DC MOTOR DRIVE USING H-BRIDGE

WAN ZATEEL AQMAER BT WAN AB HALIM

This Report Is Submitted In Partial Fulfillment Of Requirements For The Bachelor

Degree Of Electronic Engineering (Industrial Electronic)

Faculty Of Electronic And Computer Engineering

Kolej Universiti Teknikal Kebangsaan Malaysia

MAY 2006

ABSTRACT

H-Bridge circuit is a popular circuit for driving Direct Current (DC) Motor and

make it turn. It's called H-Bridge because it looks like the capital 'H' on classic

schematics. The ability of H-Bridge circuit is that the motor can be driven forward or

backward at any speed. H-Bridge circuit can be used for simple prototyping or really

extravagant for added protection and isolation. So many thing should be look to make an

H-Bridge circuit, depends on its usage and motor. Many switches can be used start from

SPDT, transistors like BJT and FET transistors, MOSFET Transistors, or power

MOSFET.

What's most important in this thesis is to acquire knowledge and learn the

characteristics of the switches, H-Bridge circuits, and DC Motor Drive. Then, second

important things come after that, that is to analyze all the characteristics and choose the

best switches to the circuit especially looking to power efficiency. This is very important

to do because people have a problem to choose best component in their H-Bridge circuits

to make a project for example a robot. The circuit design also can be renew and modified

that they can be completely separate boards, reusable to other project like toys, models,

cordless tools, and robots.

V

ABSTRAK

Litar Tetimbang-H merupakan litar yang popular untuk memacu Motor Arus

Terus (AT) dan memutarkannya. Ia dipanggil Tetimbang-H kerana litarnya kelihatan

seperti huruf 'H'. kebolehan litar ini ialah motor dapat dipacu ke hadapan atau ke

belakang pada sebarang kelajuan. Litar Tetimbang-H boleh digunakan untuk proptotaip

mudah sehinggalah yang begitu kompleks. Namun, banyak perkara yang perlu dinilai

dalam membuat litar Tetimbang-H, bergantung pada penggunaan dan jenis motor yang

digunakan. Pelbagai suis boleh diambilkira bermula daripada SPDT, transistor seperti

BJT dan FET, atau MOSFET kuasa dalam membina litar ini.

Apa yang paling penting dalam projek ini ialah untuk memperoleh pengetahuan,

kemahiran dan mempelajari ciri-ciri suis, litar Tetimbang-H, dan jenis motor arus terus.

Perkara kedua ialah untuk membuat analisis suis yang terbaik yang patut digunakan

dalam litar berdasarkan keefisien kuasa. Perkara ini amat penting kerana ramai orang

bermasalah untuk memilih komponen yang terbaik dalam membuat litar Tetimbang-H

mereka contohnya untuk membuat robot. Litar ini juga nanti dapat diperbaharui atau

diubahsuai bergantung kepada fungsinya dan projek yang ingin dibuat seperti patung

permainan, model, dan robot.

vi

CHAPTER I

INTRODUCTION

1.1 INTRODUCTION

This chapter is mainly discussing overview of this project and its possible

application. A superficial view of the project objectives, operation, design and scope

of this project is clarified briefly. An expanded detail of these features can be found in

the chapters to advance.

1.2 OBJECTIVES OF THE PROJECT

There are five objectives of doing this project. First is to study the DC Motor

drive operation. Second is to study the H-Bridge circuitry concept for controlling

brushed DC Motor. While the third is to study various of switches like BJT transistors,

mode power MOSFET or MOSFET transistors, Darlington, and decide the best to the

H-Bridge circuit. Other objective is to develop a better circuit to drive a DC Motor

that can forward and reverse in any speed. Lastly, the objective is to improve my basic

electronic circuit knowledge.

2

1.3 SCOPE OF THE PROJECT

This project needs first, basic electronic circuit knowledge. It will use tools and

components like DC motor, battery, dynamo, PWM circuit to provide PWM pulses,

and best switches. The software used are PSpice/Multisim that requires to simulate the

design circuit and to make sure all the calculation related is right, so the right

components choose. So, the wrong choosing components can be avoided. Finally the

weaknesses of circuit can be solved. All lab instruments are using while complete this

project.

1.4 OVERALL VIEW OF THE PROJECT

To make a motor turn, we take a battery, hook the positive side to one side of

our DC motor then we connect the negative side of the battery to the other motor lead.

The motor spins forward and reverse. But, if we want to be able to control the motor in

both forward and reverse with a processor, we need more circuitry. H-Bridge circuit

is a popular circuit for driving DC motors. 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. The H-Bridge design can be really simple for

prototyping or really extravagant for added protection and isolation.

3

1.5 METHOD OF RESEARCH

This project is being done by referred to the H-Bridge concepts to drive a DC

motor. So, to make sure the objectives obtained, three two circuits were made using

the H-Bridge concepts.

Reference material like journals are very important to make comparison in

finishing this project. Based on understanding about the H-Bridge concepts, a good

design circuit can be build to drive a motor in forward and reverse at any speed.

Result from analysis presented in tables and percentages to support this

project. Beside, comparison data delivered in that way to make it more systematic,

orderly and easy to understand.

1.6 THESIS SYNOPSIS

The thesis contains five chapters that explained deep about this project. First

chapter will explain about introduction to give overall concept about this project like

objectives, scope of project and thesis synopsis.

The second chapter will discuss about the research and information related to

the project. Every facts and information found from any reference books will be

observed and debated to choose the good way for the project. In easy word, this

chapter is about theoretical chapter and study about the concept of this project until the

best method found. The next chapter will discuss about the techniques and methods

that have been choose in second chapter with deeply method. The techniques divide

into two, the hardware and software used.

While the fourth chapter is about analysis, results and discussion parts. All the

analysis results like tables, voltage drop, and all the comparisons between Darlington

4

and MOSFET will be discussed in this chapter. The analysis process has been done to

both circuits and the motor.

The last chapter in this thesis is about conclusion and suggestion. In this

chapter, conclusion made based on project achieving and learning experience gained

from the starting until finishing of this project. Beside, some suggestions made to

improve the project level so the project can be better in the future.

CHAPTER II

LITERATURE REVIEW

2.1 INTRODUCTION

This chapter will discuss about the theory and concept of the project in overall

perspective. The purpose of discussion is to explain approach and method that used

in past research and observe how far the project related with theory and research itself.

Beside, this chapter also explained and showed the concept and theory used to solve

the project problem statements. Theoretical understanding is very important as a guide

in doing any research. The result or analysis can't be done if not compare to the

theoretical parts.

2.2 DC MOTOR DRIVE

The Direct Current (DC) machine is popular in a number of drive applications due

to its simple operation and control. The starting torque of dc machines is large, which is

the main reason for using it in several traction applications. A special form of dc machines

6

can also be used with either ac or dc supply. A large number of appliances and power

tools used at home, such as circular saws and blenders, are dc machines.

The study of Direct Current motor of the sort used in toys, models, cordless tools,

and robots. These motors are particularly versatile because both their speed and direction

can be readily controlled. When the motor is disconnected from the battery, it is off. When

it is connected with the red wire to the positive terminal and black to negative it turns

forward; and when the wires are reversed, the motor turns backwards.

FORWARD

REVERSE

Figure 2.1: Basics DC Motor

The main components of the dc machines are; field circuit, armature circuit,

commutator, and brushes. The field is normally an electric magnet fed by a dc power

source. In small machines, the field is often a permanent magnet.

The armature circuit is composed of the windings, commutator, and brushes.

The windings and the commutator are mounted on the rotor shaft and therefore rotate.

The brushes are mounted on the stator and are stationary, but in contact with the

rotating commutator segments.

SiliZ(

77. 1

-4-. - - —

! r--- 1 i II ! i h '

1."4

‘111illifil. I.

(

0,4 , V1111 ...11M; \

riT,:r r.%11 rt-dth I);

.411,, .11 Cozroci

in ;Itar:circ

7

The rotor windings are composed of several coils, each has two terminals

connected to the commutator segments on opposite sides. The commutator segments

are electrically isolated from one another. The segments are exposed, and the brushes

touch two opposing segments. The brushes allow the commutator allow the

commutator segments to be connected to an external dc source.

Figure2.2: Physical structure of DC Motor

Figure 2.3: Part of DC Motor

Stator field

Bs Rotor winding

Rotor field

B,?

2.2.1 DC Motor Operation

The stator field produces flux from the N pole to the S pole. The brushes

touch the terminals of the rotor coil under the pole. When the brushes are connected to

an external dc source of potential V, a current I enters the terminal of the rotor coil

under the N pole and exits from the terminal under the S pole. The presence of the

stator flux and rotor current produces a force F on the coil known as the Lorentz

force. This force produces torque that rotates the armature counterclockwise. The coil

that carries the current moves away from the brush and is connected from the external

source. The next coil moves under the brush and carries the current I. This produces a

continuous force F and continuous rotation. The function of the commutator and

brushes is to switch the coils mechanically.

Stator winding

8

Figure2.4: Inside of DC Motor

Speed II idc shunt/

separately excited)

III dc series excited I

Torque I nd X"

2.2.2 Types of DC Motors

Direct current motors can be classified into four groups based on the

arrangement of their field windings. Motors in each group exhibit distinct speed-

torque characteristics and are controlled by different means. These four groups are

separately excited motors, shunt motors, series motors, and compound motors.

Figure 2.5: Speed-torque characteristics of electric motors

2.2.2.1 Separately Excited Motors

The field winding is composed a large number of turns with small cross-

section wire. This type of field winding is designed to withstand the rated voltage of

the motor. The field and armature circuits are excited by separate sources.

9

I

Figure 2.6: Separately excited motor circuit

The equivalent circuit of a separately excited motor is shown in Figure 2.6.

The motor consists of two circuits: field and armature. The field circuit is mounted on

the stator of the motor and is energized by a separate dc source of voltage. The field

has a resistance and a high inductance. Te field inductance has no impact in the

steady-state analysis, since the source is a dc type.

2.2.2.2 Series Motors

Fick

R

Armature

Wf

10

Figure 2.7: Series motor circuit

11

The field winding of a series motor is connected in series with the armature

circuit, as shown in Figure 2.7. The great feature of series motors is their ability to be

directly driven by ac supplies. Because of this important feature, we can find dc series

motors used in household appliances and tools such as blenders, food processors,

washing machines, drills, and circular saws.

2.2.3 Comparison between Separately Excited Motor and Series Motor

Types of motor Characteristics

• Speed always constant

Separately excited • Starting speed is at medium level

motor • No effect though load changes

• Low speed at high load

Series motor • High torque at starting

• Suitable only for small load

Table 2.1: Comparison of separately excited motor and series motor

2.3 SOLID — STATE DEVICES

The solid-state power electronic switches is a power device that design to

handle high currents and voltages, operate at low junction losses, and withstand high

rates of change of voltage and current. The switching speeds of solid-state devices

should be as high as possible in order to reduce the size of the circuit magnetic

components and to reduce audible noise due to the switching action.

Figure 2.8 below show how DC motor control translates into five manual

motor-control circuits using switches. Figure A is the most closely related to the science-

fair demo. A single-pole, single-throw (SPST) switch turns power to the motor on or off,

12

while a double-pole, double-throw (DPDT) switch controls the polarity of the motor

connections.

The component we call a switch can actually contain several switches, all

activated by the same handle. These joined switches are indicated on a schematic by a

dotted line joining their symbols. Each joined switch is referred to as a pole. So a switch

component containing two switches is a double pole unit.

Throws refer to the number of circuits a switch can make. An ordinary on/off

switch makes or breaks just one connection, so it's a single-throw switch. The direction

switches at the top of Figure 2.8 select one of two connections, so they are double-throw

switches.

Figure B uses a pair of SPDT switches to control direction and on/off. If the two

switches are set so that they both connect to the same power-supply rail, the circuit brakes

the motor using the motor/generator principle. Figure C is very similar, but uses four

SPST switches. These switches must be turned on and off in specific combinations to run

and stop the motor. Note that a couple of switch settings are not allowed, because they

would short out the power supply.

Figures D and E use a second battery to reverse the motor, thereby simplifying the

arrangement of switches. However, extra batteries mean extra weight and expense. And

the batteries may wear out at different rates, since in most applications motors spend more

time going in one direction or the other. Still, the half-bridge design is worth knowing,

because it can be very useful in cheap, efficient, dual-motor designs.

13

A onioff direction

• ;; s 4- _

I I

•• 1 OTC - 1 .I., •

SPST switch controls on/off; DPDT switch sets direction

B C

+

* 0 1 3 * z do + e 2 — • • 1 OTII • • 1 — a • — • 1— 2

' UP. 2 Ur - S 101 ' ( HAIL) ' lil'. 2 DOWN FORWA'iLl '

DOWN. 2 it' - K‘,/ SE

' DOWN. 2 2OWN - S ICI ' (ENAKE)

A pair of SPDT switches controls on/off and direction; brakes to a stop

ALL OF .- ,- 5I01' (L0OL5 ' I 4 ON - -- CRWARD 2 i 3 ON - '(EVERSE. ' i 3 ON - 5101' ( HAKE) 2 I 4 ON - 5101' IHHAKE) ' 1 2 ON - NO ALLOWED 3 ' 4 ON - NO ALLOWLU

Four SPST switches (H bridge) control on/off, direction & braking

D +

E + 1

— on/off • _

+

direction

• OM • _

+ 12

• •

• _ — 2

SPST switches controls on/off; SPDT sets direction

011- DI- ' - S 101' LOOSE.' 1 ON - 20N - 'EVEI- St. 1 • 2 ON - NO t ALLOWED

Two SPST switches (half bridge) control on/off & direction

Figure 2.8: Motor controllers using manual switches

14

2.4 ELECTRONIC SWITCHES

The manual motor controllers described above can all be converted to electronic

control using one or more of the following types of electronic switches.

A relay is a mechanical switch operated by an electromagnet. The relatively small

current that energizes the electromagnet can control a larger current through the relay

switches, known as the contacts. However, most relays are not suitable for direct

connection because even the relatively small coil current is more than the Stamp's pins

can supply. This can be overcome through the use of a transistor switch to beef up current

handling.

Relays have two useful properties for small motor controllers; their contacts have

very low on-resistance, meaning that very little power is wasted and secondly they are

available in just about any combination of poles.

Solid-state multipole/multithrow switches are usually built up from many SPST

units. On the downside again, relays are slow, make noise, and wear out. They are almost

useless in schemes that switch power on and off rapidly to control motor speed (duty cycle

control).

By allowing a small base current to control a larger collector current, transistors

make good switches. They're fast, quiet, and can last forever. Transistors are usable only

as SPST switches, and need to consider polarity in selecting the transistor type and

connecting the load. Finally, even a fully-on transistor has a voltage drop between the

collector and emitter. It's typically 0.5 volts, but can be 1 volt or more in Darlington

configurations. This wastes power and generates heat, which can damage or destroy the

transistor.

15

LOAD

...C311SeS nxd iarger current (10x or rlorol to f.lovi tr.q.5 way

_causes a rriuc:n of4.7rqef

• urrent 10x • or m3ro; • flow frqs Way

0

LOAD

A sinati currar.it Itaw-f:ng this way..

It smai; an-ref:It

tnis Nay..

C. )I E: b IC-Li : e e -ritter

Figure 2.9: Transistors make good motor switches

MOSFET(metal-oxide semiconductor field-effect transistors) would seem to

eliminate all the problems of relays and conventional transistors. Their control input, the

gate, draws almost no current. It switches in response to the presence of a voltage. A

turned-on MOSFET can offer an on resistance that many relays would envy. And

reasonably priced MOSFET are available in current ratings. The only trouble with

MOSFET is that they are at their best with supply voltages above 10 volts, and with

control voltages higher than the supply.

CHAPTER III

METHODOLOGY

3.1 INTRODUCTION

This chapter will explain about the methodology or the project approached that

has been taken. Every steps in doing this project will be explain details until the

project succeed. This project consists of two parts, which is hardware and software.

The hardware consists of two circuits.

This two parts are separate circuits to make the project operates well. Then the

project will be testing to make sure no ralat happen. If ralat happen, the maintenance

process will be done to trace the ralat. But if the system function well, that mean the

process end.

17

3.2 PROBLEM SOLVING METHOD

The procedures and methods to be used to achieve the project are;

■ Literature review from the supervisor besides information that successfully

collected from interne and books about DC Motor Drive and H-Bridge circuit.

■ The theory explanation and calculation about the circuit from H-Bridge

concept is proof by doing the calculation based on the circuit.

■ Design the circuit through paper and simulate with software of the

PSpice/Multisim or Protel/Eagle.

■ Simulation circuit designed. If the circuit can't work, back to the step before.

■ When the circuit design works, transfer and build it through the PCB layout.

■ Then the testing will be made to prove the system works by connect the H-

Bridge circuit to the DC Motor drive.

■ Finally, final report will be submitted to the faculty.

Start

Troubleshoot

Theory explanation and analysis of

circuits

Design circuit

Simulate circuit

3.3 FLOW CHART

– — - - T –

Literature review

NOT OK

Test

OK

18

F

Troubleshoot Transfer and build through PCB

NOT OK

Test

OK

Connect the circuit with DC Motor

19

3.4 DESIGN CIRCUIT

By referring from concepts and circuits being found in the previous steps, the

best circuits are being design. After designing the circuits, simulation circuits in

Multisim software V8.028 (trial version) are done. This simulation used to predict that

the circuits can be functioning as expected.

3.5 PROJECT COMPONENT CHOOSING

Usually in every circuit in one system will use components like resistor,

capacitor, diode, LED, integrated circuit (IC), relays, 555 timer, triacs, transistor,

MOSFET and others. So, here is the explanation about the components used in build

this project. The explanation is about their usage, type, specification, and why they are

used. The components are:

■ Capacitor

■ Diode

■ Transistor

■ MOSFET

■ Resistor

3.5.1 Resistor

Resistor is one of very important component in every circuit. Every electronic

tools using resistor. The component is used to reduce the current and voltage or to cut

current from over flow in one electronic circuit. If the current flow through resistor is

20

big, it will produce heat. Resistor is made in many size and shape. As usual, resistor is

divides by two type, fixed and variable (rheostat or slider).

Figure 3.1: Adjustable resistor Figure 3.2: Fix resistor

Resistance is a basic property of all conductors above the temperature of

absolute zero and its refer to tendency to oppose the flow of electrical current.

3.5.2 Capacitor

Capacitors are used in a wide variety of electronics circuit applications

including ac bypass, decoupling betweeen circuits that share a common dc power

supply, dc blocking, tuning, timing, and more. The capacitor is an energy-storage

device. Capacitors store energy in an electrical field (electrostatic). The basic capacitor

consists of a pair of metallic plates that face each other, and are separated by an

insulating material, called a dielectric. The dielectric can be any insulating material,

including air.

There are two types of capacitor, fixed and variable. Several types of fixed

capacitors are paper, mylar, ceramic, mica, ployester, and others. The capacitors used

in this project are electrolytic capacitor and seramic capacitor.

21

3.5.2.1 Electrolytic Capacitor

This type of capacitor used an electrolyte to achieve a high dielectric constant.

Electrolytic capacitor is polarity sensitive. Aluminium electrolytic is used for dc

power supply riple reduction, bypassing, audio coupling, and stage-to-stage

decoupling in audio and low-frequency circuits. The aluminium electrolytic was used

almost exclusively for many years, but recently more circuits have been using

tantalum dielectric electrolytic. These capacitors offer higher frequency operation than

aluminium electrolytics and are physical much smaller.

Figure 3.3: Electrolytic capacitor

3.5.2.2 Ceramic capacitor

Ceramic capacitors range in value from a few picofarads up to 0.5uF. Ceramic

capacitors are often rated by the temperature coefficient.This specification is the

change of capacitance per change of temperature in degrees Celcius. It use ceramic

and a silver layer as a dielectric.

22

Figure 3.4: Ceramic capacitor

3.5.3 Diode

Diode is the simplest of semiconductor devices but plays a very vital role in

electronic systems, having characteristics that closely match those of a simple

switch.It will appear in a range of applications, extending from the simple to the very

complex. The characteristics of an ideal diode are those of a switch that can conduct

current in only one direction.

There are many characteristics that should be care when choosing a diode.

Data on specific semiconductor devices are normally provided by the manufacturer in

one of two forms. They includes the forward voltage, the maximum forward current,

the reverse saturation current, the revese-voltage rating, the maximum power

dissipation level at a particular temperature, capacitance levels, reverse recovery time

and operating temperature range.

3.5.4 Transistor

The transistor is a three-layer semiconductor device consisting of either two-n

and one p-type layers of material or two-p and one n-type layers of material. The

former is called an npn transistor, while the latter is called a pnp transistor. The outer

layers have witdhs much greater than the sandwiched p- or n-type material. The three

23

terminals have been indicated by the capital letters E for emitter, C for collector, and B

for base.

Since the specification sheet is the communication link between the

manufacturerand user, it is particularly important that the information provided be

recognized and correctly understood. Most specification sheets are broken down into

maximum ratings, thermal characteristics, and electrical characteristics.

3.6 CIRCUIT CONSTRUCTIONS

After successful doing simulation, the next step is to construct the circuit.

Simulation result and practical result is not exactly the same. In circuit constructions,

some steps must be followed to avoid problem. The steps are components preparation,

components testing, and construct the components to printed circuit board.

3.6.1 Components Preparation

The components needed are get from schematic figures that have been done.

List of components made to make buying componenets process easier.

3.6.2 Component Testing

The components that have buy must be tested first before fix to the printed

circuit board. This is to make sure all the components are in a good condition and can

operate well.

24

3.6.3 Construct Component at the Printed Circuit Board (PCB)

The choosed components have been constructed to the PCB guiden by the

schematic circuits of Darlington and Mosfet circuits. Then, the components being

soldered.The component legs needed to be cut to avoid short circuit and to make it

tide.

3.7 TESTING

When all the components constructed to the printed circuit board, testing

circuit done to make sure the circuits function well. There are three steps in this

process, first, components testing, circuits testing, and motor demonstration. After

finishing testing process, and make sure there are no problem with the circuits,

analysis process being done to take data, so the comparison can be done between both

circuits.