CHAPTER 1
INTRODUCTION
1.1 SOIL WATER MANAGEMENT-NEED FOR STUDY
Automatic irrigation is the use of a device to operate irrigation structures so the change of flow of water from one bay, or set of bays, to another can occur in the absence of the irrigator. Automation can be used in a number of ways: 1. To start and and stop irrigation irrigation through through supply supply channel channel outlets, outlets, 2. To sta start rt and and stop stop pum pumps, ps, 3. To cut off the the fl flow ow of water water fr from om one irrig irrigat atio ion n ar area ea – ei eith ther er a ba bay y or a section of channel and directing the water to another area. These cha These change ngess occ occur ur aut automa omatic ticall ally y wit withou houtt any dir direct ect man manual ual eff effort ort,, but the irrigator may need to spend time preparing the system at the start of the irrigation and maintaining the components so it wors properly. !educed labour: As the irrigator is not re"uired to constantly monitor the progress of an irrigation, the irrigator is available to perform other tass – uninterrupted. #mproved lifestyle: The irrigator is not re"uired to constantly chec the progress of water down the bays being irrigated. The irrigator is able to be away from the property, rela$ with the family and sleep through the night. More timely irri!tio"# #rrigators with automation are more inclined to irrigate when the plants need water, not when it suits the irrigator.
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A$$i$t$ i" t%e m!"!eme"t o& %i%er &lo' r!te$# %any irrigators are looing to increase the irrigation flow rates they receive through installing bigger channels and bay outlets. &uch flow rates generally re"uire an increase in labour as the time taen ta en to irr irriga igate te a ba bay y is red reduce uced d thu thuss re" re"uir uiring ing more fre fre"ue "uent nt cha change nge ove over. r. Automation allows for these higher flows to be managed without an increase in the amount of labour. More !(()r!te ()t-o&&# Automation of the irrigation system allows cut'off of water at the appropriate point in the bay. This is usually more accurate than manual checing because mistaes can occur if the operator is too late or too early in maing a change of water flow.
Automati mation on can help eep fertiliser fertiliser on Re*)(e* r)"o&& o& '!ter !"* ")trie"t$# Auto farm by effectively reducing run off from the property. !etaining fertiliser on farm has both economic and environmental benefits. Re*)(e* (o$t$ &or +e%i(le$ )$e* &or irri!tio"# As the irrigator is not re"uired to constantly chec progress of an irrigation, motor bies, four wheelers and other vehicles are used less. This reduces the running costs of these vehicles and they re"uire less fre"uent replacement.
(neumatic system: system : A pneumatic system is a permanent system activated by a bay sensor located at the cut'off point. )hen water enters the sensor, it pressurises the air, which is piped to a mechanism that activates the opening and closing of irrigation structures. (ortable timer system: system : A portable timer system is a temporary system which uses electronic clocs to activate the opening and closing of the irrigation structures. *ecause of its portable nature, landowners usually buy + or units to move around the whole property. Timer- &ensor ybrid: ybrid : As the name suggests, this system is a hybrid of portable timer and sensor systems. /ie a portable timer, it uses an electronic device to activate the opening and closing of the irrigation structures. owever, this system has an additional feature of the irrigator being able to place a moveable sensor down the bay, which when comes in contact with water, transmits radio signals to the timer devices at the outlets to open or close the structures and sends a radio message to a receiver . 2
1., PROECT OERIEW#
The pro0ect is designed to develop an automatic irrigation system which switches the pump motor - on sensing the moisture content of the soil. #n the field of agriculture, use of proper method of irrigation is important. The advantage of using this method is to reduce human intervention and still ensure proper irrigation. The pro0ect uses an 451 series microcontroller which is programmed to receive the input signal of varying moisture condition of the soil through the sensing arrangement. This is achieved by using an op'amp as comparator which acts as interface between the sensing arrangement and the microcontroller. nce the controller receives this signal, it generates an output that drives a relay for operating the water pump. An /67 display is also interfaced to the microcontroller to display status of the soil and water pump. The sensing arrangement is made by using two stiff metallic rods inserted into the field at a distance. 6onnections from the metallic rods are interfaced to the control unit. The concept in future can be enhanced by integrating 8&% technology, such that whenever the water pump switches -, an &%& is delivered to the concerned person regarding the status of the pump. )e can also control the pump through &%&.
3
CHAPTER ,
SOIL MOISTURE SENSOR
,.1 DESCRIPTION Soil moi$t)re $e"$or$ measure the volumetric water content in soil. &ince the direct gravimetric measurement of free soil moisture re"uires removing, drying, and weighting of a sample, soil moisture sensors measure the volumetric water content indirectly by using some other property of the soil, such as electrical resistance, dielectric constant, or interaction with neutrons, as a pro$y for the moisture content. The relation between the measured property and soil moisture must be calibrated and may vary depending on environmental factors such as soil type, temperature, or electric conductivity. !eflected microwave radiation is affected by the soil moisture and is used for remote sensing in hydrology and agriculture. (ortable probe instruments can be used by farmers or gardeners.
&oil moisture sensors typically refer to sensors that estimate volumetric water content. Another class of sensors measure another property of moisture in soils called water potential9 these sensors are usually referred to as soil water potential sensors and include tensiometers and gypsum blocs. &oil moisture plays a ey role in the life of the plant. utrients in the soil solution provide the plant with the food it needs to grow. )ater is also essential for regulating plant temperature through the process of transpiration. (lant root systems are better developed when growing in moist soil. $cessive levels of soil moisture, however, can lead to anaerobic conditions that can promote the growth of plant and soil pathogens.
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)ater is re"uired for the basic growth and maintenance of turfgrass and other landscape plants. )hen a sufficient amount of water is not present for plant needs, then stress can occur and ultimately lead to reduced "uality or death. #rrigation is common in lorida landscapes because of sporadic rainfall and the low water holding capacity of sandy soil. This inability of many of lorida soils to hold substantial water can lead to plant stress after only a few days without rainfall or irrigation. )ater conservation is a growing issue in lorida due to increased demands from a growing population. ne of the areas with the largest potential for reducing water consumption is residential outdoor water use, which accounts for up to half of publicly supplied drining water. %ost new homes built in lorida have automated irrigation systems. These irrigation systems use an irrigation timer to schedule irrigation. These automated irrigation systems have been shown to use +;< more water on average than sprinler systems that are not automated =i.e. hose and sprinler>, which can be attributed largely to the tendency to set irrigation controllers and not read0ust for varying weather conditions. #rrigation control technology that improves water application efficiency is now available. #n particular, soil moisture sensors =&%&> can reduce the number of unnecessary irrigation events.
TECHNOLOGIES
Technologies commonly used to indirectly measure volumetric water content =soil moisture> include> 1. re"uency 7omain !eflectometry =7!>: The dielectric constant of a certain volume element around the sensor is obtained by measuring the operating fre"uency of an oscillating circuit. 2. Time 7omain Transmission =T7T> and Time 7omain !eflectometry =T7!> : The dielectric constant of a certain volume element around the sensor is obtained by measuring the speed of propagation along a buried transmission line
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3. eutron moisture gauges: The moderator properties of water for neutrons are utili?ed to estimate soil moisture content between a source and detector probe. +. &oil resistivity: %easuring how strongly the soil resists the flow of electricity between two electrodes can be used to determine the soil moisture content. . 8alvanic cell: The amount of water present can be determined based on the voltage the soil produces because water acts as an electrolyte and produces electricity. The technology behind this concept is the galvanic cell.
Wor/i"#
%ost soil moisture sensors are designed to estimate soil volumetric water content based on the dielectric constant =soil bul 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. or more information on soil moisture sensors see, Field Devices for Monitoring Soil Water. *ypass type soil moisture irrigation controllers use water content information from the sensor to either allow or bypass scheduled irrigation cycles on the irrigation timer =igures 1 and 2>. The &%& controller has an ad0ustable threshold setting and, if the soil water content e$ceeds that setting, the event is bypassed. The. soil water content threshold is set by the user. Another type of control techni"ue with &%& devices is on'demandB where the controller initiates irrigation at a low threshold and terminates irrigation at a high threshold. 7iagram showing how a soil moisture sensor =&%&> is typically connected to an automated irrigation system. The irrigation timer is connected to a solenoid valve through a hot and a common wire. The common wire is spliced with the &%& system =a controller that acts as a switch, and a sensor buried in the root ?one that estimates the soil water content>. The &%& taes a reading of the amount of water in the soil and the &%& controller uses that information to open or close the switch. #f the soil water content is below the threshold established by the user, the controller will close the switch, allowing power from the timer to reach the irrigation valve and trigger irrigation. #n this e$ample the controller opens the 6
switch, bypassing irrigation, because of rainfall wetting the soil around the soil moisture sensor.
FIG ,.1 SOIL MOISTURE SENSOR INSTALLATION
,.1.1 Se"$or I"$t!ll!tio"
A single sensor can be used to control the irrigation for many ?ones =where an irrigation ?one is defined by a solenoid valve> or multiple sensors can be used to irrigate individual ?ones. #n the case of one sensor for several ?ones, the ?one that is normally the driest, or most in need of irrigation, is selected for placement of the sensor in order to ensure ade"uate irrigation in all ?ones. 7
&ome general rules for the burial of the soil moisture sensor are: C •
•
•
•
&oil in the area of burial should be representative of the entire irrigated area. &ensors should be buried in the root ?one of the plants to be irrigated, because this is where plants will e$tract water. *urial in the root ?one will help ensure ade"uate turf or landscape "uality. or turfgrass, the sensor should typically be buried at about three inches deep. &ensors need to be in good contact with the soil after burial9 there should be no air gaps surrounding the sensor. &oil should be paced firmly but not e$cessively around the sensor. #f one sensor is used to control the entire irrigation system, it should be buried in the ?one that re"uires water first, to ensure that all ?ones get ade"uate irrigation. Typically, this will be an area with full sun or the area with the most sun e$posure. &ensors should be placed at least feet from the home, property line, or an impervious surface =such as a driveway> and 3 feet from a planted bed area.
•
&ensors should also be located at least feet from irrigation heads and toward the center of an irrigation ?one.
•
&ensors should not be buried in high traffic areas to prevent e$cess compaction of the soil around the sensor.
,.1., Setti" t%e Se"$or T%re$%ol*
nce the sensor has been buried and the &%& controller has been connected to the irrigation system, the sensor needs to be calibrated and-or the soil water content threshold needs to be selected. *ased on the sandy soils in much of lorida, the following steps should be followed to calibrate or select a threshold for the soil moisture sensor controller: Ste0 1. Apply water to the area where the sensor is buried. ither set the i5rrigation ?one to apply at least 1 inch of water or use a 'gallon bucet to apply directly over the buried sensor. 8
Ste0 ,. /eave the area alone for 2+ hours, and do not apply more water. #f it rains during the 2+ hours, the process should be started over. Ste0 . The water content after 2+ hours is now the sensor threshold used to allow or bypass scheduled irrigation events. This threshold may be decreased slightly =D25<> to allow more storage for rainfall9 however, the landscape will still need to be carefully monitored to ensure that ade"uate irrigation is being supplied.
2.1.3Programming the Irrigation Timer with a Soil Moisture Sensor System &oil moisture control devices can reduce water use on the lawn by bypassing scheduled irrigation events, but it is important to mae sure the irrigation schedule is programmed into the irrigation timer correctly. (rogramming the irrigation timer correctly for the area to be irrigated can mae the use of irrigation water more efficient. *efore setting the irrigation schedule it is important to determine when the water will be applied and how much to apply with each irrigation event. #n most areas of lorida the days per wee in which irrigation is allowed is already limited by water restrictions.
,.1.2 A00li(!tio"# Ari()lt)re
%easuring soil moisture is important for agricultural applications to help farmers manage their irrigation systems more efficiently. Enowing the e$act soil moisture conditions on their fields, not only are farmers able to generally use less water to grow a crop, they are also able to increase yields and the "uality of the crop by improved management of soil moisture during critical plant growth stages.
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L!"*$(!0e irri!tio"
#n urban and suburban areas, landscapes and residential lawns are using soil moisture sensors to interface with an irrigation controller. 6onnecting a soil moisture sensor to a simple irrigation cloc will convert it into a FsmartF irrigation controller that prevents irrigation cycles when the soil is already wet, e.g. following a recent rainfall event. 8olf courses are using soil moisture sensors to increase the efficiency of their irrigation systems to prevent over'watering and leaching of fertili?ers and other chemicals into the ground. G
Re$e!r(%
&oil moisture sensors are used in numerous research applications e.g. in agricultural science and horticulture including irrigation planning, climate research, or environmental scienceincluding solute transport studies and as au$iliary sensors for soil respiration measurements. Sim0le $e"$or$ &or !r*e"er$
!elatively cheap and simple devices that do not re"uire a power source are available for checing whether plants have sufficient moisture to thrive. After inserting a probe into the soil for appro$imately H5 seconds, a meter indicates if the soil is too dry, moist or wet for plants.
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,., L,3D Motor Dri+er IC ,.,.1 L,3D De$(ri0tio"
/2I37 is a typical %otor driver or %otor 7river #6 which allows 76 motor to drive on either direction. /2I37 is a 1H'pin #6 which can control a set of two 76 motors simultaneously in any direction. #t means that you can control two 76 motor with a single /2I37 #6. 7ual 'bridge %otor 7river integrated circuit = IC > This is a motor driver #6that can drive two motor simultaneously. /2I37 #6 is a dual 'bridge motor driver #6. ne 'bridge is capable to drive a dc motor in bidirectional. /2I37 #6 is a current enhancing #6 as the output from the sensor is not able to drive motors itself so /2I37 is used for this purpose. /2I37 is a 1H pin #6 having two enables pins which should always be remain high to enable both the 'bridges. /2I3* is another #6 of /2Iserieshaving &upply voltage =Jss> is the Joltage atwhich we wish to drive the motor. 8enerallywe prefer HJ for dc motor and H to 12J for gear motor, depending upon the rating of the motor. /ogical &upply Joltage will decide what value of input voltage should becon sidered as high or low .
,.,., Wor/i" o& L,3D
There are + input pins for l2I3d, pin 2,; on the left and pin 1 ,15 on the right as shown on the pin diagram. /eft input pins will regulate the rotation of motor connected across left side and right input for motor on the right hand side. The motors are rotated on the basis of the inputs provided across the input pins as /8#6 5 or /8#6 1. #n simple you need to provide /ogic 5 or 1 across the input pins for rotating the motor.
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,.,. L,3D Loi( T!4le.
/ets consider a %otor connected on left side output pins =pin 3,H>. or rotating the motor in clocwise direction the input pins has to be provided with /ogic 1 and /ogic 5. C Pi" 6locwise 7irection , K Loi( 1 and Pi" 5 K Loi( 6L , K Loi( 6 and Pi" 5 K Loi( 1L C Pi" Anticlocwise 7irection C Pi" , K Loi( 6 and Pi" 5 K Loi( 6 L #dle Go rotationM Gi'#mpedance stateM C Pi" , K Loi( 1 and Pi" 5 K Loi( 1 L #dle Go rotationM #n a very similar way the motor can also operate across input pin 1,15 for motor on the right hand side.
,.,.2 olt!e S0e(i&i(!tio"
J66 is the voltage that it needs for its own internal operation v9 /2I37 will not use this voltage for driving the motor. or driving the motors it has a separate provision to provide motor supply J&& =J supply>. /2I3d will use this to drive the motor. #t means if you want to operate a motor at IJ then you need to provide a &upply of IJ across J&& %otor supply. The ma$imum voltage for J&& motor supply is 3HJ. #t can supply a ma$ current of H55mA per channel.&ince it can drive motors Np to 3Hv hence you can drive pretty big motors with this l2I3d.
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Fi ,., 7!$i( i"$t!ll!tio" )$i" i(#
13
,.,.8 Pi" *i!r!m !"* (ir()it *i!r!m# Fi ,. Pi" *i!r!m o& L,3*#
14
Fi ,.2 Cir()it *i!r!m o& L,3*#
15
CHAPTER
ARDUINO UNO#
.1 DESCRIPTION
Ar*)i"o is a computer hardware and software company, pro0ect, and user community that designs and manufactures microcontroller 'based its for building digital devices and interactive ob0ects that can sense and control ob0ects in the physical world. The pro0ect is based on open'source hardware and software, under the 8N /esser 8eneral (ublic /icense =/8(/> or 8N 8eneral (ublic /icense =8(/>.
The pro0ect is based on microcontroller board designs, manufactured by several vendors, using various microcontrollers. These systems provide sets of digital and analog input-output =#-> pins that can be interfaced to various e$pansion boards =FshieldsF> and other circuits. The boards feature serial communications interfaces, including Nniversal &erial *us = N&*> on some models, for loading programs from personal computers. The microcontrollers are mainly programmed using a dialect of features from the programming languages 6 and 6O O. #n addition to using traditional compiler toolchains, the Arduino pro0ect provides an integrated development environment =#7> based on the (rocessing language pro0ect. The Arduino pro0ect started in 255 as a program for students at the #nteraction 7esign #nstitute #vrea in #vrea, #taly, aiming to provide a low'cost and easy way for novices and professionals to create devices that interact with their environment using sensors and actuators. 6ommon e$amples of such devices intended for beginner hobbyists include simple robots, thermostats, and motion detectors.
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Arduino boards are available commercially in preassembled form, or as do' it'yourself its. The hardware design specifications are openly available, allowing the Arduino boards to be manufactured by anyone. Adafruit #ndustries estimated in mid'2511 that over 355,555 official Arduinos had been commercially produced, and in 2513 that ;55,555 official boards were in users@ hands. Arduino is open' source hardware. The hardware reference designs are distributed under a 6reative 6ommons Attribution &hare'Alie 2. license and are available on the Arduino website. /ayout and production files for some versions of the hardware are also available. The source code for the #7 is released under the 8N 8eneral (ublic /icense, version 2. evertheless an official *ill of %aterials of Arduino boards has never been released by the staff of Arduino. Although the hardware and software designs are freely available under copyleft licenses, the developers have re"uested that the name FArduinoF be e$clusive to the official product and not be used for derived wors without permission. The official policy document on use of the Arduino name emphasi?es that the pro0ect is open to incorporating wor by others into the official product. &everal Arduino'compatible products commercially released have avoided the Arduino name by using -duino name variants. %any Arduino'compatible and Arduino'derived boards e$ist. &ome are functionally e"uivalent to an Arduino and can be used interchangeably. %any enhance the basic Arduino by adding output drivers, often for use in school'level education, to simplify maing buggies and small robots. thers are electrically e"uivalent but change the form factor, sometimes retaining compatibility with shields, sometimes not. &ome variants use different processors, of varying compatibility.
., SUMMARY
%icrocontroller ATmega324
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perating Joltage J #nput Joltage =recommended> ;'12J #nput Joltage =limits> H'25J 7igital #- (ins 1+ =of which H provide ()% output> Analog #nput (ins H 76 6urrent per #- (in +5 mA 76 6urrent for 3.3J (in 5 mA lash %emory 32 E* of which 5. E* used by bootloader &!A% 2 E* (!% 1 E* 6loc &peed 1H %?
. POWER#
The Arduino Nno can be powered via the N&* connection or with an e$ternal power supply. The power source is selected automatically. $ternal =non' N&*> power can come either from an A6'to'76 adapter =wall'wart> or battery. The adapter can be connected by plugging a 2.1mm center'positive plug into the board@s power 0ac. /eads from a battery can be inserted in the 8nd and Jin pin headers of the ()! connector. The board can operate on an e$ternal supply of H to 25 volts. #f supplied with less than ;J, however, the J pin may supply less than five volts and the board may be unstable. #f using more than 12J, the voltage regulator may overheat and damage the board. The recommended range is ; to 12 volts. The power pins are as follows: C J#. The input voltage to the Arduino board when it@s using an e$ternal power source =as opposed to volts from the N&* connection or other regulated power source>. Pou can supply voltage through this pin, or, if supplying voltage via the power 0ac, access it through this pin
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. C J. The regulated power supply used to power the microcontroller and other components on the board. This can come either from J# via an on'board regulator, or be supplied by N&* or another regulated J supply. C 3J3. A 3.3 volt supply generated by the on'board regulator. %a$imum current draw is 5 mA. C 87. 8round pins.
.2 MEMORY AND I9O PORT#
The Atmega324 has 32 E* of flash memory for storing code =of which 5, E* is used for the bootloader>9 #t has also 2 E* of &!A% and 1 E* of (!% =which can be read and written with the (!% library>. ach of the 1+ digital pins on the Nno can be used as an input or output, using pin%ode=>, digital)rite=>, and digital!ead=> functions. They operate at volts. ach pin can provide or receive a ma$imum of +5 mA and has an internal pull'up resistor =disconnected by default> of 25'5 hms. #n addition, some pins have speciali?ed functions: C &erial: 5 =!Q> and 1 =TQ>. Nsed to receive =!Q> and transmit =TQ> TT/ serial data. TThese pins are connected to the corresponding pins of the ATmega4N2 N&*'to'TT/ &erial chip . C $ternal #nterrupts: 2 and 3. These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. &ee the attach#nterrupt=> function for details. C ()%: 3, , H, I, 15, and 11. (rovide 4'bit ()% output with the analog)rite=> function.
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C &(#: 15 =&&>, 11 =%&#>, 12 =%#&>, 13 =&6E>. These pins support &(# communication, which, although provided by the underlying hardware, is not currently included in the Arduino language. C /7: 13. There is a built'in /7 connected to digital pin 13. )hen the pin is #8 value, the /7 is on, when the pin is /), it@s off. The Nno has H analog inputs, each of which provide 15 bits of resolution =i.e. 152+ different values>. *y default they measure from ground to volts, though is it possible to change the upper end of their range using the A! pin and the analog!eference=> function. Additionally, some pins have speciali?ed functionality: C # 26: + =&7A> and =&6/>. &upport #26 =T)#> communication using the )ire library. There are a couple of other pins on the board: C A!. !eference voltage for the analog inputs. Nsed with analog!eference=>. C !eset. *ring this line /) to reset the microcontroller. Typically used to add a reset button to shields which bloc the one on the board. &ee also the mapping between Arduino pins and Atmega324 ports.
.8 COMMUNICATION#
The Arduino Nno can be programmed with the Arduino software =download>. &elect FArduino Nno w- ATmega324F from the Tools R *oard menu =according to the microcontroller on your board>. or details, see the reference and tutorials. The ATmega324 on the Arduino Nno comes preburned with a bootloader that allows you to upload new code to it without the use of an e$ternal hardware programmer. #t communicates using the original &TE55 protocol =reference, 6 header files>. Pou can also bypass the bootloader and program the microcontroller through the #6&( =#n'6ircuit &erial (rogramming> header9 see these instructions for details. The ATmega4N2 firmware source code is available . The ATmega4N2 is loaded with a 7N bootloader, which can be activated by connecting the solder 0umper on the bac of the board =near the map of #taly> and then resetting the 4N2. Pou can then use Atmel@s /#( software =)indows> or the 7N programmer =%ac & Q and /inu$> to load a new firmware. r you can use the #&( header with an 2
e$ternal programmer =overwriting the 7N bootloader>. !ather than re"uiring a physical press of the reset button before an upload, the Arduino Nno is designed in a way that allows it to be reset by software.
CHAPTER 2
SEROMOTOR
2.1 DESCRIPTION
A $er+omotor is a rotary actuator or linear actuator that allows for precise control of angular or linear position, velocity and acceleration. #t consists of a suitable motor coupled to a sensor for position feedbac. #t also re"uires a relatively sophisticated controller, often a dedicated module designed specifically for use with servomotors. &ervomotors are not a specific class of motor although the term servomotor is often used to refer to a motor suitable for use in a closed' loop control system. &ervomotors are used in applications such as robotics, 66 machinery or automated manufacturing.
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2., MECHANISM#
A servomotor is a closed'loop servomechanism that uses position feedbac to control its motion and final position. The input to its control is a signal, either analogue or digital, representing the position commanded for the output shaft. The motor is paired with some type of encoder to provide position and speed feedbac. #n the simplest case, only the position is measured. The measured position of the output is compared to the command position, the e$ternal input to the controller. #f the output position differs from that re"uired, an error signalis generated which then causes the motor to rotate in either direction, as needed to bring the output shaft to the appropriate position. As the positions approach, the error signal reduces to ?ero and the motor stops.
The very simplest servomotors use position'only sensing via a potentiometer and bang'bang control of their motor9 the motor always rotates at full speed =or is stopped>. This type of servomotor is not widely used in industrial motion control, but it forms the basis of the simple and cheap servos used for radio'controlled models. %ore sophisticated servomotors use optical rotary encoders to measure the speed of the output shaft and a variable'speed drive to control the motor speed.*oth of these enhancements, usually in combination with a (#7 control algorithm, allow the servomotor to be brought to its commanded position more "uicly and more precisely, with less overshooting. A servomotor consumes power as it rotates to the commanded position but then the servomotor rests. &tepper motors continue to consume power to loc in and hold the commanded position. &ervomotors are generally used as a high'performance alternative to the stepper motor. &tepper motors have some inherent ability to control position, as they have built'in output steps. This often allows them to be used as an open'loop 22
position control, without any feedbac encoder, as their drive signal specifies the number of steps of movement to rotate, but for this the controller needs to @now@ the position of the stepper motor on power up. Therefore, on first power up, the controller will have to activate the stepper motor and turn it to a nown position, e.g. until it activates an end limit switch. This can be observed when switching on an in0et printer 9 the controller will move the in 0et carrier to the e$treme left and right to establish the end positions. A servomotor will immediately turn to whatever angle the controller instructs it to, regardless of the initial position at power up. 2.,.1 ENCODERS#
The first servomotors were developed with synchros as their encoders. %uch wor was done with these systems in the development of radar and anti'aircraft artillery during )orld )ar ##. &imple servomotors may use resistive potentiometers as their position encoder. These are only used at the very simplest and cheapest level, and are in close competition with stepper motors. They suffer from wear and electrical noise in the potentiometer trac. Although it would be possible to electrically differentiate their position signal to obtain a speed signal, (#7 controllers that can mae use of such a speed signal generally warrant a more precise encoder. %odern servomotors use rotary encoders, either absolute or incremental. Absolute encoders can determine their position at power'on, but are more complicated and e$pensive. #ncremental encoders are simpler, cheaper and wor at faster speeds. #ncremental systems, lie stepper motors, often combine their inherent ability to measure intervals of rotation with a simple ?ero'position sensor to set their position at start'up. #nstead of servomotors, sometimes a motor with a separate, e$ternal linear encoder is used. These motor O linear encoder systems avoid inaccuracies in the drivetrain between the motor and linear carriage, but their design is made more complicated as they are no longer a pre'pacaged factory' made system. 2. MOTORS#
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The type of motor is not critical to a servomotor and different types may be used. At the simplest, brushed permanent magnet 76 motors are used, owing to their simplicity and low cost. &mall industrial servomotors are typically electronically commutated brushless motors. or large industrial servomotors, A6 induction motors are typically used, often with variable fre"uency drives to allow control of their speed. or ultimate performance in a compact pacage, brushless A6 motors with permanent magnet fields are used, effectively large versions of *rushless 76 electric motors. 7rive modules for servomotors are a standard industrial component. Their design is a branch of power electronics, usually based on a three'phase %&T or #8*T bridge. These standard modules accept a single direction and pulse count =rotation distance> as input. They may also include over'temperature monitoring, over'tor"ue and stall detection features. As the encoder type, gearhead ratio and overall system dynamics are application specific, it is more difficult to produce the overall controller as an off'the'shelf module and so these are often implemented as part of the main controller. CONTROL# %ost modern servomotors are designed and supplied around a dedicated controller module from the same manufacturer. 6ontrollers may also be developed around microcontrollers in order to reduce cost for large'volume applications. 2.2 I"ter!te* $er+o motor$#
#ntegrated servomotors are designed so as to include the motor, driver, encoder and associated electronics into a single pacage.
2.8 Ser+ome(%!"i$m
A servo system mainly consists of three basic components ' a controlled device, a output sensor , a feedbac system. This is an automatic closed loop control system. ere instead of controlling a device by applying the variable input signal, the device is controlled by a feedbac signal generated by comparing output signal and reference input signal. )hen reference input signal or command signal 24
is applied to the system, it is compared with output reference signal of the system produced by output sensor, and a third signal produced by a feedbac system. This third signal acts as an input signal of controlled device. This input signal to the device presents as long as there is a logical difference between reference input signal and the output signal of the system. After the device achieves its desired output, there will be no longer the logical difference between reference input signal and reference output signal of the system. Then, the third signal produced by comparing theses above said signals will not remain enough to operate the device further and to produce a further output of the system until the ne1$t reference input signal or command signal is applied to the system. ence, the primary tas of a servomechanism is to maintain the output of a system at the desired value in the presence of disturbances. 2.: Wor/i" Pri"(i0le o& Ser+o Motor
A servo motor is basically a 76 motor =in some special cases it is A6 motor> along with some other special purpose components that mae a 76 motor a servo. #n a servo unit, you will find a small 76 motor, a potentiometer , gear arrangement and an intelligent circuitry. The intelligent circuitry along with the potentiometer maes the servo to rotate according to response.
CHAPTER 8
PUMP 25
8.1 DESCRIPTION
A 0)m0 is a device that moves fluids = li"uids or gases>, or sometimes slurries, by mechanical action. (umps can be classified into three ma0or groups according to the method they use to move the fluid: direct lift , displacement , and gravity pumps. (umps operate by some mechanism =typically reciprocating or rotary>, and consume energy to perform mechanical wor by moving the fluid. (umps operate via many energy sources, including manual operation, electricity, engines, or wind power , come in many si?es, from microscopic for use in medical applications to large industrial pumps. %echanical pumps serve in a wide range of applications such as pumping water from wells, a"uarium filtering, pond filtering and aeration, in the car industry for water'cooling and fuel in0ection, in the energy industry for pumping oil and natural gas or for operating cooling towers. #n the medical industry, pumps are used for biochemical processes in developing and manufacturing medicine, and as artificial replacements for body parts, in particular the artificial heart and penile prosthesis. &ingle stage pump ' )hen in a casing only one impeller is revolving then it is called single stage pump. 7ouble- %ulti stage pump ' )hen in a casing two or more than two impellers are revolving then it is called double- multi stage pump. #n biology, many different types of chemical and bio'mechanical pumps have evolved, and biomimicry is sometimes used in developing new types of mechanical pumps.
8., TYPES#
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%echanical pumps may be $)4mere* in the fluid they are pumping or be placed e;ter"!l to the fluid. (umps can be classified by their method of displacement into positive displacement pumps, impulse pumps, velocity pumps, gravity pumps, steam pumps and valveless pumps. There are two basic types of pumps: positive displacement and centrifugal. Although a$ial'flow pumps are fre"uently classified as a separate type, they have essentially the same operating principles as centrifugal pumps.
5.3 Positi!e "is#la$ement #um#s % #ositi!e "is#la$ement #um# ma&es a 'ui" mo!e (y tra##ing a )*e" amount an" +or$ing ,"is#la$ing- that tra##e" !olume into the "is$harge #i#e. &ome positive displacement pumps use an e$panding cavity on the suction side and a decreasing cavity on the discharge side. /i"uid flows into the pump as the cavity on the suction side e$pands and the li"uid flows out of the discharge as the cavity collapses. The volume is constant through each cycle of operation. Positive displacement pump behavior and safety
(ositive displacement pumps, unlie centrifugal or roto'dynamic pumps, theoretically can produce the same flow at a given speed =!(%> no matter what the discharge pressure. Thus, positive displacement pumps are constant flow machines. owever, a slight increase in internal leaage as the pressure increases prevents a truly constant flow rate. A positive displacement pump must not operate against a closed valve on the discharge side of the pump, because it has no shutoff head lie centrifugal pumps. A positive displacement pump operating against a closed discharge valve continues to produce flow and the pressure in the discharge line increases until the line bursts, the pump is severely damaged, or both. A relief or safety valve on the discharge side of the positive displacement pump is therefore necessary. The relief valve can be internal or e$ternal. The pump 27
manufacturer normally has the option to supply internal relief or safety valves. The internal valve is usually only used as a safety precaution. An e$ternal relief valve in the discharge line, with a return line bac to the suction line or supply tan provides increased safety. 8.2 Po$iti+e *i$0l!(eme"t ty0e$#
A positive displacement pump can be further classified according to the mechanism used to move the fluid: •
otary-type positive displacement: internal gear, screw, shuttle bloc, fle$ible vane or sliding vane , circumferential piston, fle$ible impeller , helical twisted roots =e.g. the )endelolben pump> or li"uid'ring pumps
•
eciprocating-type positive displacement: piston or diaphragm pumps
•
!inear-type positive displacement: rope pumps and chain pumps
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CHAPTER :
CONCLUSI6N AND FUTURE SCOPE
:.1 REIEW OF WOR< DONE#
Thus automatic irrigation of plant using arduino uno to reduce manual labour wor.The system uses sensor circuit to determine the soil moisture level.And based on the nessacity of water the arduino turns on the motor circuit and the water is supplied to plants when needed. :., FUTURE SCOPE#
The future scope of the pro0ect is using thernet or wifi shield and use of twitter library which will maes the plant to tweet us when the water is needed.And this can be controlled by the users using their smartphones.
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