufacturer, suggested 10 conditions for PLC, as shown in, which became the starting
point of PLC development. The chart is a brief history of PLC.
10 conditions suggested by General Motors
(1) Should be easy to implement and modify program and sequence system.
(2) Maintenance and repair must be easy and must be a plug-in type.
(3) Should be more reliable than relay controller.
(4) Output should be able to be connected to computer.
(5) Should be smaller in size than relay controller.
(6) Should be more cost effective than relay controller.
(7) Input should be supplied with AC 115[V].
(8) Output should be supplied with AC 115[V], 2[A].
(9) Should be expendable without making much modification of the entire system.
(10) Should be equipped with programmable memory, which is expandable to at
least 4K words.
History of PLC
Year Progress
1968 The birth of the concept of PLC
1970 Introduction of logic control, 1K memory capacity and 128 I/O score
handling
1974 Timer, counter, arithmetic operation, 12K memory capacity, and 1024I/O
score handling
1976 Introduction of remote I/O system (first standard created by the US)
1977 Introduction of microprocessor PLC
1980 Introduction of high performance I/O module, high performance
communication device high functional software; started to use
microcomputer as programming tool
1983 Introduction of inexpensive small-size PLC
1985 Standardization, distributed and hierarchical control made possible by
networking with computer
1991 Fuzzy logic implemented by fuzzy only package
Basic functional sections of PLC
Programmable logic controller has five basic functional sections to perform its intended
operation completely. These functional sections are:
1. Central processing unit (CPU).
2. Memory.
3. Input module.
4. Output module.
5. Power system.
Central processing unit
Central Processing Unit (CPU) is the brain of a PLC controller. CPU itself is usually one
of the microcontrollers. Aforetime these were 8-bit microcontrollers such as 8051, and
now these are 16- and 32-bit microcontrollers. CPU also takes care of communication,
interconnectedness among other parts of PLC controller, program execution, memory
operation, overseeing input and setting up of an output. PLC controllers have complex
routines for memory checkup in order to ensure that PLC memory was not damaged
(memory checkup is done for safety reasons). Generally speaking, CPU unit makes a
great number of check-ups of the PLC controller itself so eventual errors would be
discovered early. You can simply look at any PLC controller and see that there are
several indicators in the form of light diodes for error signalization.
Memory
System memory, today mostly implemented in FLASH technology, is used by a PLC for
a process control system. Aside from this operating system it also contains a user
program translated from a ladder diagram to a binary form. FLASH memory contents
can be changed only in case where user program is being changed. PLC controllers
were used earlier instead of FLASH memory and have had EPROM memory instead of
FLASH memory which had to be erased with UV lamp and programmed on
programmers. With the use of FLASH technology this process was greatly shortened.
Reprogramming a program memory is done through a serial cable in a program for
application development.
User memory is
divided into blocks having special functions. Some parts of a memory are used for
storing input and output status. The real status of an input is stored either as "1" or as
"0" in a specific memory bit.
Each input or output has one corresponding bit in memory. Other parts of memory are
used to store variable contents for variables used in user program. For example, timer
value, or counter value would be stored in this part of the memory.
PLC controller inputs
Intelligence of an automated system depends largely on the ability of a PLC controller to
read signals from different types of sensors and input devices. Keys, keyboards and by
functional switches are a basis for man versus machine relationship. On the other hand,
in order to detect a working piece, view a mechanism in motion, check pressure or fluid
level you need specific automatic devices such as proximity sensors, marginal switches,
photoelectric sensors, level sensors, etc. Thus, input signals can be logical (on/off) or
analogue. Smaller PLC controllers usually have only digital input lines while larger also
accept analogue inputs through special units attached to PLC controller. One of the
most frequent analogue signals are a current signal of 4 to 20 mA and milivolt voltage
signal generated by various sensors. Sensors are usually used as inputs for PLCs. You
can obtain sensors for different purposes. They can sense presence of some parts,
measure temperature, pressure, or some other physical dimension.
Other devices also can serve as inputs to PLC controller. Intelligent devices such as
robots, video systems, etc. often are capable of sending signals to PLC controller input
modules (robot, for instance, can send a signal to PLC controller input as information
when it has finished moving an object from one place to the other.)
Adjustment interface also called an interface is placed between input lines and a CPU
unit. The purpose of adjustment interface to protect a CPU from disproportionate signals
from an outside world. Input adjustment module turns a level of real logic to a level that
suits CPU unit (ex. input from a sensor which works on 24 VDC must be converted to a
signal of 5 VDC in order for a CPU to be able to process it). This is typically done
through opto-isolation, and this function you can view in the following picture. Opto-
isolation means that there is no electrical connection between external world and CPU
unit. They are "optically" separated, or in other words, signal is transmitted through light.
The way this works is simple. External device brings a signal which turns LED on,
whose light in turn incites photo transistor which in turn starts conducting, and a CPU
sees this as logic zero (supply between collector and transmitter falls under 1V). When
input signal stops LED diode turns off, transistor stops conducting, collector voltage
increases, and CPU receives logic 1 as information.
2.6 PLC controller output
Automated system is incomplete if it is not connected with some output devices. Some
of the most frequently used devices are motors, solenoids, relays, indicators, sound
signalization and similar. By starting a motor, or a relay, PLC can manage or control a
simple system such as system for sorting products all the way up to complex systems
such as service system for positioning head of CNC machine. Output can be of
analogue or digital type. Digital output signal works as a switch; it connects and
disconnects line. Analogue output is used to generate the analogue signal (ex. motor
whose speed is controlled by a voltage that corresponds to a desired speed).
Output interface is similar to input interface. CPU brings a signal to LED diode and turns
it on. Light incites a photo transistor which begins to conduct electricity, and thus the
voltage between collector and emitter falls to 0.7V, and a device attached to this output
sees this as a logic zero. Inversely it means that a signal at the output exists and is
interpreted as logic one. Photo transistor is not directly connected to a PLC controller
output. Between photo transistor and an output usually there is a relay or a stronger
transistor capable of interrupting stronger signals.
Power supply
Electrical supply is used in bringing electrical energy to central processing unit. Most
PLC controllers work either at 24 VDC or 220 VAC. On some PLC controllers you'll find
electrical supply as a separate module. Those are usually bigger PLC controllers, while
small and medium series already contain the supply module. User has to determine
how much current to take from I/O module to ensure that electrical supply provides
appropriate amount of current. Different types of modules use different amounts of
electrical current.
This electrical supply is usually not used to start external inputs or outputs. User has to
provide separate supplies in starting PLC controller inputs or outputs because then you
can ensure so called "pure" supply for the PLC controller. With pure supply we mean
supply where industrial environment can not affect it damagingly. Some of the smaller
PLC controllers supply their inputs with voltage from a small supply source already
incorporated into a PLC.
Extension modules
Every PLC controller has a limited number of input/output lines. If needed this number
can be increased through certain additional modules by system extension through
extension lines. Each module can contain extension both of input and output lines. Also,
extension modules can have inputs and outputs of a different nature from those on the
PLC controller (ex. in case relay outputs are on a controller, transistor outputs can be on
an extension module).
Programming a PLC controller
PLC controller can be reprogrammed through a computer (usual way), but also through
manual programmers (consoles). This practically means that each PLC controller can
programmed through a computer if you have the software needed for programming.
Today's transmission computers are ideal for reprogramming a PLC controller in factory
itself. This is of great importance to industry. Once the system is corrected, it is also
important to read the right program into a PLC again. It is also good to check from time
to time whether program in a PLC has not changed. This helps to avoid hazardous
situations in factory rooms (some automakers have established communication
networks which regularly check programs in PLC controllers to ensure execution only of
good programs).
Almost every program for programming a PLC controller possesses various useful
options such as: forced switching on and off of the system inputs/outputs (I/O lines),
program follow up in real time as well as documenting a diagram. This documenting is
necessary to understand and define failures and malfunctions. Programmer can add
remarks, names of input or output devices, and comments that can be useful when
finding errors, or with system maintenance. Adding comments and remarks enables any
technician (and not just a person who developed the system) to understand a ladder
diagram right away. Comments and remarks can even quote precisely part numbers if
replacements would be needed. This would speed up a repair of any problems that
come up due to bad parts. The old way was such that a person who developed a
system had protection on the program, so nobody aside from this person could
understand how it was done. Correctly documented ladder diagram allows any
technician to understand thoroughly how system functions by communicating the
programmer, computer, with the controller by means of RS 232 communication cable.
The following figure show price and functionality comparision of controllers.