project report on automatic rain wiper

Automatic Rain Wiper System

Department of Electronics and Communication Engineering, Lakshmi Narain College of Technology & Science, Bhopal (M P ) 1

CHAPTER-1



CHAPTER-1

INTRODUCTION

1.1 Introduction

A windscreen wiper or windshield wiper is a device used to remove rain, snow, ice and debris

from a windscreen or windshield. Almost all motor vehicles, including cars, trucks, train

locomotives, watercraft with a cabin and some aircraft, are equipped with such wipers, which are

usually a legal requirement. A wiper generally consists of a metal arm, pivoting at one end and

with a long rubber blade attached to the other. The arm is powered by a motor, often an electric

motor, although pneumatic power is also used in some vehicles. The blade is swung back and

forth over the glass, pushing water or other precipitation from its surface. The speed is normally

adjustable, with several continuous speeds and often one or more "intermittent" settings. Most

automobiles use two synchronized radial type arms, while many commercial vehicles use one or

more pantograph arms.

Wipers may be powered by a variety of means, although most in use today are powered by an

electric motor through a series of mechanical components, typically two 4-bar linkages in series

or parallel.

So here we propose an automatic wiper system that automatically switches ON on detecting rain

and stops when rain stops. Our project brings forward this system to automate the wiper system

having no need for manual intervention. For this purpose we use rain sensor along with 555

timer and transistor to drive the wiper motor. Our system uses rain sensor to detect rain, this

signal is then processed by 555 timer and take the desired action. The rain sensor works on the

principle of using water for completing its circuit, so when rain falls on it it’s circuit gets

completed and sends out a signal to 555 timer IC and drive the motor to simulate car wiper

action.

systems become an even more appealing feature, as they work to minimize the time the driver

must take his/her hands off the wheel. These systems detect droplets of rain on the windshield

and automatically turn on and adjust the wiper system in accordance to the level of precipitation.

Current rain-sensing systems use an optical sensor to detect the presence of water on the

windshield, and relay wiper control data to the vehicle's body control module (BCM).

Unfortunately, these optical rain sensors suffer from a small sensing area, are prone to false-



positives, and are too expensive to be included as standard equipment in most vehicles.Over the

past two decades, the automotive industry has aggressively researched ways to exploit

modern computing and electronic advances in the development of safety, reliability, and

entertainment technologies. Despite this, automatic rain-sensing wiper systems are relatively

uncommon in modern vehicles for a number of reasons. They are often too expensive, too

unsightly, or too unreliable to be desired in new automobiles. Many attempts have been made

at constructing an effective, reliable, and cheap rain detection and wiper control system for

vehicles speed and intermittent interval automatically according to the amount of rain. To

measure the amount of water usually use optical sensor. In this type of sensors uses the fact that

the refraction angle and the amount of reflection of the light are different when the 2

windshield is wet. Even though optical sensors are used widely they have some disadvantage.

One of disadvantages is the sensitivity to external light. Another problem is occurs when car

drive at night or gone through tunnel and even in underground parking. For this many systems

still activate the wiper when the car comes out of tunnels or underground parking lot.

Another shortfall, maybe a major one is that the sensing area is a relatively small portion of

windshield. Hence the system operates only with limited area.

Figure 1.1 A view of Automatic Wiper

1.2 Incentivation

It is with great pleasure that we are here, being given a chance to create something that has

the potential to help people. Thanks to Electronics & Communication Department of

Laksmi Narain College of Technology & Science, Bhopal have been able to pull together



a talented team to build and test our idea. We are a team that is passionate about creativity

and passionate about creating innovative solutions that help people to help themselves.

Nowadays most of the things in this world are electronically operated and are based on

automation system. People always want something in which no manual work is involved

so this system is mainly designed to operate automatically and this was the prima focus of

our project that has enabled us to make this innovation which is also having a handful of

future scope

1.3 Objective

To build a system which would wipe out the rain from any shield with minimum man

power having handful of systems automatically operated and reduce the cost of previously

used automatic wiper system and make it available for common man.



CHAPTER-2



CHAPTER-2

THEORY

2.1 Automatic Rain Wiper

Vehicles are now available with driver-programmable intelligent (automatic) windscreen

wipers that detect the presence and amount of rain using a rain sensor. The sensor

automatically adjusts the speed of the blades according to the amount of rain detected. Rain-

sensing windscreen wipers appeared on various models in the late 20th century, one of

the first being Nissan's 200SX/Silvia. As of early 2006, rain-sensing wipers are optional

or standard on all Cadillac and most Volkswagen, and are available on many other main-

stream manufacturers.

2.2 Why Automatic Wiper

In the present automobiles the number of facilities is much higher. The driver has to

concentrate on road while driving, and with increased traffic, things get frustrating. The

features in the car like GPRS to trace the route, music system, air condition system etc may

drive away the attention of the driver. Thus an effort has been made to reduce the effort

put by driver in controlling the speed of the wiper and put more concentration on his driving.

Since this system is put into use in many higher end cars and has been successfully working,

an effort was made to reduce the cost of the system so that this system can be

implemented in common economic cars where a common man can also enjoy the benefits. It

was found that the rain sensor is the expensive unit in the present system and an effort is done in

making a sensor which is reasonable by price, the Cup Sensor. The sensing device used here is

basically a conical shaped cup with a tray on the top of the cup to collect maximum

possible amount of water. When the rain begins and the visibility to the driver is

reducing, the system has to trigger the wiper to wipe the water on the screen. It can so

happen that the driver feels the need of wiper but because the floater has not reached the

level of the probe the system may not begin its function.

Thus certain conditions were considered and the calculations were carried out for the

placement of the probes at appropriate heights. Also there is a small opening at the bottom of

the cup which eventually drains water from the cup. If the rate of filling is greater than



rate of discharge of rain water than the water level rises to the next probe level and hence the

wiper speed increases.

Figure 2.1 Water Collection In Cup Type Rain Sensor

2.3 Degree of Automation Degrees of automation are of two types

1. Full Automation-In case of full automation, no manual work is required and even power

supply can be operated automatically.

2. Semi Automation-In case of semi automation, not all the operations are operated

automatically. Some operations are handled manually.

Automation can be achieved through computers, hydraulics, pneumatics, robotics, etc., of these

sources, pneumatics form an attractive medium for low cost automation. Automation plays an

important role in automobile.



CHAPTER-3



CHAPTER-3

BLOCK DIAGRAM AND CIRCUIT DIAGRAM

Figure 3.1 Block Diagram

3.1 Block diagram description

3.1.1 Power Supply

The power supply unit is basically a 9V battery which was introduced for the early transistor

radios. It has a rectangular prism shape with rounded edges and a polarized snap connector at the

top. This type is commonly used in walkie talkies, clocks and smoke detectors. They are also

used as backup power to keep the time in certain electronic clocks. This format is commonly

available in primary carbon-zinc and alkaline chemistry, in primary lithium iron disulfide, and in

rechargeable form in nickel-cadmium, nickel-metal hydride and lithium-ion. Mercury oxide

batteries in this form have not been manufactured in many years due to their mercury content.



Figure 3.2 Battery and its Symbol

Most nine-volt alkaline batteries are constructed of six individual 1.5V LR61 cells enclosed in a

wrapper. These cells are slightly smaller than LR8D425 AAAA cells and can be used in their

place for some devices, even though they are 3.5 mm shorter. Carbon-zinc types are made with

six flat cells in a stack, enclosed in a moisture-resistant wrapper to prevent drying. Primary

lithium types are made with 3 cells in series.

3.1.2 Rain Sensor

It consists of zigzag pattern of conductive path printed on pcb. They are electrically isolated and

conducted on rain fall or water fall. The rain sensor module is an easy tool for rain detection. It

can be used as a switch when raindrop falls through the raining board and also for measuring

rainfall intensity. The module features, a rain board and the control board that is separate for

more convenience, power indicator LED and an adjustable sensitivity though a potentiometer.

When connected to 5V power supply, the LED will turn on when induction board has no rain

drop, and DC output is high. When dropping a little amount water, DC output is low.

Figure 3.3 Rain Drop Senser



3.1.3 555 Timer

IC 555 timer is a well-known component in the electronic circles but what is not known to most

of the people is the internal circuitry of the IC and the function of various pins present there in

the IC. Let me tell you a fact about why 555 timer is called so, the timer got its name from the

three 5 kilo-ohm resistor in series employed in the internal circuit of the IC.IC 555 timer is a one

of the most widely used IC in electronics and is used in various electronic circuits for its robust

and stable properties. It works as square-wave form generator with duty cycle varying from 50%

to 100%, Oscillator and can also provide time delay in circuits. The 555 timer got its name from

the three 5k ohm resistor connected in a voltage-divider pattern which is shown in the figure

below. A simplified diagram of the internal circuit is given below for better understanding as the

full internal circuit consists of over more than 16 resistors, 20 transistors, 2 diodes, a flip-flop

and many other circuit components.

3.1.4 Motor Driver

It consists of transistor and DC motor. DC motor simulates the action of car wiper. DC Motors

convert electrical energy (voltage or power source) to mechanical energy (produce rotational

motion). They run on direct current. The Dc motor works on the principle of Lorentz force which

states that when a wire carrying current is placed in a region having magnetic field, than the wire

experiences a force. This Lorentz force provides a torque to the coil to rotate.

A DC motor is any of a class of electrical machines that converts direct current electrical power

into mechanical power. The most common types rely on the forces produced by magnetic fields.

Nearly all types of DC motors have some internal mechanism, either electromechanical or

electronic, to periodically change the direction of current flow in part of the motor. Most types

produce rotary motion; a linear motor directly produces force and motion in a straight line. DC

motors were the first type widely used, since they could be powered from existing direct-current

lighting power distribution systems. A DC motor's speed can be controlled over a wide range,

using either a variable supply voltage or by changing the strength of current in its field windings.

Small DC motors are used in tools, toys, and appliances. The universal motor can operate on

direct current but is a lightweight motor used for portable power tools and appliances. Larger DC

motors are used in propulsion of electric vehicles, elevator and hoists, or in drives for steel

rolling mills.



Figure 3.4 Dc Motor

3.2 Circuit Diagram

Figure 3.5 Circuit Diagram



The main component of this circuit is a 555 timer IC that works in monostable mode. Rain

sensor made of two electrically isolated zig-zag path on PCB. They conducts on rain fall. Rain

sensor is connected between pin 2 of 555 timer and ground. From the working of a monostable

555 timer, initially (no rain) high voltage on pin 2 makes output pin 3 low. On detection of rain a

negative voltage on the trigger pin will cause a high output at pin 3.Output of one shot 555

(monostable) is connected to a transistor TIP122 which drives dc motor. DC motor and a

mechanical assembly simulate the action of car windshield wiper.

The battery supplies the power to the sensor as well as rain operated motor. Wiper motor is

automatically ON during the time of rainfall. The senor is fixed in the vehicle glass. The

conductive (Touch) sensor is used in this project. It senses the rainfall and giving control signal

to the control unit. The control unit activates the wiper motor automatically. This operation is

called “Automatic rain operated wiper”.



CHAPTER-4



CHAPTER-4

CONSTRUCTION AND WORKING

4.1 Construction

Initially the glass is supported between the wooden frames.

A motor is then clamped to the wooden bar by using suitable screws.

A four bar mechanism is responsible for the to and fro motion of the wiper.

One end of the four bar linkage is connected to the motor and other to the wiper.

A 12V battery is used to run the motor.

A conductive rain drop sensor is used.

The control unit is an Attiny-85 AVR microcontroller programmed using ARDUINO as

ISP.

A relay is used in a circuit as a magnetic switch to turn on a second circuit.

Figure 4.1 Circuit Connections

Many attempts have been made at constructing an effective, reliable, and cheap rain

detection and wiper control system for vehicles. A perfect system could subtract one more task

from the driver's workload, and allow them to better keep their eyes on the road and hands on the

wheel during foul weather. Despite this, automatic rain-sensing wiper systems are relatively



uncommon in modern vehicles for a number of reasons. They are often too expensive, too

unsightly, or too unreliable to be desired in new automobiles. While a number of different design

approaches have been made to improve upon these issues, none have been successful enough for

the technology to become widely adapted in new vehicles. By far the most common rain

detection method, and the one currently employed by Hyundai vehicles, is the use of an optical

sensor.

These optical sensors function by transmitting an infrared beam at an angle through the

windshield and measuring the reflection to determine the presence of water. This is a relatively

difficult task, requiring complex circuitry and precision manufacturing. Optical sensors are thus

somewhat expensive and can produce false readings when dirt or other particles on the

windshield cause a reflection mimicking that of rain. Because it relies on an infrared beam for

detection, the optical sensor also suffers from a very small sensing area on the windshield,

limiting its effectiveness in rapidly responding to light rain. In addition, the sensor housing is

physically bulky, reducing its appeal in luxury vehicles. These issues can largely be mitigated by

using a capacitive sensor rather than an optical one. Instead of sending an infrared beam through

the windshield glass, a capacitive sensor works by emitting an electric field which can pass

through the glass to interact with objects resting on it. Because water and other objects such as

dirt or rocks interfere with the electric field in very different ways, the sensor will be less likely

to be fooled if designed correctly. Unlike a standard capacitor, which confines the electric field

lines between two conductors in a tight package, a capacitive sensor allows the field lines 8 to

spread out, and is designed to maximize the fringing of the electric field lines away from the

conductors.

4.2 Working

The battery supplies the power to the sensor as well as rain operated motor. Wiper motor is

automatically ON during the time of rainfall. The senor is fixed in the vehicle glass. The

conductive (Touch) sensor is used in this project. It senses the rainfall and giving control

signal to the control unit. The control unit activates the wiper motor automatically. This

operation is called “Automatic rain operated.



Figure 4.2Working Block Diagram

The 12V battery supplies the power to run the motor and 9V battery is used to run the

sensor.

• Wiper is automatically ON during the time of rainfall.

• The sensor is fixed on the vehicle glass. The conductive sensor is used in this project.

• As soon as the rain drops falls on the sensor it senses and gives a control signal to the

control unit. Then control unit sends signals to the relay, which helps to run the wiper

motor automatically.

• The output of the Rain Drop Sensor goes low when water is detected.

• This output given to pin PB4 of the Attiny-85, it waits till the pin PB4 is driven low and

if so, it sets pin PB0 high.

• The pin PB0 is connected to the base of the NPN transistor (BC548) through a 1k

current limiting resistor, this switches the transistor ON.

• Now that the transistor is ON, the coil of the SPDT Relay is activated.

• This in turn connects the 12V Battery to the motor, switching it ON.



•

CHAPTER-5



CHAPTER-5

PCB DETAILS

5.1 PCB

Printed circuit board is the most common name but may also be called “printed wiring boards”

or “printed wiring cards”. A printed circuit board (PCB) mechanically supports and electrically

connects electronic components using conductive tracks, pads and other features etched from

copper sheets laminated onto a non-conductive substrate. Components – capacitors, resistors or

active devices – are generally soldered on the PCB. Advanced PCBs may contain components

embedded in the substrate.

Figure 5.1 PCB

PCBs can be single sided (one copper layer), double sided (two copper layers) or multi-layer

(outer and inner layers). Conductors on different layers are connected with vias. Multi-layer

PCBs allow for much higher component density.

5.2 Composition

A PCB is sort of like a layer cake or lasagna- there are alternating layers of different materials

which are laminated together with heat and adhesive such that the result is a single object.

5.2.1 FR4

The base material, or substrate, is usually fiberglass. Historically, the most common

designator for this fiberglass is “FR4”.

This solid core gives the PCB its rigidity and thickness. There are also flexible PCBs

built on flexible high-temperature plastic (Kapton or the equivalent).



Cheaper PCBs and perf boards (shown above) will be made with other materials such as

epoxies or phenolics which lack the durability of FR4 but are much less expensive.

5.2.2 Copper

The next layer is a thin copper foil, which is laminated to the board with heat and

adhesive.

On common, double sided PCBs, copper is applied to both sides of the substrate.

In lower cost electronic gadgets the PCB may have copper on only one side.

This can be as few as 1 layer or as many as 16 layers or more.

The copper thickness can vary and is specified by weight, in ounces per square foot. The

vast majority of PCBs have 1 ounce of copper per square foot but some PCBs that handle

very high power may use 2 or 3 ounce copper.

Each ounce per square translates to about 35 micrometers or 1.4 thousandths of an inch of

thickness of copper.

5.2.3 Solder Mask

The layer on top of the copper foil is called the soldermask layer. This layer gives the

PCB its green (or, at SparkFun, red) color.

It is overlaid onto the copper layer to insulate the copper traces from accidental contact

with other metal, solder, or conductive bits.

This layer helps the user to solder to the correct places and prevent solder jumpers.

5.2.4 Silk Screen

The white silkscreen layer is applied on top of the solder mask layer.

The silkscreen adds letters, numbers, and symbols to the PCB that allow for easier

assembly and indicators for humans to better understand the board.

We often use silkscreen labels to indicate what the function of each pin or LED.

Silkscreen is most commonly white but any ink color can be used. Black, gray, red, and

even yellow silkscreen colors are widely available; it is, however, uncommon to see more

than one color on a single board.



5.3 PCB MANUFACTURING PROCESS

5.3.1 PCB Design and Fabrication Process:

The major steps in the PCB design and fabrication process are as follows:

1. Design and test the prototype circuit—by hand;

2. Capture the circuit’s schematic—using OrCAD Capture or similar software;

3. Perform the physical layout of the circuit—using OrCAD Layout or similar software;

4. Fabricate, populate and test the PCB.

Figure 5.2 Flow Chart

5.3.2 Prototyping

With a basic idea in mind, a circuit schematic is developed and analyzed to ensure the desired

functionality and performance. When creating a circuit for PCB production, a designer would

also select specific components at this time. Commonly, the next step is to prototype and to test

the circuit. It is also possible to use the schematic capture software along with related software to

simulate the circuit without building it on a prototyping board.

5.3.3 Schematic Capture



Schematic capture software comes in several forms. Schematic capture allows the PCB designer

to create an electronic schematic. This electronic schematic contains more information than its

paper relatives. For example, every part symbol in Capture contains information telling what

footprint the symbol is associated with. (Footprints are the symbols used in layout software to

define the physical design of each component.)

Capture parts symbols are used in a symbolic manner. Thus, the part symbol on Capture’s screen

does not show what the actual physical component looks like. It does allow the designer to

connect all the components in a circuit and to test the workings of the circuit by exporting files to

other software. For our purpose, Capture provides the starting point for creating a physical layout

in layout software.

5.3.3 Physical Layout

A blueprint of a house tells the size of lumber to use, as well as the dimensions of the living

room wall and the dimensions of the window cut into it. It gives all the physical information

necessary to build the house. Physical layout software can be thought of as a “blueprint” for a

PCB.

There are several programs available for doing physical layout. The basic building blocks used in

Layout are footprints. A footprint contains all the physical dimensions related to a particular part.

For example, a 14-pin dip footprint defines where each of the 14 drill holes are to be located, as

well as associated information, such as text defining the part number of the component.

In Layout the footprints of the various parts are placed and then routed. Routing refers to

defining where the copper interconnects in the circuit will be located. Interconnects are coppe

paths on the surface of the PCB that connect one pin to another. Interconnects are also known a

“routes” or “traces”.

5.3.4 Physical Creation of PCB

PREPARATION OF SCREEN:

Nylon bolting cloth (Silk screen cloth) is stretched and attached to a wooden frame.

Photosensitive chemical (silcot-6) and ammonium bicarbonate is spread on cloth and dried in

total darkness. The screen is exposed to UV light and is developed in water.



PRINTING:

The screen is placed on suitable copper laminated sheet on copper side and circuit black printing

ink (acid resistant paint) is spread on it. After printing the PCB should be allowed to dry for at

least 10 hrs. in a dust proof chamber.

ETCHING:

The removal of excess copper on the copper laminated PCB apart from the printed circuit is

known as etching. Generally PCB is placed in F3C13 solution and kept for one hour.

DRILLING:

Under this operation drilling should be done as per circuit lay with the suitable drill and high

speed machine. Drilling should always be done from copper side to avoid possibility of coming

out of copper circuit and chipping out of Bakelite.

GREEN MAKING:

It is done with special epoxy paint and special thinner is requited for cleaning the screen. It

provides as better and also prevents frequency overlapping between the tacks at high frequency

operation.

TINNING:

It is an electroplating process (tin plating) done to increases the conductivity of the conducting

medium and to avoid oxidizing effect.

COMPONENT MOUNTING:

All components are mounted at their respective position as per the components layout. Proper

precautions should be taken during mounting process.

SOLDERING:

Soldering is a process in which two or more metal items are joined together by melting and

flowing a filler metal (solder) into the joint, the filler metal having a lower melting point than the

workpiece.

A soldered connection ensures metal continuity. The soldering process involves: Melting of the

flux which in turn removes the oxide films on the metal to be soldered. Melting the solder which



removes the impurities. The solder partially dissolve of the metal in the connection. The solder

cools and fuses wit the metal.

The soldering techniques involve knowledge of:

Soldering iron

Soldering wire

Soldering procedure

Replacing components

Knowledge of good and bad soldering joints.

Disordering techniques

Soldering iron is an essential tool for soldering. A. Soldering iron should give

sufficient heat a melt solder by heat transfer when the iron tip is applied to a

connection to be soldered. The selection of the soldering iron can be made as regard

to its tips size shape and wattage.

The soldering material is used to join together two or more metals at temperatures

below their melting point. The solder alloy consists of Lead (37%) and Tin (63%).

The continuous connection between two metal joint is made by solder materials.

Flux is a material used to aid soldering process. Flux is needed to scratch away the

small film of oxide on the surface of metals to be soldered.

5.3.5 SOLDERING PROCEDURE

The soldering procedure involves selection of soldering iron cleaning of components to be

soldered and cleaning of the PCB to be soldered. The soldering iron should be selected according

to the job and should be powerful enough to provide heat. The tip of the soldering iron should be

selected as per the space available for soldering. The component that has to be soldered should

be properly bent and its leads should properly inserted in the PCB. Before. If one has already

identified the fault component, then one should not try to remove or desolder the component.

The components should simply be cut and taken out.



5.3.6 REPLACEMENT OF COMPONENT

In case of single sided PCB, the component to be removed can be disordered with the help of

iron and flux. The only precaution that has to be taken is that track should not break while

removing. In case of Through Hole PCB, care has the to be taken so that component while

removing does not damaged the Through Hole. In this case the component is soldered on one

side and the lead flows through the hole to the other sides, so disordering and removing becomes

very difficult and required practice.

Figure 5.3 PCB layout



CHAPTER-6



CHAPTER-6

COMPONENTS DESCRIPTION

6.1 COMPONENT LIST

Ref Value Item count

BT1 +9V 1

BT2 BATTERY 4V 1

C1 .1uF 1

C2 100Uf 1

P1 CONN_2 1

P2 Motor 1

Q1 TIP122 1

R1 1M 1

R2 100k 1

U1 LM555N 1

PB PCB (4 X4) 1

Table 6.1

6.2 COMPONENT DESCRIPTION

6.2.1 RESISTOR

Resistors are electronic components which have a specific, never-changing electrical resistance.

The resistor’s resistance limits the flow of electrons through a circuit.They are passive

components, meaning they only consume power (and can’t generate it). Resistors are usually

added to circuits where they complement active components like op-amps, microcontrollers, and

other integrated circuits. Commonly resistors are used to limit current, divide voltages, and pull-

up I/O lines.

Resistor units



The electrical resistance of a resistor is measured in ohms. The symbol for an ohm is the greek

capital-omega: Ω. The (somewhat roundabout) definition of 1Ω is the resistance between two

points where 1 volt (1V) of applied potential energy will push 1 ampere (1A) of current.

Schematic idea

All resistors have two terminals, one connection on each end of the resistor. When modeled on a

schematic, a resistor will show up as one of these two symbols:Resistors come in a variety of

shapes and sizes. They might be through-hole or surface-mount. They might be a standard, static

resistor, a pack of resistors, or a special variable resistor

Resistors will come in one of two termination-types: through-hole or surface-mount. These types

of resistors are usually abbreviated as either PTH (plated through-hole) or SMD/SMT (surface-

mount technology or device).Through-hole resistors come with long, pliable leads which can be

stuck into a breadboard or hand-soldered into a prototyping board or printed circuit board (PCB).

These resistors are usually more useful in breadboarding, prototyping, or in any case where

you’d rather not solder tiny, little 0.6mm-long SMD resistors. The long leads usually require

trimming, and these resistors are bound to take up much more space than their surface-mount

counterparts.

The most common through-hole resistors come in an axial package. The size of an axial resistor

is relative to its power rating. A common ½W resistor measures about 9.2mm across, while a

smaller ¼W resistor is about 6.3mm long. Surface-mount resistors are usually tiny black

rectangles, terminated on either side with even smaller, shiny, silver, conductive edges. These

resistors are intended to sit on top of PCBs, where they’re soldered onto mating landing pads.

Because these resistors are so small, they’re usually set into place by a robot, and sent through an

oven where solder melts and holds them in place.

Resistor composition

Resistors can be constructed out of a variety of materials. Most common, modern resistors are

made out of either a carbon, metal, or metal-oxide film. In these resistors, a thin film of

conductive (though still resistive) material is wrapped in a helix around and covered by an

insulating material. Most of the standard, no-frills, through-hole resistors will come in a carbon-

film or metal-film composition.



Figure 6.2 Resistor

Other through-hole resistors might be wire wound or made of super-thin metallic foil. These

resistors are usually more expensive, higher-end components specifically chosen for their unique

characteristics like a higher power-rating, or maximum temperature range.

Surface-mount resistors are usually either thick or thin-film variety. Thick-film is usually

cheaper but less precise than thin. In both resistor types, a small film of resistive metal alloy is

sandwiched between a ceramic base and glass/epoxy coating, and then connected to the

terminating conductive edges.

Resistor Markings

Though they may not display their value outright, most resistors are marked to show what their

resistance is. PTH resistors use a color-coding system (which really adds some flair to circuits),

and SMD resistors have their own value-marking system.\Through-hole, axial resistors usually

use the color-band system to display their value. Most of these resistors will have four bands of

color circling the resistor.

The first two bands indicate the two most-significant digits of the resistor’s value. The third band

is a weight value, which multiplies the two significant digits by a power of ten. The final band

indicates the tolerance of the resistor. The tolerance explains how much more or less the actual

resistance of the resistor can be compared to what its nominal value is. No resistor is made to

perfection, and different manufacturing processes will result in better or worse tolerances. For

example, a 1kΩ resistor with 5% tolerance could actually be anywhere between 0.95kΩ and

1.05kΩ.



Figure 6.3 Resistor color coding

Power Rating

The power rating of a resistor is one of the more hidden values. Nevertheless it can be important,

and it’s a topic that’ll come up when selecting a resistor type.Power is the rate at which energy is

transformed into something else. It’s calculated by multiplying the voltage difference across two

points by the current running between them, and is measured in units of a watt (W). Every

resistor has a specific maximum power rating. In order to keep the resistor from heating up too

much, it’s important to make sure the power across a resistor is kept under it’s maximum rating.

The power rating of a resistor is measured in watts, and it’s usually somewhere between ⅛W

(0.125W) and 1W. Resistors with power ratings of more than 1W are usually referred to as

power resistors, and are used specifically for their power dissipating abilities.Finding a resistor’s

power rating

A resistor’s power rating can usually be deduced by observing its package size. Standard

through-hole resistors usually come with ¼W or ½W ratings. More special purpose, power

resistors might actually list their power rating on the resistor.



6.2.2 VARIABLE RESISTOR

A variable resistor is a device that is used to change the resistance according to our needs in an

electronic circuit. It can be used as a three terminal as well as a two terminal device. Mostly they

are used as a three terminal device. Variable resistors are mostly used for device calibration.

There resistor, like fixed resistor, are used to control flow and provide desired amounts of

voltage in electric circuits. But unlike fixed resistors, the resistance value of variable linear

resistors can be varied from 0 to a specified value.

Figure 6.4 Variable Resistor

Working of Variable Resistor

A variable resistor consists of a track which provides the resistance path. Two terminals of the

device are connected to both the ends of the track. The third terminal is connected to a wiper that

decides the motion of the track. The motion of the wiper through the track helps in increasing

and decreasing the resistance.The track is usually made of a mixture of ceramic and metal or can

be made of carbon as well. As a resistive material is needed, carbon film type variable resistors

are mostly used. They find applications in radio receiver circuits, audio amplifier circuits and TV

receivers. For applications of small resistances, the resistance track may just be a coil of wire.

The track can be in both the rotary as well as straight versions. In a rotary track some of them

may include a switch. The switch will have an operating shaft which can be easily moved in the

axial direction with one of its ends moving from the body of variable resistor switch.



The rotary track resistor with has two applications. One is to change the resistance. The switch

mechanism is used for the electric contact and non-contact by on/off operation of the switch.

There are switch mechanism variable resistors with annular cross-section which are used for the

control of equipments. Even more components are added onto this type of a variable resistor so

as to make them compatible for complicated electronic circuits. A high-voltage variable resistor

such as a focus pack is an example. This device is capable of producing a variable focus voltage

as well as a screen voltage. It is also connected to a variable resistance circuit and also a fixed

resistance circuit [bleeder resistor] to bring a change in the applied voltage. For this both the

fixed and variable resistor are connected in series.

A track made in a straight path is called a slider. As the position of a slider cannot be seen or

confirmed according to the adjustment of resistance, a stopping mechanism is usually included to

prevent the hazards caused due to over rotation.

The variable resistors are of the following three types.

Figure 6.6 Types of Rheostat

1.Variable wire-wound

There resistor are made in chrome wire wound on a ceramic core and covered with an isolative

coating. An adjustable tap b rides the exposed wire which makes electrical contact with the wire

2. Potentiometer



Its outer terminals are fixed and the middle terminal is variable. The variation is provided by a

wiper connected to a control shaft. When a control shaft is moved, the wiper moves over a

resistive element. This movement provides a continuous variation in resistance between the

middle terminal and either outside terminal.

3. Trimmer

These are used in electronic circuits to trim the circuit to the required operating conditions by

inserting a small screw driver into a slot and turning one or more times.The materials used in the

construction of a trimmer are carbon composition, carbon film cermet and wire. The trimmers

are available for resistance values ranging from 50 to 5M \, with a power rating from 1/4 to

3/4 watt.

6.2.3 CAPACITOR

A capacitor (originally known as a condenser) is a passive two-terminal electrical component

used to temporarily store electrical energy in an electric field is composed of two parallel

conducting plates separated by non-conducting region that is called dielectric, such as vacuum,

ceramic, air, aluminum, etc. The capacitance formula of the capacitor is represented by,

Figure 6.7 Capacitor

C is the capacitance that is proportional to the area of the two conducting plates (A) and

proportional with the permittivity ε of the dielectric medium. The capacitance decreases with the

distance between plates (d). We get the greatest capacitance with a large area of plates separated

by a small distance and located in a high permittivity material. The standard unit of capacitance

is Farad, most commonly it can be found in micro-farads, pico-farads and nano-farads.



Capacitor Symbol:

Figure 6.8 Symbol

Unit:

Capacitance is measured in units called farads. The farad is extremely large unit and capacitors

used in modern electronic circuits are only minute fraction of farad. Three prefixes (multipliers)

are used, µ (micro), n (nano) and p (pico):

µ means 10-6 (millionth), so 1000000µF = 1F

n means 10-9 (thousand-millionth), so 1000nF = 1µF

p means 10-12 (million-millionth), so 1000pF = 1nF

Capacitor Categories:

Table no 6.3 Cap Category

6.2.4 Types of Capacitors:

Paper Capacitor

It is one of the simple forms of capacitors. Here, a waxed paper is sandwiched between two

aluminium foils. Process of making this capacitor is quite simple. Take place of aluminium foil.

Cover this foil with a waxed paper. Now, cover this waxed paper with another aluminium foil.

Then roll up this whole thing as a cylinder. Put two metal caps at both ends of roll. This whole

assembly is then encapsulated in a case. By rolling up, we make quite a large cross-sectional area

of capacitor assembled in a reasonably smaller space.

Based on Polarity Polarized and Non Polarized

Based on Material Electrolyte and Non Electrolyte

Based on Shape Axial and Radial

Based on Value Fixed and Variable



Figure 6.9 Aluminum foil

Air Capacitor

There are two sets of parallel plates. One set of plates is fixed and another set of plates is

movable. When the knob connected with the capacitor is rotated, the movable set of plates

rotates and overlapping area as between fixed and movable plates vary. This causes variation in

effective cross-sectional areas of the capacitor. Consequently, the capacitance varies when one

rotates the knob attached to the air capacitor. This type of capacitor is generally used to tune the

bandwidth of a radio receiver.

Plastic Capacitor

When various plastic materials are used as dielectric material, the capacitors are said to be plastic

capacitors. The plastic material may be of polyester, polystyrene, polycarbonate or poly

propylene. Each of these materials has slightly different electrical characteristics, which can be

used to advantage, depending upon the proposed application. This type of capacitors is

constructional, more or less same as paper capacitor. That means, a thin sheet one of the earlier

mentioned plastic dielectrics, is kept between two aluminium foils. That means, here the flexible

thin plastic sheet is used as dielectric instead of waxed paper. Here, the plastic sheet covered by

aluminium foil from two sides, is first rolled up, then fitted with metal end caps, and then the

whole assembly is encapsulated in a case.

Plastic Film Capacitor

Plastic capacitor can be made also in form of film capacitor. Here, thin strips or films of plastic

are kept inside metallic strips.



Figure 6.10 Plastic capacitor

Each metallic strip is connected to side metallic contact layer alternatively; as shown in the

figure below. That means, if one metallic strip is connected to left side contact layer, then the

very next is connected to right side contact layer. And there are plastic films in between these

metallic strips. The terminals of this type of capacitors are also connected to side contact layer

and whole assembly is covered with insulated non metallic cover as shown.

Silvered Mica Capacitor

A silvered mica capacitor is very accurate and reliable capacitor. This type of capacitors has very

low tolerance. But on the other hand, cost of this capacitor is quite higher compared to other

available capacitors in the market. But this high cost capacitor can easily be compensated by its

high quality and performance. A small ceramic disc or cylinder is coated by silver compound.

Here, electrical terminal is affixed on the silver coating and the whole assembly is encapsulated

in a casing.

Ceramic Capacitor

Construction of ceramic capacitor is quite simple. Here, one thin ceramic disc is placed between

two metal discs and terminals are soldered to the metal discs.

Mixed Dielectric Capacitor

The way of constructing this capacitor is same as paper capacitor. Here, instead of moving

waxed paper as dielectric, paper impregnated with polyester is used as dielectric between two

conductive aluminium foils.

Electrolyte Capacitor



Very large value of capacitance can be achieved by this type of capacitor. But working voltage

level of this electrolyte capacitor is low and it also suffers from high leakage current. The main

disadvantage of this capacitor is that, due to the use of electrolyte, the capacitor is polarized. The

polarities are marked against the terminals with + and – sign and the capacitor must be connected

to the circuit in proper polarity.

Figure 6.11 Electrolytic Capacitor

A few micro meter thick aluminium oxide or tantalum oxide film is used as dielectric of

electrolyte capacitor. As this dielectric is so thin, the capacitance of this type of capacitor is very

high. This is because; the capacitance is inversely proportional to thickness of the dielectric. Thin

dielectric obviously increases the capacitance value but at the same time, it reduces working

voltage of the device. Tantalum type capacitors are usually much smaller in size than the

aluminium type capacitors of same capacitance value. That is why, for very high value of

capacitance, aluminium type electrolyte capacitors do not get used generally. In that case,

tantalum type electrolyte capacitors get used.

Aluminium electrolyte capacitor is formed by a paper impregnated with an electrolyte and two

sheets of aluminium. These two sheets of aluminium are separated by the paper impregnated

with electrolyte. The whole assembly is then rolled up in a cylindrical form, just like a simple

paper capacitor. This roll is then placed inside a hermetically sealed aluminium canister. The

oxide layer is formed by passing a charging current through the device, and it is the polarity of

this charging process that determines the resulting terminal polarity that must be subsequently

observed. If the opposite polarity is applied to the capacitor, the oxide layer is destroyed.



Table 6.4 Cap Types

6.2.4 TRANSISTOR

A transistor is a semiconductor device used to amplify or switch electronic signals and electrical

power. It is composed of semiconductor material usually with at least three terminals for

connection to an external circuit. A voltage or current applied to one pair of the transistor's

terminals changes the current through another pair of terminals. Because the controlled (output)

power can be higher than the controlling (input) power, a transistor can amplify a signal. Today,

some transistors are packaged individually, but many more are found embedded in integrated

circuits.Transistors are fundamentally three-terminal devices. On a bi-polar junction transistor

(BJT), those pins are labeled collector (C), base (B), and emitter (E).

Figure 6.12 Transistor Symbol



TIP122

The Darlington NPN Bipolar Power Transistor is designed for general-purpose amplifier and

low-speed switching applications.

Features

1. Collector-Emitter Volt (Vceo): 100V

2. Collector-Base Volt (Vcbo): 100V

3. Collector Current (Ic): 5.0A

4. hfe: 1,000 @ 500mA

5. Power Dissipation (Ptot): 65W

6. Type: NPN

6.2.5 555:-

IC 555 timer is a well-known component in the electronic circles but what is not known to most

of the people is the internal circuitry of the IC and the function of various pins present there in

the IC. Let me tell you a fact about why 555 timer is called so, the timer got its name from the

three 5 kilo-ohm resistor in series employed in the internal circuit of the IC.

IC 555 timer is a one of the most widely used IC in electronics and is used in various electronic

circuits for its robust and stable properties. It works as square-wave form generator with duty

cycle varying from 50% to 100%, Oscillator and can also provide time delay in circuits. The 555

timer got its name from the three 5k ohm resistor connected in a voltage-divider pattern which is

shown in the figure below. A simplified diagram of the internal circuit is given below for better

understanding as the full internal circuit consists of over more than 16 resistors, 20 transistors, 2

diodes, a flip-flop and many other circuit components. The Comparator are the basic electronic

component which compares the two input voltages i.e. between the inverting (-) and the non-

inverting (+) input and if the non-inverting input is more than the inverting input then the output

of the comparator is high. Also the input resistance of an ideal comparator is infinite.

Voltage Divider: As we know that the input resistance of the comparators is infinite hence the

input voltage is divided equally between the three resistors. The value being Vin/3 across each

resistor.



Flip/Flop: Flip/Flop is a memory element of Digital-electronics. The output (Q) of the flip/flop is

‘high’ if the input at ‘S’ terminal is ‘high’ and ‘R’ is at ‘Low’ and the output (Q) is ‘low’ when

the input at ‘S’ is ‘low’ and at ‘R’ is high.

Figure 6.13 Pin diagram

6.2.6 Pin functions

1. Ground: This pin is used to provide a zero voltage rail to the Integrated circuit to divide the

supply potential between the three resistors shown in the diagram.

2. Trigger: As we can see that the voltage at the non-inverting end of the comparator is Vin/3, so

if the trigger input is used to set the output of the F/F to ‘high’ state by applying a voltage equal

to or less than Vin/3 or any negative pulse, as the voltage at the non-inverting end of the

comparator is Vin/3.

3. Output: It is the output pin of the IC, connected to the Q’ (Q-bar) of the F/F with an inverter in

between as show in the figure.

4. Reset: This pin is used to reset the output of the F/F regardless of the initial condition of the

F/F and also it is an active low Pin so it connected to ‘high’ state to avoid any noise interference,

unless a reset operation is required. So most of the time it is connected to the Supply voltage as

shown in the figure.



5. Control Voltage: As we can see that the pin 5 is connected to the inverting input having a

voltage level of (2/3) Vin. It is used to override the inverting voltage to change the width of the

output signal irrespective of the RC timing network.

6. Threshold: The pin is connected to the non-inverting input of the first comparator. The output

of the comparator will be high when the threshold voltage will be more than (2/3) Vin thus

resetting the output (Q) of the F/F from ‘high’ to ‘low’.

7. Discharge: This pin is used to discharge the timing capacitors (capacitors involved in the

external circuit to make the IC behave as a square wave generator) to ground when the output of

Pin 3 is switched to ‘low’.

8. Supply: This pin is used to provide the IC with the supply voltage for the functioning and

carrying of the different operations to be fulfilled with the 555 timer.

6.2.7 Connector

The battery has both terminals in a snap connector on one end. The smaller circular (male)

terminal is positive, and the larger hexagonal or octagonal (female) terminal is the negative

contact.

Figure 6.14 Connector

The connectors on the battery are the same as on the connector itself; the smaller one connects to

the larger one and vice versa. The same snap-style connector is used on other battery types in the

Power Pack (PP) series. Battery polarization is normally obvious since mechanical connection is

usually only possible in one configuration. A problem with this style of connector is that it is

very easy to connect two batteries together in a short circuit, which quickly discharges batteries,

generating heat and possibly a fire.



Because of this hazard, 9-volt batteries should be kept in the original packaging until they are

going to be used. An advantage is that several nine-volt batteries can be connected to each other

in series to provide higher voltages.



CHAPTER-7



CHAPTER-7

ADVANTAGES AND LIMITATIONS

7.1 Advantages

1. It can be easily and quickly installed in automobiles.

2. Low Power consumption

3. Simple and Portable

4. Easy to implement

5. Cost Effective

7.2 limitations

1. It is relatively uncommon.

2. It is a small circuit.

3. Sensitive to external light

4. It is totally dependent on timer circuit.



CHAPTER-8



CHAPTER-8

APPLICATIONS

1. This small circuit finds numerous applications.

2. Useful to vehicles.

3. It can be implemented at house window for cleaning.

4. A slight modification in it leads to a better cleaning system.

5. Prevents glass shield or bars from getting corroded.



CHAPTER-9



CHAPTER-9

FUTURE SCOPE

Using more appropriate rain senor we can make more precise automatic wiper system. By adding

microcontroller based system we can implement some security features for automobiles. Using

micro controller can make this project more effective as it will enable the wiper rotate through

180 angle rather than 360. We can use a capacitive sensor which will enable it work along line of

sight. The speed controlling mechanism can be added in this project which will make it work

according to the intensity and speed of water coming on the sensor.



CHAPTER-10



CHAPTER-10

COST OF PROJECT

SNO. COMPONENT QUANTITY COST

1 POWER SUPPLY 2 150

2 CAPACITOR 2 50

3 RESISTOR 2 15

4 TRANSISTOR 1 40

5 MOTOR 1 40

6 CONNECTOR 2 25

7 LM555N IC 1 40

8 RAIN SENSORS 1 150

9 PCB(4 X4) 1 150

10 RHEOSTAT 1 40

Total cost-700



CHAPTER-11



CHAPTER-11

CONCLUSION

As almost everything described already for this design, we would like to say there are still

numerous kinds of enhancements one can implement on this project to make it even more

convenient. The project we have made and presented is quite efficient and it is cost effective

also. It has great advantage of over the optical sensor covering all the design specifications

together with the requirements of common man. The speed controlling mechanism can be added

in this project which will make it work according to the intensity and speed of water coming on

the sensor. The basic maneuvering is done only to make it cost effective and reliable.



REFERENCES

1. http://www.ece.rutgers.edu/sites/default/files/capstone13

2. http://www.electronicshub.org

3. https://www.eeweb.com/project/automatic /wiper

4. http://www.projectsof8051.com/projects/1105-automatic rain wiper.pdf

5. http://www.pcb.electrosoft-engineering.com/04-articles-custom-system-design-and-pcb

6. https://www.elprocus.com

project report on automatic rain wiper

Engineering

Transcript of project report on automatic rain wiper