AUTOMATIC SOLAR IRRIGATION PUMP CONTROL SYSTEM BASED ON SOIL MOISTURE SENSOR CHAPTER – 1 INTRODUCTION This project aims in providing a user friendly, reliable and automated irrigation pump controlling system for illiterates. Now a day’s technology is running with time, it completely occupied the life style of human beings. Even though there is such an importance for technology in our routine life there are even people whose life styles are very far to this well known term technology. So it is our responsibility to design few reliable systems which can be even efficiently used by them. This basic idea gave birth to the project soil moisture sensor based irrigation pump controller and this project aims in introducing the automation technology into the lives of the illiterates. The purpose of this project is to monitor soil moisture and control a irrigation pump using microcontroller powered by solar. This can be achieved by the use of soil moisture sensor, which senses the water content in the soil. This sensor output is given to a Microcontroller based control system for further data processing. This project also consists of relays are used to control the pump motor. Whenever the soil moisture content goes below some predefined level, and then this information is sent to Microcontroller based control system. Based on Dept. of EEE 1 Trinity College of Engg. & Tech. Knr
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AUTOMATIC SOLAR IRRIGATION PUMP CONTROL SYSTEM BASED ON SOIL MOISTURE SENSOR
CHAPTER – 1
INTRODUCTION
This project aims in providing a user friendly, reliable and automated irrigation
pump controlling system for illiterates. Now a day’s technology is running with time, it
completely occupied the life style of human beings. Even though there is such an
importance for technology in our routine life there are even people whose life styles are
very far to this well known term technology. So it is our responsibility to design few
reliable systems which can be even efficiently used by them. This basic idea gave birth to
the project soil moisture sensor based irrigation pump controller and this project aims in
introducing the automation technology into the lives of the illiterates.
The purpose of this project is to monitor soil moisture and control a irrigation
pump using microcontroller powered by solar. This can be achieved by the use of soil
moisture sensor, which senses the water content in the soil. This sensor output is given to
a Microcontroller based control system for further data processing.
This project also consists of relays are used to control the pump motor. Whenever
the soil moisture content goes below some predefined level, and then this information is
sent to Microcontroller based control system. Based on the command received the
Microcontroller switches ON or OFF the irrigation pump motor. This system uses relay
which are controlled by the starter.
Dept. of EEE 1 Trinity College of Engg. & Tech. Knr
AUTOMATIC SOLAR IRRIGATION PUMP CONTROL SYSTEM BASED ON SOIL MOISTURE SENSOR
The features of the project are:
1. Automatic Soil moisture sensing system.
2. Irrigation motor control.
The major building blocks of this project
1. Regulated Power Supply.
2. Microcontroller.
3. Soil moisture sensor.
4. Electromagnetic relay with driver.
5. Crystal oscillator.
6. Reset.
7. Pump Motor (for water pumping).
8. LCD.
Dept. of EEE 2 Trinity College of Engg. & Tech. Knr
AUTOMATIC SOLAR IRRIGATION PUMP CONTROL SYSTEM BASED ON SOIL MOISTURE SENSOR
Regulated Power Supply:
Fig.1: Regulated Power Supply
Block Diagram:
Fig: 2: Block diagram
Dept. of EEE 3 Trinity College of Engg. & Tech. Knr
AUTOMATIC SOLAR IRRIGATION PUMP CONTROL SYSTEM BASED ON SOIL MOISTURE SENSOR
CHAPTER – II
SOLAR PANEL
Solar panel refers either to a photovoltaic module, a solar hot water panel, or to a
set of solar photovoltaic (PV) modules electrically connected and mounted on a
supporting structure. A PV module is a packaged, connected assembly of solar cells. Solar
panels can be used as a component of a larger photovoltaic system to generate and supply
electricity in commercial and residential applications. Each module is rated by its DC
output power under standard test conditions (STC), and typically ranges from 100 to 320
watts. The efficiency of a module determines the area of a module given the same rated
output – an 8% efficient 230 watt module will have twice the area of a 16% efficient 230
watt module. There are a few solar panels available that are exceeding 19% efficiency. A
single solar module can produce only a limited amount of power; most installations
contain multiple modules. A photovoltaic system typically includes a panel or an array of
solar modules, an inverter, and sometimes a battery and/or solar tracker and
interconnection wiring.
Solar panels are devices that convert light into electricity. They are called "solar"
panels because most of the time, the most powerful source of light available is the Sun,
called Sol by astronomers. Some scientists call them photovoltaics which means,
basically, "light-electricity."
A solar panel is a collection of solar cells. Lots of small solar cells spread over a
large area can work together to provide enough power to be useful. The more light that
hits a cell, the more electricity it produces, so spacecraft are usually designed with solar
panels that can always be pointed at the Sun even as the rest of the body of the spacecraft
moves around, much as a tank turret can be aimed independently of where the tank is
going.
These panels are designed with solar cells composed of semiconductor materials.
The main function of Solar panels is, it converts solar energy into DC electrical energy
generally of 12V, which is further used for the rest of the circuit. The number of cells
required and their size depends on the rating of the load. The collection of solar cells can
produce maximum electricity. But, the solar panel must place exactly at right angles to
the sun rays.
Dept. of EEE 4 Trinity College of Engg. & Tech. Knr
AUTOMATIC SOLAR IRRIGATION PUMP CONTROL SYSTEM BASED ON SOIL MOISTURE SENSOR
CHAPTER – IV
SOIL MOISTURE SENSOR
The moisture sensor is buried in the ground at required depth. The working of the moisture sensor is simple and straightforward. The moisture sensor just senses the moisture of the soil. The change in moisture is proportional to the amount of current flowing through the soil.
Fig.4. Circuit Diagram of Soil Moisture Sensor
Most soil moisture sensors are designed to estimate soil volumetric water content
based on the dielectric constant (soil bulk permittivity) of the soil. The dielectric constant
can be thought of as the soil's ability to transmit electricity. The dielectric constant of soil
increases as the water content of the soil increases. This response is due to the fact that the
dielectric constant of water is much larger than the other soil components, including air.
Thus, measurement of the dielectric constant gives a predictable estimation of water
content.
Bypass type soil moisture irrigation controllers use water content information from
the sensor to either allow or bypass scheduled irrigation cycles on the irrigation timer
(Figures 1 and 2). The SMS controller has an adjustable threshold setting and, if the soil
water content exceeds that setting, the event is bypassed. The soil water content threshold
is set by the user. Another type of control technique with SMS devices is “on-demand”
where the controller initiates irrigation at a low threshold and terminates irrigation at a
high threshold.
Dept. of EEE 8 Trinity College of Engg. & Tech. Knr
AUTOMATIC SOLAR IRRIGATION PUMP CONTROL SYSTEM BASED ON SOIL MOISTURE SENSOR
A moisture sensor is used to sense the level of moisture content present in the
irrigation field. It has a level detection module in which we can set a reference value. This
circuit can be used with analog probes that produce a voltage proportional to soil moisture
such as VG400 probe . The moisture content of the soil is found by using the soil moisture
sensor such as VG400 which produces an equivalent output voltage proportional to the
conductivity between the two probes.
Fig. 5: Soil Moisture Sensor probe.
Moisture sensor module
The prongs should be oriented horizontally, but rotated onto their side – like a
knife poised to cut food – so that water does not pool on the flat surface of the prongs. The
horizontal orientation of the sensor ensures the measurement is made at a particular soil
depth. The entire sensor can be placed vertically, but because soil moisture of ten varies
by depth, this is not usually the desired orientation. To position the sensor, use a thin
implement such as a trenching shovel to make a pilot hole in the soil. Place the sensor into
the hole, making sure the entire length of the sensor is covered. Press down on the soil
along either side of the sensor with your fingers. Continue to compact the soil around the
sensor by pressing down on the soil with your fingers until you have made at least five
passes along the sensor. This step is important, as the soil adjacent to the sensor surface
has the strongest influence on the sensor reading. Removing the sensor when removing the
sensor from the soil, do not pull it out of the soil by the cable! Doing so may break
internal connections and make the sensor unusable
Dept. of EEE 9 Trinity College of Engg. & Tech. Knr
AUTOMATIC SOLAR IRRIGATION PUMP CONTROL SYSTEM BASED ON SOIL MOISTURE SENSOR
4.1. RELAY
The electromagnetic relay consists of a multi-turn coil, wound on an iron core, to
form an electromagnet. When the coil is energised, by passing current through it, the core
becomes temporarily magnetised. The magnetised core attracts the iron armature. The
armature is pivoted which causes it to operate one or more sets of contacts. When the coil
is de-energised the armature and contacts are released. The coil can be energised from a
low power source such as a transistor while the contacts can switch high powers such as
the mains supply. The relay can also be situated remotely from the control source. Relays
can generate a very high voltage across the coil when switched off. This can damage other
components in the circuit. To prevent this a diode is connected across the coil.
A relay is an electrical switch that opens and closes under the control of another
electrical circuit. In the original form, the switch is operated by an electromagnet to open
or close one or many sets of contacts. A relay is able to control an output circuit of higher
power than the input circuit.
The above diagram shows the representation of a relay. By default when there is
no excitation in the coil the NC (Normally Closed) and C (Common Terminal) are
connected through the contact internally. When the coil is excited by providing the
required coil voltage, the contact switches from the NC to NO (Normally Open) side. In
this case, the C and NC terminals are connected internally.
Fig.6. Circuit Diagram of Relay
Dept. of EEE 10 Trinity College of Engg. & Tech. Knr
AUTOMATIC SOLAR IRRIGATION PUMP CONTROL SYSTEM BASED ON SOIL MOISTURE SENSOR
The main operation of a relay comes in places where only a low-power signal can
be used to control a circuit. It is also used in places where only one signal can be used to
control a lot of circuits. The application of relays started during the invention of
telephones. They played an important role in switching calls in telephone exchanges. They
were also used in long distance telegraphy. They were used to switch the signal coming
from one source to another destination. After the invention of computers they were also
used to perform Boolean and other logical operations. The high end applications of relays
require high power to be driven by electric motors and so on. Such relays are called
contactors.
TYPES OF RELAYS
1. Latching Relay
Latching relays are also called impulse relays. They work in the bistable mode, and
thus have two relaxing states. They are also called keep relays or stay relays because as
soon as the current towards this relay is switched off, the relay continues the process that it
was doing in the last state. This can be achieved only with a solenoid which is operating in
a ratchet and cam mechanism. It can also be done by an over-centre spring mechanism or
a permanent magnet mechanism in which, when the coil is kept in the relaxed point, the
over-centre spring holds the armature and the contacts in the right spot of a remanent core.
power consumption occurs only for a particular time.
2. Reed Relay
These types of relays have been given more importance in the contacts. In order to
protect them from atmospheric protection they are safely kept inside a vacuum or inert
gas. Though these types of relays have a very low switching current and voltage ratings,
they are famous for their switching speeds.
3. Polarized Relay
This type of relay has been given more importance on its sensitivity. These relays
have been used since the invention of telephones. They played very important roles in
early telephone exchanges and also in detecting telegraphic distortion. The sensitivity of
these relays are very easy to adjust as the armature of the relay is placed between the poles
of a permanent magnet.
Dept. of EEE 11 Trinity College of Engg. & Tech. Knr
AUTOMATIC SOLAR IRRIGATION PUMP CONTROL SYSTEM BASED ON SOIL MOISTURE SENSOR
4. Buchholz Relay
This relay is actually used as a safety device. They are used for knowing the
amount of gas present in large oil-filled transformers. They are designed in such a way
that they produce a warning if it senses either the slow production of gas or fast
production of gas in the transformer oil.
5. Overload protection Relay
As the name implies, these relays are used to prevent the electric motors from
damage by over current and short circuits. For this the heating element is kept in series
with the motor. Thus when over heat occurs the bi-metallic strip connected to the motor
heats up and in turn releases a spring to operate the contacts of the relay.
6. Mercury Wetted Relay
This relay is almost similar to the reed relay explained earlier. The only difference
is that instead of inert gases, the contacts are wetted with mercury. This makes them more
position sensitive and also expensive. They have to be vertically mounted for any
operation. They have very low contact resistance and so can be used for timing
applications..
7. Machine Tool Relay
They are mainly used for the controlling of all kinds of machines. They have a
number of contacts with easily replaceable coils. This enables them to be easily converted
from NO contact to NC contact. Many types of these relays can easily be setup in a
control panel. Though they are very useful in industrial applications, the invention of PLC
has made them farther away from industries.
8. Contactor Relay
This is one of the most heavy load relay ever used. They are mainly used in
switching electric motors. They have a wide range of current ratings from a few amps to
hundreds. The contacts of these relays are usually made with alloys containing a small
percentage of silver. This is done so as to avoid the hazardous effects of arcing. These
type of relays are mainly categorized in the rough use areas. So, they produce loud noises
while operated and hence cannot be used in places where noise is a problem.
Dept. of EEE 12 Trinity College of Engg. & Tech. Knr
AUTOMATIC SOLAR IRRIGATION PUMP CONTROL SYSTEM BASED ON SOIL MOISTURE SENSOR
9. Solid State relay
SSR relays, as its name implies are designed with the help of solid state
components. As they do not have any moving objects in their design they are known for
their high reliability.
10. Solid State Contactor Relay
These relays combine both the features of solid state relays and contactor relays.
As a result they have a number of advantages. They have a very good heat sink and can be
designed for the correct on-off cycles. They are mainly controlled with the help of PLC,
micro-processors or microcontrollers.
4.2. SELECTION OF MOTOR DRIVE SYSTEM
The selection criteria of electrical motors depend on the cost and compatibility at
which the motors work. In this project the induction motor is chosen, as the AC motors are
more advantageous than DC motors. The comparison of electrical motors and drawbacks
with DC motors .The most common and simple industrial motor is the three phase AC
induction motor. The various aspects at which the three phase AC induction motor was
selected is also listed.
DC MOTORS AC MOTORS
The commutator and brushes makes the motor
bulky, costly and heavy
Not bulky and heavy
Costly Expensive
It requires frequent maintenance Less maintenance
Requires battery or inverter They can be used in all locations, as
the supply is AC
Table 1: Comparison between AC Motors and DC Motors
Thus the three phase induction motor is:
• Self-starting.
• Less armature reaction and brush sparking because of the absence of commutators and
brushes that may cause sparks.
Dept. of EEE 13 Trinity College of Engg. & Tech. Knr
AUTOMATIC SOLAR IRRIGATION PUMP CONTROL SYSTEM BASED ON SOIL MOISTURE SENSOR
• Robust in construction.
• Economical.
• Easier to maintain.
According to Faraday’s law an emf induced in any circuit is due to the rate of
change of magnetic flux linkage through the circuit. As the rotor winding in an induction
motor are either closed through an external resistance or directly shorted by end ring, and
cut the stator rotating magnetic field, an emf is induced in the rotor copper bar and due to
this emf a current flows through the rotor conductor. The relative velocity between the
rotating flux and static rotor conductor is the cause of current generation; hence as per
Lenz’s law the rotor will rotate in the same direction to reduce the cause i.e. the relative
velocity.
From the working principle of three phase induction motor it may observed
that the rotor speed should not reach the synchronous speed produced by the stator. If the
speeds equals, there would be no such relative velocity, so no emf induction in the rotor,
& no current would be flowing, and therefore no torque would be generated. Consequently
the rotor cannot reach at the synchronous speed. The difference between the stator
(synchronous speed) and rotor speeds is called the slip. The rotation of the magnetic field
in an induction motor has the advantage that no electrical connections need to be made to
the rotor.
Dept. of EEE 14 Trinity College of Engg. & Tech. Knr