automatic irrigation system for farmer with out controller

8/4/2019 Automatic Irrigation System for Farmer With Out Controller

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AUTOMATIC IRRIGATION SYSTEM FOR FARMERS

ABSTRACT:

The continuous increasing demand of the food requires the

rapid improvement in food production technology. In a country

like India, where the economy is mainly based on agriculture and

the climatic conditions are isotropic, still we are not able to make

full use of agricultural resources. The main reason is the lack of

rains & scarcity of land reservoir water. The continuous extraction

of water from earth is reducing the water level due to which lot of

land is coming slowly in the zones of un-irrigated land. Another

very important reason of this is due to unplanned use of waterdue to which a significant amount of water goes waste.

In the field of agriculture, use of proper method of irrigation

is important and it is well known that irrigation by drip is very

economical and efficient. In the modern drip irrigation systems,

the most significant advantage is that water is supplied near the

root zone of the plants drip by drip due to which a large quantityof water is saved. At the present era, the farmers have been

using irrigation technique in India through the manual control in

which the farmers irrigate the land at the regular intervals. This

process sometimes consumes more water or sometimes the

water reaches late due to which the crops get dried. Water

deficiency can be detrimental to plants before visible wilting

occurs. Slowed growth rate, lighter weight fruit follows slight

water deficiency. This problem can be perfectly rectified if we use

automatic micro controller based drip irrigation system in which

the irrigation will take place only when there will be intense

requirement of water.


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The proposed Automatic Irrigation System for Farmers

project makes the irrigation automated. With the use of low cost

sensors and the simple circuitry, we can make this project as a

low cost product, which can be bought even by a poor farmer.

This project is best suited for places where water is scares and

has to be used in limited quantity.

The circuit comprises sensor parts built using an operational

amplifier. Two stiff copper wires are inserted in the soil to sense

whether the Soil is wet or dry. These sensors are buried in the

ground at required depth. Once the soil has reached desired

moisture level the sensors send a signal to the microcontroller to

turn on / off the relay. That is, the microcontroller is used to

control the whole system, which monitors the sensors and when

sensors sense the dry condition then the microcontroller will

switch on the motor and it will switch off the motor when sensors

sense the wet condition.

The system is built with Sensors, LM324 Comparator IC, and

a Relay. The software part of the system is designed using C

language. The Keil IDE is used as a development tool.

This project uses regulated 5V, 500mA power supply. The

AC mains supply is applied to a 12V step down transformer. The

transformer output is 12V AC which is rectified using a bridge

rectifier. The output of bridge rectifier is DC 12V which is filtered

by a capacitor, and then regulated using 7812 voltage regulator.

The output of 7812 is +12V DC which is the required voltage for

relay operation. The output of 7812 regulator is further filtered by

a capacitor, and then regulated using 7805 voltage regulator. The

output of 7805 is +5V DC which is the required voltage for


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microcontroller operation. Also an LED in series with 470 Ohms

resistor is used for power on indication.

INDEX

1. INTRODUCTION

OBJECTIVE OF THE PROJECT

BLOCK DIAGRAM

2. DESCRIPTION OF THE PROJECT


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BLOCK DIAGRAM DESCRIPTION

SCHEMATIC

3. HARDWARE DESCRIPTION

PRINTED CIRCUIT BOARD

AC MOTOR

COMPARATOR(LM358)

4. SOFTWARE DESCRIPTION

KEIL C

5. CONCLUSION

6. BIBLIOGRAPHY

INTRODUCTION

Objective:

The main aim of this embedded application is to save the

power as well as automatic starts the ac motor.

BLOCK DIAGRAM:

SENSORS


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Description:

This application is in the area of embedded systems.

An embedded system is some combination of computer

hardware and software, either fixed in capability or programmable,

that is specifically designed for a particular function

Since the embedded system is dedicated to specific tasks,

design engineers can optimize it reducing the size and cost of the

product and increasing the reliability and performance. Embedded

systems are controlled by one or more main processing cores that is

typically either a microcontroller or a digital signal

COMPARATOR DRIVER RELAY
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processor (DSP). Embedded systems control many devices in

common use today.

Irrigation is the key to a successful garden. Long gone are

the days of manual watering or relying on a friend to water when

you are on vacation or away on business. The Project presentedhere waters your plants regularly when you are out for vocation.

The circuit comprises sensor parts built using op-amp IC LM358.

Op-amp is configured here as a comparator. Two stiff copper

wires are inserted in the soil to sense the whether the Soil is wet

or dry. The comparator monitors the sensors and when sensors

sense the dry condition then the project will switch on the motor

and it will switch off the motor when the sensors are in wet. when

it receives the signals from the comparator.

SCHEMATIC:
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PRINTED CIRCUIT BOARD

Printed circuit boards may be covered in two topics namely

1) Technology

2) Design

Introduction to printed circuit boards:

It is called PCB in short, printed circuit consists of

conductive circuit pattern


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Applied to one or both sides of an insulating base, depending

upon that, it is called single sided PCB or double-sided PCB.

(SSB and DSB).

Conductor materials available are silver, brass, aluminium and

copper. Copper is most widely used. The thickness of conducting

material depends upon the current carrying capacity of circuit.

Thus a thicker copper layer will have more current carrying

capacity.

The printed circuit boards usually serves three distinct functions.

1) it provides mechanical support for the components

mounted on it.

2) It provides necessary electrical interconnections.

3) It acts as heat sink that is provides a conduction path

leading to removal of the heat generated in the circuit.

Advantages of PCB

1) When a number of identical assemblies are required. PCBs

provide cost saving because once a layout is approved there is

no need to check the circuit every time.

2) For large equipments such as computers, the saving on

checking connections or wires is substantial.

3) PCBs have controllable and predictable electrical and

mechanical properties.

4) A more uniform product is produced because wiring errors

are eliminated.


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5) The distributed capacitances are constant from one

production to another.

6) Soldering is done in one operation instead of connecting

discrete components by wires.

7) The PCB construction lands itself for automatic assembly.

8) Spiral type of inductors may be printed.

9) Weight is less.

10) It has miniaturization potential.

11) It has reproducible performance.

12) All the signals are accessible for testing at any point along

conductor track.

Classifications of laminates :

Laminates

Glass base lamination Paper

base

lamination

There materials are built from several layers of paper or

glass, which are bound together under heat and pressure to form

rigid sheets. The binder is usually a phenolic resin in the case of

glass base.


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The copper layer is formed on either side or two sides of the

laminate. Because of the different filters and binding resins the

characteristic properties of copper clad laminates change.

The rigid sheets of filters which form reinforcement use

paper in the form of alpha cellulose, craft or rags. These are

cheaper and have easy machinbillity. Glass filter uses glass fibers

which are woven to give cloth like appearance. This gives a high

mechanical strength, they are better moisture resistant than

above type.

Binding resins are either phenolic or epoxy as mentioned

before in addition to these; phenol formaldehyde and polyestersare also used. Of these, Epoxy resin has

Good electrical and mechanical properties.

Manufacture of cu clad laminate:

The base of laminate is either paper or glass fiber cloth, as

mentioned before.

The copper foil is produced by electroplating a thin layer of

copper on a large rotating drum of stainless steel. As the drum

runs the deposited copper layer is peeled off and forms a

continuous length, which is coiled into rolls for use. To ensure

good adhesion between copper foils and base material,

surface of copper on the laminate and both are kept under

hydraulic press for proper adhesion.

AC Motor

AC motors are configured in many types and sizes, including

brush less, servo, and gear motor types. A motor consists of a
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rotor and a permanent magnetic field stator. The magnetic field

is maintained using either permanent magnets or

electromagnetic windings. AC motors are most commonly used in

variable speed and torque.

Motion and controls cover a wide range of components that

in some way are used to generate and/or control motion. Areas

within this category include bearings and bushings, clutches and

brakes, controls and drives, drive components, encoders and

resolves, Integrated motion control, limit switches, linear

actuators, linear and rotary motion components, linear position

sensing, motors (both AC and AC motors), orientation positionsensing, pneumatics and pneumatic components, positioning

stages, slides and guides, power transmission (mechanical),

seals, slip rings, solenoids, springs.

In any electric motor, operation is based on simple

electromagnetism. A current-carrying conductor generates amagnetic field; when this is then placed in an external magnetic

field, it will experience a force proportional to the current in the

conductor, and to the strength of the external magnetic field. As

you are well aware of from playing with magnets as a kid,

opposite (North and South) polarities attract, while like polarities

(North and North, South and South) repel. The internal

configuration of a AC motor is designed to harness the magnetic

interaction between a current-carrying conductor and an external

magnetic field to generate rotational motion.
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Let's start by looking at a simple 2-pole AC electric motor (here

red represents a magnet or winding with a "North" polarization,

while green represents a magnet or winding with a "South"

polarization).

Every AC motor has six basic parts -- axle, rotor (a.k.a.,

armature), stator, commutator, field magnet(s), and brushes. In

most common AC motors (and all that Beamers will see), the

external magnetic field is produced by high-strength permanent

magnets1

. The stator is the stationary part of the motor -- thisincludes the motor casing, as well as two or more permanent

magnet pole pieces. The rotor (together with the axle and

attached commutator) rotates with respect to the stator. The

rotor consists of windings (generally on a core), the windings

being electrically connected to the commutator. The above

diagram shows a common motor layout -- with the rotor inside

the stator (field) magnets.

The geometry of the brushes, commutator contacts, and

rotor windings are such that when power is applied, the polarities

of the energized winding and the stator magnet(s) are

misaligned, and the rotor will rotate until it is almost aligned with

the stator's field magnets. As the rotor reaches alignment, the

brushes move to the next commutator contacts, and energize the

next winding. Given our example two-pole motor, the rotation

reverses the direction of current through the rotor winding,

leading to a "flip" of the rotor's magnetic field, and driving it to

continue rotating.
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In real life, though, AC motors will always have more than

two poles (three is a very common number). In particular, this

avoids "dead spots" in the commutator. You can imagine how

with our example two-pole motor, if the rotor is exactly at the

middle of its rotation (perfectly aligned with the field magnets), it

will get "stuck" there. Meanwhile, with a two-pole motor, there is

a moment where the commutator shorts out the power supply

(i.e., both brushes touch both commutator contacts

simultaneously). This would be bad for the power supply, waste

energy, and damage motor components as well. Yet another

disadvantage of such a simple motor is that it would exhibit ahigh amount of torque ripple" (the amount of torque it could

produce is cyclic with the position of the rotor).

So since most small AC motors are of a three-pole design,

let's tinker with the workings of one via an interactive animation

(JavaScript required):

You'll notice a few things from this -- namely, one pole is

fully energized at a time (but two others are "partially"

energized). As each brush transitions from one commutator

contact to the next, one coil's field will rapidly collapse, as the

next coil's field will rapidly charge up (this occurs within a few

microsecond). We'll see more about the effects of this later, but

in the meantime you can see that this is a direct result of the coil

windings' series wiring:

There's probably no better way to see how an average AC

motor is put together, than by just opening one up. Unfortunately

this is tedious work, as well as requiring the destruction of a

perfectly good motor.
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This is a basic 3-pole ACmotor, with 2 brushes and three

commutator contacts.

Single-phase induction motors

A three phase motor may be run from a single phase power source.(Figure below) However, it will not self-start. It may be hand started in

either direction, coming up to speed in a few seconds. It will only

develop 2/3 of the 3- power rating because one winding is not used.

3-motor runs from 1- power, but does not start.

The single coil of a single phase induction motor does not produce a

rotating magnetic field, but a pulsating field reaching maximum

intensity at 0o and 180o electrical. (Figure below)

Single phase stator produces a nonrotating, pulsating magnetic field.

Another view is that the single coil excited by a single phase current

produces two counter rotating magnetic field phasors, coinciding twice
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per revolution at 0o (Figure above-a) and 180o (figure e). When the

phasors rotate to 90o and -90o they cancel in figure b. At 45o and -45o

(figure c) they are partially additive along the +x axis and cancel along

the y axis. An analogous situation exists in figure d. The sum of these

two phasors is a phasor stationary in space, but alternating polarity in

time. Thus, no starting torque is developed.

However, if the rotor is rotated forward at a bit less than the

synchronous speed, It will develop maximum torque at 10% slip with

respect to the forward rotating phasor. Less torque will be developed

above or below 10% slip. The rotor will see 200% - 10% slip with

respect to the counter rotating magnetic field phasor. Little torque (see

torque vs slip curve) other than a double freqency ripple is developed

from the counter rotating phasor. Thus, the single phase coil will

develop torque, once the rotor is started. If the rotor is started in the

reverse direction, it will develop a similar large torque as it nears the

speed of the backward

Rotating phasor.

Single phase induction motors have a copper or aluminum squirrel

cage embedded in a cylinder of steel laminations, typical of poly-phase

induction motors.

Permanent-split capacitor motor

One way to solve the single phase problem is to build a 2-phase motor,

deriving 2-phase power from single phase. This requires a motor with

two windings spaced apart 90

o

electrical, fed with two phases ofcurrent displaced 90o in time. This is called a permanent-split capacitor

motor in Figure below.


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Permanent-split capacitor induction motor.

This type of motor suffers increased current magnitude and backward

time shift as the motor comes up to speed, with torque pulsations at

full speed. The solution is to keep the capacitor (impedance) small to

minimize losses. The losses are less than for a shaded pole motor. This

motor configuration works well up to 1/4 horsepower (200watt),

though, usually applied to smaller motors. The direction of the motor is

easily reversed by switching the capacitor in series with the other

winding. This type of motor can be adapted for use as a servo motor,

described elsewhere is this chapter.

Single phase induction motor with embedded stator coils.

Single phase induction motors may have coils embedded into the

stator as shown in Figure above for larger size motors. Though, the

smaller sizes use less complex to build concentrated windings with

salient poles.
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Capacitor-start induction motor

In Figure below a larger capacitor may be used to start a single phase

induction motor via the auxiliary winding if it is switched out by a

centrifugal switch once the motor is up to speed. Moreover, the

auxiliary winding may be many more turns of heavier wire than used ina resistance split-phase motor to mitigate excessive temperature rise.

The result is that more starting torque is available for heavy loads like

air conditioning compressors. This motor configuration works so well

that it is available in multi-horsepower (multi-kilowatt) sizes.

Capacitor-start induction motor.

Capacitor-run motor induction motor

A variation of the capacitor-start motor (Figure below) is to start the

motor with a relatively large capacitor for high starting torque, but

leave a smaller value capacitor in place after starting to improve

running characteristics while not drawing excessive current. The

additional complexity of the capacitor-run motor is justified for larger

size motors.


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Capacitor-run motor induction motor.

A motor starting capacitor may be a double-anode non-polar

electrolytic capacitor which could be two + to + (or - to -) series

connected polarized electrolytic capacitors. Such AC rated electrolytic

capacitors have such high losses that they can only be used forintermittent duty (1 second on, 60 seconds off) like motor starting. A

capacitor for motor running must not be of electrolytic construction,

but a lower loss polymer type.

Resistance split-phase motor induction motor

If an auxiliary winding of much fewer turns of smaller wire is placed at

90o

electrical to the main winding, it can start a single phase inductionmotor. (Figure below) With lower inductance and higher resistance, the

current will experience less phase shift than the main winding. About

30o of phase difference may be obtained. This coil produces a

moderate starting torque, which is disconnected by a centrifugal

switch at 3/4 of synchronous speed. This simple (no capacitor)

arrangement serves well for motors up to 1/3 horsepower (250 watts)

driving easily started loads.

Resistance split-phase motor induction motor.
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This motor has more starting torque than a shaded pole motor (next

section), but not as much as a two phase motor built from the same

parts. The current density in the auxiliary winding is so high during

starting that the consequent rapid temperature rise precludes frequent

restarting or slow starting loads.

Nola power factor corrrector

Frank Nola of NASA proposed a power factor corrector for improving

the efficiency of AC induction motors in the mid 1970's. It is based on

the premise that induction motors are inefficient at less than full load.

This inefficiency correlates with a low power factor. The less than unity

power factor is due to magnetizing current required by the stator. This

fixed current is a larger proportion of total motor current as motor load

is decreased. At light load, the full magnetizing current is not required.

It could be reduced by decreasing the applied voltage, improving the

power factor and efficiency. The power factor corrector senses power

factor, and decreases motor voltage, thus restoring a higher power

factor and decreasing losses.

Since single-phase motors are about 2 to 4 times as inefficient as

three-phase motors, there is potential energy savings for 1- motors.

There is no savings for a fully loaded motor since all the stator

magnetizing current is required. The voltage cannot be reduced. But

there is potential savings from a less than fully loaded motor. A

nominal 117 VAC motor is designed to work at as high as 127 VAC, as

low as 104 VAC. That means that it is not fully loaded when operated

at greater than 104 VAC, for example, a 117 VAC refrigerator. It is safe

for the power factor controller to lower the line voltage to 104-110

VAC. The higher the initial line voltage, the greater the potential

savings. Of course, if the power company delivers closer to 110 VAC,

the motor will operate more efficiently without any add-on device.Any

substantially idle, 25% FLC or less, single phase induction motor is a


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candidate for a PFC. Though, it needs to operate a large number of

hours per year. And the more time it idles, as in a lumber saw, punch

press, or conveyor, the greater the possibility of paying for the

controller in a few years operation. It should be easier to pay for it by a

factor of three as compared to the more efficient 3--motor. The cost

of a PFC cannot be recovered for a motor operating only a few hours

per day

Summary: Single-phase induction motors

Single-phase induction motors are not self-starting without an

auxiliary stator winding driven by an out of phase current of near

90o. Once started the auxiliary winding is optional.

The auxiliary winding of apermanent-split capacitor motorhas a

capacitor in series with it during starting and running.

A capacitor-start induction motor only has a capacitor in series

with the auxiliary winding during starting.

A capacitor-run motor typically has a large non-polarized

electrolytic capacitor in series with the auxiliary winding for

starting, then a smaller non-electrolytic capacitor during running.

The auxiliary winding of a resistance split-phase motordevelops

a phase difference versus the main winding during starting by

virtue of the difference in resistance.

Learn about "Capacitor Start - Induction Run" Motors

The starter winding has a capacitor incorporated which makes the

single-phase motor a self-starting one. Read here to know about the

different types of widely used capacitor-motors


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Introduction

We know that the single-phase induction motor can be made self-

starting in numerous ways. One such most used method was the Split

Phase motors which we discussed in my last article. In this article, we

will discuss about the Capacitor Start Induction Run Motors.

Capacitor-Start Induction-Run Motors

We know about the activity of a capacitor in a pure A.C. Circuit. When

a capacitor is so introduced, the voltage lags the current by some
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phase angle. In these motors, the necessary phase difference between

the Is and Im is obtained by introducing a capacitor in series with the

starter winding. The capacitor used in these motors are of electrolytic

type and usually visible as it is mounted outside the motor as a

separate unit.

During starting, as the capacitor is connected in series with the starter

winding, the current through the starter winding Is leads the voltage V,

which is applied across the circuit. But the current through the main

winding Im, still lags the applied voltage V across the circuit. Thus

more the difference between the Is and Im, better the resulting

rotating magnetic field.

When the motor reaches about 75% of the full load speed, the

centrifugal switch S opens and thus disconnecting the starter winding

and the capacitor from the main winding. It is important to point out

from the phasor diagram that the phase difference between Im and Is

is almost 80 degrees as against 30 degrees in a split-phase induction

motor. Thus a capacitor-start induction-run motor produces a better

rotating magnetic field than the split-phase motors. It is evident from
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the phasor diagram that the current through the starter winding Is

leads the voltage V by a small angle and the current through the main

winding Im lags the applied voltage. It is to be appreciated that the

resultant current I, is small and is almost in phase with the applied

voltage V.

As discussed earlier in my last article on split-phase motors, the torque

developed by a split-phase induction motor is directly proportional to

the sine of the angle between Is and Im. Also the angle is 30 degrees in

case of split-phase motors. But incase of capacitor-start induction-run

motors, the angle between Is and Im is 80 degrees. It is then obvious

that the increase in the angle (from 30 degrees to 80 degrees) alone

increases the starting torque to nearly twice the value developed by a

standard split-phase induction motor. The speed-torque characteristics

curve is exhibiting the starting and running torques of a capacitor-start

induction-run motor.
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Types of Motors

There are different types of Capacitor-start motors designed and used

in various fields. They are as follows:

1. Single-voltage, externally reversible type,

2. Single-voltage, non-reversible type,

3. Single-voltage reversible and with thermostat type,

4. Single-voltage, non-reversible with magnetic switch type,

5. Two-voltage, non-reversible type,

6. Two-voltage, reversible type,

7. Single-voltage, three-lead reversible type,

8. Single-voltage, instantly-reversible type,

9. Two speed type, and

10. Two-speed with two-capacitor type.

These motors can be used for various purposes depending upon the

need of the user. The starting, speed/torque characteristics of each of

the above motors can be analyzed before employing them in work.

COMPARATOR(LM358):

Features


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Internally Frequency Compensated for Unity Gain

Large DC Voltage Gain: 100dB

Wide Power Supply Range:

LM258/LM258A, LM358/LM358A: 3V~32V (or 1.5V

~ 16V)

LM2904: 3V~26V (or 1.5V ~ 13V)

Input Common Mode Voltage Range Includes Ground

Large Output Voltage Swing: 0V DC to Vcc -1.5V DC

Power Drain Suitable for Battery Operation.

Description

The LM2904, LM358/LM358A, LM258/LM258A consist of two

independent, high gain, Internally frequency compensated

operational amplifiers which were designed specifically to

operate from a single power supply over a wide range of voltage.

Operation from split power supplies is also possible and the low

power supply current drain is independent of the magnitude of

the power supply voltage. Application areas include transducer

amplifier, DC gain blocks and all the conventional OP-AMP circuits

which now can be easily implemented in single power supply

systems.


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Power Supply:

BR1

100 uf1000 uf

LM7812 LM7805

Red led

100 ohm470 ufI/P power

O/P power

Power supply

The power supply consists of ac voltage transformer, diode

rectifier, ripple filter, and voltage regulators. The transformer is an AC

device, which increases or decreases the input supply voltage withoutchange in frequency. There are 2 types of transformers. One of Step-

up and the other is Step-down. Here we are using a Step-down

transformer, which decreases the 230 supply volts to 12 volts. The

rectifier is a device which converts an AC voltage to the pulsating DC

voltage. Here IN4007 diodes are used as rectifiers. A bridge type full


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wave rectifier is constructed using these diodes, as its efficiency is

81.2% and ripple factor is 0.482.

After the rectification, the output voltage signal contains both an

average dc component and a time varying ac component called the

ripple. To reduce or eliminate the ac component, one needs low pass

filter(s). The low pass filter allows the dc component to pass through it

but attenuate the ac at 60 Hz or its harmonics, i.e., 120 Hz. Here we

use 1000Mf, 470Mf & 100Mf capacitors at the o/p and i/p of regulators.

The 12v DC output of the filter is passed through voltage regulators of

7812 & 7805. 78 indicates that it is a regulator for positive voltage.

There is a corresponding 79 model for negative voltage. 12

indicates that it has an output of 12 V. similarly we are connecting a7805 to the 7812 regulator o/p, to generate 5volts. An LED in series to

a 100ohms resistor is connected in parallel to the output voltage to

indicate the supply. And also a switch is connected in series to the o/p

voltage terminal to ON/OFF the supply.

Transformer:

Definition: -

The transformer is a static electro-magnetic device that

transforms one alternating voltage (current) into another voltage

(current). However, power remains the some during the

transformation. Transformers play a major role in the transmission and

distribution of ac power.


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Principle: -

Transformer works on the principle of mutual induction. A

transformer consists of laminated magnetic core forming the magnetic

frame. Primary and secondary coils are wound upon the two cores of

the magnetic frame, linked by the common magnetic flux. When an

alternating voltage is applied across the primary coil, a current flows in

the primary coil producing magnetic flux in the transformer core. This

flux induces voltage in secondary coil.

Transformers are classified as: -

(a) Based on position of the windings with respect to core i.e.

(1) Core type transformer

(2) Shell type transformer

(b) Transformation ratio:

(1) Step up transformer

(2) Step down transformer

(a) Core & shell types: Transformer is simplest electrical machine,

which consists of windings on the laminated magnetic core.

There are two possibilities of putting up the windings on the core.

(1) Winding encircle the core in the case of core type transformer

(2) Cores encircle the windings on shell type transformer.(b) Step up and Step down: In these Voltage transformation takes

place according to whether the

Primary is high voltage coil or a low voltage coil.

(1) Lower to higher-> Step up

(2) Higher to lower-> Step down

DIODES

It is a two terminal device consisting of a P-N junction formed

either of Ge or Si crystal. The P and N type regions are referred to as

anode and cathode respectively. Commercially available diodes usually

have some means to indicate which lead is P and which lead is N.


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FEATURE

Low forward voltage

High current capabilityLow leakage current

High surge capability

Low cost

MECHANICAL DATA

Case:Molded plastic use UL 94V-0 recognized

Flame retardant epoxy

Terminals:Axial leads, solderable per

MIL-STD-202, method 208

Polarity:Color band denotes cathode

Mounting Position:Any


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RESISTORS: -

A Resistor is a heat-dissipating element and in the electronic

circuits it is mostly used for either controlling the current in the circuit

or developing a voltage drop across it, which could be utilized for many

applications. There are various types of resistors, which can be

classified according to a number of factors depending upon:

Material used for fabrication

Wattage and physical size

Intended application

Ambient temperature rating

Cost


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Basically the resistor can be split in to the following four parts from the

construction view point.

(1) Base

(2) Resistance element

(3) Terminals

(4) Protective means.

The following characteristics are inherent in all resistors and may

be controlled by design considerations and choice of material i.e.

Temperature coefficient of resistance, Voltage coefficient of

resistance, high frequency characteristics, power rating, tolerance &

voltage rating of resistors. Resistors may be classified as

(1)Fixed

(2)Semi variable

(3)Variable resistor.

CAPACITORS

The fundamental relation for the capacitance between two flat

plates separated by a dielectric material is given by:-

C=0.08854KA/D

Where: -

C= capacitance in pf.

K= dielectric constant

A=Area per plate in square cm.

D=Distance between two plates in cm

Design of capacitor depends on the proper dielectric material

with particular type of application. The dielectric material used for

capacitors may be grouped in various classes like Mica, Glass, air,

ceramic, paper, Aluminum, electrolyte etc. The value of capacitance

never remains constant. It changes with temperature, frequency and


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aging. The capacitance value marked on the capacitor strictly applies

only at specified temperature and at low frequencies.

LED (Light Emitting Diodes):

As its name implies it is a diode, which emits light when forward

biased. Charge carrier recombination takes place when electrons from

the N-side cross the junction and recombine with the holes on the P

side. Electrons are in the higher conduction band on the N side

whereas holes are in the lower valence band on the P side. During

recombination, some of the energy is given up in the form of heat and

light. In the case of semiconductor materials like Gallium arsenide

(GaAs), Gallium phoshide (Gap) and Gallium arsenide phoshide

(GaAsP) a greater percentage of energy is released duringrecombination and is given out in the form of light. LED emits no light

when junction is reverse biased.

LM7812 AND LM7805:

Features Output Current of 1.5A

Output Voltage Tolerance of 5%

Internal thermal overload protection

Internal Short-Circuit Limited

No External Component

Output Voltage 5.0V, 6V, 8V, 9V, 10V,

12V, 15V, 18V, 24V

Offer in plastic TO-252, TO-220 & TO-263

Direct Replacement for LM78XX

Description:

The Bay Linear LM78XX is integrated linear positive regulator

with three terminals. The LM78XX offer several fixed output voltages


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making them useful in wide range of applications. When used as a

zener diode/resistor combination

replacement, the LM78XX usually results in an effective output

impedance improvement of two orders of magnitude, lower quiescent

current.

The LM78XX is available in the TO-252, TO-220 & TO-263 Packages

Applications:

Post regulator for switching DC/DC converter

Bias supply for analog circuits


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CONCLUSION:

The project AUTOMATIC IRRIGATION SYSTEM FOR

FARMERS has been successfully designed and tested. It has

been developed by integrating features of all the hardware

components used. Presence of every module has been reasonedout and placed carefully thus contributing to the best working of

the unit.


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Secondly, using highly advanced ICs and with the help of

growing technology the project has been successfully

implemented.

Finally we conclude that EMBEDDED SYSTEM system is an

emerging field and there is a huge scope for research and

development.


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BIBLIOGRAPHY

The 8051 Micro controller and Embedded

Systems

-Muhammad Ali Mazidi

Janice Gillispie Mazidi

The 8051 Micro controller Architecture,

Programming & Applications

-Kenneth J.Ayala

Fundamentals Of Micro processors and

Micro computers

-B.Ram

Micro processor Architecture, Programming

& Applications

-Ramesh S.Gaonkar

Electronic Components

-D.V.Prasad

Wireless Communications

- Theodore S. Rappaport


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Mobile Tele Communications

- William C.Y. Lee

References on the Web:

www.national.com

www.atmel.com

www.microsoftsearch.com

www.geocities.com
http://www.national.com/http://www.atmel.com/http://www.microsoftsearch.com/http://www.geocities.com/http://www.national.com/http://www.atmel.com/http://www.microsoftsearch.com/http://www.geocities.com/

automatic irrigation system for farmer with out controller

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