Moisture control project is uses full and interesting project. It can help to farmer. It is consist of BJT, Resisters, Capacitors, 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.

1. PATRUNICHIDANANDASASTRY
ELECTRONICSANDCOMMUNICALTION
ENGINEERING
AUTOMATICMOISTURECONTROL
SYSTEMINPLANTS
SUBMITTEDBY
PATRUNI CHIDANANDASASTRY
UNIVERSITYROLL-10500310053
DEPERATMENT-ELECTRONICS ANDCOMM. ENG.
CLASS ROLL-22
SUBMITTEDTO
BANKURA UNNAYANI INSTITUTE OF ENGINEERING
DEPARTMENT OF E.C.E
GUIDED BY
MRS TANUSREE PATRA

2. 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
………………………. …………………………

3. 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.

4. CONTEXT
 INTRODUCTION
 POWER SUPPLY
 DESIGNE PRINCIPLE
 CIRCUTI EXPLANATION
 COMPONENT DESCRIPTION
 WORKING PRINCIPLE
 BLOCK OF WORK
 CONCLUSION
 APPENDIX

5. 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.

6. 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-

7. 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 mostlow voltage circuits with a current1A.
BLOCK DIAGRAM OF POWERSUPPLY:
STEPDOWN TRANSFORMER
16-016 (1Amp.)
BRIDGE RECTIFIER SECTION
FILLTER CIRCUIT
12 V. POSETIVE
VOLTAGE REGULATER
05V. POSETIVE
VOLTAGE REGULATER

8. 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

9. 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
LM78121 3
IN OUT
2

10. 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.

11. 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 sourceor 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

12. FIG. PIN OUT DIAGRAMOF 555 TIME
PIN1: Ground: - All the voltages are measured with respectto 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.

13. 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

14. 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.

15. 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

16. 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.

17. 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

18. 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 schottkydiode
6)Tunnel diode
7)Light Emitting diode
8) Photo sensitive diode.

19. 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

20. 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 transistor 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

21. 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

22. 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

23. 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

24. IC-VCE locus for the turn-on transient is plotted below. This light triggered
circuit can be used to turn on / off a load suchas 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:-

25. Simple electromechanicalrelay.
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

26. 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

27. 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

28. 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 relative
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

29. 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 .

30. 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,

31. MOISTURE CONTROLCIRCUIT DIAGRAM
Q2
BC547R2
R
R4
Ground
+5 V
R1
R BC547

32. BLOCK DIAGRAM MOISTURE CONTROL FOR TREE
WATER PUMPDRIVER
GREEN FARM
POWER SUPPLY

33. APPENDIX 1

34. 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