A

MAJOR PROJECT

REPORT

ON

MOBILE PHONE OPERATED ROBOTI

To Wards Partial Fulfillment of the Requirement of Uttar Pradesh Technical

University

For Bachelor of Technology in Medical Engineering

PREPARED AND SUBMITTED BY:

AMIT KUMAR AGRAHARI ROLL NO.0503240010AMIT SINGH VERMA ROLL NO.0503240011

SUBMITTED TO: - MR.VINEET(PROJECT INCHARGE)

DEPARTMENT OF MECHANICAL ENGINEERING

Introduction

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Conventionally, wireless-controlled robots use remote control, which have the drawbacks of limited working range, limited frequency range and limited control .Use of a mobile phone for robotics control can overcome these limitations. It provides the advantages of robust control, working range as larger as the coverage area of the service provider, no interference with other controllers and up to twelve controls.

Although the appearance and capabilities of robots vary vastly, all robots share the

features of a mechanical, movable structure under some form of control. The control of robot involves three distinct phases: perception, processing and action, generally, the preceptor are sensors mounted on the robot, processing is done by the on board microcontroller or processor, and the task (action) is performed using motors with some other actuators.

Radio control (often abbreviated to R/C or simply RC) is the use of radio signals to remotely control a device. The term is used frequently to refer to the control of model vehicles from a hand-held radio transmitter. Industrial, military, and scientific research organizations make [traffic] use of radio-controlled vehicles as well.A remote control vehicle is defined as any mobile device that is controlled by a means that does not restrict its motion with an origin external to the device. This is often a radio control device, cable between control and vehicle, or an infrared controller. A remote control vehicle (Also called as RCV) differs from a robot in that the RCV is always controlled by a human and takes no positive action autonomously

PROJECT OVERVIEW

In this project, the robot is controlled by the mobile phone that makes a call to the mobile phone attached to the robot .In the course of a call, if any button is pressed; a tone corresponding to the button pressed is heared at the other end of the call. This tone is called ‘dual tone-multiple-frequency’ (DTMF) tone .The robot perceives the DTMF tone with the help of the phone stacked in the robot.

The received tone is processed by the 8051 microcontroller with the help of

DTMF decoder MT8870.The decoder decodes the DTMF tone into its equivalent binary digit and this binary number is sent to the L293d.The L293d take a decision for any given input and outputs its decision to motor drivers in order to drive the motor for forward or backward motion or a turn.

The mobile that makes a call to the mobile stacked in the robot as a remote. So this simple robotic project does not require the construction of receiver and transmitter units.

DTMF signaling is used for telephone signaling over the line in voice-frequency band to the call switching center. The version of DTMF used for telephone tone dialing is known as ‘Touch Tone’.

DTMF assigns a specific frequency (consisting of two separate tones) to each key so that it can easily be identified by the electronics circuit. The signal generated by the DTMF encoder is a direct algebraic summation, in real time, of the amplitude of two sine (cosine) waves of different frequency, i.e., pressing ‘5’ will send a tone made by adding 1336Hz and 770Hz to the other end of end of the line .

IN SHORT:

In this project, a Robot is controlled by mobile phone using DTMF technique. The Robot is guided by a mobile phone that makes a call to the mobile   phone  attached to the robot. In the course of a call, if any button is pressed, a tone corresponding to the button pressed is heard at the other end of the call. This tone is called DTMF(dual-tone-multiple-frequency).The robot perceives this DTMF tone with the help of the phone stacked in the robot. The received tone is processed by the microcontroller with then help of DTMF decoder MT8870. The decoder decodes the DTMF tone into its equivalent binary digit and this binary number is sent to the microcontroller. The microcontroller is programmed to take a decision for any given input and outputs its decision to motor drivers in order to drive the motors in forward direction or backward direction or turn. The mobile phone that makes a call to mobile phone stacked in the robot act as a remote. So this robotic project does not require the construction of receiver and transmitter units

CIRCUIT DESCRIPTION:

Fig.1 shows the block diagram of the Digital electronics-based mobile phone-operated land rover. The important components of this rover are a DTMF decoder and H-BRIDGE ,

An HT9170 series DTMF decoder is used here. All types of the MT8870 series use digital counting techniques to detect and decode all the 16DTMF tone pairs into 4-bit code output. The built in dial tone rejection circuit eliminates the need for pre-filtering. When the input signal given at pin 2(IN-) in single-ended input configuration is recognised to be effective, the correct 4-bit decode signal of the DTMF tone is transferred to Q1 (PIN11) through Q4 (PIN14) outputs.

LIST OF COMPNENTS USED

S.NO Name Quantity Colour Pins

1 Op-amp LM358 (IC) 1 Black 8

2 DC Geadred Motors 2 Black 2

3 Sip resistance ( 10 k ohm) 1 Black 9

4 Resistance 330 ohm 3 Orange-orange-brown 2

5 Resistance 1 mega ohm 2 Green-brown 2

6 Not gate ( 7404) 1 Black 14

7 Motor Driver L293D( H-Bridge)

1 Black 16

8 Trimmer Variable Resistance

10 k ohm

1 Blue 3

9 Designed PCB 1 -

10 Microcontroller 8051 1 Black 40

11 Led ( Red) 1 RED -

12 DTMF 9170 1 -

13 Jumper Wire ( Single Stand Wire)

-

14 IC Base ( 8,14,16,40 pin) 3 Black -

15 Battery ( 9v) + Connector 1 -

16. Step down transformer ( 9-0-9) 1 -

17. Bridge diode ( 1 amp ) 1 Black 4

18. Voltage regulator 7805 1 Black 3

19. Led + 100 ohm ( indicator) 1 -

20. 10k ohm resistance 1 -

21. 10 microfarad capacitor 1 -

22. 33 picofarad capacitor 1 2

23. Tactile swithes 1 2

BLOCK DIAGRAM OF PROJECT:

CHAPTER 1:DTMF

Dual-tone multi-frequency signaling (DTMF) is used for telecommunication signaling over analog telephone lines in the voice-frequency band between telephone handsets and other communications devices and the switching center. The version of DTMF that is used in push-button telephones for tone dialing is known as Touch-Tone, was first used by AT&T in commerce as a registered trademark, and is standardized by ITU-T Recommendation Q.23. It is also known in the UK as MF4.

Other multi-frequency systems are used for internal signaling within the telephone network.

The Touch-Tone system, using the telephone keypad, gradually replaced the use of rotary dial starting in 1963, and since then DTMF or Touch-Tone became the industry standard for both cell phones and landline service.

MULTIFREQUENCY SIGNALING

Prior to the development of DTMF, automated telephone systems employed pulse

dialing (Dial Pulse or DP in the U.S.) or loop disconnect (LD) signaling to dial numbers. It

functions by rapidly disconnecting and re-connecting the calling party's telephone line,

similar to flicking a light switch on and off. The repeated interruptions of the line, as

the dial spins, sounds like a series of clicks. The exchange equipment interprets these dial

pulses to determine the dialed number. Loop disconnect range was restricted by telegraphic

distortion and other technical problems[which?] , and placing calls over longer distances

required either operator assistance (operators used an earlier kind of multi-frequency dial)

or the provision of subscriber trunk dialing equipment.

Multi-frequency signaling (see also MF) is a group of signaling methods, that use a

mixture of two pure tone (pure sine wave) sounds. Various MF signaling protocols were

devised by the Bell System and CCITT. The earliest of these were for in-band signaling

between switching centers, where long-distance telephone operators used a 16-

digit keypad to input the next portion of the destination telephone number in order to

contact the next downstream long-distance telephone operator. This semi-automated

signaling and switching proved successful in both speed and cost effectiveness. Based on

this prior success with using MF by specialists to establish long-distance telephone

calls, Dual-tone multi-frequency(DTMF) signaling was developed for the consumer to

signal their own telephone-call's destination telephone number instead of talking to a

telephone operator.

AT&Ts Compatibility Bulletin No. 105 described the product as "a method for pushbutton

signaling from customer stations using the voice transmission path." In order to prevent

using a consumer telephone to interfere with the MF-based routing and switching between

telephone switching centers, DTMF's frequencies differ from all of the pre-existing MF

signaling protocols between switching centers: MF/R1, R2, CCS4, CCS5, and others that

were later replaced by SS7 digital signaling. DTMF, as used in push-button telephone tone

dialing, was known throughout the Bell System by the trademark Touch-Tone. This term

was first used by AT&T in commerce on July 5, 1960 and then was introduced to the public

on November 18, 1963, when the first push-button telephone was made available to the

public. It was AT&T's registered trademark from September 4, 1962 to March 13, 1984,[2] and is standardized by ITU-T Recommendation Q.23. It is also known in the UK as MF4.

Other vendors of compatible telephone equipment called the Touch-Tone feature Tone

dialing or DTMF, or used their own registered trade names such as the Digitone of Northern

Electric (now known as Nortel Networks).

The DTMF system uses eight different frequency signals transmitted in pairs to represent

sixteen different numbers, symbols and letters - as detailed below.

The DTMF keypad is laid out in a 4×4 matrix, with each row representing a low frequency,

and each column representing a high frequency. Pressing a single key (such as '1' ) will send

a sinusoidal tone for each of the two frequencies (697 and 1209 hertz (Hz)). The original

keypads had levers inside, so each button activated two contacts. The multiple tones are the

reason for calling the system multifrequency. These tones are then decoded by the switching

center to determine which key was pressed.

DTMF keypad frequencies (with sound clips)

1209 Hz 1336 Hz 1477 Hz 1633 Hz

697 Hz 1 2 3 A

770 Hz 4 5 6 B

852 Hz 7 8 9 C

941 Hz * 0 # D

CHAPTER-2: MICROCONTROLLER

MICROCONTROLLER

Contents

1. Introduction2. Types 3. Amazing Inventions with microcontrollers/Applications4. Inside 80515. Pin diagram6. Pin Description

2.1.1 INTRODUCTION:

A microcontroller is a kind of miniature computer that you can find in all kinds of gizmos. Some examples of common, every-day products that have microcontroller’s built-in are shown in Figure 1-1. If it has buttons and a digital display, chances are it also has a programmable microcontroller brain. Figure 1-1. Every-Day Examples of Devices that Contain Microcontrollers Try making a list and counting how many devices with microcontrollers you use in a typical day. Here are some examples: if your clock radio goes off, and you hit the snooze button a few times in the morning, the first thing you do in your day is interact with a microcontroller. Heating up some food in the microwave oven and making a call on a cell phone also involve operating microcontrollers. That’s just the beginning. Here are a few more examples: turning on the television with a handheld remote, playing a handheld game, using a calculator, and checking your digital wristwatch. All those devices have microcontrollers inside them that interact with you.

Figure 2.2: Every-Day Examples of Devices that Contain MicrocontrollersAtmel 89c51 microcontroller module shown in Figure 4 has a microcontroller built onto it. It’s the black chip with lettering on it that reads “Atmel 89c51”. The rest of the components on the microcontroller module are also found in consumer appliances you use every day. All together, they are correctly called an embedded computer system. This name is almost always shortened to just “embedded system”. Frequently, such modules are commonly just called “microcontrollers.”

Fig 2.3: 40 Pins Atmel 89c51 microcontroller module(Internal structure)

2.2 TYPES OF MICROCONTROLLER

2.2.1 INTEL 8051 AND ITS FAMILYIn 1981, Intel Corporation introduces an 8-bit microcontroller called 8051. The Intel 8051 became widely popular and allowed other companies to produce any flavor of 8051 but with condition that ‘code remains compatible with 8051’.

Other two members in 8051 family of microcontroller are 8052 & 8031Some other companies producing member of 8051 family are:

1. Intel 2. Atmel 3. Dallas Semiconductors 4. Philips/ Signetics5. Siemens

2.2.2 PIC MICROCONTROLLER (Microchip Technology)

Fig 2.4: Microcontroller Module

2.3 AMAZING INVENTIONS WITH MICROCONTROLLERS:- 1. Consumer appliances aren’t the only things that contain microcontrollers. Robots, machinery,

aerospace designs and other high-tech devices are also built with microcontrollers. Let’s take a look at some examples that were created with Atmel 89c51 microcontroller module. Robots have been designed to do everything from helping students learn more about microcontrollers, to mowing the lawn, to solving complex mechanical problems. Figure1-4 shows two example robots. On each of these robots, students use the Atmel 89c51 microcontroller module to read sensors, control motors, and communicate with other computers.

Fig 2.5: Applications of microcontroller

2. Microcontrollers are also used in scientific, high technology, and aerospace projects. The weather station shown on the left of Figure 1-7 is used to collect environmental data related to coral reef decay. The Atmel 89c51 microcontroller inside it gathers this data from a variety of sensors and stores it for later retrieval by scientists. The submarine in the center is an undersea

exploration vehicle, and its thrusters, cameras and lights are all controlled by Atmel 89c51 microcontroller. The rocket shown on the right is one that was part of a competition to launch a privately owned rocket into space. Nobody won the competition, but this rocket almost made it! Atmel 89c51 microcontroller controlled just about every aspect of the launch sequence.

Figure 2.6: High-tech and Aerospace Microcontroller Examples Ecological data collection by EME Systems (left), undersea research by Harbor Branch Institute

3.)From common household appliances all the way through scientific and aerospace applications, the microcontroller basics you will need to get started on projects like these are introduced here. By working through the activities in this book, you will get to experiment with and learn how to use a variety of building blocks found in all these high-tech inventions. You will build circuits for displays, sensors, and motion controllers. You will learn how to connect these circuits to the Atmel 89c51 microcontroller, and then write computer programs that make it control displays, collect data from the sensors, and control motion. Along the way, you will learn many important electronic and computer programming concepts and techniques. By the time you’re done, you might find yourself well on the way to inventing a gizmo of your own design.

2.4 INSIDE 8051:

ROM

P1 P0

FILTER FOR P2 INPUT VOLTAGE.

Internal Oscilattor

P3 Microprocessor

Fig2.7: Inside 8051

2.5 8051 PIN DIAGRAM

Fig

2.8: Pin Description

2.6 Pin Description:

1.)VCC: Supply voltage.

2.)GND: Ground.

3.) Port 1: Port 1 is an 8-bit bi-directional I/O port. Port pins P1.2 to P1.7 provide internal pull-ups. P1.0 and P1.1 require external pull-ups. P1.0 and P1.1 also serve as the positive input (AIN0) and the negative input (AIN1), respectively, of the on-chip precision analog comparator. The Port 1 output buffers can sink 20 mA and can drive LED displays directly. When 1s are written to Port 1 pins, they can be used as inputs. When pins P1.2 to P1.7 are used as inputs and are externally pulled low, they will source current (IIL) because of the internal pull-ups. Port 1 also receives code data during Flash programming and verification.

4.)Port 3: Port 3 pins P3.0 to P3.5, P3.7 are seven bi-directional I/O pins with internal pull-ups. P3.6 is hard-wired as an input to the output of the on-chip comparator and is not accessible as a general-purpose I/O pin. The Port 3 output buffers can sink 20 mA. When 1s are written to Port 3 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull-ups. Port 3 also serves the functions of various special features of the AT89S2051/S4051 as listed below:Port 3 also receives some control signals for Flash programming and verification.

5.) RST:Reset input. Holding the RST pin high for two machine cycles while the is running resets the device. Each machine cycle takes 6 or clock cycles.

6.) XTAL1:Input to the inverting amplifier and input to the internal clock operating circuit.

7.) XTAL2:Output from the inverting amplifier.

Characteristics:XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip . Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 . There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications

Microcontroller interfacing with l293d:

Components used with microcontroller:

1. Capacitor: The capacitor's function is to store electricity, or electrical energy.The capacitor also functions as a filter, passing alternating current (AC), and blocking direct current (DC).The capacitor is constructed with two electrode plates facing each other, but separated by an insulator.When DC voltage is applied to the capacitor, an electric charge is stored on each electrode. While the capacitor is charging up, current flows. The current will stop flowing when the capacitor has fully charged.When a circuit tester, such as an analog meter set to measure resistance, is connected to a 10 microfarad (µF) electrolytic capacitor, a current will flow, but only for a moment. You can confirm that the meter's needle moves off of zero, but returns to zero right away.When you connect the meter's probes to the capacitor in reverse, you will note that current once again flows for a moment. Once again, when the capacitor has fully charged, the current stops flowing. So the capacitor can be used as a filter that blocks DC current. (A "DC cut" filter.)

However, in the case of alternating current, the current will be allowed to pass. Alternating current is similar to repeatedly switching the test meter's probes back and forth on the capacitor. Current flows every time the probes are switched.The value of a capacitor (the capacitance), is designated in units called the Farad ( F ).The capacitance of a capacitor is generally very small, so units such as the microfarad ( 10-

6F ), nanofarad ( 10-9F ), and picofarad (10-12F ) are used.Recently, an new capacitor with very high capacitance has been developed. The Electric Double Layer capacitor has capacitance designated in Farad units. These are known as "Super Capacitors."Sometimes, a three-digit code is used to indicate the value of a capacitor. There are two ways in which the capacitance can be written. One uses letters and numbers, the other uses only numbers. In either case, there are only three characters used. [10n] and [103] denote the same value of capacitance. The method used differs depending on the capacitor supplier. In the case that the value is displayed with the three-digit code, the 1st and 2nd digits from the left show the 1st figure and the 2nd figure, and the 3rd digit is a multiplier which determines how many zeros are to be added to the capacitance. Picofarad ( pF ) units are written this way.For example, when the code is [103], it indicates 10 x 103, or 10,000pF = 10 nanofarad( nF ) = 0.01 microfarad( µF ).If the code happened to be [224], it would be 22 x 104 = or 220,000pF = 220nF = 0.22µF.Values under 100pF are displayed with 2 digits only. For example, 47 would be 47pF.The capacitor has an insulator( the dielectric ) between 2 sheets of electrodes. Different kinds of capacitors use different materials for the dielectric.

Breakdown voltageWhen using a capacitor, you must pay attention to the maximum voltage which can be used. This is the "breakdown voltage." The breakdown voltage depends on the kind of capacitor being used. You must be especially careful with electrolytic capacitors because the breakdown voltage is comparatively low. The breakdown voltage of electrolytic capacitors is displayed as Working Voltage.The breakdown voltage is the voltage that when exceeded will cause the dielectric (insulator) inside the capacitor to break down and conduct. When this happens, the failure can be catastrophic.

Types of Capacitors

There are a very large variety of different types of Capacitors available in the market place and each one has its own set of characteristics and applications from small delicate trimming capacitors up to large power metal can type capacitors used in high voltage power correction and smoothing circuits. Like resistors, there are also variable types of capacitors which allow us to vary their capacitance value for use in radio or "frequency tuning" type circuits. Either way, capacitors play an important part in electronic circuits so here are a few of the more "Common" types of capacitors available.

1. Dielectric

Dielectric Capacitors are usually of the variable type such as used for tuning transmitters, receivers and transistor radios. They have a set of fixed plates and a set of moving plates that mesh with the fixed plates and the position of the moving plates with respect to the fixed plates determines the overall capacitance. The capacitance is generally at maximum when the plates are fully meshed. High voltage type tuning capacitors have relatively large spacings or air-gaps between the plates with breakdown voltages reaching many thousands of volts.

Variable Capacitor Symbols

As well as the continuously variable types, preset types are also available called Trimmers. These are generally small devices that can be adjusted or "pre-set" to a particular capacitance with the aid of a screwdriver and are available in very small capacitances of 100pF or less and are non-polarized.

2. Film Capacitors

Film Capacitors are the most commonly available of all types of capacitors, consisting of a relatively large family of capacitors with the difference being in their dielectric properties. These include polyester (Mylar), polystyrene, polypropylene, polycarbonate, metallized paper, teflon etc. Film type capacitors are available in capacitance ranges from 5pF to 100uF depending upon the actual type of capacitor and its voltage rating. Film capacitors also come in an assortment of shapes and case styles which include:

Wrap & Fill (Oval & Round)  -  where the capacitor is wrapped in a tight plastic tape and have the ends filled with epoxy to seal them.

  Epoxy Case (Rectangular & Round)  -  where the capacitor is encased in a

moulded plastic shell which is then filled with epoxy.

  Metal Hermetically Sealed (Rectangular & Round)  -  where the capacitor is

encased in a metal tube or can and again sealed with epoxy.

with all the above case styles available in both Axial and Radial Leads.

Examples of film capacitors are the rectangular metallized film and cylindrical film & foil types as shown below.

Radial Lead Type

Axial Lead Type

The film and foil types of capacitors are made from long thin strips of thin metal foil with the dielectric material sandwiched together which are wound into a tight roll and then sealed in paper or metal tubes. These film types require a much thicker dielectric film to reduce the risk of tears or punctures in the film, and is therefore more suited to lower capacitance values and larger case sizes.

Metallized foil capacitors have the conductive film metallized sprayed directly onto each side of the dielectric which gives the capacitor self-healing properties and can therefore use much thinner dielectric films. This allows for higher capacitance values and smaller case sizes for a given capacitance. Film and foil capacitors are generally used for higher power and more precise applications.

3. Ceramic Capacitors

Ceramic Capacitors or Disc Capacitors as they are generally called, are made by coating two sides of a small porcelain or ceramic disc with silver and are then stacked together to make a capacitor. For very low capacitance values a single ceramic disc of about 3-6mm is

used. Ceramic capacitors have a high dielectric constant (High-K) and are available so that relatively high capacitances can be obtained in a small physical size. They exhibit large non-linear changes in capacitance against temperature and as a result are used as de-coupling or by-pass capacitors as they are also non-polarized devices. Ceramic capacitors have values ranging from a few picofarads to one or two microfarads but their voltage ratings are generally quite low.

Ceramic types of capacitors generally have a 3-digit code printed onto their body to identify their capacitance value. For example, 103 would indicate 10 x 103pF which is equivalent to 10,000 pF or 0.01μF. Likewise, 104 would indicate 10 x 104pF which is equivalent to 100,000 pF or 0.1μF and so on. Letter codes are sometimes used to indicate their tolerance value such as: J = 5%, K = 10% or M = 20% etc.

4. Electrolytic Capacitors

Electrolytic Capacitors are generally used when very large capacitance values are required. Here instead of using a very thin metallic film layer for one of the electrodes, a semi-liquid electrolyte solution in the form of a jelly or paste is used which serves as the second electrode (usually the cathode). The dielectric is a very thin layer of oxide which is grown electro-chemically in production with the thickness of the film being less than ten microns. This insulating layer is so thin that it is possible to make large value capacitors of a small size. The majority of electrolytic types of capacitors are Polarized, that is the voltage applied to the capacitor terminals must be of the correct polarity as an incorrect polarization will break down the insulating oxide layer and permanent damage may result.

Electrolytic Capacitors are generally used in DC power supply circuits to help reduce the ripple voltage or for coupling and decoupling applications. Electrolytic's generally come in two basic forms; Aluminum Electrolytic and Tantalum Electrolytic capacitors.

Electrolytic Capacitor

1. Aluminium Electrolytic Capacitors

There are basically two types of Aluminium Electrolytic Capacitor, the plain foil type and the etched foil type. The thickness of the aluminium oxide film and high breakdown voltage give these capacitors very high capacitance values for their size. The etched foil type differs from the plain foil type in that the aluminium oxide on the anode and cathode foils has been chemically etched to increase its surface area and permittivity. This gives a smaller sized capacitor than a plain foil type of equivalent value but has the disadvantage of not being able to withstand high AC currents compared to the plain type. Also their tolerance range is

quite large up to 20%. Etched foil electrolytic's are best used in coupling, DC blocking and by-pass circuits while plain foil types are better suited as smoothing capacitors in power supplies. Typical values of capacitance range from 1uF to 47000uF. Aluminium Electrolytic's are "polarized" devices so reversing the applied voltage on the leads will cause the insulating layer within the capacitor to be destroyed along with the capacitor, "so be aware".

2. Tantalum Electrolytic Capacitors

Tantalum Electrolytic Capacitors or Tantalum Beads, are available in both wet (foil) and dry (solid) electrolytic types with the dry or solid tantalum being the most common. Solid tantalums use manganese dioxide as their second terminal and are physically smaller than the equivalent aluminium capacitors. The dielectric properties of tantalum oxide is also much better than those of aluminium oxide giving a lower leakage currents and better capacitance stability which makes them suitable for timing applications. Also tantalum capacitors although polarized, can tolerate being connected to a reverse voltage much more easily than the Aluminium types but are rated at much lower working voltages. Typical values of capacitance range from 47nF to 470uF.

Aluminium & Tantalum Electrolytic Capacitor

We have used two paper capacitors of 33picofaraday in parallel with the crystal oscillator and the other one is an electrolytic capacitor of 10 micro faraday as shown below:

a. 33pF ceramic capacitors:

b. 10uF electrolytic capacitors:

2. Crystal oscillator:

Fig: crystal oscillatorA crystal oscillator is an electronic circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency. This frequency is commonly used to keep track of time (as in quartz wristwatches), to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers. The most common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits designed around them were called "crystal oscillators"

3. Switch :An electrical switch is any device used to interrupt the flow of electrons in a circuit. Switches are essentially binary devices: they are either completely on ("closed") or completely off ("open"). There are many different types of switches, and we will explore some of these types in this chapter. Though it may seem strange to cover this elementary electrical topic at such a late stage in this book series, I do so because the chapters that follow explore an older realm of digital technology based on mechanical switch contacts rather than solid-state gate circuits, and a thorough understanding of switch types is necessary for the undertaking. Learning the function of switch-based circuits at the same time that you learn about solid-state logic gates makes both topics easier to grasp, and sets the stage for an enhanced learning experience in Boolean algebra, the mathematics behind digital logic circuits. The simplest type of switch is one where two electrical conductors are brought in contact with each other by the motion of an actuating mechanism. Other switches are more complex, containing electronic circuits able to turn on or off depending on some physical stimulus (such as light or magnetic field) sensed. In any case, the final output of any switch will be (at least) a pair of wire-connection terminals that will either be connected together by the switch's internal contact mechanism ("closed"), or not connected together ("open"). Any switch designed to be operated by a person is generally called a hand switch, and they are manufactured in several varieties:

Toggle switches are actuated by a lever angled in one of two or more positions. The common light switch used in household wiring is an example of a toggle switch. Most toggle switches will come to rest in any of their lever positions, while others have an internal spring mechanism returning the lever to a certain normal position, allowing for what is called "momentary" operation.

Pushbutton switches are two-position devices actuated with a button that is pressed and released. Most pushbutton switches have an internal spring mechanism returning the button to its "out," or "unpressed," position, for momentary operation. Some pushbutton switches will latch alternately on or off with every push of the button. Other pushbutton switches will stay in their "in," or "pressed," position until the button is pulled back out. This last type of pushbutton switches usually has a mushroom-shaped button for easy push-pull action.

CHAPTER-3: MOTOR DRIVER

MOTOR DRIVER CIRCUITS:

Physical motion of some form helps differentiate a robot from a computer. It would be nice if a motor could be attached directly to a chip that controlled the movement. But, most chips can't pass enough current or voltage to spin a motor. Also, motors tend to be electrically noisy (spikes) and can slam power back into the control lines when the motor direction or speed is changed.

Specialized circuits (motor drivers) have been developed to supply motors with power and to isolate the other ICs from electrical problems. These circuits can be designed such that they can be completely separate boards, reusable from project to project.

A very popular circuit for driving DC motors (ordinary or gearhead) is called an H-bridge. It's called that because it looks like the capital letter 'H' when viewed on a discrete schematic. The great ability of an H-bridge circuit is that the motor can be driven forward or backward at any speed, optionally using a completely independent power source.

An H-bridge design can be really simple for prototyping or really extravagant for added protection and isolation. An H-bridge can be implemented with various kinds of components (common bipolar transistors, FET transistors, MOSFET transistors, power MOSFETs, or even chips).

The example provided on this page features:

TTL/CMOS compatible Microchip/Maxim 4424/4427A or IXYS IXDN404 MOSFET driver chips that protect the logic chips, isolate electrical noise, and prevent potential short-circuits inherently possible in a discrete H-bridge.

Schottky diodes to protect against overvoltage or undervoltage from the motor. Capacitors to reduce electrical noise and provide peak power to the driver chip. Pull-up resistors that prevent unwanted motor movement while the microcontroller

powers up or powers down.

A diode-less version of this circuit successfully drove Bugdozer to mini-sumo victory. The more robust (diode protected) version is used on Sweet and Roundabout.

Resistors R1 and R2

R1 and R2 are pull-up resistors. These can be any value from 10 kilohm to 100 kilohm.

These make sure the inputs are both on unless a signal from the microcontroller tells one or the other to turn off. With both on or both off, the motor doesn't spin because there's no voltage difference between them.

Think of these as default values. Unless a different value is specified, the lines are pulled up. This means the circuit can come loose or be disconnected completely and the motor won't spin or stutter.

Technically, R1 and R2 could be eliminated, although then the motors are likely to jerk when the microcontroller powers up or powers down.

Driver Chip IC1

IC1 is a dual MOSFET transistor driver chip. Anything from the TC4424 family will do. The MAX4427 and TC4427A is the same but with a lower amperage rating. The IXDN404 has the highest amperage rating (best choice). The DIP part can be purchased atDigiKey or Mouser as part #IXDN404PI.

WARNING:

Direct motor driving with this chip is only possible for motors that draw less than 100 mA (TC4427A), 150 mA (TC4424), or 340 mA (IXDN404) under load. To determine if your motors qualify, use a multimeter to measure how much current your motor uses under load (for example, when actually driving your robot around) when the motors are connected directly to the battery (not through these chips).

This chip is not really supposed to drive a motor by itself. If you find the chip gets very hot and the motor doesn't spin (or barely spins or stalls when loaded) then you need to have the chip drive some real power MOSFETs like it is supposed to. It's not that much more difficult and it really makes a huge difference in performance.

This chip provides two independent inputs that are compatible with CMOS or TTL chips. This circuit design uses IN A to vary power (on, off, or pulsed in-between) and IN B to determine direction.

OUT A follows the IN A signal but uses the full voltage from the power source, not the tiny voltage from the input signal itself. OUT B follows IN B in the same way.

For example, if IN A is turned on completely (2.4 volts or better) and IN B is turned off completely (0.8 volts or less) then OUT A turns on completely (up to 22 volts) and OUT B turns off completely (GND). The motor gets 22 volts.

This chip is constructed to protect the static sensitive MOSFETs, but also to protect the input sources from current being jammed back by the motors. Optoisolator ICs could be used at the inputs if greater protection, freedom from noise, or electrically-isolated operation is desired. However, I've never had to resort to optoisolators.

Normally four transistors are needed in an H-bridge. Each transistor forms a corner in the letter 'H', with the motor being the bar in the middle.

In this design, each output of the chip forms a complete vertical side of the letter 'H', with the motor still being in the middle. Because a side is now a single output, short-circuits can't form from the top of a side to the bottom of a side. No matter what the inputs, all power must travel from one side to the other -- through the motor.

A mechanical switch, relay, or logical gate could be used to turn the inputs on and off. It would work just fine at providing no movement (on/on or off/off), forward movement (on/off), or reverse movement (off/on). To provide power levels in between (like 50%), rapid pulses of on or off can be provided by pulse-width modulation using a chip or timer.

An important note regarding current rating: The plastic DIP package can only dissipate enough heat when the power usage is below 730 milliwatts. For example, it isn't possible to continuously run the TC4424 chip at both its absolute maximum voltage (22 V) and absolute maximum amperage (3 A) rating. That would result in 66 watts of power usage. (That's almost 100x the maximum allowed.)

Diodes D1 and D3

My original source had D1 and D3 listed as small-signal diodes. I couldn't find any at the time, so, I used 1N5817 Schottky diodes instead. It turns out that Schottky diodes are much better for motor circuts because they react more quickly.

The key factors in substitution are:

Are the diodes rated to turn on with less voltage than the TC4424's or IXDN404's internal transistor base voltage? (600 millivolts)

Are the diodes rated to handle the maximum reverse voltage? (22 volts or 35 volts)

Are the diodes rated to handle the maximum current? (3 amps or 4 amps)

In the case of the 5817s, the datasheets answers are:

Yes. (400 millivolts or less) No. (20 volts -- so this is the circuit's new absolute voltage

maximum) Yes, peak (25 amps)

When a motor accelerates or decelerates for any reason (signal, load, or friction), there is reluctance for the electric field present in the motor coils to change. More properly, the changing field induces power. This "refunded" power can jam back into the chips.

D1 and D3 protect the chips from overvoltage by turning on when more voltage is coming from the motor than is coming from the batteries. The batteries absorb the power.

The turn-on rating of the diode must be lower than the turn-on rating of the chip, or else the diode won't turn on early enough to protect the chip.

Because the diode is installed in "reverse", the power can't flow from the batteries to the motors. If the diode was installed differently, power would immediately flow to the motors, bypassing the chip outputs (or worse, short-circuiting through the chip).

By the way, this arrangement is why the reverse or breakdown voltage of the diodes is important. If the reverse voltage rating was less than the full battery voltage, the battery would break down the reversed diode and just shoot through. In this case, the 1N5817 has a 20 V reverse breakdown voltage, so it can be used with batteries and power supplies up to this voltage.

Diodes D2 and D4

D2 and D4 are also Schottky diodes; the same as D1 and D3.

D2 and D4 protect the chips from undervoltage (less than ground) by turning on when the voltage in the motor is below GND. Once again, the batteries take care of the problem, rather than power flowing backwards from the chip.

D1 through D4 could be eliminated. In fact, Bugdozer runs without the diodes. However, parasitic voltages can and do temporarily overwhelm voltage regulators (reset!) and can even destroy the driver chips.

Actual Implementation of Motor Driver

Despite what may seem complicated at first, the photograph below includes added features such as an LP2954 5V voltage regulator, a bicolor LED, and two switches for testing.

One H-bridge drives one motor. For a common two-wheeled robot, obviously two copies of the H-bridge circuit are needed.

(Click the picture above for a movie)

Pressing the right-side button makes the motor turn counter-clockwise and lights the LED green.

Pressing the left-side button makes the motor turn clockwise and lights the LED red.

Pressing both the buttons turns on the brakes (stopping the motor) and turns off the LED.

Pressing the brakes quickly enough provides variable speed (between 0% and 100%).

Better H-bridge motor drivers

Where do you go from here?

I originally wrote this web page in December 2000. I've received a lot of email regarding this subject, especially from people seeking to drive larger motors or achieve better performance. My friend, Don Kerste, recently gave me grief for still using an IXDN404 chip in my newer robots.

If you are making a small robot or device that uses a miniature gearmotor that requires less than 100 mA continuously when running, then this motor driver with a 4424, 4427, or IXDN404 chip without diodes is perfectly adequate. If you need more current, up to a total of 340 mA, make sure to use the IXDN404 chip and go ahead and add the 1N5817 diodes.

If you need even more current, but you are locked into using this chip, then you can obtain almost 2/3 of an amp (~680 mA) continuously by stacking two chips together with copper foil in between. This allows the chips to dissipate heat.

Soldering two identical IXDN404PI motor driver DIP chips together with copper foil for a cheap

heatsink.

Suppose this is still not enough current. In other words, the chip is heating up too much or the motor isn't turning. Not every motor driver is appropriate for every situation. This is a simple, low-cost, low-power motor driver.

L293D (MOTOR DRIVING CIRCUIT):L293D is a dual H-Bridge motor driver, so with one IC we can interface two DC motors which can be controlled in both clockwise and counter clockwise direction and if you have motor with fix direction of motion the you can make use of all the four I/Os to connect up to four DC motors. L293D has output current of 600mA and peak output current of 1.2A per channel. Moreover for protection of circuit from back EMF output diodes are included within the IC. The output supply (VCC2) has a wide range from 4.5V to 36V, which has made L293D a best choice for DC motor driver.

A simple schematic for interfacing a DC motor using L293D is shown below

As you can see in the circuit, three pins are needed for interfacing a DC motor (A, B, Enable). If you want the o/p to be enabled completely then you can connect Enable to VCC and only 2 pins needed from controller to make the motor work.As per the truth mentioned in the image above it’s fairly simple to program the microcontroller. Its also clear from the truth table of BJT circuit and L293D the programming will be same for both of them, just keeping in mind the allowed combinations of A and B. We will discuss about programming in C as well as assembly for running motor with the help of a microcontroller. As seen from above, l293d is an 16 pin IC(integrated Circuit) shown below along with its pin configuration:

Fig: l293d imageL293D PIN CONFIGURATION AND input- output logic function table:

Chapter-5: RESISTORS

FIXED RESISTORS:

Carbon composition:   These types were once very common, but are now seldom used. They are formed by mixing carbon granules with a binder which was then made into a small rod. This type of resistor was large by today's standards and suffered from a large negative temperature coefficient. The resistors also suffered from a large and erratic irreversible changes in resistance as a result of heat or age. In addition to this the granular nature of the carbon and binder lead to high levels of noise being generated when current flowed.

Carbon film:   This resistor type is formed by "cracking" a hydrocarbon onto a ceramic former. The resulting deposited film had its resistance set by cutting a helix into the film. This made these resistors highly inductive and of little use for many RF applications. They exhibited a temperature coefficient of between -100 and -900 parts per million per degree Celcius. The carbon film is protected either by a conformal epoxy coating or a ceramic tube.

Metal oxide:   This type of resistor is now the most widely used form of resistor. Rather than using a carbon film, this resistor type uses a metal oxide film deposited on a ceramic rod. As with the carbon film, the the resistance can be adjusted by cutting a helical grove in the film. Again the film is protected using a conformal epoxy coating. This type of resistor has a temperature coefficient of around + or - 15 parts per million per degree Celcius, giving it a far superior performance tot hat of any carbon based resistor. Additionally this type of resistor can be supplied to a much closer tolerance, 5% or even 2% being standard, with 1% versions available. They also exhibit a much lower noise level than carbon types of resistor.

Wire wound:   This resistor type is generally reserved for high power

applications. These resistors are made by winding wire with a higher than normal resistance (resistance wire) on a former. The more expensive varieties are wound on a ceramic former and they may be covered by a vitreous or silicone enamel. This resistor type is suited to high powers and

exhibits a high level of reliability at high powers along with a comparatively low level of temperature coefficient, although this will depend on a number of factors including the former wire used, etc

.

VARIABLE RESISTANCES:

Preset(open style)

Presets(closed style)

Multiturn preset

PRESETS SMD PRESETS ROTARY CONTROL SLIDE CONTROL

 

TRIMMERS

VARIABLE RESISTOR

CHAPTER-6: MOTORS

An electric motor converts electrical energy into mechanical energy. Electric motors

operate through interacting magnetic fields and current-carrying conductors to generate

force, although a few use electrostatic forces. The reverse process, producing electrical

energy from mechanical energy, is accomplished by an alternator, generator or dynamo.

Many types of electric motors can be run as generators, and vice versa. For example a

starter/generator for a gas turbine, or traction motors used on vehicles, often perform both

tasks.

Electric motors are found in applications as diverse as industrial fans, blowers and pumps,

machine tools, household appliances, power tools, and disk drives. They may be powered

by direct current(e.g., a battery powered portable device or motor vehicle), or by alternating

current from a central electrical distribution grid. The smallest motors may be found

in electric wristwatches. Medium-size motors of highly standardized dimensions and

characteristics provide convenient mechanical power for industrial uses. The very largest

electric motors are used for propulsion of large ships, and for such purposes as pipeline

compressors, with ratings in the millions of watts. Electric motors may be classified by the

source of electric power, by their internal construction, by their application, or by the type

of motion they give.

The physical principle of production of mechanical force by the interactions of an electric

current and a magnetic field was known as early as 1821. Electric motors of increasing

efficiency were constructed throughout the 19th century, but commercial exploitation of

electric motors on a large scale required efficient electrical generators and electrical

distribution networks.

Some devices, such as magnetic solenoids and loudspeakers, although they generate some

mechanical power, are not generally referred to as electric motors, and are usually

termed actuatorsand transducers, respectively.

Comparison of motor types

Comparison of motor types[16]

Type Advantages Disadvantages Typical Application Typical Drive

AC Induction(Shaded Pole)

Least expensiveLong lifehigh power

Rotation slips from frequencyLow starting torque

FansUni/Poly-phase AC

AC Induction(split-phase capacitor)

High powerhigh starting torque

Rotation slips from frequency

AppliancesStationary Power Tools

Uni/Poly-phase AC

Universal motorHigh starting torque, compact, high speed

Maintenance (brushes)Medium lifespan

Drill, blender, vacuum cleaner, insulation blowers

Uni-phase AC or Direct DC

AC SynchronousRotation in-sync with freq - hence no sliplong-life (alternator)

More expensive

Industrial motorsClocksAudio turntablestape drives

Uni/Poly-phase AC

Stepper DCPrecision positioningHigh holding torque

High initial costRequires a controller

Positioning in printers and floppy drives

DC

Brushless DCLong lifespanlow maintenanceHigh efficiency

High initial costRequires a controller

Hard drivesCD/DVD playerselectric vehicles

DC

Brushed DCLow initial costSimple speed control

Maintenance (brushes)Medium lifespan

Treadmill exercisersautomotive motors (seats, blowers, windows)

Direct DC or PWM

Pancake DCCompact designSimple speed control

Medium costMedium lifespan

Office EquipFans/Pumps

Direct DC or PWM

Servo motor

A servomechanism, or servo is an automatic device that uses error-sensing feedback to correct the

performance of a mechanism. The term correctly applies only to systems where the feedback or error-

correction signals help control mechanical position or other parameters. For example, an automotive power

window control is not a servomechanism, as there is no automatic feedback which controls position—the

operator does this by observation. By contrast the car's cruise control uses closed loop feedback, which

classifies it as a servomechanism.

Synchronous electric motor

Main article: Synchronous motor

A synchronous electric motor is an AC motor distinguished by a rotor spinning with coils passing magnets at

the same rate as the alternating current and resulting magnetic field which drives it. Another way of saying this

is that it has zero slip under usual operating conditions. Contrast this with an induction motor, which must slip to

produce torque. A synchronous motor is like an induction motor except the rotor is excited by a DC field. Slip

rings and brushes are used to conduct current to rotor. The rotor poles connect to each other and move at the

same speed hence the name synchronous motor.

Induction motor

Main article: Induction motor

An induction motor (IM) is a type of asynchronous AC motor where power is supplied to the rotating device by

means of electromagnetic induction. Another commonly used name is squirrel cage motor because the rotor

bars with short circuit rings resemble a squirrel cage (hamster wheel). An electric motor converts electrical

power to mechanical power in its rotor (rotating part). There are several ways to supply power to the rotor. In a

DC motor this power is supplied to the armature directly from a DC source, while in an induction motor this

power is induced in the rotating device. An induction motor is sometimes called a rotating transformer because

the stator (stationary part) is essentially the primary side of the transformer and the rotor (rotating part) is the

secondary side. Induction motors are widely used, especially polyphase induction motors, which are often used

in industrial drives.

Electrostatic motor (capacitor motor)

Main article: Electrostatic motor

An electrostatic motor or capacitor motor is a type of electric motor based on the attraction and repulsion of

electric charge. Usually, electrostatic motors are the dual of conventional coil-based motors. They typically

require a high voltage power supply, although very small motors employ lower voltages. Conventional electric

motors instead employ magnetic attraction and repulsion, and require high current at low voltages. In the

1750s, the first electrostatic motors were developed by Benjamin Franklin and Andrew Gordon. Today the

electrostatic motor finds frequent use in micro-mechanical (MEMS) systems where their drive voltages are

below 100 volts, and where moving, charged plates are far easier to fabricate than coils and iron cores. Also,

the molecular machinery which runs living cells is often based on linear and rotary electrostatic motors.

DC Motors

A DC motor is designed to run on DC electric power. Two examples of pure DC designs are Michael

Faraday's homopolar motor (which is uncommon), and the ball bearing motor, which is (so far) a novelty. By far

the most common DC motor types are the brushed and brushless types, which use internal and external

commutation respectively to create an oscillating AC current from the DC source—so they are not purely DC

machines in a strict sense.

Brushed DC motors

Main article: Brushed DC electric motor

DC motor design generates an oscillating current in a wound rotor, or armature, with a split ring commutator,

and either a wound or permanent magnet stator. A rotor consists of one or more coils of wire wound around a

core on a shaft; an electrical power source is connected to the rotor coil through the commutator and its

brushes, causing current to flow in it, producing electromagnetism. The commutator causes the current in the

coils to be switched as the rotor turns, keeping the magnetic poles of the rotor from ever fully aligning with the

magnetic poles of the stator field, so that the rotor never stops (like a compass needle does) but rather keeps

rotating indefinitely (as long as power is applied and is sufficient for the motor to overcome the shaft torque load

and internal losses due to friction, etc.)

Many of the limitations of the classic commutator DC motor are due to the need for brushes to press against the

commutator. This creates friction. Sparks are created by the brushes making and breaking circuits through the

rotor coils as the brushes cross the insulating gaps between commutator sections. Depending on the

commutator design, this may include the brushes shorting together adjacent sections—and hence coil ends—

momentarily while crossing the gaps. Furthermore, the inductance of the rotor coils causes the voltage across

each to rise when its circuit is opened, increasing the sparking of the brushes. This sparking limits the

maximum speed of the machine, as too-rapid sparking will overheat, erode, or even melt the commutator. The

current density per unit area of the brushes, in combination with their resistivity, limits the output of the motor.

The making and breaking of electric contact also causes electrical noise, and the sparks additionally cause RFI.

Brushes eventually wear out and require replacement, and the commutator itself is subject to wear and

maintenance (on larger motors) or replacement (on small motors). The commutator assembly on a large motor

is a costly element, requiring precision assembly of many parts. On small motors, the commutator is usually

permanently integrated into the rotor, so replacing it usually requires replacing the whole rotor.

Large brushes are desired for a larger brush contact area to maximize motor output, but small brushes are

desired for low mass to maximize the speed at which the motor can run without the brushes excessively

bouncing and sparking (comparable to the problem of "valve float" in internal combustion engines). (Small

brushes are also desirable for lower cost.) Stiffer brush springs can also be used to make brushes of a given

mass work at a higher speed, but at the cost of greater friction losses (lower efficiency) and accelerated brush

and commutator wear. Therefore, DC motor brush design entails a trade-off between output power, speed, and

efficiency/wear.

A: shunt

B: series

C: compound

f = field coil

There are five types of brushed DC motor:

A. DC shunt wound motor

B. DC series wound motor

C. DC compound motor (two configurations):

Cumulative compound

Differentially compounded

D. Permanent Magnet DC Motor (not shown)

Brushless DC motors

Main article: Brushless DC electric motor

Some of the problems of the brushed DC motor are eliminated in the brushless design. In this motor, the

mechanical "rotating switch" or commutator/brushgear assembly is replaced by an external electronic switch

synchronised to the rotor's position. Brushless motors are typically 85-90% efficient or more (higher efficiency

for a brushless electric motor of up to 96.5% were reported by researchers at the Tokai University in Japan in

2009),[17] whereas DC motors with brushgear are typically 75-80% efficient.

Midway between ordinary DC motors and stepper motors lies the realm of the brushless DC motor. Built in a

fashion very similar to stepper motors, these often use a permanent magnet external rotor, three phases of

driving coils, one or moreHall effect sensors to sense the position of the rotor, and the associated drive

electronics. The coils are activated, one phase after the other, by the drive electronics as cued by the signals

from either Hall effect sensors or from the back EMF (electromotive force) of the undriven coils. In effect, they

act as three-phase synchronous motors containing their own variable-frequency drive electronics. A specialized

class of brushless DC motor controllers utilize EMF feedback through the main phase connections instead of

Hall effect sensors to determine position and velocity. These motors are used extensively in electric radio-

controlled vehicles. When configured with the magnets on the outside, these are referred to by modellers as

outrunner motors.

Brushless DC motors are commonly used where precise speed control is necessary, as in computer disk

drives or in video cassette recorders, the spindles within CD, CD-ROM (etc.) drives, and mechanisms within

office products such asfans, laser printers and photocopiers. They have several advantages over conventional

motors:

Compared to AC fans using shaded-pole motors, they are very efficient, running much cooler than the

equivalent AC motors. This cool operation leads to much-improved life of the fan's bearings.

Without a commutator to wear out, the life of a DC brushless motor can be significantly longer

compared to a DC motor using brushes and a commutator. Commutation also tends to cause a great deal

of electrical and RF noise; without a commutator or brushes, a brushless motor may be used in electrically

sensitive devices like audio equipment or computers.

The same Hall effect sensors that provide the commutation can also provide a

convenient tachometer signal for closed-loop control (servo-controlled) applications. In fans, the

tachometer signal can be used to derive a "fan OK" signal.

The motor can be easily synchronized to an internal or external clock, leading to precise speed

control.

Brushless motors have no chance of sparking, unlike brushed motors, making them better suited to

environments with volatile chemicals and fuels. Also, sparking generates ozone which can accumulate in

poorly ventilated buildings risking harm to occupants' health.

Brushless motors are usually used in small equipment such as computers and are generally used to

get rid of unwanted heat.

They are also very quiet motors which is an advantage if being used in equipment that is affected by

vibrations.

Modern DC brushless motors range in power from a fraction of a watt to many kilowatts. Larger brushless

motors up to about 100 kW rating are used in electric vehicles. They also find significant use in high-

performance electric model aircraft.

Coreless or ironless DC motors

Nothing in the design of any of the motors described above requires that the iron (steel) portions of the rotor

actually rotate; torque is exerted only on the windings of the electromagnets. Taking advantage of this fact is

the coreless or ironless DC motor, a specialized form of a brush or brushless DC motor. Optimized for

rapid acceleration, these motors have a rotor that is constructed without any iron core. The rotor can take the

form of a winding-filled cylinder, or a self-supporting structure comprising only the magnet wire and the bonding

material. The rotor can fit inside the stator magnets; a magnetically soft stationary cylinder inside the rotor

provides a return path for the stator magnetic flux. A second arrangement has the rotor winding basket

surrounding the stator magnets. In that design, the rotor fits inside a magnetically soft cylinder that can serve as

the housing for the motor, and likewise provides a return path for the flux.

Because the rotor is much lighter in weight (mass) than a conventional rotor formed from copper windings

on steel laminations, the rotor can accelerate much more rapidly, often achieving a mechanical time

constant under 1 ms. This is especially true if the windings use aluminum rather than the heavier copper. But

because there is no metal mass in the rotor to act as a heat sink, even small coreless motors must often be

cooled by forced air.

Related limited-travel actuators have no core and a bonded coil placed between the poles of high-flux thin

Printed Armature or Pancake DC Motors

A rather unusual motor design the pancake/printed armature motor has the windings shaped as a disc running

between arrays of high-flux magnets, arranged in a circle, facing the rotor and forming an axial air gap. This

design is commonly known the pancake motor because of its extremely flat profile, although the technology has

had many brand names since its inception, such as ServoDisc.

The printed armature (originally formed on a printed circuit board) in a printed armature motor is made from

punched copper sheets that are laminated together using advanced composites to form a thin rigid disc. The

printed armature has a unique construction, in the brushed motor world, in that it does not have a separate ring

commutator. The brushes run directly on the armature surface making the whole design very compact.

An alternative manufacturing method is to use wound copper wire laid flat with a central conventional

commutator, in a flower and petal shape. The windings are typically stabilized by being impregnated with

electrical epoxy potting systems. These are filled epoxies that have moderate mixed viscosity and a long gel

time. They are highlighted by low shrinkage and low exotherm, and are typically UL 1446 recognized as a

potting compound for use up to 180°C (Class H) (UL File No. E 210549).

The unique advantage of ironless DC motors is that there is no cogging (vibration caused by attraction between

the iron and the magnets) and parasitic eddy currents cannot form in the rotor as it is totally ironless. This can

greatly improve efficiency, but variable-speed controllers must use a higher switching rate (>40 kHz) or direct

current because of the decreased electromagnetic induction.

These motors were originally invented to drive the capstan(s) of magnetic tape drives, in the burgeoning

computer industry. Pancake motors are still widely used in high-performance servo-controlled systems,

humanoid robotic systems, industrial automation and medical devices. Due to the variety of constructions now

available the technology is used in applications from high temperature military to low cost pump and basic

servo applications.

Universal motors

A series-wound motor is referred to as a universal motor when it has been designed to operate on either AC

or DC power. The ability to operate on AC is because the current in both the field and the armature (and hence

the resultant magnetic fields) will alternate (reverse polarity) in synchronism, and hence the resulting

mechanical force will occur in a constant direction.

Operating at normal power line frequencies, universal motors are often found in a range rarely larger than one

kilowatt (about 1.3 horsepower). Universal motors also form the basis of the traditional railway traction

motor in electric railways. In this application, the use of AC to power a motor originally designed to run on DC

would lead to efficiency losses due to eddy current heating of their magnetic components, particularly the motor

field pole-pieces that, for DC, would have used solid (un-laminated) iron. Although the heating effects are

reduced by using laminated pole-pieces, as used for the cores of transformers and by the use of laminations of

high permeability electrical steel, one solution available at start of the20th Century was for the motors to be

operated from very low frequency AC supplies, with 25 and 16.7 hertz (Hz) operation being common. Because

they used universal motors, locomotives using this design were also commonly capable of operating from

a third rail powered by DC.

An advantage of the universal motor is that AC supplies may be used on motors which have some

characteristics more common in DC motors, specifically high starting torque and very compact design if high

running speeds are used. The negative aspect is the maintenance and short life problems caused by

the commutator. As a result, such motors are usually used in AC devices such as food mixers and power tools

which are used only intermittently, and often have high starting-torque demands. Continuous speed control of a

universal motor running on AC is easily obtained by use of a thyristor circuit, while (imprecise) stepped speed

control can be accomplished using multiple taps on the field coil. Household blenders that advertise many

speeds frequently combine a field coil with several taps and a diode that can be inserted in series with the

motor (causing the motor to run on half-wave rectified AC).

Universal motors generally run at high speeds, making them useful for appliances such as blenders, vacuum

cleaners, and hair dryers where high RPM operation is desirable. They are also commonly used in portable

power tools, such asdrills, sanders (both disc and orbital), circular and jig saws, where the motor's

characteristics work well. Many vacuum cleaner and weed trimmer motors exceed 10,000 RPM,

while Dremel and other similar miniature grinders will often exceed 30,000 RPM.

Universal motors also lend themselves to electronic speed control and, as such, are an ideal choice

for domestic washing machines. The motor can be used to agitate the drum (both forwards and in reverse) by

switching the field winding with respect to the armature. The motor can also be run up to the high speeds

required for the spin cycle.

Motor damage may occur due to overspeeding (running at an RPM in excess of design limits) if the unit is

operated with no significant load. On larger motors, sudden loss of load is to be avoided, and the possibility of

such an occurrence is incorporated into the motor's protection and control schemes. In some smaller

applications, a fan blade attached to the shaft often acts as an artificial load to limit the motor speed to a safe

value, as well as a means to circulate cooling airflow over the armature and field windings.

AC motors

Main article: AC motor

In 1882, Nikola Tesla discovered the rotating magnetic field, and pioneered the use of a rotary field of force to

operate machines. He exploited the principle to design a unique two-phase induction motor in 1883. In

1885, Galileo Ferrarisindependently researched the concept. In 1888, Ferraris published his research in a

paper to the Royal Academy of Sciences in Turin.

Tesla had suggested that the commutators from a machine could be removed and the device could operate on

a rotary field of force. Professor Poeschel, his teacher, stated that would be akin to building a perpetual motion

machine.[18] Tesla would later attain U.S. Patent 0,416,194, Electric Motor (December 1889), which resembles

the motor seen in many of Tesla's photos. This classic alternating current electro-magnetic motor was

an induction motor.

Michail Osipovich Dolivo-Dobrovolsky later invented a three-phase "cage-rotor" in 1890. This type of motor is

now used for the vast majority of commercial applications.

Components

A typical AC motor consists of two parts:

An outside stationary stator having coils supplied with AC current to produce a rotating magnetic field,

and;

An inside rotor attached to the output shaft that is given a torque by the rotating field.

Torque motors

A torque motor (also known as a limited torque motor) is a specialized form of induction motor which is capable

of operating indefinitely while stalled, that is, with the rotor blocked from turning, without incurring damage. In

this mode of operation, the motor will apply a steady torque to the load (hence the name).

A common application of a torque motor would be the supply- and take-up reel motors in a tape drive. In this

application, driven from a low voltage, the characteristics of these motors allow a relatively constant light

tension to be applied to the tape whether or not the capstan is feeding tape past the tape heads. Driven from a

higher voltage, (and so delivering a higher torque), the torque motors can also achieve fast-forward and rewind

operation without requiring any additional mechanics such as gears or clutches. In the computer gaming world,

torque motors are used in force feedback steering wheels.

Another common application is the control of the throttle of an internal combustion engine in conjunction with

an electronic governor. In this usage, the motor works against a return spring to move the throttle in accordance

with the output of the governor. The latter monitors engine speed by counting electrical pulses from the ignition

system or from a magnetic pickup [19] and, depending on the speed, makes small adjustments to the amount

of current applied to the motor. If the engine starts to slow down relative to the desired speed, the current will

be increased, the motor will develop more torque, pulling against the return spring and opening the throttle.

Should the engine run too fast, the governor will reduce the current being applied to the motor, causing the

return spring to pull back and close the throttle.

Slip ring

The slip ring is a component of the wound rotor motor as an induction machine (best evidenced by the

construction of the common automotive alternator), where the rotor comprises a set of coils that are electrically

terminated in slip rings. These are metal rings rigidly mounted on the rotor, and combined with brushes (as

used with commutators), provide continuous unswitched connection to the rotor windings.

In the case of the wound-rotor induction motor, external impedances can be connected to the brushes. The

stator is excited similarly to the standard squirrel cage motor. By changing the impedance connected to the

rotor circuit, the speed/current and speed/torque curves can be altered.

(Slip rings are most-commonly used in automotive alternators as well as in synchro angular data-transmission

devices, among other applications.)

The slip ring motor is used primarily to start a high inertia load or a load that requires a very high starting torque

across the full speed range. By correctly selecting the resistors used in the secondary resistance or slip ring

starter, the motor is able to produce maximum torque at a relatively low supply current from zero speed to full

speed. This type of motor also offers controllable speed.

Motor speed can be changed because the torque curve of the motor is effectively modified by the amount of

resistance connected to the rotor circuit. Increasing the value of resistance will move the speed of maximum

torque down. If the resistance connected to the rotor is increased beyond the point where the maximum torque

occurs at zero speed, the torque will be further reduced.

When used with a load that has a torque curve that increases with speed, the motor will operate at the speed

where the torque developed by the motor is equal to the load torque. Reducing the load will cause the motor to

speed up, and increasing the load will cause the motor to slow down until the load and motor torque are equal.

Operated in this manner, the slip losses are dissipated in the secondary resistors and can be very significant.

The speed regulation and net efficiency is also very poor.

Stepper motors

Closely related in design to three-phase AC synchronous motors are stepper motors, where an internal rotor

containing permanent magnets or a magnetically soft rotor with salient poles is controlled by a set of external

magnets that are switched electronically. A stepper motor may also be thought of as a cross between a DC

electric motor and a rotary solenoid. As each coil is energized in turn, the rotor aligns itself with the magnetic

field produced by the energized field winding. Unlike a synchronous motor, in its application, the stepper motor

may not rotate continuously; instead, it "steps" — starts and then quickly stops again — from one position to

the next as field windings are energized and de-energized in sequence. Depending on the sequence, the rotor

may turn forwards or backwards, and it may change direction, stop, speed up or slow down arbitrarily at any

time.

Simple stepper motor drivers entirely energize or entirely de-energize the field windings, leading the rotor to

"cog" to a limited number of positions; more sophisticated drivers can proportionally control the power to the

field windings, allowing the rotors to position between the cog points and thereby rotate extremely smoothly.

This mode of operation is often called microstepping. Computer controlled stepper motors are one of the most

versatile forms of positioning systems, particularly when part of a digital servo-controlled system.

Stepper motors can be rotated to a specific angle in discrete steps with ease, and hence stepper motors are

used for read/write head positioning in computer floppy diskette drives. They were used for the same purpose

in pre-gigabyte era computer disk drives, where the precision and speed they offered was adequate for the

correct positioning of the read/write head of a hard disk drive. As drive density increased, the precision and

speed limitations of stepper motors made them obsolete for hard drives—the precision limitation made them

unusable, and the speed limitation made them uncompetitive—thus newer hard disk drives use voice coil-

based head actuator systems. (The term "voice coil" in this connection is historic; it refers to the structure in a

typical (cone type) loudspeaker. This structure was used for a while to position the heads. Modern drives have

a pivoted coil mount; the coil swings back and forth, something like a blade of a rotating fan. Nevertheless, like

a voice coil, modern actuator coil conductors (the magnet wire) move perpendicular to the magnetic lines of

force.)

Stepper motors were and still are often used in computer printers, optical scanners, and digital photocopiers to

move the optical scanning element, the print head carriage (of dot matrix and inkjet printers), and the platen.

Likewise, many computer plotters (which since the early 1990s have been replaced with large-format inkjet and

laser printers) used rotary stepper motors for pen and platen movement; the typical alternatives here were

either linear stepper motors or servomotors with complex closed-loop control systems.

So-called quartz analog wristwatches contain the smallest commonplace stepping motors; they have one coil,

draw very little power, and have a permanent-magnet rotor. The same kind of motor drives battery-powered

quartz clocks. Some of these watches, such as chronographs, contain more than one stepping motor.

Stepper motors were upscaled to be used in electric vehicles under the term SRM (Switched Reluctance

Motor).

Linear motors

Main article: Linear motor

A linear motor is essentially an electric motor that has been "unrolled" so that, instead of producing

a torque (rotation), it produces a straight-line force along its length by setting up a traveling electromagnetic

field.

Linear motors are most commonly induction motors or stepper motors. You can find a linear motor in

a maglev (Transrapid) train, where the train "flies" over the ground, and in many roller-coasters where the rapid

motion of the motorless railcar is controlled by the rail. On a smaller scale, at least one letter-size (8.5" x 11")

computer graphics X-Y pen plotter made by Hewlett-Packard (in the late 1970s to mid 1980's) used two linear

stepper motors to move the pen along the two orthogonal axes.

Feeding and windings

Doubly-fed electric motor

Main article: Doubly-fed electric machine

Doubly-fed electric motors have two independent multiphase windings that actively participate in the energy

conversion process with at least one of the winding sets electronically controlled for variable speed operation.

Two is the most active multiphase winding sets possible without duplicating singly-fed or doubly-fed categories

in the same package. As a result, doubly-fed electric motors are machines with an effective constant torque

speed range that is twice synchronous speed for a given frequency of excitation. This is twice the constant

torque speed range as singly-fed electric machines, which have only one active winding set.

A doubly-fed motor allows for a smaller electronic converter but the cost of the rotor winding and slip rings may

offset the saving in the power electronics components. Difficulties with controlling speed near synchronous

speed limit applications.[20]

Singly-fed electric motor

Main article: Singly-fed electric machine

Singly-fed electric motors incorporate a single multiphase winding set that is connected to a power supply.

Singly-fed electric machines may be either induction or synchronous. The active winding set can be

electronically controlled. Induction machines develop starting torque at zero speed and can operate as

standalone machines. Synchronous machines must have auxiliary means for startup, such as a starting

induction squirrel-cage winding or an electronic controller. Singly-fed electric machines have an effective

constant torque speed range up to synchronous speed for a given excitation frequency.

The induction (asynchronous) motors (i.e., squirrel cage rotor or wound rotor), synchronous motors (i.e., field-

excited, permanent magnet or brushless DC motors, reluctance motors, etc.), which are discussed on this

page, are examples of singly-fed motors. By far, singly-fed motors are the predominantly installed type of

motors.

Nanotube nanomotor

Main article: Nanomotor

Researchers at University of California, Berkeley, recently developed rotational bearings based upon multiwall

carbon nanotubes. By attaching a gold plate (with dimensions of the order of 100 nm) to the outer shell of a

suspended multiwall carbon nanotube (like nested carbon cylinders), they are able to electrostatically rotate the

outer shell relative to the inner core. These bearings are very robust; devices have been oscillated thousands

of times with no indication of wear. These nanoelectromechanical systems (NEMS) are the next step in

miniaturization and may find their way into commercial applications in the future.

See also:

Molecular motors

Electrostatic motor

Efficiency

To calculate a motor's efficiency, the mechanical output power is divided by the electrical input power:

,

where η is energy conversion efficiency, Pe is electrical input power, and Pm is mechanical output power.

In simplest case Pe = VI, and Pm = Tω, where V is input voltage, I is input current, T is output torque, and ω is

output angular velocity. It is possible to derive analytically the point of maximum efficiency. It is typically at less

than 1/2 the stall torque.

Implications

Because a DC motor operates most efficiently at less than 1/2 its stall torque, an "oversized" motor runs with

the highest efficiency: using a bigger motor than necessary enables the motor to operate closest to no load, or

peak operating conditions.

Torque capability of motor types

When optimally designed for a given active current (i.e., torque current), voltage, pole-pair number, excitation

frequency (i.e., synchronous speed), and core flux density, all categories of electric motors or generators will

exhibit virtually the same maximum continuous shaft torque (i.e., operating torque) within a given physical size

of electromagnetic core. Some applications require bursts of torque beyond the maximum operating torque,

such as short bursts of torque to accelerate an electric vehicle from standstill. Always limited by magnetic core

saturation or safe operating temperature rise and voltage, the capacity for torque bursts beyond the maximum

operating torque differs significantly between categories of electric motors or generators.

Note: Capacity for bursts of torque should not be confused with Field Weakening capability inherent in fully

electromagnetic electric machines (Permanent Magnet (PM) electric machine are excluded). Field Weakening,

which is not readily available with PM electric machines, allows an electric machine to operate beyond the

designed frequency of excitation without electrical damage.

Electric machines without a transformer circuit topology, such as Field-Wound (i.e., electromagnet) or

Permanent Magnet (PM) Synchronous electric machines cannot realize bursts of torque higher than the

maximum designed torque without saturating the magnetic core and rendering any increase in current as

useless. Furthermore, the permanent magnet assembly of PM synchronous electric machines can be

irreparably damaged, if bursts of torque exceeding the maximum operating torque rating are attempted.

Electric machines with a transformer circuit topology, such as Induction (i.e., asynchronous) electric machines,

Induction Doubly-Fed electric machines, and Induction or Synchronous Wound-Rotor Doubly-Fed (WRDF)

electric machines, exhibit very high bursts of torque because the active current (i.e., Magneto-Motive-Force or

the product of current and winding-turns) induced on either side of the transformer oppose each other and as a

result, the active current contributes nothing to the transformer coupled magnetic core flux density, which would

otherwise lead to core saturation.

Electric machines that rely on Induction or Asynchronous principles short-circuit one port of the transformer

circuit and as a result, the reactive impedance of the transformer circuit becomes dominant as slip increases,

which limits the magnitude of active (i.e., real) current. Still, bursts of torque that are two to three times higher

than the maximum design torque are realizable.

The Synchronous WRDF electric machine is the only electric machine with a truly dual ported transformer

circuit topology (i.e., both ports independently excited with no short-circuited port). The dual ported transformer

circuit topology is known to be unstable and requires a multiphase slip-ring-brush assembly to propagate

limited power to the rotor winding set. If a precision means were available to instantaneously control torque

angle and slip for synchronous operation during motoring or generating while simultaneously providing

brushless power to the rotor winding set (see Brushless wound-rotor doubly-fed electric machine), the active

current of the Synchronous WRDF electric machine would be independent of the reactive impedance of the

transformer circuit and bursts of torque significantly higher than the maximum operating torque and far beyond

the practical capability of any other type of electric machine would be realizable. Torque bursts greater than

eight times operating torque have been calculated.

Materials

There is an impending shortage of many rare raw materials used in the manufacture of hybrid and electric cars

(Nishiyama 2007) (Cox 2008). For example, the rare earth element dysprosium is required to fabricate many of

the advancedelectric motors used in hybrid cars (Cox 2008). However, over 95% of the world's rare earth

elements are mined in China (Haxel et al. 2005), and domestic Chinese consumption is expected to consume

China's entire supply by 2012 (Cox 2008).[citation needed]

While permanent magnet motors, favored in hybrids such as those made by Toyota, often use rare earth

materials in their magnets, AC traction motors used in production electric vehicles such as the GM EV1, Toyota

RAV4 EV and Tesla Roadster do not use permanent magnets or the associated rare earth materials. AC

motors typically use conventional copper wire for their stator coils and copper or aluminum rods or bars for their

rotor. AC motors do not significantly use rare earth materials.