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SUBMITTED BY

PATRUNI CHIDANANDA SASTRY

UNIVERSITY ROLL-10500310053

DEPERATMENT-ELECTRONICS AND COMM. ENG.

CLASS ROLL-22

SUBMITTED TO

BANKURA UNNAYANI INSTITUTE OF ENGINEERING

DEPARTMENT OF E.C.E

GUIDED BY

MRS TANUSREE PATRA

DEPART MENT OF

ELECTRONICS & COMMUNICATION ENGG.

BANKURA UNNAYANI INSTITUTE OF ENGINEERING

CERTIFICATE

This is to certify that the project work entitle

AUTOMATIC MOISTURE CONTROLL SYSTEM IN PLANTS

Being submitted by

PATRUNI CHIDANANDA SASTRY

ROLL NO -10500310053 CLASS ROLL-22

DEPERTMENT –ELECTRONICS AND COMMUNICATION ENGINEERING

In partial fulfilment for the award of the degree of bachelor of

technology in E.C.E, of BUIE is a bonfire work carried out at BUIE

under my guidance.

The matter embodied in this project report has been submitted to

any other university for the award of any other degree or diploma.

Mr. MRINMOY SARKAR Mrs TANUSREE PATRA

H.O.D ECE DEPT Project Guide

………………………. …………………………

ACKNOWLEDGEMENT

Many people have contributed of the success of this project.

Although a single sentence we hard by suffices, we would like

to thank almighty god for blessing us with His grace and

taking our endeavour tom a successful culmination. We

extend our sincere and heartfelt thank to Mr. MRINMOY

SARKAR sir, Head of department, Electronics &

communication for providing is the right ambience for

carrying out the work on this project and the facilities

provided to us. We are profoundly indebted to our project

guide, Mrs TANUSREE PATRA whose act of timely advice,

encouragement and we sincerely express our gratitude to

them.

We would like to extend our gratitude to all the staffs of the

department of ECE for the help and support rendered to us.

We have benefited a lot from the feedback, suggestions and

blessings given to us by them.

CONTEXT

INTRODUCTION

POWER SUPPLY

DESIGNE PRINCIPLE

CIRCUTI EXPLANATION

COMPONENT DESCRIPTION

WORKING PRINCIPLE

BLOCK OF WORK

CONCLUSION

APPENDIX

INTRODUCTION

Moisture control project is uses full and interesting project. It can help to

farmer. It is consist of BJT, Resisters, Capacitors, and I C etc. Moisture control device will be completed by four sections. The basis of operation for this system

is the Over – watering and under watering both are harmful for plants. Roots need air as well as water. If the soil is constantly saturated, air cannot reach the

roots and they suffocate. Also, excess water weakens the plant and makes it susceptible to various diseases, particularly fungal attacks, under watering on

the other hand, is equally harmful, plants not receiving enough water droop from the top down and leaf edge turn brown. Moisture monitor provides a solution to the above problem by monitoring the moisture level of the soil and

producing an audio – visual alert when the moisture goes below a preset level, indicating that the plant needs to be watered.

CIRCUIT AND WORKING:

Stainless steel probes to measure the relative soil moisture content by measuring resistance, A microcontroller with built-in analogy to digital converter as the

heart of the system, and high-current power MOSFETs to drive pumps, electrically operated water valves, or other devices. Correct moisture content in

soil is maintained by constantly monitoring the relative moisture content in each plant's pot with the stainless forked probe, and operating the pumps to raise

moisture level. Each plant is constantly measured, and its moisture level is converted to a number between 0 and 1023 (Base ten.) Stored in the DATA

EEPROM on the microcontroller are Min. and Max. Values for each plant. When a plant's moisture level drops below the min. value, that plant's pump is

turned on. When the moisture goes above the Max. Setting for that plant, the pump turns off. Also stored in DATA EEPROM on the microcontroller are Min.

Time between water and Max. Time between water. These settings allow the system to be optimized for exotic plants which require special watering routines and these parameters can be set anywhere from 0 to 4095 hours, which is 0 to

170.625 days. A plant will not be watered until the Minimum number of hours has passed since it was last watered. Note that the min. time can be set to 0, in

which case it does not affect the systems operation. The maximum watering time specifies a time after which a plant will be watered, even if the moisture

level is above the Minimum moisture level setting for that plant. Note that it will never get watered if the moisture level is above the maximum. (Example of

timed watering: For a cactus type plant, you could set the max. moisture to 500, the min. to 0, the min. time to 1 week, and the max. time to 4 weeks. The plant

would get watered about once a month, but the soil would get dry between watering, as may be found in soils where cactus are native) This system can be

programmed via it's "Learn" button, or a Personal Computer connected to the RS232 interface. The firmware provides to the RS232 interface a well-defined protocol which allows reading and writing of all SRAM and DATA EEPROM,

in both Byte (8 bit) modes and Word (16 bit). This allows the settings of ALL operational parameters, and allows the reading and writing of the eight 16-byte

strings in DATA EEPROM. (More on that later.) The RS232 interface is not intended for direct end user use with a serial terminal (although it can be used

that way,) but rather to support Software which could be written to provide many other features. To program using the "Learn" button, one simply inserts

the probes into their plants, turns the RUN/STOP switch to STOP, and goes about watering their plants as normal, but they press the "Learn" button before

and after watering. Soon, the system will have learned (And stored to non-

volatile DATA EEPROM) the min. and max. Moisture levels that you normally keep your plants at. Once it's learned this, just switch the switch to RUN, and it

Waters the plants whenever you have, would have, and based on moisture level.

POWER SUPPLY:

The power supply design for catering a fixed demand connected in this project. The basic requirement for designing a power supply is as follows, voltage

required for operating the devices. Here +5 volt required for circuit. Current requirement of each device or load must be added to estimate the final capacity

of the power supply. The power supply always specified with one or multiple voltage outputs along with a current capacity. As it is estimate the requirement

of power is approximately as follows, output voltage = +5volt.Capacity = 1000mA The power supply is basically consisting of three sections as follows,

Rectifier diodes (large current)Rectifier diodes are used in power supplies to convert alternating current (AC) to direct current (DC), a process called rectification. They are also used elsewhere in circuits where a large current must pass through the diode. All rectifier diodes are made from silicon and therefore have a forward voltage drop of 0.7V. The table shows maximum current and maximum reverse voltage for some popular rectifier diodes. The 1N4007 is suitable for most low voltage circuits with a current 1A.

BLOCK DIAGRAM OF POWERSUPPLY:

STEPDOWN TRANSFORMER

16-016 (1Amp.)

BRIDGE RECTIFIER SECTION

FILLTER CIRCUIT

12 V. POSETIVE

VOLTAGE REGULATER

05V. POSETIVE

VOLTAGE REGULATER

DESIGN PRINCIPLE:

The AC230V.50Hz mains are stepped down by transformer 16-0-16 to deliver

the secondary output of 16 volts, 1Amp. The transformer output is rectified by a

bridge rectifier comprising diodes D3 through D6, filtered by capacitor C1, C2,

C3 and regulated by IC1 LM7812 to provide regulated 12V. Supply. Then

Capacitor C4, C5 bypasses any ripple in the regulated by IC2LM7805 to

provide regulated 05V. Output. In mobile application of the circuit, where

mains 230V AC is not available, it is advisable to use an external 12V battery.

For activating the lasers used in conjunction with LDR1 and LDR2, separate

batteries may be used. There are two methods for designing power supply, the

average value method and peak value method. In case of small power supply

peak value method is quit economical, for a particular value of DC output the

input AC requirement is appreciably less. In this method the DC output is

approximately equal to vamp. A full wave bridge rectifier designed using four

nos. diodes and the output of the rectifier with a capacitor. There are five nos.

capacitors connected in this power supply, one for filtering and providing back

up to positive power supply and other four nos. for repel factor reducing and

filter action to the power supply. The capacitor value is decided so that it will

back up for the voltage and current during the discharging period of the DC

output. In this case the output with reference to the centre tap of the transformer

is taken in to consideration, through the rectifier designed is a full wave bridge

rectifier but the voltage across the load is a half wave rectified output. The

regulator section used her is configured with a series regulator LM7805 the 05

represents the output voltage and 78 series indicates the positive voltage

regulator for power supply. The positive regulator works satisfactory between

voltage 05+2 to 35 volts DC. The output remains constant within of voltage.

The output remains constant within this range of voltage.

FIG.3 POWER SUPPLY CIRCUIT DIAGRAM

Circuit Explanations: -

When ac signal is given to the primary of the transformer, due to the magnetic

effect of the coil magnetic flux is induced in the coil (primary) and transfer to the secondary coil of the transformer due to the transformer action.”

Transformer is an electromechanical static device which transformer electrical energy from one coil to another without changing its frequency”. Here the

diodes are connected in a bridge fashion. The secondary coil of the transformer is given to the bridge circuit for rectification purposes.

VOLTAGE REGULATORS:-

The regulator 7812 &7805 positive regulator offer contained fixed – voltage capability up to 1.0 ampere of load current and input voltage up to 35 volts

This unit provides a unique on chip trimming system to set the output voltages

10uF/63V

IN4007 x4 LM7805

1 3 IN OUT

.1uF

+5V VCC

1000uF/35V

10uF/63V

2

- + AC 230V

2

1

3

4

T1

12-0 -12V. 1A

1 3

2 5

GROUND

.1uF

LM7812 1 3 IN OUT

2

to within +/- 1.5% of nominal on the IC . It provides a line as well as load regulation. All protective feature like thermal shutdown current limiting, and

safe area control have been design into these units and since these regulator requires only a small output capacitor for satisfactory performance ease of

application is assured. Although the voltage fixed the output voltage can be increased by voltage divider method. The low quiescent current of the device

ensures good regulation when this method is used.

COMPONENTS DESCRIPTION:- 555 (TIMER):- Features:-

Timing from microseconds through hours Operates In both as table and

constable modes. Adjustable duty cycle. High current output can source or sink 200Ma Output can drive TTL Temperature stability of 0.005% per oC

Normally on and normally off output.

Usages:-

Precision timing.

Pulse generation.

Sequential timing.

Time delay generation.

Pulse width modulation.

Pulse position modulation.

Missing pulse detector.

1 GND 8 VCC 2 TRIGGER 7 DISCHARGES 3 OUTPUT 6 THRESHOLD 4 RESET 5 CONTROLVOLTAGE

IC

555

FIG. PIN OUT DIAGRAM OF 555 TIME

PIN1: Ground: - All the voltages are measured with respect to this terminal.

PIN: 2 Trigger: - The output of the timer depends on the amplitude of the

External trigger pulse applied to this pin. The out is low if

The voltage at this pin is greater than 2/3 Vac. However,

When a negative going pulse of the amplitude larger than 1/3

Vcc is applied to this pin, the comparator 2 output goes

Low, which in turn switches the output of the timer high?

The output remains high as long as the trigger terminal is

Held at low voltage.

PIN:3 Output:- There are two ways of load can be connected to the output

terminal, either between pin 3 and ground or between pin 3 and supply voltage

+Vcc in the output is low, the load current flows through the load connected

between pin 3 +Vcc in the output terminal and is called the sink current.

However the current through the grounded load is zero when the output is low.

For this reason the load connected between pin 3 and +Vcc is called the

normally on load and that connected between pin 3 and ground is called the

normally off load. On the other hand, when the output is high the current

through load connected between PIN 3 and +Vcc (normally on load) is zero.

However the output terminal supplies current to the normally off load. This

current is called the source current. The maximum value of sink or source

current is 200mA.

PIN4: Reset: - The 555 timer can be reset by applying a negative pulse to this

pin. When this reset function is not in use, the rest terminal should be connected

to + VCc avoid any possibility of false triggering.

PIN5: Control voltage:-An external voltage applied to this terminal changes the

threshold as well as the trigger voltage. In other wards by imposing a voltage on

this pin or by connecting a pot between this pin and ground, the pulse width of

the output wave from can be varied. When not used the control pin should be

passed to ground with a 0.01uF capacitor to prevent any noise problems.

PIN 6: Threshold :- This is the non-inverting input terminal of comparator 1,

which monitors the voltage across the external capacitor when the voltage at

this pin is > threshold voltage 2/3 Vcc the output of comparator 1 goes high

which in turn switches the output of this timer low.

PIN7: Discharge: - this pin is connected internally to the collector of transistor

Q1 as shown in fig. When the output is high, Q1 is off and acts as an open

circuit to the external capacitor C connected across it. On the other hand when

the output is lowQ1 is saturated and acts as a short circuit, shorting out the

external capacitor C to ground.

PIN 8:- +Vcc The supply voltage of +5volt to +18 is applied to this pin with

respect to ground (pin 1).

THE ASTABLE OPERATION:-

An astable multivibrator, often called a free running multivibrator is a

rectangular wave generating circuit. Unlike the mono-stable multivibrator this

circuit does not require an external trigger to change the state of the circuit does

not require an external triggering to change the stat of the output hence the

name free – running. However the time during which the output is either high or

low is determined by the two resistors and capacitor which are externally

connected to the 555 timer.

Operation:-

The 555 timer connected as an astable multivibrator initially when the output is

his capacitor C starts charging toward Vcc through Ra and Rb However as soon

as voltage across the capacitor equals 2/3 Vcc comparator 1 trigger the flip-flop

and the output switches low Now the voltage across C equals1/3 Vcc

comparator 2’s output trigger the flip- flop and the output goes high. Then the

cycle repeats the output voltage and capacitor voltage. The capacitor is

periodically charged and discharged between 2/3 Vac and 1/3 Vcc respectively.

The time during which the capacitor charges from 1/3 Vcc equal to the time the

output is high and is given by

Tc = 0.69(Ra+ Rb) C

Where Ra and Rb are in ohms and C is in farads. Similarly, the time during

which time capacitor discharges from 2/3 Vcc is equal to the time the output is

low and is given by.

Td = o.69(Rb)C

Where is in ohms and C is in farads. Thus the total period of the output

waveform is

T = tc+ td = 0.69(Ra + Rb) C

RESISTANCE:-

Obstruction produced by any object in the path of current is known as resistance. It is represented by R and its measuring unit os Ohm . Ohm is a

smaller unit. Its larger unit are kilo Ohm & Mega Ohm. Different object have different resistance and their result due to resistivity is also different. Some

object produce obstruction in the path of current due to resistance where as some produces heat, light etc. Following materials are used as resistance.

1) Carbon

2) Eureka

3) Manganese

4)Nichrome

5)Tungsten

Dependency of resistance:

Resistance of any conductor depends upon the following factor.

I)Length of the wire

II) Cross sectional area of the wire.

III) Heat.

Type of Resistance. Now a day various types’ resistance are used and each resistance has some special use. The use of this resistance depends upon the

requirement of the circuit. The resistance of various types are given below.

Carbon Resistance.

Carbon Film Resistance.

Metal Film Resistance.

Wire wound Resistance.

Thick Film Resistance

Thin Film Resistance.

Safety Resistance.

Chip Resistance.

Network Resistance.

Enamel power Resistance None Flame Fusible ie. When more current flow from

the limited current than it fuses and breaks the circuit. But speciality of this resistance is that while fusing it gives no flame. Voltage depending Resistance.

CAPACITOR:-

In the 60BC static electricity was discovered in Greece, But this electricity exists for every short time. So it was felt necessary to store it. Although till the 18th century capacitor was not invented but in the year 1746 Dutch scientist van

Mussenbrock invented it. Firstly capacitor was termed as Leyder Jar. It was used to charge with static electricity. It had the capacity to charge the electricity

in low space. That’s why scientist Volta named it condenser in 1782.Popular English Scientist Michael Faraday decided the nature of capacitance and

electricity after 18th century. After this the unit of capacitance was named as Farad.Now a days, condenser is known as capacitor. Its function is to store the

electrical energy and give this energy again to the circuit when necessary. In other words, it charges and discharges the electricity.

Besides this the functions of a capacitor are as

follows:

1) It block the flow of DC and permits the flow of AC.

2) it is used for coupling of the two sections.

3) It by passes (grounds) the unwanted frequency.

4) It feds the desired signal to any section.

5) It is used for phase shifting.

6) It is also used for delay in time.

7) It is also used for filtration.

8) It is used to get turned frequency.

9) It compares the two signals.

10) It is used as meter starter.

In fact a capacitor works as a water tank. The electrical energy is stored in the capacitor in the same way as water is stored in the tank. It is known as charging

of capacitor. The stored electrical energy can be received again from the capacitor in the same way as water received from the tank. It is known as

discharging of the capacitor. Capacitor is an electrical components. A capacitor essentially consists of two conducting surfaces which is made by two metallic

plate. separated by a layer of an insulating medium called dielectric. The conducting surfaces may be in the form of it the circular (or rectangular) plates

or be of spherical or cylindrical shape. The purpose of a capacitor is to store electrical energy by electrostatic stress in the dielectric (the word ‘condenser’ is

a misnomer since a capacitor does not ‘condense’ electricity as such, it merely stores it). A parallel plate capacitor is a one plate joined with ‘+ tive’ end of the

supply and the other plate joined with ‘– tive’ end or earthed. It is experimentally found that in the presence of an earthed plate. The capability of

capacitor to store electricity is known as capacitance of that capacitor. It is denoted by C. The measuring unit of capacitance is farad, but Farad is very large unit. It is smaller units are kilo, Micro Farad etc. a battery in two ways.

First anode of the diode to negative terminal of the battery and cathode to the positive terminal of the battery. Second method is to connect the anode of

diode to the positive terminal of the battery and cathode to the negative terminal of the battery. Mostly, electrical energy is used in the form of AC but at some

places it is used in the from of DC the process of making DC from AC is known as rectification.

TRANSISTOR: -

Invention of transistor was done by great American scientist Mr. Vardon and Mr. Bradone in 1947. After the invention of transistor there is a treat revolution

in electronics field. It (Transistor ) is totally an electronics device which is generally made of semiconductor materials germanium or silicon. In pure

condition semiconductor. is generally non conductor . By adding two types of impurities we make two types of semiconductor.

1) N – Type semiconductor.

2) P – Type semiconductor.

By adding the P and N type semiconductor make a junction and the device called a diode. There are two junction in a transistor, so it is called a unijunction

or Bipolar transistor. In a transistor there are two junctions one provide a very

low resistance for current flow and the other provide a very high resistance. One transistor transfers the current from low resistance towards high resistance

due to this reason it called a transfer of resistor or transistor. On the Basis of construction, there are two types there are there terminals , namely emitter, base

and collector. The terminal which emits the charge, called a emitter and that which collect charge is called collector. The middle layer between the emitter

and collector is called base, which makes two junction one with emitter and other with collector, the junction between base and emitter is called emitter

junction and that between base and collector is called collector junction. The function of base is to control the collector current. In symbolic representation

of P – N – P transistor the direction of arrow is towards inside but N- P –N transistor the direction of arrow is towards outside.

Identification of Germanium or silicon transistor :

For the construction of transistors two types of semiconductors are used, namely si and Ge. Germanium transistors are generally is metallic body whereas

the Si transistor may be both in metallic or silica body. In this condition it is a difficult job to identify them. By measuring the resistance between emitter and

collector by multimeter, we can identify neither the transistor is P-N-P type nor N-P-N type .

TYPE OF DIODES:

According to the construction and working diode are of following types.

1)Rectifier diode.

2) Signal diode

3) Zener diode

4)Vector diode

5) Hot carrier of schottky diode

6)Tunnel diode

7)Light Emitting diode

8) Photo sensitive diode.

RECTIFIER DIODE:-

These diode are used to convert AC into DC these are used as half wave

rectifier or full wave rectifier. Three points must be kept in mind while using any type of diode.

1)Maximum forward current capacity.

2) Maximum reverse voltage capacity.

3) Maximum forward voltage capacity .

The number and voltage capacity of some of the important diodes available in

the market.

Bridge rectifier:

In Bridge rectifier there are four semiconductor diodes and four electrodes are taken out from them. These are used as bridge rectifier. In order to check four

diodes of bridge rectifier, check two ends like a single diode.

Indentify the terminals of transistor :- Generally there are three terminals in transistors which are called emitter,

base and collector, but in high frequency transistor there is an additional terminal called shiel. This terminal is generally connected to the body of

transistor. In each type of transistor there are different ways to identify these terminals, In some transistor, to search that terminals there may be a guide

point, by which we can know the emitter, base and collector terminals . It some type of transistor, which are made of different companies, then the

Identification method may be different. The identification of terminals of that type and other Si transistors, we do according to following shapes of all that

transistor are semiconductor are semicircular and terminals are in straight line. To identify the terminals, we take transistors in hand in a way that the portion of

transistor on which numbers written, remain towards us and terminals remain lower side. Then the left - most terminal is collector and right most is emitter

and middle one is base. These transistor are called Si planer transistors. Below is

the circuit of a relay driver using the NPN transistor BC 548. The relay is connected between the positive rail and the collector of the transistor. When the input signal passes through the I K resistor to the base of the transistor, it conducts and pulls the relay. By adding a 470 uF electrolytic capacitor at the base of the relay driver transistor, a short lag can be induced so that the transistor switches on only if the input signal is persisting. Again,even if the input signal ceases, the transistor remains conducting till the capacitor discharges completely. This avoids relay clicking and the offers clean switching of the relay.

TRANSISTOR AS A SWITCH:

Electronic circuits inevitably involve reactive elements, in some cases

intentionally but always at least as parasitic elements. Although their influence

on circuit performance may be subordinate for a particular circuit reactive

elements introduce an ultimate limitation on frequency response/switching

speed. Energy storage in reactive elements introduces consideration ‘past

history’ into the analysis of a circuit. This note examines switching delays

associated with circuit capacitance and inductance. There are related delays

associated with device internal phenomena, generally significant only for very

fast changes. These device-specific contributions are considered elsewhere,;

ordinarily they are of little import other than for significant time intervals less

than (roughly) 10 to 100 nanoseconds. Switching is examined here in the

context of a bipolar junction transistor circuit. Switching a Capacitative Load

The circuit on the right is a simplified CE amplifier with an external capacitor

load; the capacitor may represent an inevitable circuit parasitic or it might

approximate the capacitance that would be added by an additional stage of

amplification. A voltage pulse is applied, increasing the base input voltage from

an initial zero level for which the trans istor is cut-off, to a level at which the

emitter junction is turned ON. The junction becomes cut-off again on the

trailing edge of the pulse. The pulse width is assumed to be wide enough so that

turn-on and turn-off transients are disjoint. The basic question considered is the

locus of the operating point on the IC-VCE plane. Qualitative Evaluation

Consider the circuit performance qualitatively at first; this is done with

reference to the figure to the right. A representative constant base-current

characteristic is shown, and superimposed on the graph is the load line for the

circuit. Initially (base voltage zero) the transistor is cut-off and there is no

collector current; the collector voltage then is VCC. This is the abscissa point

labeled 'cutoff' on the figure, and is the quiescent point so long as no base

voltage is applied. Note particularly that energy is stored in the capacitor, i.e.,

the capacitor is charged so that the voltage across it is VCC. Now suppose an

abrupt base voltage change occurs corresponding to the leading edge of the base

voltage pulse. (As a practical matter ‘abrupt’ means the change occurs within a

time interval much shorter that that within which the circuit can respond; the

analysis will indicate how small this interval need be.) Base current rises

abruptly to a finite value, approximately equal to (pulse-height - 0.7 volt)/ RB.

The collector voltage however remains at VCC initially, since the capacitor

charge cannot change instantaneously. Hence the operating point jumps

abruptly, as shown, to the collector characteristic corresponding to the base

current. Note that the transistor is not saturated initially whatever the base

current because the collector voltage is constrained by the capacitor. Note also

that initially there is no current through and so no voltage drop across the

collector resistor. It is the capacitor that supplies the BJT collector current (so

that to the extent that the collector current remains constant the collector voltage

drops linearly). As the capacitor discharges, lowering the collector voltage,

current through the collector resistor increases and current from the capacitor

decreases. Roughly equal magnitudes of change are involved, at least to the

extent that the transistor collector current for a fixed base current remains

constant. As the collector voltage decreases the operating point moves down the

constant base current characteristic until the intersection with the load line is

reached. At this point the collector current is provided entirely through the

collector resistor. There is no current drawn from the capacitor, and so no

further decrease in collector voltage. This is the steady-state condition that

persists until the amplitude of the base-voltage pulse changes. The transistor

may or may not be saturated in steady state; this depends on the circuit element

values fixing the intersection of the load line and the collector characteristic. In

general the turn-on will be fairly rapid, because the transistor provides a

relatively high-current discharge path for the capacitor. Assume now the steady

state has been reached, and then after that the base voltage is brought back to

zero voltage, once again cutting off the transistor; this is at the trailing edge of

the base pulse. The collector current drops immediately (ideally) to zero.

However the capacitor again does not permit the collector voltage to change

abruptly. Hence the operating point drops abruptly to intersect the axis; zero

current, same voltage. Current now flows through the collector resistor to

charge the capacitor, and the operating point moves along the abscissa to return

to steady state at VCC. Quantitative Evaluation A PSpice analysis of the

switching circuit considered was performed, using the BC 547 PSpice model

and circuit element values as shown to the left. The computed currents as a

function of time are shown in the figure below. The transistor collector current

(which should be distinguished from the current provided by the power supply)

jumps immediately on turn-on to a magnitude determined by the collector

characteristic corresponding to the base current; the transistor is not saturated at

this point and there is no current-limiting because of saturation. A turn-on

current spike of this sort (see plot below) can cause damage if the current is not

limited to a safe value by one means or another. In this example that the base

resistor provides limiting, but the point really is that the matter should not be

left to chance. The supply current, on the other hand, initially is zero; the

capacitor holds the voltage drop across the collector resister to zero. As the

supply current increases (the capacitor is discharging through the transistor and

consequently the collector voltage is decaying) the collector current decreases in

this illustration. As is not uncommon in such switching the base current

magnitude used generally is intended to saturate the transistor. Because the

capacitor at first prevents the transistor from saturating an initially larger current

speeds the capacitor discharge. Eventually steady state is reached; there is no

current contributed by the capacitor, and the power supply provides the

collector current. When the transistor is cutoff on the trailing edge of the base

voltage pulse the collector current drops to zero immediately. The supply

current, however, continues to flow, recharging the capacitor. A plot of the

computed collector and power supply current is shown below. Switching an

Inductive Load Because of a fundamental conflict between the physical laws

associated with the inductive effect and the practical and economic constraints

of monolithic construction the phrase integrated circuit inductor is by and large

an oxymoron. On the other hand discrete inductors are important in a number of

applications; high-current mechanical relay switches are a specific example. A

simplified transistor-actuated switch circuit is shown to the left; the dotted

rectangle represents a relay coil having a winding resistance RL and an

inductance L; associated mechanical switch contacts are not shown explicitly

since they are not involved in the present discussion. As was done in the

capacitor switching illustration a pulse is applied which temporarily switches

the transistor from a cutoff state to a conducting state. Also, as in that earlier

illustration, we first examine the circuit behavior during the pulse qualitatively.

Qualitative Evaluation The inductance is a more sinister circuit element than a

capacitor in the sense that it stores energy dynamically, i.e., via a current flow

through the inductor. For capacitor loading turning off a power supply is a

relatively benign operation, although there are some hazards. Capacitors

discharge their stored energy if there is a current path, but if not they remain

effectively dormant in an energized state. An inductor, on the other hand, stores

its energy in a current flow, and in general turning off the power supply means

turning off current flow. An inductor responds to a changing current by

generating a voltage which attempts to mitigate the change; the faster the

change the larger the generated voltage magnitude. Unfortunately the typical

result, particularly where care is not taken, is to produce a destructive release of

the stored energy. A sketch of a representative pulse trajectory on the IC-VCE

plane is drawn below. Initially the transistor is cutoff and the operating point is

at (VCC, 0). When the base drive turns the transistor ON the operating point

must lie on the transistor characteristic that corresponds to the base current

applied. On the other hand the inductance prevents the collector current from

changing immediately. To accommodate both requirements concurrently the

collector voltage drops immediately and moves to the zero-current intersection

of the collector characteristic; the collector voltage change involved is induced

by the inductive reaction to an attempt to change the current. Note however that

the current is in the process of increasing. As the current increases operation

moves up the saturation part of the collector characteristic and over until the

load line is intersected. This corresponds to the steady-state operating point. In

most instances the operating point will be selected to saturate the transistor so

that the collector dissipation will be relatively small. Quantitative Evaluation A

PSpice computation of the turn-on transient follows first. The turn-off process

(which involves the diode branch) is considered separately. During turn-on the

diode is reverse-biased and so this branch is inactive and can be ignored. The

computed turn-on transient response is shown in the figure following below

(input step starts at 10μs). Note that the collector current remains zero initially

and then rises approximately exponentially (along the collector characteristic)

into steady state (with a small overshoot). Similarly the collector voltage

initially drops rapidly towards zero (through saturation), and remains low as the

current rises (along the saturation portion of the collector characteristic). As the

operating point moves to the intersection of the load line and the collector

characteristic the voltage and current increase to their steady-state values. The

IC-VCE locus for the turn-on transient is plotted below. This light triggered

circuit can be used to turn on / off a load such as lamp.

ELECTROMAGNETIC SWITCH

A relay is an electrically operated switch. Current flowing through the

coil of the relay creates a magnetic field which attracts a lever and

changes the switch contacts.

Features:

Relays can switch AC and DC.

Relays can switch high voltages.

Relays are a better choice for switching large currents (> 5A).

Relays can switch many contacts at once.

Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used

where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several

circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits, repeating the signal coming in from one circuit and

re-transmitting it to another. Relays were used extensively in telephone exchanges and early computers to perform logical operations. A type of relay

that can handle the high power required to directly control an electric motor or other loads is called a contactor. Solid-state relays control power circuits with

no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in

modern electric power systems these functions are performed by digital instruments still called "protective relays".

Basic design and operation:-

Simple electromechanical relay.

Small "cradle" relay often used in electronics. The "cradle" term refers to the

shape of the relay's armature. A simple electromagnetic relay consists of a coil

of wire wrapped around a soft iron core, an iron yoke which provides a low

reluctance path for magnetic flux, a movable iron armature, and one or more

sets of contacts (there are two in the relay pictured). The armature is hinged to

the yoke and mechanically linked to one or more sets of moving contacts. It is

held in place by a spring so that when the relay is de-energized there is an air

gap in the magnetic circuit. In this condition, one of the two sets of contacts in

the relay pictured is closed, and the other set is open. Other relays may have

more or fewer sets of contacts depending on their function. The relay in the

picture also has a wire connecting the armature to the yoke. This ensures

continuity of the circuit between the moving contacts on the armature, and the

circuit track on the printed circuit board(PCB) via the yoke, which is soldered to

the PCB. When an electric current is passed through the coil it generates a

magnetic field that activates the armature, and the consequent movement of the

movable contact(s) either makes or breaks (depending upon construction) a

connection with a fixed contact. If the set of contacts was closed when the relay

was de-energized, then the movement opens the contacts and breaks the

connection, and vice versa if the contacts were open. When the current to the

coil is switched off, the armature is returned by a force, approximately half as

strong as the magnetic force, to its relaxed position. Usually this force is

provided by a spring, but gravity is also used commonly in industrial motor

starters. Most relays are manufactured to operate quickly. In a low-voltage

application this reduces noise; in a high voltage or current application it reduces

arcing. When the coil is energized with direct current, a diode is often placed

across the coil to dissipate the energy from the collapsing magnetic field at

deactivation, which would otherwise generate a voltage spike dangerous to

semiconductor circuit components. Some automotive relays include a diode

inside the relay case. Alternatively, a contact protection network consisting of a

capacitor and resistor in series (snubber circuit) may absorb the surge. If the coil

is designed to be energized with alternating current(AC), a small copper

"shading ring" can be crimped to the end of the solenoid, creating a small out-

of-phase current which increases the minimum pull on the armature during the

AC cycle.[1]A solid-state relay uses a thyristor or other solid-state switching

device, activated by the control signal, to switch the controlled load, instead of a

solenoid. An opto coupler(a light-emitting diode(LED) coupled with a photo

transistor) can be used to isolate control and controlled circuits. A contactor is

a very heavy-duty relay used for switching electric motor sand lighting loads,

although contactors are not generally called relays. Continuous current ratings

for common contactors range from 10 amps to several hundred amps. High-

current contacts are made with alloys containing silver. The unavoidable arcing

causes the contacts to oxidize; however, silver oxide is still a good

conductor.[2]Such devices are often used for motor starters. A motor starter is a

contactor with overload protection devices attached. The overload sensing

devices are a form of heat operated relay where a coil heats a bi-metal strip, or

where a solder pot melts, releasing a spring to operate auxiliary contacts. These

auxiliary contacts are in series with the coil. If the overload senses excess

current in the load, the coil is de-energized. Contactor relays can be extremely

loud to operate, making them unfit for use where noise is a chief concern. One

of the serious problems in relay operated circuits is the relay clicking or

chattering during the on/off of the relay driver transistor. This problem is severe

if the input circuit is a light/temperature sensor. During the transition of

light/temperature levels, the relay clicks which may cause sparking of contacts.

By using a simple tip, this problem can be avoided.

WATER PUMP:

Generally water pumps are centrifugal. In some special application, positive

displacement pumps and regenerative turbine pumps are used. *A centrifugal

pump is a rotating machine in which flow and pressure are generated

dynamically. The inlet is not walled off from the outlet as is the case with

positive displacement pumps, whether they are reciprocating or rotary in

configuration. Rather, a centrifugal pump delivers useful energy to the fluid or

“pumpage” largely through velocity changes that occur as this fluid flows

through the impeller and the associated fixed passageways of the pump; that is,

it is a rotodynamic” pump. All impeller pumps are rotodynamic, including those

with radial-flow, mixed-flow, and axial-flow impellers: the term“centrifugal

pump” tends to encompass all rotodynamic pumps. Although the actual flow

patterns within a centrifugal pump are three-dimensional and unsteady in

varying degrees, it is fairly easy, on a one-dimensional, steady-flow basis, to

make the connection between the basic energy transfer and performance

relationships and the geometry or what is commonly termed the “hydraulic

design” (more properly the “fluid dynamical design”) of impellers and stators or

stationary passageways of these machines. In fact, disciplined one-dimensional

thinking and analysis enables one to deduce pump operational characteristics

(for example, power and head versus flow rate) at both the optimum or design

conditions and off-design conditions. This enables the designer and the user to

judge whether a pump and the fluid system in which it is installed will

operate smoothly or with instabilities. The user should then be able to

understand the offerings of a pump manufacturer, and the designer should be

able to provide a machine that optimally fits the user’s requirements. *The fluid

arrives at the pump suction nozzle as it flows through the suction piping. The

fluid must be available to the pump with sufficient energy so that the pump can

work with the fluid’s energy. The pump cannot suck on or draw the liquid into

the pump.

Positive displacement (I’D) pumps take the fluid at the suction nozzle and

physically capture and contain the fluid in some kind of moveable enclosure.

The enclosure may be a housing with a pulsing diaphragm, or between the teeth

of rotating gears. There are many designs. The moveable enclosure expands and

generates a low pressure zone, to take the fluid into the pump. The captured

fluid is physically transported through the pump from the suction nozzle to the

discharge nozzle. Inside the pump, the expanded moveable enclosure then

contracts or the available space compresses. This generates a zone of high

pressure inside the pump, and the fluid is expelled into the discharge piping,

prepared to overcome the resistance or pressure in the system. The flow that a

PD pump can generate is mostly a function of the size of the pump housing, the

speed of the motor or driver, and the tolerances between the parts in re lative

motion. The pressure or head that a PD pump can develop is mostly a function

of the thickness of the casing and the tolerances, and the strength of the pump

components. As the pump performs its duty over time, and fluid passes through

the pump, erosion and abrasive action will cause the close tolerance parts to

wear. These parts may be piston rings, reciprocating rod seals, a flexing

diaphragm, or meshed gear teeth. As these parts wear, the pump will lose its

efficiency and ability to pump. These worn parts must be changed with a degree

of frequency based on time and the abrasive and lubricating nature of the fluid.

Changing these parts should not be viewed as breakdown maintenance. Nothing

is broken. This periodic servicing is actually a production function to return the

pump to its best or original efficiency. Centrifugal pumps also require that the

fluid be available to the pump’s suction nozzle with sufficient energy.

Centrifugal pumps cannot suck or draw the liquid into the pump housing. The

principal pumping unit of a centrifugal pump is the volute and impeller. The

impeller is attached to a shaft. The shaft spins and is powered by the motor or

driver. We use the term driver because some pumps are attached to pulleys or

transmissions. The fluid enters into the eye of the impeller and is trapped

between the impeller blades. The impeller

blades contain the liquid and impart speed to the liquid as it passes from the

impeller eye toward the outside diameter of the impeller. As the fluid

accelerates in velocity, a zone of low pressure is created in the eye of the

impeller (the Bernoulli Principle, as velocity goes up,pressure goes down). This

is another reason the liquid must enter into the pump with sufficient energy. The

liquid leaves the outside diameter of the impeller at a high rate of speed (the

speed of the motor) and immediately slams into the internal casing wall of the

volute. At this point the liquid’s centrifugal velocity comes to an abrupt halt and

the velocity is converted into pressure (the Bernoulli Principle in reverse).

Because the motor is spinning, there is also rotary velocity. The fluid is

conducted from the cutwater around the internal volute housing in an ever-

increasing escape channel. As the pathway increases, the rotary velocity

decreases and even more energy and pressure is added to the liquid (again

Bernoulli’s Principle). The liquid leaves the pump at discharge pressure,

prepared to overcome the resistance in the system. The flow from a centrihgal

pump is mostly governed by the speed of the driver and the height of the

impeller blades. The pressure or head that the pump can generate is mostly

governed by the speed of the motor and the diameter of the impeller. Other

factors play a lesser role in the pump’s flow and pressure, like the number,

pitch, and thickness of the impeller blades, the internal clearances, and the

presence and condition of the wear bands. In simple terms, we could say that

PD pumps perform work by manipulating the available space inside the pump.

Centrihgal pumps perform work by manipulating the velocity of the fluid as it

moves through the pump.

AUTOMATIC WATER PUMP CONTROL SYSTEM

This circuit not only indicates the amount of moisture present in the farm but also gives a indicate with green light when the farms full of moisture. Water

pump control system is construct by two section , sensor circuit and LED driver. Transistor. Resistor are use as required for biasing , simple ware use for

sensor . This circuit can be measure moisture of farm and control to water pump. Each transistor connected with resistor name as RC, RE,R1 and R2.

Sensor were is connected through the resistor. The circuit uses the widely available BC547 transistor to indicate the water level through LEDs. When the water is empty the wires in the tank are open circuited and the 180K resistors

pulls the switch low hence opening the switch and LEDs are OFF. As the water starts filling up, first the wire in the field connected to S1 and the +supply are

shorted by moisture. This closes the switch S1 and turns the LED1 ON.As the water continues to fill the field. The LED is indication can be increased to

transistor circuit . When the water is full, the base of the transistor BC548 is pulled high by the water and this saturates the transistor ON. This circuit is

very useful for automatic controlling of moisture level while filling the container of level . As the water layer crosses the particular level which is

predefined. The corresponding LED glow. Thus this circuit can be use as indication of knowing the current content of water in the farm .

WORKING PRINCIPLE:

One electrode probe is with 5V AC is placed at the bottom of tank. Next probes are placed step by step above the bottom probe. When the water/liquid comes in

contact with the electrode tip, a conductive path is established between the sense electrode and the tank wall/reference electrode, which in turn makes the

transistors conduct to glow LED and indicate the level of water. The ends of probes are connected to corresponding points in the circuit as shown in circuit diagram. Insulated Aluminum wires with end insulation removed will do for the

probe. Arrange the probes in order on a PVC pipe according to the depth and immerse it in the tank. AC voltage is use to prevent electrolysis at the probes.

Table 3-1 Operating sequences Water level System response (assuming power supply +V = 6.0V) Below 25%ProbeThere is no conductive path between

Ground Probe and other probes. Thus no LED glows because the circuit is not completed.Between25% Probe and 50%ProbeWater provides a conductive path

between 25% Probe and Ground Probe. Thus switch S1 of theBC547 transistor activates the LED1 (green).Between50% Probe and 75%ProbeWater provides a

conductive path between 50% Probe and Ground Probe, which is in parallel with the 25% Probe – Ground Probe path If this second path resistance is also

within the range, Then switch S2of theBC547 transistor activates the LED2 (white).Between75% Probe and full Water provides a conductive path between 75% Probe and Ground Probe, which is in parallel with the 25% Probe –

Ground Probe & 50% probe - ground path, If this third path resistance is also within the range, Then switch S3 of theBC547 transistor activates the LED3

(yellow).At Full Water provides a conductive path between full Probe and Ground Probe, which is in parallel with the 25% Probe – Ground

Probe,50% probe - ground path, If this fourth path resistance is also within the range,

MOISTURE CONTROL CIRCUIT DIAGRAM

Q2 BC547 R2

R

R4

Ground

+5 V

R1 R BC547

BLOCK DIAGRAM MOISTURE CONTROL FOR TREE

WATER PUMP DRIVER

GREEN FARM

POWER SUPPLY

APPENDIX 1

CONCLUSION

So this project is being applicable in the fields of

Research in agriculture field

Horticulture of tea and maze gardens

Agricultural lands for wheat, barly

Green houses cultivations

And the total investment for the whole a longed project to implement

in the lands will be Rs 15000-30,000

Due to inadequate costly it is preferred to be used in group farms and

agricultural land rather than individual fields

So hopping the development in agriculture lands this is a small

ray of hope