Post on 24-Oct-2015
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A technical student is expected to do some experimentation and research work on the subject, which he had learnt, at the classes during the course of his studies . Such an effort when well organized with a definite aim or purpose is called a PROJECT.The object of a project is to evolve technical thinking ,analyse the problem , search for the solution , work in a team , present the findings to the
Professors and above all make a logical Engineer .Through a project student displays his spirit of inquisitiveness , creativity , ability to understand a problem and analytical ways of solving the problem
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1. Introduction 2.Principle of Project 2.1 Circuit Design 2.2 Component Selection 2.3 Component Description
3.Project Development 3.1 PCB Preparation 3.2 PCB Testing 3.3 Assembling of the Unit 4.Testing of the Project Model 5.Result of the test 6. Cost Estimate of the Project 7.Conclusion 8.References
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INTRODUCTION
Rain Alarm ProjectWater is basic need in every one’s life. Saving and proper usage of water is very important. Here is an easy project which will give the alarm when there is rain, so that we can make some actions and save the rain water. As a result, we can increase the water levels of underground water by using underwater recharge technique. Rain water detector will detect the rain and make an alert; rain water detector is used in the irrigation field, home automation, communication, automobiles etc. Here is the simple and reliable circuit of rain water detector which can be constructed at low cost.
Rain Alarm Project Block Diagram:
Rain water sensor is the main component in the circuit. For this rain sensor, no need to go and buy in the market or online. We can do it ourselves just by taking the piece of
Bakelite or mica board and aluminum wire. Bakelite or mica board should be made completely flat and aluminum wire should be pasted on the flat board as shown in the figure below of rain water sensor. Care should be taken that there should be no spaces between the wire and board. When the rain water sensor is completed, it should get connected to the circuit and voltage should be passed through the wires.
Rain water sensor diagram is shown below:
If there is no rain, the resistance between the wires will be very high and there will
be no conduction between the wires in the sensor. If there is rain, the water drops will fall on the rain sensor which will also decrease the resistance between the wires and wires on the sensor board will conduct and trigger the NE555 timer through the transistors circuitry. Once NE555 is triggered, it will make the output pin high and which will make the buzzer to make alarm.
Rain Alarm Project Circuit Diagram:Rain water detector alarm circuit is shown below.
Circuit Explanation: The points A and B of the circuit are connected to the
points A and B of the rain sensor respectively. When rain
is falling, the rain water will fall on the rain sensor which
has aluminum wires on mica or Bakelite sheet. Due to the
water on sensor, the aluminum wire ‘w’ develops
resistance and gets conducted because of battery
connector, the sensor and also to the circuit.
When the aluminum wires are connected, the transistor
Q1will get turned on and make LED to glow and also Q2
will also be turned ON. When the Q2 is saturated, the
capacitor C1 will be shorted and make the transistor Q3
to be turned ON. C1 will get charged by the resistor R4.
The reset pin of 555timer which is connected to the
emitter of Q3 will be made positive when Q3 reaches to
the saturation mode.
The 555 timer is configured in astable mode. When the
reset pin of the 555 timer is made positive because of
saturation mode of Q3, it will generate the pulse at the pin
3 and make speaker to ring alarm. Capacitor is
connected in between the pin 3 of 555 timer and speaker
because to block the DC signal and allow only the
variations in the signal which make the speaker to make
sound. The diode D2 will not allow any reverse current
from the timer.
Because of the resistor R4 and capacitor C1, Q3 will
get in cut-off after sometime and make the reset pin of
555timer in negative and speaker will stops making
sound. The time for 555timer to make speaker sound
depends on the values of C1 and R4.
When there is no rain, the aluminum wire of the sensor
will not have any resistance or conduction cannot trigger
the circuit.
Note:
Rain senor should be kept in the open place at 30 to
40 degrees from the ground. As a result, rain water will
not present on the sensor for long time.
This circuit will automatically switch of the alarm after
sometime and LED will glow continuously until the rain
stops.
DESIGN OF POWER SUPPLY CIRCUIT :
The Power is given to the transformer
which steps down the input voltage to 10 times less i.e.
20 V .This low voltage is fed to bridge rectifier which
rectifies the ac waveform to dc wave form with some
ripples .These ripples are filtered through capacitance
filter and is fed to linear regulator .The output of
regulator is further filtered to produce clean DC
Voltage. The different linear regulator are used to
produce different voltages i.e. +5V.+15V,-5C,-15V.
78M15
Transformer Rectifier Filter Regulator
POWER SUPLLY CIRCUIT BOARD
COMPONENT SELECTION
Selection of Transformer
To generate a voltage of +15 Volt we have
selected a transformer whose input is 230 V +/-10 %
and output is 9-0-9 Volts and deliver the current up to
500mA.
Selection of Rectifier Diodes
The rectifier diodes of 1Amp rating has been
chosen to keep the safety factor of 100%.
Selection of Filters
Since the load is not high we have chosen the
capacitive filtering to avoid the ripple . To keep the
cost low and sufficient ripple we chose the
Capacitor value.
Selection of R
The resistance has been selected of sufficient
wattage to avoid overheating and of correct value.
Selection of Capacitor
Capacitors have been used for filtering the noise
at the control voltage and for minimizing the ripple.
Selection of Relay
To switch 15V to astable multivibrator small
current relay of SPDT type is used. we have chosen the
relay whose contact current is around 1 Amp. and
holding current is less than 20 mA.
Selection of Speaker
We have chosen 8 ohm 10 Watt speaker.
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DESCRIPTION OF COMPONENTS
RESISTORS:
These are current resisting devices . These
are made of carbon , metallic wire wound etc. These
are read through this acronym BBROYGBVGW. This
stands for ,Black ,Brown , Red, Orange,
Yellow ,Green ,Blue , Violet, Gray and ,White
respectively .These colours are printed as lines on the
resistor the first and second colour lines indicate the
number corresponding to colour .The number indicated
by the colour are shown in table below .The third
line indicate the number of zeros ,the fourth line
indicate the percentage of tolerance of the resistor
BLACK 0 YELLOW 4 GRAY 8
BROWN 1 GREEN 5 WHITE 9
RED 2 BLUE 6 Gold 5%
ORANGE 3 VIOLET 7 Silver 10%
e.g.Red ,Red ,Black Gold = 22 +/-5% ;
Red Red Brown = 220 ; Red Red Red = 2200 ;
Red Red Orange = 22K;Red Red Yellow = 220 K;
Red Red Green = 2.2M ;Red Red Yellow = 22 M
These are available in various wattages like
1/4W ,1/2 W,1 W,2W,5W,10W,20W,50W,100W,200W.
In electronics most common use is up to 5Watt. Higher
the wattages bigger the sizes. The value and wattage
of resisters are to be selected as per the applications.
The tolerence in variation of the rated value is also
selected as per the applications. The resisters are
fabricated directly on the IC itself.
DIODES
These devices allows to flow current in
only one direction . These devices are also called
unidirectional devices .Earlier these devices were
made of vacuum tubes, now a days these are semi
conductor solid state devices. These are PN junction
devices .The PN means doping of the semi conductor
with positive and negative electronic valence atoms .
The silicon diodes have knee voltage drop of 0.7
volts i.e. forward biased voltage drop whereas
germanium diodes have 0.3 voltage drop. The different
diodes are used for different purposes. The diodes
work in forward biased condition or reverse biased
conditions.
These are available with different current
rating , voltage rating , power rating and are used for
different applications. The diodes of higher wattages
are of bigger sizes. The Symbol of Diode and the
ideal curves of diodes are shown below.
current
voltage
Doide Symbol ideal curve
Current
Forward Region
Break Down Voltage
V
oltage Knee Voltage =0.7V
Reverse Region
Diode Characteristics
Diodes are of different types like
Photodiode ,Varactor diode, Schotkey Diode ,PIN
diode ,Zener Diode etc.
Zener Diode
Small signal and rectifier diodes are never
operated in the break down region because this may
damage them. The zener diode is made to operate in
breakdown region , sometimes called breakdown diode.
The zener diode is the back bone of voltage regulators ,
Symbol of Zener Diode
circuits that hold the load voltage almost constant
despite large changes in the line voltage and load
resistance.
Light Emitting Diode
In a forward biased diode , free electrons
cross the junction and fall in to holes. As these electrons
fall from a higher to a lower energy level , they
radiate energy .In ordinary diodes this energy goes off
in the form of heat .But in the light emitting diode
(LED) the energy radiates as light.LEDs that radiate red,
green, yellow, blue, orange or infrared are
manufactured by using elements like gallium, arsenic,
and phosphorous. LEDs that produce visible radiations
are useful with instruments , calculators etc. The
infrared LED finds application in burglar systems and
other areas requiring invisible radiations. The seven
segment displays uses 7 LEDs .
The symbol of LED
TRANSFORMERS:
This are the devices which converts the
primary ac voltage to different secondary ac
voltages .If the secondary voltage is higher then
primary voltage then the transformer is called step
up transformer , if the secondary is less then
primary voltage then it is called step down
transformer , if secondary is same as primary
voltage then it is called unity transformer .This unity
transformer is also used as isolation transformer . This
devices are highly efficient upto 99.9%. i.e. very low
power loss.
The transformers are required for making
dc supply , tuning circuit etc. The current rating of
primary and secondary winding determines the SWG
gauge of the copper wire.
CAPACITORS
This are the storage devices but has in buit
Resistance that’s why the storage voltage does not last
for longer period. The use of capacitor is for tuning the
circuit, filtering the noise to ground, creating the timing
pulse as in our case .The capacitors can not be
fabricated on Ics because of the technical difficulty.
The different values of capacitor that are
available are 1pf,2pf,2.2pf,100pf,200pf,1000pf,0.001uf,
0.01uf,0.1uf,2uf,10uf,22uf,33uf,47uf,56uf, 68uf, 82uf,
100uf,220uf,330uf etc The capacitors are selected based
on capacitance and voltage rating .Higher the voltage
higher the size of the capacitor. These are available in
following types
Electrolytic Capacitor
These capacitors have electrolyte as the
dielectric between the two plates. These are available
with polarity + and -.These are available with vertical
mount or horizontal mount configuration.
Paper CapacitorL: These capacitors are available in
low range of capacitance. The paper is used as dieletric
media between the two plates.
Mica Capacitor: These capacitors are also available in
low range of capacitance. The mica is used as dieletric
media between the two plates.
Disc Capacitor: These are available from 1pF to
1ooooUF
RELAYS
These are electromagnetic devices which
makes or breaks the contact as per the control voltage.
there are solid state relays which do not consume
much power for their operation , but are not available in
higher current rating . Relays are being substituted by
SCRs also called thyrister for on/off control
PROJECT
DEVELOPMENTPREPARATION OF THE PCB
Schematic Preparation Schematic is a circuit that is drawn
either with the help of software or by manually on
paper with standard symbols. If the circuit is big and
complicated then multi layer schematic is made
otherwise single layer schematic is made . The
schematic is drawn with coloured pen to indicate
the different layers , power lines , signal lines and
ground lines.
Artwork Preparation
After making the schematic on a
paper , same is duplicated on transparent acrylic
plastic sheet . This circuit is called artwork . The
artwork is made either bigger or smaller or same
size of the desired PCB .The artwork is drawn with
different colour tapes to identify the signal lines,
power lines and ground lines . The artwork should be
proper without leaving any connection or making any
excess connection or shorts .
Film Making The artwork is reduced or enlarged or made of same size of the PCB on the film through the camera . The camera produces both the positive and negative films . These films are used to made PCB .
Etching of copper claded board The films are put on copper claded
board and the board is exposed to light. The time of
exposure depends on many factors. After the exposure
of the board it is rinsed in the etching solution.
During this etching operation the exposed copper
gets dissolved in the solution whereas unexposed
copper remains intact with the board .This unexposed
copper in turn makes the pattern what we see on
PCB. The board is then washed in water with gentle
brush .
Driling of holes The PCB is now ready for drilling
operation .The holes are now drilled at all places
wherever the components are to be put .The size of
the drills should not be either more then the required
or less then the required . If the hole is large the it will
be difficult to solder and lot of lead will be consumed.
If the hole is small then component will not be
inserted easily.
Tinning of pcb The PCB is tinned after putting the mask
on PCB .This is done to insulate the patterns and
avoid any short. The mask covers the areas where
the soldering is to be done.
PCB TESTING
PCB is checked for all interconnections
through multimeter , whether the tracks are broken or
short at any place , thereby correction is done through
soldering.
ASSEMBLING OF THE UNIT
Components are assembled in proper direction
and avoid the touching of the components to one
another. Heatsink is to be put wherever required with a
heat sink compound. After assembling the components ,
they are soldered and thereafter cleaned with CTC
liquid.
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TESTING OF THE COMPLETE UNIT
The power is given to the circuit
through the switch and the chain is connected. The
chain is disconnected , the siren starts and continues
to remain on till the power is switched off or for one
hour as set the by monostable multivibrator whichever
is earlier. This process continues as long as power is
given to this device and the chain is broken .If the chain
is not broken the siren is not blown.
Hence the unit is tested and work to our
satisfaction .
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COST ESTIMATE
S.NO
Required Material with full Spec.
Reqd Qty.
Cost /unit
Total Cost
1. Speaker 8 ohm 10 watt 1 50.00 50.00
2. Ckt. assembly casing 1 25.00 25.00
3. The external casing 1 50.00 50.00
4. Diode 5 2.00 10.00
5. Resistor 2 2.00 4.00
6. Potentiometer 1 3.00 3.00
7. Capacitors 220uF/63V 1 25.00 25.00
8. Relay 2 35.00 70.00
9. IC Bases 1 15.00 15.00
10. IC NE555/NE556 2 35.00 70.00
11. IC Regulator 78L15 1 30.00 30.00
12. Chain 1 15.00 15.00
13. Power Switches 1 20.00 20.00
14. Voltage Transformer 1 45.00 45.00
15. Cu Claded board 1 60.00 60.00
16. Etching Solutions ½ Litre 150.00 75.00
17. Dilute HCL ½ Litre 160.00 80.00
18. Insulation Coating 1/4 Litre 60.00 15.00
19. Heat sink for regulator 2 30.00 60.00
20. Soldering Iron 1 45.00 45.00
21. Drilling Machine 1 130.00 130.00
22. Multimeter 1 300.0 300.00
23. Testers 1 15.00 15.00
24. Desoldering Pump 1. 75.00 75.00
25. Fluxes 50 gms 35.00 35.00
26. Soldering lead 50 gms 40.00 40.00
27. Wires 10 Meter 2.00 20.00
TOTAL COST OF THE PROJECT 1382.00
Applications of Rain Alarm Project:
1. In the irrigation, it will detect the rain and immediately
alert the farmer.
2. In automobiles, when the rain detector detects the rain
it will immediately active the wipers and inform to the
driver.
3. In communications, it will boost the power of the
antenna and increase the signal strength to send or
receive the signals.
4. In normal house hold, with the help of rain water
detector we can automatically save the rain water.
(This can be done only when home automation is done
and equipment to save the rain water. In this, rain
water detector will detect the rain and helps to switch
ON the equipment which will automatically save rain
water for different purposes).
5. This can also be used if there is a chemical rain also.
This is very common in industrial areas.
CONCLUSION
With the use of the circuits we can develop
many application and solve our day to day problems. In this
circuit the sound of the siren can be increased by using the
audio power amplifier.
The chain need not be of steel , it can be any thin
wire as well. But we can use the steel chain as well , it will
serve double purpose ,first it is difficult to break secondly if it
broken it will raise the alarm .
We can use this device at many places whether in
traveling or at security of the houses /residential areas.
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REFERENCES
1.Electronic Principle by
Albert Paul Malvino
2.Electronics Devices and circuits by
Allen Mottershead.
3.Digital Computer Fundamentals By
Thomas C.Bartee
4.Digital Principles and Applications By
Albert Paul Malvino and Donold P . Leach
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