PC BASED TESTING OF MULTI-TURN POTENTIOMETER USING MICROCONTROLLER

A PROJECT REPORT

Submitted by

ABHILASH DAS

CHITANSHU CHAUHAN

In fulfillment for the award of the degree

Of

BACHELOR OF ENGINEERING

In

ELECTRONICS AND COMMUNICATION ENGINEERING

ENGINEERING COLLEGE, TUWA

GUJARAT TECHNOLOGICAL UNIVERSITY, AHMEDABAD

November, 2012-13

ENGINEERING COLLEGE, TUWA

ELECTRONICS AND COMMUNICATION ENGINEERING

E.C.TPage 1

ACKNOWLEDGEMENT

We sincerely express our deep sense of gratitude and regards to Prof. Jayesh Gandhi (External

Guide, Department of Electronics) for their invariable guidance and constant encouragement in

successfully completing the project. We express our thankfulness to Prof. Dinesh Nagar (Head,

Department of Electronics Engg.) and Prof. Pragnesh Patel(Assistant professor, Department of

Electronics Engg.)for his kind support and help.

We are also thankful to all of them who gave us unconditional support and help during the

preparation of this project.

Abhilash Das(090550111049)

Chitanshu Chauhan(090550111050)

E.C.TPage 2

GUJARAT TECHNOLOGICAL ENGINEERING COLLEGE OF UNIVERSITY COLLEGE, TUWA

CERTIFICATE

This is to certify that the project report entitled “PC BASED TESTING OF

MULTI-TURN POTENTIOMETER USING MICROCONTROLLER”

submitted by ABHILASH DAS AND CHITANSHU CHAUHAN to the

department of ELECTRONICS ENGINEERING, ENGINEERING

COLLEGE , TUWA affiliated by GUJARAT TECHNOLOGICAL

UNIVERSITY partial fulfillment of the requirement for the award of the degree of

“Bachelor of Engineering” in ELECTRONICS ENGINEERING is a bonafide

record of work carried out by them, in 2013, End Semester, under our supervision

and guidance.

Prof. Dinesh Nagar Prof. Jayesh Gandhi Prof. Pragnesh Patel

(Head of Department) (Associate Professor) (Assistant Professor)

E.C.TPage 3

ABSTRACT

Potentiometers are used extensively in many applications such as in lab

experiment, regulators, joy-sticks, etc. Now days there are many companies

manufacturing potentiometers. Various types of potentiometers are available in

market for various usages. Now any company or industry tends to test its product

before launching it in the market. Even they pass a limited number of products to

their fixed users for feedback. Our project is based on the actual testing of

potentiometer so as to check if the potentiometer is working properly or not. If it is

not working properly then the R&D Dept. will rectify the problem and this process

is repeated until the product gives perfect readings.

E.C.TPage 4

TABLE OF CONTENTS

CHAPTER 1

INTRODUCTION……………………………………...............................11

CHAPTER 2

BLOCK DIAGRAM…………………..……….……………………….…14

CHAPTER 3

CIRCUIT DIAGRAM…………………...…...............................................15

CHAPTER 4

POTENTIOMETER

4.1 What Is Potentiomete……………….……………………………..…18

4.2 Construction Of Potentiometer………..…………………………….19

4.3 Working Of Potentiometer……………..…………………………....21

4.3.1 How To Read One……………….……………………………21

4.3.2 Theory Of Operation…………….……………………………22

4.4 Potentiometer Application……………….……………………………24

CHAPTER 5

ARDUINO

5.1 What Is Arduino?................................... ...........................................28

5.2 History………………………………………………….…………...30

5.3 Hardware Description…………..…………………..........................30

5.4 Arduino Board Model……………………………………………....31

E.C.TPage 5

5.5 Arduino Software………………………..…….................................31

5.6 Project Oriented Application…………………………..………..…..33

CHAPTER 6

STEPPER MOTOR

6.1 Introduction & Working……………………………..…………..…35

CHAPTER 7

L293D

7.1 Moter driver……………………………………................................39

7.1.1 Specification……………………………….............................39

7.2 Role Of L293D………………………………...……………………40

7.3 Working Theory Of H-Bridge………………...…………………….42

7.4 Speed Control Using AWM………………...……………………....43

CHAPTER 8

RS-232

8.1 Introduction Of RS-232………………..……….……...…………...45

8.2 RS-232 Specification………………..…….…………….………....46

CHAPTER 9

PYTHON SOFTWEAR

9.1 Introduction of Python……………..……………………...………..49

9.2 Python Program……………………………………………...……..50

CHAPTER 10

PCB

E.C.TPage 6

10.1 Introduction…………………….………………………...……….54

10.2 Constraction………………………………………………….……57

Literature Survey……………………………….……………………………59

E.C.TPage 7

LIST OF FIGURES

Fig 2.1 Block Diagram …….…………………….……………….……………...14

Fig 3.1 Circuit Diagram ……….…………………………………........................16

Fig. 4.1 Potentiometer………………………………………….…….……...…..19

Fig. 4.2 Small Potentiometer………………………………………….…………19

Fig. 4.3 Construction………………………………………………….………...22

Fig. 4.4 Measuring Potentiometer…………………………………….………...22

Fig. 4.5 Linear Potentiometer………………………………………….…….….25

Fig. 5.1 Arduino MEGA Development………………………………….….…..29

Fig. 5.2 Arduino UNO Device…………………………………………….…....29

Fig. 5.3 Arduino Programming Environment…………………………….........32

Fig. 6.1 Construction Of Stepper Motor…………………….…………….……36

Fig. 6.2 Stepper Motor…………………………………………………….…....36

Fig. 6.3 Actual Potentiometer Mounted on Stepper motor………………..……37

Fig. 6.4 Actual Stepper Motor…………………………………………….…….37

Fig. 7.1 Motor Driver Circuit…………………………………………………..40

Fig. 7.2 L293D Pin Diagram……………………………………........................41

Fig. 7.3 Connection Diagram Of L293D…………………………………….....41

Fig. 7.4 H-Bridge Circuit…………………………………………………….....42

Fig. 8.1 RS-232 Pin Diagram…………………………………………….….....45

Fig. 9.1 Copper Clade…………………………………………….....................50

E.C.TPage 8

Fig 9.2 PCB Sink In FeCl3 Solution………………………………..………….51

Fig 9.3 Drilling Machine And Setup……………………………………….......52

Fig 10.1 Flowchart………………………………………………………………58

E.C.TPage 9

LIST OF TABLES

Table 5.1………………………………………………………………………….28

Table 7.1………………………………………………………………………….37

E.C.TPage 10

CHAPTER 1

INTRODUCTION

E.C.TPage 11

CHAPTER 1

INTRODUCTION:

Potentiometers are now a days used extensively in many applications such

as regulators, joy-sticks, etc. Some years even they were even used in television.

Various parts of TV were using potentiometers for manipulating various functions.

Even they are used transducers such as gaming joy-sticks for controlling motions

both virtually and really. In industries, potentiometers are tested before launching

and their various kinds of linearity’s are measured so as to find the accuracy and

increase the work performance of the device. This is most important advantage of

TESTING the pot. Many sensors use pot. and that is the main reason to check its

accuracy and linearity and make it maximum.

E.C.TPage 12

CHAPTER 2

BLOCK DIAGRAM

E.C.TPage 13

BLOCK DIAGRAM

Fig 2.1 Block diagram

E.C.TPage 14

RS232

PCL293

CHAPTER 3

CIRCUIT DIAGRAM

CIRCUIT DIAGRAM

E.C.TPage 15

E.C.TPage 16

CHAPTER 4

POTENTIOMETER

POTENTIOMETER

E.C.TPage 17

4.1 What is Potetiometer

4.2 Construction of Potentiometer

4.3 Working of Potentiometer

4.3.1 How to Read One

4.3.2 Theory of Operation

4.4 Potentiometer Application

What is a potentiometer?

A potentiometer, informally a pot, is a three-terminal resistor with a sliding contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat.

A potentiometer measuring instrument is essentially a voltage divider used for measuring electric potential (voltage); the component is an implementation of the same principle, hence its name.

Potentiometers are commonly used to control electrical devices such as volume controls on audio equipment. Potentiometers operated by a mechanism can be used as position transducers, for example, in a joystick. Potentiometers are rarely used to directly control significant power (more than a watt), since the power dissipated in the potentiometer would be comparable to the power in the controlled load.

E.C.TPage 18

Fig. 4.1 Potentiometer Fig. 4.2 Small Potentiometer

Construction of Potentiometer.

Potentiometers comprise a resistive element, a sliding contact (wiper) that moves along the element, making good electrical contact with one part of it, electrical terminals at each end of the element, a mechanism that moves the wiper from one end to the other, and a housing containing the element and wiper.

Many inexpensive potentiometers are constructed with a resistive element formed into an arc of a circle usually a little less than a full turn, and a wiper rotating around the arc and contacting it. The resistive element, with a terminal at each end, is flat or angled. The wiper is connected to a third terminal, usually between the other two. On panel potentiometers, the wiper is usually the center terminal of three. For single-turn potentiometers, this wiper typically travels just under one revolution around the contact. The only point of ingress for contamination is the narrow space between the shaft and the housing it rotates in.

Another type is the linear slider potentiometer, which has a wiper which slides along a linear element instead of rotating. Contamination can potentially enter anywhere along the slot the slider moves in, making effective sealing more difficult and compromising long-term reliability. An advantage of the slider potentiometer is that the slider position gives a visual indication of its setting. While the setting of a rotary potentiometer can be seen by the position of a

E.C.TPage 19

marking on the knob, an array of sliders can give a visual impression of, for example, the effect of a multi-channel equaliser.

The resistive element of inexpensive potentiometers is often made of graphite. Other materials used include resistance wire, carbon particles in plastic, and a ceramic/metal mixture called cermet. Conductive track potentiometers use conductive polymer resistor pastes that contain hard-wearing resins and polymers, solvents, and lubricant, in addition to the carbon that provides the conductive properties. Others are enclosed within the equipment and are intended to be adjusted to calibrate equipment during manufacture or repair, and not otherwise touched. They are usually physically much smaller than user-accessible potentiometers, and may need to be operated by a screwdriver rather than having a knob. They are usually called "preset potentiometers". Some presets are accessible by a small screwdriver poked through a hole in the case to allow servicing without dismantling.

Multi-turn potentiometers are also operated by rotating a shaft, but by several turns rather than less than a full turn. Some multi-turn potentiometers have a linear resistive element with a slider which moves along it moved by a worm gear; others have a helical resistive element and a wiper that turns through 10, 20, or more complete revolutions, moving along the helix as it rotates. Multi-turn potentiometers, both user-accessible and preset, allow finer adjustments; rotation through the same angle changes the setting by typically a tenth as much as for a simple rotary potentiometer.

A string potentiometer is a multi-turn potentiometer operated by an attached reel of wire turning against a spring, enabling it to convert linear position to a variable resistance.

User-accessible rotary potentiometers can be fitted with a switch which operates usually at the anti-clockwise extreme of rotation. Before digital electronics became the norm such a component was used to allow radio and television receivers and other equipment to be switched on at minimum volume with an audible click, then the volume increased, by turning a knob. Multiple resistance elements can be ganged together and controlled by the same shaft, for example, in stereo audio amplifiers for volume control.

E.C.TPage 20

Fig.4.3 construction

Working of potentiometer

Potentiometers work by having a resistive element inside. Both end terminals are attached to it, and do not move. The wiper travels along the strip when the knob is turned. The closer the wiper is to the end terminal it is wired in conjunction with, the less the resistance, because the path of the current will be shorter. The further away it moves from the terminal, the greater the resistance will be.

The symbol for a potentiometer is the same one as a resistor, save for an arrow in the middle. In a circuit where they are used strictly as variable resistors or rheostats, only two terminals are wired to the other components. All three terminals are wired separately when they function as voltage dividers. Light dimmers in houses and volume controls on electronics are two common applications. Others include switches and position sensors.

E.C.TPage 21

How to Read One

Fig 4.4 Measuring Potentiometer

To read a potentiometer, you need a multi-meter. Put in on the proper ohmmeter setting, which should be higher than that of the resistance rating of the potentiometer as noted on the package or the device. If you don't know the resistance rating, use the lowest setting of the multi-meter and increase it until you get a reading.

When reading the potentiometer, one multi-meter lead must always be on the wiper or middle part, and the other one can be on either of the remaining terminals. For example, place one multi-meter lead on the wiper, and the other on the left terminal of the potentiometer. If you place one lead on the left terminal and the other on the right, you will read the entire value of the pot, and the resistance will not vary when you turn the knob.

Note that Inexpensive ones may approximate only fifty percent of their rated value when they are measured.

E.C.TPage 22

Theory Of Operation

A potentiometer with a resistive load, showing equivalent fixed resistors for clarity.

The potentiometer can be used as a voltage divider to obtain a manually adjustable output voltage at the slider (wiper) from a fixed input voltage applied across the two ends of the potentiometer. This is the most common use of them.

The voltage across can be calculated by:

If is large compared to the other resistances (like the input to an operational amplifier), the output voltage can be approximated by the simpler equation:

(dividing throughout by and cancelling terms with as denominator)

As an example, assume

, , , and

E.C.TPage 23

Since the load resistance is large compared to the other resistances, the output voltage will be approximately:

Due to the load resistance, however, it will actually be slightly lower: ≈ 6.623 V.

One of the advantages of the potential divider compared to a variable resistor in series with the source is that, while variable resistors have a maximum resistance where some current will always flow, dividers are able to vary the output voltage from maximum ( )

to ground (zero volts) as the wiper moves from one end of the potentiometer to the other. There is, however, always a small amount of contact resistance.

In addition, the load resistance is often not known and therefore simply placing a variable resistor in series with the load could have a negligible effect or an excessive effect, depending on the load.

Potentiometer applications

Potentiometers are rarely used to directly control significant amounts of power (more than a watt or so). Instead they are used to adjust the level of analog signals (for example volume controls on audio equipment), and as control inputs for electronic circuits. For example, a light dimmer uses a potentiometer to control the switching of a TRIAC and so indirectly to control the brightness of lamps.

Preset potentiometers are widely used throughout electronics wherever adjustments must be made during manufacturing or servicing.

User-actuated potentiometers are widely used as user controls, and may control a very wide variety of equipment functions. The widespread use of potentiometers in consumer electronics declined in the 1990s, with rotary encoders, up/down push-buttons, and other digital controls now more common. However they remain in many applications, such as volume controls and as position sensors.

E.C.TPage 24

Audio control

Fig.4.5 Linear potentiometers ("faders")

Low-power potentiometers, both linear and rotary, are used to control audio equipment, changing loudness, frequency attenuation and other characteristics of audio signals.

The 'log pot' is used as the volume control in audio power amplifier, where it is also called an "audio taper pot", because the amplitude response of the human ear is approximately logarithmic. It ensures that on a volume control marked 0 to 10, for example, a setting of 5 sounds subjectively half as loud as a setting of 10. There is also an anti-log pot or reverse audio taper which is simply the reverse of a logarithmic potentiometer. It is almost always used in a ganged configuration with a logarithmic potentiometer, for instance, in an audio balance control.

Potentiometers used in combination with filter networks act as tone controls or equalizers.

Television

Potentiometers were formerly used to control picture brightness, contrast, and color response. A potentiometer was often used to adjust "vertical hold", which affected the synchronization between the receiver's internal sweep circuit (sometimes a multivibrator) and the received picture signal, along with other things such as audio-video carrier offset, tuning frequency (for push-button sets) and so on.

E.C.TPage 25

Motion Control

Potentiometers can be used as position feedback devices in order to create "closed loop" control, such as in a servomechanism

Transducers

Potentiometers are also very widely used as a part of displacement transducers because of the simplicity of construction and because they can give a large output signal.

Computation

In analog computers, high precision potentiometers are used to scale intermediate results by desired constant factors, or to set initial conditions for a calculation. A motor-driven potentiometer may be used as a function generator, using a non-linear resistance card to supply approximations to trigonometric functions. For example, the shaft rotation might represent an angle, and the voltage division ratio can be made proportional to the cosine of the angle.

E.C.TPage 26

CHAPTER 5

ARDUINO

E.C.TPage 27

5.1 What is arduion

5.2 History

5.3 Hardware

5.4 Arduion Board Models

5.5 Arduion software

5.6 Project Oriented Application

5.1 What is Arduino?Arduino is an open-source electronics prototyping platform based on

flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested increating interactive objects or environments. Arduino can sense the environment by receiving input from a variety of sensors and can affect its surroundings by controlling lights, motors, and other actuators. The microcontroller on the board is programmed using the Arduino programming language (based on Wiring) and the Arduino development environment (based on Processing). Arduino projects can be stand-alone or they can communicate with software running on a computer. The boards can be built by hand or purchased preassembled; the software can be downloaded for free. The hardware reference designs (CAD files) are available under an open-source license.

E.C.TPage 28

Figure 5.1 Arduino MEGA Development Board

Figure 5.2 Arduino UNO Device

E.C.TPage 29

5.2 History

The project began in Ivrea, Italy (the site of the computer company Olivetti), in 2005 to make a device for controlling student-built interaction design projects less expensive than other prototyping systems available at the time. Founders Massimo Banzi and David Cuartielles named the project after Arduin of Ivrea, the main historical character of the town. "Arduino" is an Italian masculine first name, meaning "strong friend". The English version of the name is "Hardwin".

5.3 Hardware Description

An Arduino board consists of an 8-bit Atmel AVR microcontroller with complementary components to facilitate programming and incorporation into other circuits. An important aspect of the Arduino is the standard way that connectors are exposed, allowing the CPU board to be connected to a variety of interchangeable add-on modules (known as shields). Official Arduinos have used the megaAVR series of chips, specifically the ATmega8, ATmega168, ATmega328,ATmega1280, and ATmega2560. An Arduino's microcontroller is also pre-programmed with a boot loader that simplifies uploading of programs to the on-chip flash memory, compared with other devices that typically need an external programmer.

E.C.TPage 30

5.4 Arduino Board Models

Table 5.1 List of Various Arduino Environments

Arduino Processor Freq.(MHz)

Volt Flash(kB)

EEPROM

(kB)

SRAM

(kB)

DigitalI/O pins

Analog Input pins

ADK ATMEGA2560

16 5 V 256 4 8 54 16

UNO ATMEGA328

16 5 V 32 1 2 14 6

NANO ATMEGA168/328

16 5 V 16/32 0.5/1 1/2 14 8

MEGA2560

ATMEGA2560

16 5 V 256 4 8 54 16

MEGA ATMEGA1280

16 5 V 128 4 8 54 16

LilyPad ATMEGA168V / 328V

8 2.7V-

5.5V

16 0.5 1 14 6

Leonardo

ATMEGA32u4

16 5V 32 1 2 14 12

Fio ATMEGA328P

8 3.3 V 32 1 2 14 12

Duemilanove

ATMEGA168/328P

16 5V 16/32 0.5/1 1/2 14 6

Due AT91SAM3X8E

84 3.3 V 512 0 96 54 12

Diecimila

ATMEGA168

16 5 V 16 0.5 1 14 6

5.5 Arduino Software

The Arduino IDE is a cross-platform application written in Java, and is derived from the IDE for the Processing programming language and the Wiring project. It is designed to introduce programming to artists and other newcomers unfamiliar with software development. It includes a code editor with features such as syntax highlighting, brace matching, and automatic indentation, and is also capable of compiling and uploading programs to the board with a single click. The Arduino IDE comes with a C/C++ library called "Wiring" (from the project of the same name), which makes many common input/output operations much easier. Arduino programs are written in C/C++, although users only need define two functions to make a runnable program:

E.C.TPage 31

setup() – a function run once at the start of a program that can initialize settings

loop() – a function called repeatedly until the board powers off

Figure 5.3 Arduino Programming Environment

E.C.TPage 32

5.6 Project oriented Application

Arduino is the best choice for us to deal with such a complex embedded system.

It is loaded with the huge collection of in-built libraries. We found it to be the best working environment for the implementation of

an embedded system. much suitable for multi-tasking application as well as for the

functionprogramming.

It provides such a nice user friendly environment than any other platforms available with a much reduced code size.

Gives On-board loader and comparatively less in physical dimensions. Provides real time debugging by serial port. Choice of microcontroller with different sizes like Atmega88, Atmega168,

Atmega328. Provides a very good flexibility for serial programming. Works very well with Master-slave environment. Provides support with all protocols and respective gadgets. Having a huge online forum support where you can get almost all of your

solution within a very short duration of time which is not available for any other environment till date.

E.C.TPage 33

CHAPTER 6STEPPER MOTOR

STEPPER MOTOR

E.C.TPage 34

6.1 Introduction & Working

Introduction & Working A stepper motor (or step motor) is a brushless DC electric motor that divides a

full rotation into a number of equal steps. The motor's position can then be

commanded to move and hold at one of these steps without any feedback sensor

(an open-loop controller), as long as the motor is carefully sized to the

application.

Now in our project we are using a hybrid stepper motor which will give a turn

of 1.8’. Now as we are using a ten turn potentiometer:

For 1 turn = 360

so,

for 10 turns = 3600

now, we can have 3600/1.8 = 2000 readings.

This results are thus for clockwise rotations.

E.C.TPage 35

Fig. 6.1 Internal Structure Of Stepper Motor

Fig. 6.2 Stepper Motor

E.C.TPage 36

Fig. 6.3 Actual Potentiometer mounted on Stepper motor

Fig. 6.4 Actual Stepper Motor

E.C.TPage 37

CHAPTER 7 MOTOR DRIVER

E.C.TPage 38

MOTOR DRIVER

7.1 Motor Driver

7.1.1 Specification

7.2 Role of L293D

7.3 Working Theory of H-Bridge

7.4 Speed Control Using PWM

7.1 Motor Driver:The most common method to drive motors in two directions under control of a Microcontroller is with motor driver. Motor driver can be used to drive a motor from low voltage supply from Microcontroller or from any other Electronic Circuitry. So for driving any Motor as per our requirement under the control of Microcontroller, Motor driver is necessary as from digital output pin of Microcontroller, We cannot drive motor directly because digital output pin of Controller cannot provide sufficient voltage and current to motor to drive it.

E.C.TPage 39

Figure 7.1 Motor Driver Circuit

7.1.1 Specification

We have used Motor Driver Module which has two motor drivers (L293d) . So we can control/drive four motors simultaneously in both forward and reverse direction Can drive 4 DC motors or 2 stepper motors or 2 Servo Up to 4 bi-directional DC motors with individual 8-bit speed selection 4 H-Bridges: per bridge provides 0.6A (1.2A peak current) with thermal protection, can

run motors on 4.5V to 36V DC Arduino reset button 2 external terminal power interface, for seperate logic/motor supplies Compatible with

Arduino Mega, Uno, Diecimila & Duemilanove.

7.2 Role of L293D

As microcontrollers PORT are not powerful enough to drive DC motors directly so we need some kind of drivers. A very easy and safe is to use L293D chips. It is a 16 PIN chip.

E.C.TPage 40

Figure 7.2 L293D Pin Diagram (Image from: www.extremeelectronics.co.in)

This chip is designed to control 2 DC motors. There are 2 INPUT and 2 OUTPUT PINs for each motors. The connections are is as follow.

E.C.TPage 41

Figure 7.3 Connection Diagram of L293D (Image from: www.extremeelectronics.co.in)

Table. 7.1

So we saw we just need to set appropriate level at two PINs of the microcontroller to control the motor.

7.3 Working   Theory   of   H ‐ Bridge  

The name of the H-bridge circuit is derived from shape of the circuit which looks like Alphabetic letter ‘H’. It is capable of controlling motion of the motor.It is also known as "Full Bridge". Basically there are four switching elements in the H‐Bridge As shown in the figure below.

E.C.TPage 42

A BStop Low LowClockwise Low HighAnti clockwise High LowStop High High

Figure 7.4 H-Bridge Circuit (Image from: http://www.visionrobo.com/)

As you can see in the figure above there are four switching elements named as "High side left", "High side right", "Low side right", "Low side left". When these switches are turned on in pairs motor changes ts direction accordingly. Like, if we switch on High side left and Low side right then motor rotate in forward direction, as current flows from power switch to high side left to low side right to ground.

7.4 Speed control using PWM

Speed control means intentional change of drive speed to a value required for performing the specific work process. Suppose you want to run motor by half of its rating speed then send 50% duty cycle square wave at enable pin effectively

E.C.TPage 43

CHAPTER 8

RS-232

RS-232

7.1 Introduction of RS-232

7.2 RS-232 Specification

E.C.TPage 44

Introduction of RS-232

This article is about the RS-232 standard. For RS-232 variants, see serial port.

Fig. 8.1 Pindiagram of RS-232

A DB-25 connector as described in the RS-232 standard

In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer serial ports. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. The current version of the standard is TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997.

An RS-232 port was once a standard feature of a personal computer for connections to modems, printers, mice, data storage, uninterruptible power supplies, and other peripheral devices. However, the low transmission speed, large voltage swing, and large standard connectors motivated development of the

E.C.TPage 45

universal serial bus, which has displaced RS-232 from most of its peripheral interface roles. Many modern personal computers have no RS-232 ports and must use an external converter to connect to older peripherals. RS-232 devices are still found, especially in industrial machines or scientific instruments.

RS-232 Specifications:

TRANSMITTED SIGNALVOLTAGE LEVELS:

Binary 0: +5 to +15 Vdc(called a “space” or “on”)Binary 1: -5 to -15 Vdc(called a “mark” or “off”)

RECEIVED SIGNALVOLTAGE LEVELS:

Binary 0: +3 to +13 VdcBinary 1: -3 to -13 Vdc

DATA FORMAT:

Start bit: Binary 0Data: 5, 6, 7 or 8 bitsParity: Odd, even, mark or space(not used with 8-bit data)Stop bit: Binary 1,one or two bits

E.C.T

Page 46

CHAPTER 9

PCB (Printed Circuit Board)

E.C.TPage 47

PCB (Printed Circuit Board)

9.1 Introduction

9.2 Construction & Preparation

INTROCUCTION

A printed circuit board, or PCB, is used to mechanically support and electrically

connect electronic components using conductive pathways, tracks or signal traces

etched from copper sheets laminated onto a non-conductive substrate.

E.C.TPage 48

When the board has only copper tracks and features, and no circuit elements such as capacitors, resistors or active devices have been manufactured into the actual substrate of the board, it is more correctly referred to as printed wiring board (PWB) or etched wiring board. Use of the term PWB or printed wiring board although more accurate and distinct from what would be known as a true printed circuit board, has generally fallen by the wayside for many people as the distinction between circuit and wiring has become blurred. Today printed wiring (circuit) boards are used in virtually all but the simplest commercially produced electronic devices, and allow fully automated assembly processes that were not possible or practical in earlier era tag type circuit assembly processes.

A PCB populated with electronic components is called a printed circuit assembly (PCA), printed circuit board assembly or PCB Assembly (PCBA). In informal use the term "PCB" is used both for bare and assembled boards, the context clarifying the meaning.

Alternatives to PCBs include wire wrap and point-to-point construction. PCBs must initially be designed and laid out, but become cheaper, faster to make, and potentially more reliable for high-volume production since production and soldering of PCBs can be automated. Much of the electronics industry's PCB design, assembly, and quality control needs are set by standards published by the IPC organization.

CONSTRUCTION AND PREPARATION

In our project we designed and prepared the PCB by ourselves only. It was an interesting experience indeed. Basically we designed the PCB in the very conventional way but did slight modifications. Step by Step methods I’ve explained below as follows:

STEP 1

First of all we took a copper clade and cut it according to our use. Then we washed it with dilute HCl for better clarity of the future circuit which will be implemented on it.

E.C.TPage 49

Fig .9.1 Copper Clade

STEP 2

Secondly, we designed the circuit and printed it on a glossy printing paper and simply we put it on the copper clade and just ironed it using a basic iron.

STEP 3

Now we prepared a solution containing water, Iron Tetrachloride (FeCl3) and Hydrochloric Acid (HCl) and sink it in it and stir it for about 15-20 minutes.

E.C.TPage 50

Fig. 9.2 PCB Sink in FeCl3 Solution

STEP 4

Now we washed it with water and cleaned it. Now we drilled it using a Drilling Machine and then rubbed it using a Steel Wool for getting our actual PCB circuit ready to use.

E.C.T

Page 51

Fig 9.3 Drilling Machine and setup

E.C.TPage 52

CHAPTER 10

PYTHON

PYTHON

10.1 Introduction of Python

10.2 Project program and Flowchart

INTRODUCTION TO PYTHON:

E.C.TPage 53

Python is a general-purpose, interpreted high-level programming language whose design philosophy emphasizes code readability. Its syntax is said to be clear and expressive. Python has a large and comprehensive standard library.

Python supports multiple programming paradigms, primarily but not limited to object-oriented, imperative and, to a lesser extent, functional programming styles. It features a fully dynamic type system and automatic memory management, similar to that of Scheme, Ruby, Perl, and Tcl. Like other dynamic languages, Python is often used as a scripting language, but is also used in a wide range of non-scripting contexts. Using third-party tools, Python code can be packaged into standalone executable programs. Python interpreters are available for many operating systems.

CPython, the reference implementation of Python, is free and open source software and has a community-based development model, as do nearly all of its alternative implementations. CPython is managed by the non-profit Python Software Foundation.

Python has a large standard library, commonly cited as one of Python's greatest strengths, providing tools suited to many tasks. This is deliberate and has been described as a "batteries included" Python philosophy. The modules of the standard library can be augmented with custom modules written in either C or Python. Boost C++ Libraries includes a library, Boost.Python, to enable interoperability between C++ and Python. Because of the wide variety of tools provided by the standard library, combined with the ability to use a lower-level language such as C and C++, which is already capable of interfacing between other libraries, Python can be a powerful glue language between languages and tools.

The standard library is particularly well tailored to writing Internet-facing applications, with a large number of standard formats and protocols (such as MIME and HTTP) already supported. Modules for creating graphical user interfaces, connecting to relational databases, arithmetic with arbitrary precision decimals, manipulating regular expressions, and doing unit testing are also included.

Some parts of the standard library are covered by specifications (for example, the WSGI implementation wsgiref follows PEP 333[), but the majority of the modules are not. They are specified by their code, internal documentation, and test suite (if supplied). However, because most of the standard library is cross-platform Python

E.C.TPage 54

code, there are only a few modules that must be altered or completely rewritten by alternative implementations.

The standard library is not essential to run Python or embed Python within an application. Blender 2.49 for instance omits most of the standard library.

For software testing, the standard library provides the unittest and doctest modules.

About Python

Python is a remarkably powerful dynamic programming language that is used in a wide variety of application domains. Python is often compared to Tcl, Perl, Ruby, Scheme or Java. Some of its key distinguishing features include:

very clear, readable syntax strong introspection capabilities intuitive object orientation natural expression of procedural code full modularity, supporting hierarchical packages exception-based error handling very high level dynamic data types extensive standard libraries and third party modules for virtually every task extensions and modules easily written in C, C++ (or Java for Jython,

or .NET languages for IronPython) embeddable within applications as a scripting interface

Python plays well with others

Python can integrate with COM, .NET, and CORBA objects.

For Java libraries, use Jython, an implementation of Python for the Java Virtual Machine.

For .NET, try IronPython , Microsoft's new implementation of Python for .NET, or Python for .NET.

E.C.TPage 55

Python is also supported for the Internet Communications Engine (ICE) and many other integration technologies.

If you find something that Python cannot do, or if you need the performance advantage of low-level code, you can write extension modules in C or C++, or wrap existing code with SWIG or Boost.Python. Wrapped modules appear to your program exactly like native Python code. That's language integration made easy. You can also go the opposite route and embed Python in your own application, providing your users with a language they'll enjoy using.

Our Project Oriented PYTHON Program:

import serial

s = serial.Serial(6)

ps = ''

ch = ''

count = 0

E.C.TPage 56

while (True):

ch = s.read()

if ch != '\r':

ps = ps + ch

else:

print ps

ps = ''

count = count +1

if count == 3:

print '**************'

count = 0

FLOWCHART

E.C.TPage 57

Fig. 10.1 Flowchart

LITERATURE SURVEY

E.C.TPage 58

There is lot of data available on internet for Arduino and Python.

Arduino

^ a b Shiffman, Daniel (September 23, 2009). "Interview with Casey Reas and Ben Fry". Rhizome.org.

^ "Wiring". wiring.org.co

^ a b c d e f "Project homepage". arduino.cc.

^ "Prix Ars Electronica 2006   — Digital Communities   — ANERKENNUNGEN   — listing" (in German). Retrieved 2009-02-18.

^ "Prix Ars Electronica 2006   — Digital Communities   — ANERKENNUNGEN   — description" (in German). Retrieved 2009-02-18.

^ Lahart, Justin (2009-11-27). "Taking an Open-Source Approach to Hardware". The Wall Street Journal. Retrieved 2012-03-24.

^ "View Name: Arduino". Behind the Name. Retrieved 2012-09-15.

^ Reas, Casey; Fry, Ben (2010). Getting Started With Processing. Sebastopol: O'Reilly. ISBN 978-1-4493-7980-3.

Python

^ a b "Why was Python created in the first place?". General Python FAQ. Python Software Foundation. Retrieved 22 March 2007.

^ Kuchling, Andrew M. (22 December 2006). "Interview with Guido van Rossum (July 1998)". amk.ca. Retrieved 12 March 2012.

^ van Rossum, Guido (1993). "An Introduction to Python for UNIX/C Programmers". Proceedings of the NLUUG najaarsconferentie (Dutch UNIX users group). "even though the design of C is far from ideal, its influence on Python is considerable."

E.C.TPage 59

^ a b "Classes". The Python Tutorial. Python Software Foundation. Retrieved 20 February 2012. "It is a mixture of the class mechanisms found in C++ and Modula-3"

^ Simionato, Michele. "The Python 2.3 Method Resolution Order". Python

Software Foundation. "The C3 method itself has nothing to do with Python, since

it was invented by people working on Dylan and it is described in a paper intended

for lispers"

E.C.TPage 60