DESIGN AND CONSTRUCTION OF A PROTOTYPE REMOTE CONTROL FOR HOME APPLIANCE USING r.f

BY

A PROJECT SUBMITTED TO THE DEPARTMENT OF ELECTRICAL AND ELECTRONIC ENGINEERING

TECHNOLOGY

ABIA STATE POLYTECHNIC, ABA

IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE NATIONAL DIPLOMA (ND) IN

ELECTRICAL /ELECTRONIC ENGINEERING

January, 2016

CERTIFICATION

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This is to certify that this project research “DESIGN AND CONSTRUCTION OF MOVING LED DISPLAY BOARD” was carried out by with matriculation numbers

DECLARATION

I hereby declare that this project “DESIGN AND CONSTRUCTION OF DOT MATRIX DISPLAY SYSTEM was designed and constructed by me to the Department of Electrical Electronic Engineering Abia State Polytechnic, Aba in partial fulfillment of the requirement for the award of National Diploma (ND) I further declare that this work has not been submitted to this or any other institution for the award of degree, diploma or equivalent course.

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ACKNOWLEDGEMENT

My profound gratitude goes to my parents Mr and Mrs ………… for their invaluable contribution to my educational pursuit and every others sector of life.

My warm regards goes to my elder brother, ---------. for his support and various suggestions during the writing of this project, and to my younger siblings, Eunice and Prosper for their love and understanding.

I also want to appreciate the efforts of my friends and well wishers who in one way or the other contributed to my happiness and sustenance during my stay in school.

To my supervisor, and Engr for his instructions, my lecturers; for their numerous teachings and impartation in my life, while an undergraduate.

And not forgetting Consort for providing me with some of the materials needed for the write up of this project and for his coaching.

Thanks to you all.

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TABLE OF CONTENT

CHAPTER ONE

INTRODUCTION

1.1 Brief Over View 6

1.2 Aim And Objectives 6

1.3 Scope of project 6

1.4 Work Organization. 7

CHAPTER TWO

LITERATURE REVIEW

2.1 Review of Remote Control System 9

2.2 Descriptions of Project 11

2.3 Use of Project 12

CHAPTER THREE

DESIGN METHODOLOGY AND ANALYSIS

3.1 Information Gathering 13

3.2 Hardware Component Analysis 14

3.2.1 Transformer 14

3.2.2 Bridge Rectifier 15

3.2.3 Diode 17

3.2.4 Capacitor 25

3.2.5 Voltage Regulator 30

3.2.6 Light Emitting Diode 32

3.2.7 Resistor 33

3.2.8 Micro Controller 37

3.2.9 Crystal Oscillator 38

3.2.10 Transistor 40

3.2.11 Relays 48

3.2.12 Infra Red Transmitter and Receiver 50

3.3 System Design Approach 51

3.4 Choice of Design 54

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3.5 System Component 54

CHAPTER FOUR

SYSTEM HARDWARE AND COSTRUCTION

4.1 The Hardware Subsystem 55

4.1.0 Basic Power Supply Design 55

4.2Micro Controller 57

4.3 The Input Interface Design 65

4.4 The Output Interface Design 66

4.5 System Testing 69

4.5.0 Test Plan 69

4.5.1 Test Data 69

4.6 Choice of Programming Language 71

4.7 Expected Test Result 71

4.8 Performance Evaluation 71

CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

5.1 Problem Encountered 72

5.2 Recommendation 72

5.3 Conclusion 73

Reference 74

Appendixes A 7581

Appendixes B82

Appendixes C

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CHAPTER ONE

INTRODUCTION1.1 BRIEF OVER VIEW

The need for a remote control alert system that can control domestic

appliances and various lighting points and sockets has often been a concern for

users. At times users find it inconvenient and time consuming to go around

turning their appliances on or off each time there is power outage or each time

they are leaving the house for work. It has also often led to damage of appliances

due to the fact that an appliance was not turned off before leaving the house.

1.2 AIMS AND OBJECTIVE The Objective of putting up this project, therefore, is to design an

equipment that can facilitate a convenient and easy way of controlling our

domestic appliances, lighting points and sockets especially in powering

them, without always going to appliances physically by ourselves.

This objective will be accomplished using various components which

include a Microcontroller (AT89C51) which acts as the backbone of the

project together with other components.

1.3 SCOPE OF PROJECT In this project report, the diagrams will range from simple block

diagrams to complex circuit diagrams which will comprise mostly

of common electrical and electronics symbols. Some of the

diagrams that will feature in this report will be used as the main

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block on which certain parameters will be explained upon. Relevant

electronic components will also be shown and described.

This project report will also contain an outline of the circuit diagram

as it is seen physically. The package design diagram will be

included showing the width, height in millimeter (mm).

1.4 WORK ORGANIZATIONChapter 1 serves as the introductory chapter where I try to relay the

concept and acceptable reasons why the project should be implemented for the

intending user of the work. Thus, showing the block diagram of the design and a

scope of diagram for the entire project design.

Chapter 2 deals with the literature review where it will be discussing the

origin of this project design. In the origin of the project, we will be looking at

what brings about the three phase selector in our day to day activity and how the

idea of designing this project comes about.

A description of the Project is also given where the 2 sections of the

project are discussed and the various components contained in the sections also

mentioned.

The use and importance of this project design will also be mentioned here. It

will be looking at the best place where this project design can be use and where it

cannot. This chapter will also make room for adding additional information that

will help in the actualization of this project design.

Chapter 3 treats the methodology of this project design. It comprises of the

information gathering; the source of the materials used in designing and writing

the project report, data analysis; the components and devices used in the course

of designing this project will be analysis to know their basic means of operation

and how they will help in putting up this design, system design approach; the

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possible way to tackled the project design from scratch, bottom-up; it will treat

how the practical detail was gotten before considering about the general principle

of the system design, choice of design system; it focuses on why the project

design was done using a microcontroller rather than using only digital logic, and

also the data flow arrangement and system flow chart.

In chapter 4, the detail design work will be presented. It will include the

schematic of the design of the various sections of the design and the source code

(in C language) used in programming the microcontroller.

Chapter 5 will be discussing the system testing, Expected results, and

Performance evaluation.Summary and conclusion of the design will be presented

in Chapter 6. It will be looking at the problems encountered in designing the

project and possible solutions to them. From the problems and solutions of this

work, the suggestion for further improvement will be stated.

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CHAPTER TWO

LITERATURE REVIEW

2.1 REVIEW OF REMOTE CONTROL SYSTEMS

One of the earliest examples of remote control alert was developed in 1893

by Nikola Tesla. With the invention of Relays previously in 1835 by Joseph

Henry it became possible to use remote controls to drive other devices. This is

because of the ability or relays to serve as a switch that can control devices when

energized by electricity. Again with the invention of Integrated Circuits like 555

timers and Microcontrollers, more functionality was added to whole concept of

Remote control alert.

The first remote intended to control a television was developed by Zenith

radio Corporation in the early 1950’s and made use of wire to connect to the

television set. The remote — unofficially called "Lazy Bones" — used a wire to

connect to the television set. To improve the cumbersome setup, a wireless

remote control alert was created in 1955. The remote called "Flashmatic" worked

by shining a beam of light onto a photoelectric cell. Unfortunately, the cells did

not distinguish between light from the remote and light from other sources. The

Flashmatic also required that the remote control be pointed accurately at the

receiver. In 1956 Robert Adler developed "Zenith Space Command", a wireless

remote. It was mechanical and used ultrasound to change the channel and

volume. When the user pushed a button on the remote control it clicked and

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struck a bar, hence the term "clicker". Each bar emitted a different frequency and

circuits in the television detected this noise. The invention of the transistor made

possible cheaper electronic remotes that contained a piezoelectric crystal that was

fed by an oscillating electric current at a frequency near or above the upper

threshold of human hearing, though still audible to dogs. The receiver contained a

microphone attached to a circuit that was tuned to the same frequency. Some

problems with this method were that the receiver could be triggered accidentally

by naturally occurring noises, and some people, especially young women, could

hear the piercing ultrasonic signals. There was even a noted incident in which a

toy xylophone changed the channels on these types of TVs since some of the

overtones from the xylophone matched the remote's ultrasonic frequency.

The impetus for a more complex type of television remote control alert came in

the late 1970s with the development of the Ceefax teletext service by the BBC.

Most commercial remote controls at that time had a limited number of functions,

sometimes only four: next station, previous station, increase or decrease volume.

This type of control did not meet the needs of teletext sets where pages were

identified with three-digit numbers. A remote control to select teletext pages

would need buttons for each number from zero to nine, as well as other control

functions, such as switching from text to picture, and the normal television

controls of volume, station, brightness, colour intensity and so on. Early teletext

sets used wired remote controls to select pages but the continuous use of the

remote control alert required for teletext quickly indicated the need for a wireless

device. So BBC engineers began talks with one or two television manufacturers

which led to early prototypes in around 1977-78 that could control a much larger

number of functions. ITT was one of the companies and later gave its name to the

ITT protocol of infrared communication. In the early 1980s, when

semiconductors for emitting and receiving infrared radiation were developed,

remote controls alert gradually switched to that technology which, as of 2006, is

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still widely used. Remotes using radio technologies, such as Bose Audio Systems

and those based on Bluetooth also exist.

By the early 2000s, the number of consumer electronic devices in most homes

greatly increased. According to the Consumer Electronics Association, an

average American home has four remotes. To operate a home theater as many as

five or six remotes may be required, including one for cable or satellite receiver,

VCR or digital video recorder, DVD player, TV and audio amplifier. Several of

these remotes may need to be used sequentially, but, as there are no accepted

interface guidelines, the process is increasingly cumbersome. Many specialists,

including Jakob Nielsen [2], a renowned usability specialist and Robert Adler,

the inventor of the modern remote, note how confusing, unwieldy and frustrating

the multiplying remotes have become.

Most modern remote control alert systems for appliances use infrared

diode to emit a beam of light that reaches the device or equipment.

Therefore the concept of remote control is further expanded in another

form by applying it in a circuit that is used to power many appliances

automatically by pressing buttons on the remote control.

2.2 DESCRIPTION OF PROJECT

This project is basically a device used to control our domestic appliances,

lighting points and sockets. It is a remote control alert based system which is

used to power our appliances, lighting points and sockets ON or OFF.

The project consists of two sections which are; the Transmitting side and

the Receiving side. The receiving side consists of a power supply section, a

microcontroller and Relays. It also houses the Infrared Receiving Sensor circuit.

The transmission side is a smaller component which is inform of a hand

held component. It has a power supply section that is powered using a 9v battery.

The transmission side also has a microcontroller which coordinates the various

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button inputs. The last major component contained in the transmitter side id the

Infrared emitter/sender which transmits signals received from the input buttons to

the receiving side of the system. This transmission is accomplished wirelessly

through the Infrared emitter/sender on the Transmitter section.

2.3 USE OF PROJECT

This Project is intended generally for everyone and especially for users of

various domestic appliances including lights, fans, televisions etc. This project

will be used to power any of these appliances at any desired time.

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INFRAREDRECIEVER

POWER SUPPLY

MICRCONTROLLER

CONTROL 1

CONTROL 2

CONTROL 3

CONTROL 3

CONTROL 3

CHAPTER THREE

DESIGN METHODOLOGY AND ANALYSIS

3.1 INFORMATION GATHERING

The source of information used in putting up this design includes:

o the information super-highway (Internet)

o the electronics data sheet

o textbooks

o previous works and

o general intuition

They play a major role in the actualization of this design by providing

ready and accessible information at any time.

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3.2 HARDWARE COMPONENTS ANALYSISIn this section, we have to discuss the principal electronic

components and devices that were put together in designing the

hardware of this project . There functions, mode of operation and

other features that they have wil l be compared against other

electronic component that could do the same job in the design.

3.2.1 Transformers

A transformer is a device consist ing of two closely coupled

coils (called primary and secondary). An ac voltage applied to the

primary appears across the secondary, with a voltage

mult ipl ication proport ional to the turns rat io of the transformer

and a current mult ipl ication inversely proport ional to the turns

ratio. Power is conserved. Figs 3.1 shows the circuit symbol for a

laminated-core transformer ( the kind used in this design- 50Hz ac

power conversion).

Figs 3.0. Circuit symbol of a Transformer

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Transformers are quite efficient (output power is very nearly

equal to input power); thus, a step-up transformer gives higher

voltage at lower current . A transformer of turns rat io n increases

the impedance by n 2 . There is very l i t t le primary current if the

secondary is unloaded.

Transformers serve two important functions in electronic

instruments:

they change the ac l ine voltage to a useful (usually lower)

value that can be used by the circuit , and

they “isolate” the electronic device from actual connection to

the power l ine, because the windings of a transformer are

electr ically insulated from each other.

Power transformers (meant for use from the 220V power l ine)

come in an enormous variety of secondary voltages and currents:

output as low as 1 volt or so up to thousand volts , current rat ings

from a few mill iamps to hundreds of amps.

3.2.2 Bridge Rectif ier

A bridge rectif ier can be made using four individual diodes,

but i t is also available in special packages (l ike the one used in

this design) containing the four diodes required. I t is cal led a

full-wave rectif ier because i t uses all the AC wave (both posit ive

and negative sections) . 1.4V is used up in the bridge rectifier

because each diode uses 0.7V when conducting and there are

always two diodes conducting, as shown in the diagram below.

Bridge rectif iers are rated by the maximum current they can pass

and the maximum reverse voltage they can withstand ( this must

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be at least three times the supply RMS voltage so the rectif ier

can withstand the peak voltages).

By contrast, rect if ier diodes and bridges for use in power

supplies are hefty objects with current rat ings going from 1 to 25

amps or more and breakdown voltages going from 100 volts to

1000 volts . They have relat ively high leakage currents ( in the

range of micro amps to

milliamps) and plenty of

junction capacitance.

Figs 3.1: Circuit symbol for bridge rectifier

Fig 3.2: Output: ful l-wave varying DC

Current Flow in the Bridge Rectifier

For both positive and negative swings of the transformer, there is a forward path through the diode bridge. Both conduction paths cause current to f low in the same direction through the load resistor , accomplishing full-wave rectificat ion.

While one set of diodes is forward biased , the other set is reverse biased and effectively el iminated from the circuit .

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`

Figs 3.3 (a) Posit ive swing of rectif icat ion

(b) Negative swing of rectif icat ion

3.2.3 Diodes

Diodes are semiconductor devices which might be described as passing

current in one direction only. The latter part of that statement applies equally to

vacuum tube diodes. Diodes however are far more versatile devices than that.

They are extremely versatile in fact.

Diodes can be used as voltage regulators, tuning devices in rf tuned

circuits, frequency multiplying devices in rf circuits, mixing devices in rf circuits,

switching applications or can be used to make logic decisions in digital circuits.

There are also diodes which emit "light", of course these are known as light-

emitting-diodes or LED's. As we say diodes are extremely versatile.

Schematic symbols for Diodes

A few schematic symbols for diodes are:

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Figure 3.4 - schematic symbols for diodes

Types of Diodes

The first diode in figure 1 is a semiconductor diode which could be a small

signal diode of the 1N914 type commonly used in switching applications, a

rectifying diode of the 1N4001 (400V 1A) type or even one of the high power,

high current stud mounting types. You will notice the straight bar end has the

letter "k", this denotes the "cathode" while the "a" denotes anode. Current can

only flow from anode to cathode and not in the reverse direction, hence the

"arrow" appearance. This is one very important property of diodes.

The second of the diodes is a zener diode which are fairly popular for the

voltage regulation of low current power supplies. Whilst it is possible to obtain

high current zener diodes, most regulation today is done electronically with the

use of dedicated integrated circuits and pass transistors.

The next of the diodes in the schematic is a varactor or tuning diode.

Depicted here is actually two varactor diodes mounted back to back with the DC

control voltage applied at the common junction of the cathodes. These cathodes

have the double bar appearance of capacitors to indicate a varactor diode. When a

DC control voltage is applied to the common junction of the cathodes, the

capacitance exhibited by the diodes (all diodes and transistors exhibit some

degree of capacitance) will vary in accordance with the applied voltage. A typical

example of a varactor diode would be the Philips BB204G tuning diodes of

which there are two enscapsulated in a TO-92 transistor package. At a reverse

voltage Vr (cathode to anode) of 20V each diode has a capacitance of about 16

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pF and at Vr of 3V this capacitance has altered to about 36 pF. Being low cost

diodes, tuning diodes have virtually replaced air variable capacitors in radio

applications today.

The next diode is the simplest form of vacuum tube or valve. It simply has the

old cathode and anode. These terms were passed on to modern solid state

devices. Vacuum tube diodes are mainly only of interest to restorers and tube

enthusiasts.

The last diode depicted is of course a light emitting diode or LED. A led actually

doesn't emit as much light as it first appears, a single LED has a plastic lens

installed over it and this concentrates the amount of light. Seven LED's can be

arranged in a bar fashion called a seven segment LED display and when decoded

properly can display the numbers 0 - 9 as well as the letters A to F.

Rectifying Diodes

The principal early application of diodes was in rectifying 50 / 60 Hz AC

mains to raw DC which was later smoothed by choke transformers and / or

capacitors. This procedure is still carried out today and a number of rectifying

schemes for diodes have evolved, half wave, full wave and bridge rectifiers.

Figure 3.5 - rectifying diodes

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As examples in these applications the half wave rectifier passes only the

positive half of successive cycles to the output filter through D1. During the

negative part of the cycle D1 does not conduct and no current flows to the load.

In the full wave application it essentially is two half wave rectifiers combined

and because the transformer secondary is centre tapped, D1 conducts on the

positive half of the cycle while D2 conducts on the negative part of the cycle.

Both add together. This is more efficient. The full wave bridge rectifier operates

essentially the same as the full wave rectifier but does not require a centre tapped

transformer.

A further application of rectifying diodes is in the conversion or detection of Rf

modulated signals to audio frequencies. Typical examples are AM modulated

signals being detected and early detection schemes for FM also used diodes for

detecting modulation.

Voltage Regulating Diodes

For relatively light current loads zener diodes are a cheap solution to

voltage regulation. Zener diodes work on the principle of essentially a constant

voltage drop at a predetermined voltage (determined during manufacture). An

example is a Philips BZX79C12 type with a regulation range between 11.4V and

12.7V but typically 12V and a total power dissipation of 500 mW in a DO-35

package. The dissipation can be extended by using a series pass transistor. Notice

in figure 3 there is a resistor to minimize current drawn but mainly as an aid to

dropping the supply voltage and reducing the burden on the zener diodes.

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Fig 3.6 - zener voltage regulation diodes

In the second schematic of figure 3 we have three zener diodes in series

providing voltages of 5V, 10V, 12V, 22V and 27V all from a 36V supply. This

configuration is not necessarily recommended especially when the current being

drawn is seriously mismatched between voltages.

Varactor or Tuning Diodes

These types of diodes work on the principle that all diodes exhibit some

capacitance. Indeed the zener diode BZX79C12 quoted above has, according to

the data book, a capacitance of 65-85 pF at 0V and measured at 1 Mhz.

For AM Radio band applications a specific diode has been devised. The

Philips BB212 in a TO-92 case is one such type. Each of the diodes has a

capacitance of 500 - 620 pF at a reverse bias of 0.5V and <22 pF at 8V. This

diode's capacitance ratio is quoted at 22.5:1 which could not be achieved easily if

at all with an air variable capacitor. This type of diode is depicted in figure 1

above.

Several obvious advantages come immediately to mind, a small transistor

type package, very low cost, ease of construction on a circuit board, can be

mounted away from heat generating devices, frequency determining circuitry

entirely dependent upon resistor values and ratios, DC voltage control can be

either from frequency synthesiser circuits or perhaps a multi-turn potentiometer.

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Such a potentiometer aids band spreading and fine tuning if two potentiometers

are used. The only real limitation is your imagination and the calculations

involved.

Diodes as frequency multipliers

Just one more example of the versatility of diodes is the frequency

doubling circuit depicted in Figure 4. Now if that looks a lot like the full wave

rectifier from figure 2 above you would be correct. That is why the ripple

frequency for 50 / 60 Hz always comes out at 100 / 120 Hz.

Fig 3.7 - diodes as frequency multipliers

Here the input is a wide band transformer and the signal passes to a full

wave rectifier comprising two 1N914 diodes. The DC component caused by the

rectification passes to ground through RFC which of course presents a high

impedance to the rf portion of the signal but essentially a short circuit for DC.

The original signal should be down about 40 dB and with this type of circuit

there would be a loss of somewhere around 7.5 dB so the 2 X signal would

require further amplification to restore that loss.

Diodes as mixers

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With some subtle re-arrangement to figure 4 we can get the circuit to

function as a two diode frequency mixer. Note that there are other diode

arrangements as well in this application. See mixers.

Figure 3.8 - diodes as frequency mixers

The diodes here act as switches and it can be mathematically shown that

only the sum and difference signals will result. For example, if F1 was 5 Mhz and

F2 was 3 Mhz then the sum and difference signals from the diodes would be 8

Mhz and 2 Mhz. None of the original signals appear at the output and this is a

most important property of using diodes as mixers.

It should be noted that although 1N914 diodes are depicted you would

normally use hot carrier diodes in any serious application and the diodes need to

be well matched.

Applications of switching Diodes

Similar types of diodes have been developed specifically for band

switching purposes. Although a typical 1N914 type switching diode can be used

for such purposes it is preferable to use diodes which have been optimised for

such purposes because the Rd on is much lower. This means the diode resistance

Rd can have a serious affect on rf circuits in particular the "Q" of a tuned circuit.

One example of a low Rd device is the Philips BA482 diode used for band

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switching in television tuners. It has a typical Rd of 0.4 ohms at a forward current

of 10 mA.

In figure 5 we have one application where switching diodes operate. All

diodes serve to switch in or out capacitors in the diagram which is presented here

just to illustrate one single application of switching diodes, many, many more

applications exist. Again the limit is your imagination.

Figure 3.9 - applications of switching diodes

The switching diodes in figure 4 switch in or out successively higher

values of capacitors as each control select line is "grounded". The voltage from

the +5V feed line proceeds through the diode at DC thus opening the diode and

making it appear "transparent" for rf purposes. The capacitor with the value

attached is then "switched" into circuit. Other components marked RFC and Cbp

are chokes and bypass capacitors for "clean" switching. The bypass capacitors

and choke values would be determined by the frequency of operation.

We could just have easily have switched inductors instead of capacitors.

Note why Rd is quite important on overall circuit performance. If we were using

inductors the diode resistance Rd would have a significant affect on inductor "Q"

which in turn would affect filter performance, if it was in fact an LC filter

application.

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Switching Diodes in Logic Circuits

There are a whole range of digital building blocks available and just by

way of one illustration of using diodes we have presented the 74HC4040 twelve

stage binary ripple counter (there are others with varying number of stages).

In the schematic of figure 7 we have this counter which divides by

successive division of two for twelve stages. Initially because there is no voltage

drop across the resistor a high appears on all anodes as well as on pin 4 the

master reset causing the counter to reset forcing all outputs low and in turn a

voltage drop across each diode and across the resistor and a low on reset.

Progressively each of the outputs change from low to high for a certain period of

time and without unduly complicating matters when all outputs as selected by our

diode combination (in this particular case 1 + 2 + 32 + 64 = 99) are

simultaneously high the voltage drop across the resistor will cease and cause pin

11 (reset which was formerly low) to go high and reset all the internal ripple

counters.

Fig 3.10 - applications of switching diodes in digital logic circuits

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At the same time pin 4 changes state also with reset. It can been shown this

happens once every 99 periods. Simply by placing diodes on the right outputs we

can select to divide by any number up to 4095 using this particular counter.

3.2.4 Capacitors

A capacitor is an electrical device that can store energy in the electric field

between a pair of closely spaced conductors (called 'plates'). When voltage is

applied to the capacitor, electric charges of equal magnitude, but opposite

polarity, build up on each plate.

Capacitors are used in electrical circuits as energy-storage devices. They can also

be used to differentiate between high-frequency and low-frequency signals and

this makes them useful in electronic filters.

Capacitors are occasionally referred to as condensers.

The capacitor's capacitance (C) is a measure of the amount of charge (Q) stored

on each plate for a given potential difference or voltage (V) which appears

between the plates:

C = Q/V

In SI units, a capacitor has a capacitance of one farad when one coulomb of

charge causes a potential difference of one volt across the plates. Since the farad

is a very large unit, values of capacitors are usually expressed in microfarads

(µF), nanofarads (nF) or picofarads (pF).

The capacitance is proportional to the surface area of the conducting plate and

inversely proportional to the distance between the plates. It is also proportional to

the permittivity of the dielectric (that is, non-conducting) substance that separates

the plates.

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Stored energy

As opposite charges accumulate on the plates of a capacitor due to the separation

of charge, a voltage develops across the capacitor owing to the electric field of

these charges. Ever-increasing work must be done against this ever-increasing

electric field as more charge is separated. The energy (measured in joules, in SI)

stored in a capacitor is equal to the amount of work required to establish the

voltage across the capacitor, and therefore the electric field. The energy stored is

given by:

E stored =1/2cv2 = 1/2(Q2/C) = 1/2VQ

where V is the voltage across the capacitor.

The maximum energy that can be (safely) stored in a particular capacitor is

limited by the maximum electric field that the dielectric can withstand before it

breaks down. Therefore, all capacitors made with the same dielectric have about

the same maximum energy density (joules of energy per cubic meter).

Circuits with DC sources

Electrons cannot easily pass directly across the dielectric from one plate of the

capacitor to the other as the dielectric is carefully chosen so that it is a good

insulator. When there is a current through a capacitor, electrons accumulate on

one plate and electrons are removed from the other plate. This process is

commonly called 'charging' the capacitor -- even though the capacitor is at all

times electrically neutral. In fact, the current through the capacitor results in the

separation of electric charge, rather than the accumulation of electric charge. This

separation of charge causes an electric field to develop between the plates of the

capacitor giving rise to voltage across the plates. This voltage V is directly

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proportional to the amount of charge separated Q. Since the current I through the

capacitor is the rate at which charge Q is forced through the capacitor (dQ/dt),

this can be expressed mathematically as:

I = dQ2/dT = C dV/dt

For circuits with a constant (DC) voltage source, the voltage across the capacitor

cannot exceed the voltage of the source. (Unless the circuit includes a switch and

an inductor, as in SMPS, or a switch and some diodes, as in a charge pump).

Thus, an equilibrium is reached where the voltage across the capacitor is constant

and the current through the capacitor is zero. For this reason, it is commonly said

that capacitors block DC current.

Circuits with AC sources

The capacitor current due to an AC voltage or current source reverses direction

periodically. That is, the AC current alternately charges the plates in one

direction and then the other. With the exception of the instant that the current

changes direction, the capacitor current is non-zero at all times during a cycle.

For this reason, it is commonly said that capacitors 'pass' AC current. However,

at no time do electrons actually cross between the plates, unless the dielectric

breaks down or becomes excessively 'leaky'. In this case it would probably

overheat, malfunction, burn out, or even fail catastrophically possibly leading to

an explosion.

Since the voltage across a capacitor is the integral of the current, as shown above,

with sine waves in AC or signal circuits this results in a phase difference of 90

degrees, the current leading the voltage phase angle. It can be shown that the AC

voltage across the capacitor is in quadrature with the AC current through the

capacitor. That is, the voltage and current are 'out-of-phase' by a quarter cycle.

The amplitude of the voltage depends on the amplitude of the current divided by

the product of the frequency of the current with the capacitance, C.

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Capacitor networks

Series or parallel arrangements

Capacitors in a parallel configuration each have the same potential difference

(voltage). Their total capacitance (Ceq) is given by:

Ceq = C1 + C2 + …..+ Cn

The reason for putting capacitors in parallel is to increase the total amount of

charge stored. In other words, increasing the capacitance also increases the

amount of energy that can be stored. Its expression is:

Estored = 1/2CV2

The current through capacitors in series stays the same, but the voltage across

each capacitor can be different. The sum of the potential differences (voltage) is

equal to the total voltage. Their total capacitance is given by:

In parallel the effective area of the combined capacitor has increased, increasing

the overall capacitance. While in series, the distance between the plates has

effectively been increased, reducing the overall capacitance.

29

In practice capacitors will be placed in series as a means of economically

obtaining very high voltage capacitors, for example for smoothing ripples in a

high voltage power supply. Three "600 volt maximum" capacitors in series, will

increase their overall working voltage to 1800 volts. This is of course offset by

the capacitance obtained being only one third of the value of the capacitors used.

This can be countered by connecting 3 of these series set-ups in parallel, resulting

in a 3x3 matrix of capacitors with the same overall capacitance as an individual

capacitor but operable under three times the voltage. In this application, a large

resistor would be connected across each capacitor to ensure that the total voltage

is divided equally across each capacitor and also to discharge the capacitors for

safety when the equipment is not in use.

Another application is for use of polarized capacitors in alternating current

circuits; the capacitors are connected in series, in reverse polarity, so that at any

given time one of the capacitors is not conducting.

3.2.5 Voltage Regulator

A Voltage Regulator (also called a "regulator") has only

three legs and appears to be a comparatively simple device but i t

is actually a very complex integrated circuit . A regulator converts

varying input voltage and produces a constant "regulated" output

voltage. Voltage regulators are available in a variety of outputs ,

typically 5 volts, 9 volts and 12 volts. The last two digits in the

name indicate the output voltage. The "LM78XX" series of voltage

regulators are designed for posit ive input.

Table 1: Voltage regulators and their voltages

Name Voltage

30

LM7805 + 5 volts

LM7809 + 9 volts

LM7812 + 12 volts

LM7905 - 5 volts

LM7909 - 9 volts

LM7912 - 12 volts

Figs 3.11: Block diagram of internal configuration of LM 7805

Voltage regulator

Fig 3.12: Circuit symbol of a Voltage Regulator

31

Fig 3.13: Physical appearance of a 5V Voltage

Regulator

Voltage regulators are very robust . They can withstand over-

current draw due to short circuits and also over-heating. In both

cases the regulator wil l shut down before damage occurs. The only

way to destroy a regulator is to apply reverse voltage to i ts input.   Reverse polari ty destroys the regulator a lmost instantly. To

avoid this possibil i ty, a diode is connected across the power

supply. This is especial ly important when using nine volt battery

supplies as i t is common to ' test ' the battery by connecting i t one

way and then the other . Even this short ' test ' could destroy the

regulator if a protection diode is not used.

As a general rule the input voltage should be l imited to 2 to 3

volts above the output voltage. The LM78XX series can handle up

to 30 volts input, but the power difference between the input

voltage/current ra tio and output voltage/current ra t io appears as

heat . If the input voltage is unnecessari ly high the regulator wil l

get very hot . Unless sufficient heat-sinking is provided the

regulator wil l shut down.

32

The 7805’s has a quiescent current of 5mA and 78L05’s

quiescent current is 3mA. I t regulates with 2 volts dropout from

unregulated input to regulated output.

3.2.6 Light Emitting Diode

Light emitting diodes , commonly called LED’s are real

unsung heroes in the electronics world. They do dozens of

different jobs and are found in al l kinds of devices. Among other

things, they form the numbers on digital clocks , t ransmit

information from remote controls , l ight up watches and tel l you

when your appliances are turned on. Collected together, they can

form images on a jumbo television screen or i l luminate a traff ic

l ight .

Basically, LED’s are just t iny l ight bulbs that f i t easi ly into an

electr ical circuit . But unlike ordinary incandescent bulbs , they

don't have a fi lament that wil l burn out , and they don't get

especial ly hot . They are i l luminated solely by the movement of

electrons in a semiconductor material , and they last just as long as

a standard transistor.

Many circuits use a LED as a visual indicator of some sort even if

only as an indicator of power supply being turned on.

Most LED’s operate a t 1.7V although this is not always the case

and i t is wise to check. The dropping resistor is s imply the net of

supply voltage minus the 1.7V led voltage then divided by the led

brightness current expressed as "amps" ( ohms law ) . Note the

orientation of both cathode and anode with respect to the ground

end and the supply end. Usually with a led the longer lead is the anode

33

3.2.7 Resistors

Resistance is the property of a component which restricts the flow of

electric current. Energy is used up as the voltage across the component drives

the current through it and this energy appears as heat in the component.

Resistance is measured in ohms, the symbol for ohm is an omega .

1 is quite small for electronics so resistances are often given in k and M .

1 k = 1000     1 M = 1000000 .

Resistors used in electronics can have resistances as low as 0.1 or as high as 10

M .

Resistors connected in Series

Fig 3.14: Resistors connected in Series

When resistors are connected in series their combined resistance is equal to

the individual resistances added together. For example if resistors R1 and R2 are

connected in series their combined resistance, R, is given by:

34

Combined resistance in series:   R = R1 + R2

This can be extended for more resistors:

R = R1 + R2 + R3 + R4 + ... Note that the combined

resistance in series will always be greater than any of

the individual resistances

35

When resistors are connected in parallel their combined resistance is less

than any of the individual resistances. There is a special equation for the

combined resistance of two resistors R1 and R2:

For more than two resistors connected in parallel a more difficult equation must

be used. This adds up the reciprocal ("one over") of each resistance to give the

reciprocal of the combined resistance, R:

The simpler equation for two resistors in parallel is much easier to use!

Note that the combined resistance in parallel will always be less than any of the

individual resistances.

Resistor values - the resistor colour code

Resistance is measured in ohms, the symbol of ohm is an omega .

1 is quite small so resistor values are often given in k and M .

1 k = 1000     1 M = 1000000 .

Resistor values are normally shown using colored bands.

Each color represents a number as shown in the table.

Most resistors have 4 bands:

The first band gives the first digit.

The second band gives the second digit.

The third band indicates the number of zeros.

The fourth band is used to shows the tolerance (precision) of the resistor,

this may be ignored for almost all circuits but further details are given

below.

36

Fig 3.15: Resistor

color codes

This resistor has red (2), violet (7), yellow (4 zeros) and gold bands.

So its value is 270000 = 270 k .

On circuit diagrams the is usually omitted and the value is written 270K.

Small value resistors (less than 10 ohm)

The standard colour code cannot show values of less than 10 . To show

these small values two special colours are used for the third band: gold which

means × 0.1 and silver which means × 0.01. The first and second bands represent

the digits as normal.

For example: red, violet, gold bands represent 27 × 0.1 = 2.7 

blue, green, silver bands represent 56 × 0.01 = 0.56 

Tolerance of resistors (fourth band of colour code)

The tolerance of a resistor is shown by the fourth band of the colour code.

Tolerance is the precision of the resistor and it is given as a percentage. For

example a 390 resistor with a tolerance of ±10% will have a value within 10%

of 390 , between 390 - 39 = 351 and 390 + 39 = 429 (39 is 10% of 390).

A special colour code is used for the fourth band tolerance:

silver ±10%,   gold ±5%,   red ±2%,   brown ±1%.

If no fourth band is shown the tolerance is ±20%.

Tolerance may be ignored for almost all circuits because precise resistor values

are rarely required.

37

3.2.8 MICROCONTROLLER

A microcontroller (or MCU) is a computer-on-a-chip used to control

electronic devices. It is a type of microprocessor emphasizing self-sufficiency

and cost-effectiveness, in contrast to a general-purpose microprocessor (the kind

used in a PC). A typical microcontroller contains all the memory and interfaces

needed for a simple application, whereas a general purpose microprocessor

requires additional chips to provide these functions.

A microcontroller is a single integrated circuit with the following key

features:

central processing unit - ranging from small and simple 8-bit processors to

sophisticated 32- or 64-bit processors

input/output interfaces such as serial ports

peripherals such as timers

RAM for data storage

ROM, EEPROM or Flash memory for program storage

clock generator - often an oscillator for a quartz timing crystal, resonator or

RC circuit

This integration drastically reduces the number of chips and the amount of wiring

and Printed Circuit Board (PCB) space that would be needed to produce

equivalent systems using separate chips.

The Atmel AT89 series is an Intel 8051-compatible family of 8 bit

microcontrollers (µCs) manufactured by the Atmel Corporation. Based on the

Intel 8051 core, the AT89 series remains very popular as general purpose

microcontrollers, due to their industry standard instruction set, and low unit cost.

38

This allows a great amount of legacy code to reused without modification in new

applications.

3.2.9 CRYSTAL OSCILLATORS

A 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.

Using an amplifier and feedback, it is an especially accurate form of an electronic

oscillator. The crystal used therein is sometimes called a "timing crystal". On

schematic diagrams a crystal is sometimes labeled with the abbreviation XTAL

Crystals and frequency

Fig 3.16 :Schematic symbol and equivalent circuit for a quartz crystal in an

oscillator

The crystal oscillator circuit sustains oscillation by taking a voltage signal from

the quartz resonator, amplifying it, and feeding it back to the resonator. The rate

of expansion and contraction of the quartz is the resonant frequency, and is

determined by the cut and size of the crystal.

39

A regular timing crystal contains two electrically conductive plates, with a slice

or tuning fork of quartz crystal sandwiched between them. During startup, the

circuit around the crystal applies a random noise AC signal to it, and purely by

chance, a tiny fraction of the noise will be at the resonant frequency of the

crystal. The crystal will therefore start oscillating in synchrony with that signal.

As the oscillator amplifies the signals coming out of the crystal, the crystal's

frequency will become stronger, eventually dominating the output of the

oscillator. Natural resistance in the circuit and in the quartz crystal filter out all

the unwanted frequencies.

One of the most important traits of quartz crystal oscillators is that they can

exhibit very low phase noise. In other words, the signal they produce is a pure

tone. This makes them particularly useful in telecommunications where stable

signals are needed, and in scientific equipment where very precise time

references are needed.

The output frequency of a quartz oscillator is either the fundamental resonance or

a multiple of the resonance, called an overtone frequency.

A typical Q for a quartz oscillator ranges from 104 to 106. The maximum Q for a

high stability quartz oscillator can be estimated as Q = 1.6 × 107/f, where f is the

resonance frequency in MHz

Environmental changes of temperature, humidity, pressure, and vibration can

change the resonant frequency of a quartz crystal, but there are several designs

that reduce these environmental effects. These include the TCXO, MCXO, and

OCXO (defined below). These designs (particularly the OCXO) often produce

devices with excellent short-term stability. The limitations in short-term stability

are due mainly to noise from electronic components in the oscillator circuits.

Long term stability is limited by aging of the crystal.

40

Due to aging and environmental factors such as temperature and vibration, it is

hard to keep even the best quartz oscillators within one part in 10−10 of their

nominal frequency without constant adjustment. For this reason, atomic

oscillators are used for applications that require better long-term stability and

accuracy.

Although crystals can be fabricated for any desired resonant frequency, within

technological limits, in actual practice today engineers design crystal oscillator

circuits around relatively few standard frequencies, such as 10 MHz, 20 MHz and

40 MHz Using frequency dividers, frequency multipliers and phase locked loop

circuits, it is possible to synthesize any desired frequency from the reference

frequency.

Care must be taken to use only one crystal oscillator source when designing

circuits to avoid subtle failure modes of meta stability in electronics. If this is not

possible, the number of distinct crystal oscillators, PLLs, and their associated

clock domains should be rigorously minimized, through techniques such as using

a subdivision of an existing clock instead of a new crystal source. Each new

distinct crystal source needs to be rigorously justified, since each one introduces

new, difficult to debug probabilistic failure modes, due to multiple crystal

interactions, into equipment.

3.2.10 TRANSISTOR

Transistors can be regarded as a type of switch, as can many electronic

components. They are used in a variety of circuits and you will find that it is rare

that a circuit built in a school Technology Department does not contain at least

one transistor. They are central to electronics and there are two main types; NPN

and PNP. Most circuits(e.g. this project design) tend to use NPN. There are

41

hundreds of transistors which work at different voltages but all of them fall into

these two categories.

Types of transistor

There are two types of standard transistors, NPN and PNP, with different

circuit symbols. The letters refer to the layers of semiconductor

material used to make the transistor. Most transistors used today are NPN

because this is the easiest type to make from silicon. This page is mostly about

NPN transistors.

The leads are labeled base (B), collector (C) and emitter (E).

These terms refer to the internal operation of a transistor but they are not much

help in understanding how a transistor is used, so just treat them as labels!

A Darlington   pair is two transistors connected together to give a very high

current gain.

In addition to standard (bipolar junction) transistors, there are field-effect

transistors which are usually referred to as FETs. They have different circuit

symbols and properties.

Transistor currents

The diagram shows the two current paths through a transistor. The small base

current controls the larger collector current. When the switch is closed a small

42

Fig 3.17: Transistor circuit symbols

current flows into the base (B) of the transistor. It is just enough to make LED B

glow dimly. The transistor amplifies this small

current to allow a larger current to flow through from

its collector (C) to its emitter (E). This collector

current is large enough to make LED C light

brightly.

Fig 3.18 : Transistor Currents

When the switch is open no base current flows, so the transistor switches off the

collector current. Both LEDs are off. A transistor amplifies current and can be

used as a switch.

This arrangement where the emitter (E) is in the controlling circuit (base current)

and in the controlled circuit (collector current) is called common emitter mode. It

is the most widely used arrangement for transistors.

43

Functional model of an NPN transistor

Fig 3.19: Functional Model of a transistor

The operation of a transistor is difficult to explain and understand in terms of

its internal structure. It is more helpful to use this functional model:

The base-emitter junction behaves like a diode.

A base current IB flows only when the voltage VBE across the base-emitter

junction is 0.7V or more.

The small base current IB controls the large collector current Ic.

Ic = hFE × IB   (unless the transistor is full on and saturated)

hFE is the current gain (strictly the DC current gain), a typical value for hFE

is 100 (it has no units because it is a ratio)

The collector-emitter resistance RCE is controlled by the base current IB:

o IB = 0   RCE = infinity   transistor off

o IB small   RCE reduced   transistor partly on

o IB increased   RCE = 0   transistor full on ('saturated')

Additional notes:

A resistor is often needed in series with the base connection to limit the

base current IB and prevent the transistor being damaged.

44

Transistors have a maximum collector current Ic rating.

The current gain hFE can vary widely, even for transistors of the same type!

A transistor that is full on (with RCE = 0) is said to be 'saturated'.

When a transistor is saturated the collector-emitter voltage VCE is reduced

to almost 0V.

When a transistor is saturated the collector current Ic is determined by the

supply voltage and the external resistance in the collector circuit, not by

the transistor's current gain. As a result the ratio Ic/IB for a saturated

transistor is less than the current gain hFE.

The emitter current IE = Ic + IB, but Ic is much larger than IB, so roughly IE

= Ic.

The Transistor as a Switch

Because a transistor's collector current is proportionally limited by its base

current, it can be used as a sort of current-controlled switch. A relatively small

flow of electrons sent through the base of the transistor has the ability to exert

control over a much larger flow of electrons through the collector.

Suppose we had a lamp that we wanted to turn on and off by means of a

switch. Such a circuit would be extremely simple:

Fig 3.20: Transistor as switch

For the sake of illustration, let's insert a transistor in place of the switch to show

how it can control the flow of electrons through the lamp. The controlled current

through a transistor must go between collector and emitter. Since it's the current

45

through the lamp that we want to control, we must position the collector and

emitter of our transistor where the two contacts of the switch are now. We must

also make sure that the lamp's current will move against the direction of the

emitter arrow symbol to ensure that the transistor's junction bias will be correct:

Fig 3.21

In this example I happened to choose an NPN transistor. A PNP transistor could

also have been chosen for the job, and its application would look like this:

Fig 3.22

The choice between NPN and PNP is really arbitrary. All that matters is that the

proper current directions are maintained for the sake of correct junction biasing

(electron flow going against the transistor symbol's arrow).

Going back to the NPN transistor as in former circuit above, we are faced with

the need to add something more so that we can have base current. Without a

connection to the base wire of the transistor, base current will be zero, and the

transistor cannot turn on, resulting in a lamp that is always off. Remember that

for an NPN transistor, base current must consist of electrons flowing from emitter

to base (against the emitter arrow symbol, just like the lamp current). Perhaps the

simplest thing to do would be to connect a switch between the base and collector

wires of the transistor like this:

46

Fig 3.23

If the switch is open, the base wire of the transistor will be left "floating" (not

connected to anything) and there will be no current through it. In this state, the

transistor is said to be cutoff. If the switch is closed, however, electrons will be

able to flow from the emitter through to the base of the transistor, through the

switch and up to the left side of the lamp, back to the positive side of the battery.

This base current will enable a much larger flow of electrons from the emitter

through to the collector, thus lighting up the lamp. In this state of maximum

circuit current, the transistor is said to be saturated.

Fig 3.24

Of course, it may seem pointless to use a transistor in this capacity to control the

lamp. After all, we're still using a switch in the circuit, aren't we? If we're still

using a switch to control the lamp -- if only indirectly -- then what's the point of

having a transistor to control the current? Why not just go back to our original

circuit and use the switch directly to control the lamp current?

There are a couple of points to be made here, actually. First is the fact that

when used in this manner, the switch contacts need only handle what little base

current is necessary to turn the transistor on, while the transistor itself handles the

majority of the lamp's current. This may be an important advantage if the switch

47

has a low current rating: a small switch may be used to control a relatively high-

current load. Perhaps more importantly, though, is the fact that the current-

controlling behavior of the transistor enables us to use something completely

different to turn the lamp on or off. Consider this example, where a solar cell is

used to control the transistor, which in turn controls the lamp:

Fig 3.25

Or, we could use a thermocouple to provide the necessary base current to turn the

transistor on:

Fig 3.26

Even a microphone of sufficient voltage and current output could be used to turn

the transistor on, provided its output is rectified from AC to DC so that the

emitter-base PN junction within the transistor will always be forward-biased:

48

Fig 3.27

The point should be quite apparent by now: any sufficient source of DC

current may be used to turn the transistor on, and that source of current need only

be a fraction of the amount of current needed to energize the lamp. Here we see

the transistor functioning not only as a switch, but as a true amplifier: using a

relatively low-power signal to control a relatively large amount of power. Please

note that the actual power for lighting up the lamp comes from the battery to the

right of the schematic. It is not as though the small signal current from the solar

cell, thermocouple, or microphone is being magically transformed into a greater

amount of power. Rather, those small power sources are simply controlling the

battery's power to light up the lamp.

3.2.11 RELAYS

Fig 3.28: Relay

A relay is an electrically operated switch. Current flowing through the

coil of the relay creates a magnetic field which attracts a lever and changes the

49

switch contacts. The coil current can be on or off so relays have two switch

positions and they are double throw (changeover) switches.

Relays allow one circuit to switch a second circuit which can be

completely separate from the first. For example a low voltage battery circuit can

use a relay to switch a 230V AC mains circuit. There is no electrical connection

inside the relay between the two circuits; the link is magnetic and mechanical.

The coil of a relay passes a relatively large current, typically 30mA for a

12V relay, but it can be as much as 100mA for relays designed to operate from

lower voltages. Most ICs (chips) cannot provide this current and a transistor is

usually used to amplify the small IC current to the larger value required for the

relay coil. The maximum output current for the popular 555 timer IC is 200mA

so these devices can supply relay coils directly without amplification.

Relays are usually SPDT or DPDT but they can have many more sets of

switch contacts, for example relays with 4 sets of changeover contacts are readily

available. For further information about switch contacts and the terms used to

describe them please see the page on switches.

Most relays are designed for PCB mounting but you can solder wires

directly to the pins providing you take care to avoid melting the plastic case of

the relay.

The supplier's catalogue should show you the relay's connections. The coil

will be obvious and it may be connected either way round. Relay coils produce

brief high voltage 'spikes' when they are switched off and this can destroy

transistors and ICs in the circuit. To prevent damage you must connect a

protection diode across the relay coil.

50

The animated picture shows a working relay with its coil and switch

contacts. You can see a lever on the left being attracted by magnetism when the

coil is switched on. This lever moves the switch contacts. There is one set of

contacts (SPDT) in the foreground and another behind them, making the relay

DPDT.

The relay's switch connections are usually labeled COM, NC and NO:

COM = Common, always connect to this; it is the moving part of the

switch.

NC = Normally Closed, COM is connected to this when the relay coil is

off.

NO = Normally Open, COM is connected to this when the relay coil is on.

Connect to COM and NO if you want the switched circuit to be on when

the relay coil is on.

Connect to COM and NC if you want the switched circuit to be on when

the relay coil is off.

3.2.12 INFRA RED TRANSMITTERS AND RECIEVERS

Infrared (IR) radiation is electromagnetic radiation of a wavelength

longer than that of visible light, but shorter than that of radio waves. The name

means "below red" (from the Latin infra, "below"), red being the color of

visible light of longest wavelength. Infrared radiation spans three orders of

magnitude and has wavelengths between approximately 750 nm and 1 mm.

Infra-red light is just below the red portion of the visible spectrum, and so is

invisible to the human eye.

Infrared transmitters are the devices that transmit signals through Infrared

and these signals are received by Infrared receivers. Infrared receivers are signal

51

sensors which are capable of receiving infrared rays and are able to transform

this rays to an intended function.

3.3 SYSTEM DESIGN APPROACH

A domestic remote control alert system is a system that should be designed

with a sense of accuracy and preciseness. This should be done so as to ensure that

the reqiured result is achieved. Again, the need to achieve a fast and well

coordinated remote control alert system resulted in designing a work that uses a

microcontroller and relays so that the various loads will be programmed and

controlled by their respective relays together with all the other components used.

Bottom-Up

It's a long-standing principle of design style that the functional elements of a

system should not be too large. If some component of a design grows beyond the

stage where it's readily comprehensible, it becomes a mass of complexity which

conceals errors as easily as a big city conceals fugitives. Such work will be hard

to read, hard to test, and hard to debug.

In accordance with this principle, a large program must be divided into pieces,

and the larger the program, the more it must be divided.

Experienced system designers divide up their design differently. As well as top-

down design, they follow a principle which could be called bottom-up design--

changing the design to suit the problem.

It's worth emphasizing that bottom-up design doesn't mean just building the same

circuit in a different order. When you work bottom-up, you usually end up with a

different circuit.

52

In typical circuit design, once you abstract out the parts which are merely

bookkeeping, what's left is much shorter; the higher you build up the language,

the less distance you will have to travel from the top down to it. This brings

several advantages:

1. By making the circuit do more of the work, bottom-up design yields

designs which are smaller and more agile. A smaller circuit doesn't have to

be divided into so many components, and fewer components means circuit

which are easier to read or modify. Fewer components also means fewer

connections between components, and thus less chance for errors there. As

industrial designers strive to reduce the number of moving parts in a

machine, experienced system designers use bottom-up design to reduce the

size and complexity of their circuit.

2. Bottom-up design promotes component re-use. When you design two or

more circuits, many of the components you added for the first circuit will

also be useful in the succeeding ones. Once you've acquired a large

substrate of utilities, designing a new circuit can take only a fraction of the

effort it would require if you had to start.

3. Bottom-up design makes circuits easier to interpret.

4. Because it causes you always to be on the lookout for patterns in your

circuit, working bottom-up helps to clarify your ideas about the design of

your circuit. If two distant components of a circuit are similar in form,

you'll be led to notice the similarity and perhaps to redesign the circuit in a

simpler way.

53

3.4 CHOICE OF DESIGN

The benefits of a automated solution was recognized from the start. The reason

for making this choice of design is that it is programmable and can easily be

modified. This reason, thus, makes it possible to improve on its features.

3.5 SYSTEM COMPONENTS

1. Vero Board

2. 12v Transformer

3. Bridge Rectifier

4. 3300uf Capacitor

5. 7805 voltage regulator

6. 104 picofarad/0.01uf capacitor

7. Atmel 89C51 microcontroller

8. 16mhz Crystal Oscillator

9. 30pico farad (pf) capacitors

10. 10uf capacitors

11. 1 kilo ohm resistors

12. 2 kilo ohm resistors

13. Relays

14. Transistors

15. Zener Diodes

16. LEDs

17. 220 ohms resistor

18. Infrared Sensors

19. Push Buttons

20. 9v battery

21. 10 kilo ohm resistor

22. 100 ohm resistor

54

55

CHAPTER FOUR

SYSTEM HARDWARE AND CONSTRUCTION

4.1 THE HARDWARE SUBSYSTEMS

The design of the essential interfaces and sub sections that makes the 2

sections of the project are treated here. There function and mode of operation,

which are not treated in chapter 3, will be presented here.

Let start with the power supply design. Basically, it employs a 5V

regulated power supply that powers the microcontroller which needs nothing but

a 5V and the NPN transistors used. A 12V supply is also used in the design

which is meant to power a 12V relay.

4.1.0 Basic Power Supply Design

There are many types of power supply. Most are designed to convert high

voltage AC mains electricity to a suitable low voltage supply for electronics

circuits and other devices. A power supply can by broken down into a series of

blocks, each of which performs a particular function.

For example a 5V regulated supply:

Fig 4.0: Block diagram of power supply

Each of the blocks is described in more detail below:

Transformer - steps down high voltage AC mains to low voltage AC.

Rectifier - converts AC to DC, but the DC output is varying.

Smoothing - smooths the DC from varying greatly to a small ripple.

Regulator - eliminates ripple by setting DC output to a fixed voltage.

56

Power supplies made from these blocks are described below with a circuit

diagram and a graph of their output:

Transformer only

Transformer + Rectifier

Transformer + Rectifier + Smoothing

Transformer + Rectifier + Smoothing + Regulator

Transformer only

Fig 4.1

The low voltage AC output is suitable for lamps, heaters and special AC motors.

It is not suitable for electronic circuits unless they include a rectifier and a

smoothing capacitor.

Transformer + Rectifier

Fig 4.2

57

The varying DC output is suitable for lamps, heaters and standard motors. It is

not suitable for electronic circuits unless they include a smoothing capacitor.

Transformer + Rectifier + Smoothing

Fig 4.3

The smooth DC output has a small ripple. It is suitable for most electronic

circuits.

Transformer + Rectifier + Smoothing + Regulator

Fig 4.4

The regulated DC output is very smooth with no ripple. It is suitable for all

electronic circuits.

4.2 Microcontroller (AT89C51)

Description

The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer

with 4K bytes of Flash programmable and erasable read only memory (PEROM).

58

The device is manufactured using Atmel’s high-density nonvolatile memory

technology and is compatible with the industry-standard MCS-51 instruction set

and pinout. The on-chip

Flash allows the program memory to be reprogrammed in-system or by a

conventional nonvolatile memory programmer. By combining a versatile 8-bit

CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful

microcomputer which provides a highly-flexible and cost-effective solution to

many embedded control applications.

The AT89C51 provides the following standard features: 4K

bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five

vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator

and clock circuitry. In addition, the AT89C51 is designed with static logic for

operation down to zero frequency and supports two software selectable power

saving modes. The Idle Mode stops the CPU while allowing the RAM,

timer/counters,

serial port and interrupt system to continue functioning. The Power-down Mode

saves the RAM contents but freezes the oscillator disabling all other chip

functions until the next hardware reset.

It has the following Features:

• Compatible with MCS-51™ Products

• 4K Bytes of In-System Reprogrammable Flash Memory

– Endurance: 1,000 Write/Erase Cycles

• Fully Static Operation: 0 Hz to 24 MHz

• Three-level Program Memory Lock

• 128 x 8-bit Internal RAM

• 32 Programmable I/O Lines

• Two 16-bit Timer/Counters

59

• Six Interrupt Sources

• Programmable Serial Channel

• Low-power Idle and Power-down Modes

Pin Configuration of AT89C51

Fig 4.5: Microcontroller Pin Configuration

60

Fig 4.6 : Internal Block Diagram of AT89C51

Pin Description

VCC

Supply voltage.

GND

Ground.

61

Port 0

Port 0 is an 8-bit open-drain bi-directional I/O port. As an

Output port, each pin can sink eight TTL inputs. When 1s are written to port 0

pins, the pins can be used as high impedance inputs.

Port 0 may also be configured to be the multiplexed low order

Address/data bus during accesses to external program and data memory. In this

mode P0 has internal pull-ups.

Port 0 also receives the code bytes during Flash programming,

and outputs the code bytes during program verification. External pull-ups are

required during program verification.

Port 1

Port 1 is an 8-bit bi-directional I/O port with internal pull-ups.

The Port 1 output buffers can sink/source four TTL inputs.

When 1s are written to Port 1 pins they are pulled high by the internal pull-ups

and can be used as inputs. As inputs, Port 1 pins that are externally being pulled

low will source current (IIL) because of the internal pull-ups.

Port 1 also receives the low-order address bytes during Flash programming and

verification.

Port 2

Port 2 is an 8-bit bi-directional I/O port with internal pull-ups.

The Port 2 output buffers can sink/source four TTL inputs.

When 1s are written to Port 2 pins they are pulled high by the internal pull-ups

and can be used as inputs. As inputs, Port 2 pins that are externally being pulled

low will source current (IIL) because of the internal pull-ups. Port 2 emits the

high-order address byte during fetches

from external program memory and during accesses to external data memory that

use 16-bit addresses (MOVX @DPTR). In this application, it uses strong internal

62

pull-ups when emitting 1s. During accesses to external data memory that use 8-

bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special

Function Register.

Port 2 also receives the high-order address bits and some control signals during

Flash programming and verification.

Port 3

Port 3 is an 8-bit bi-directional I/O port with internal pullups.

The Port 3 output buffers can sink/source four TTL inputs.

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 AT89C51 as listed below:

Table 2: Port pins and their alternate functions

Port 3 also receives some control signals for Flash programming

and verification.

63

RST

Reset input. A high on this pin for two machine cycles while

the oscillator is running resets the device.

ALE/PROG

Address Latch Enable output pulse for latching the low byte of the address

during accesses to external memory. This pin is also the program pulse input

(PROG) during Flash programming. In normal operation ALE is emitted at a

constant rate of 1/6 the oscillator frequency, and may be used for external timing

or clocking purposes. Note, however, that one ALE pulse is skipped during each

access to external Data Memory. If desired, ALE operation can be disabled by

setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a

MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting

the ALE-disable bit has no effect if the microcontroller is in external execution

mode.

PSEN

Program Store Enable is the read strobe to external program memory.

When the AT89C51 is executing code from external program memory, PSEN is

activated twice each machine cycle, except that two PSEN activations are

skipped during each access to external data memory.

EA/VPP

External Access Enable. EA must be strapped to GND in order to enable

the device to fetch code from external program memory locations starting at

0000H up to FFFFH.

Note, however, that if lock bit 1 is programmed, EA will be internally latched on

reset. EA should be strapped to VCC for internal program executions. This pin

also receives the 12-volt programming enable voltage (VPP) during Flash

programming, for parts that require 12-volt VPP.

64

XTAL1

Input to the inverting oscillator amplifier and input to the internal clock

operating circuit.

XTAL2

Output from the inverting oscillator amplifier.

Oscillator Characteristics

XTAL1 and XTAL2 are the input and output, respectively, of an inverting

amplifier which can be configured for use as an on-chip oscillator, as shown in

Figure 1. 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 is driven as shown in Figure 2. 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 must be observed.

Idle Mode

In idle mode, the CPU puts itself to sleep while all the on chip peripherals

remain active. The mode is invoked by software. The content of the on-chip

RAM and all the special functions registers remain unchanged during this mode.

The idle mode can be terminated by any enabled interrupt or by a hardware reset.

It should be noted that when idle is terminated by a hard ware reset, the device

normally resumes program execution, from where it left off, up to two machine

cycles before the internal reset algorithm takes control. On-chip hardware inhibits

access to internal RAM in this event, but access to the port pins is not inhibited.

To eliminate the possibility of an unexpected write to a port pin when Idle is

terminated by reset, the instruction following the one that invokes Idle should not

be one that writes to a port pin or to external memory.

65

Fig 4.7. Oscillator Connections

Note: C1, C2 = 30 pF ± 10 pF for Crystals

= 40 pF ± 10 pF for Ceramic Resonators

4.3 THE INPUT INTERFACE DESIGN

The input interface of the system is designed to be inform of buttons.

These input buttons form part of the remote control transmitter. When this

buttons are depressed, it sends a signal inform of command to the microcontroller

on the transmitter circuit. On receiving the command, the microcontroller

interprets them and sends out the resulting interpretation to the infrared

transmitter which then communicates with the receiver on the receiver circuit.

The buttons are interfaced with the microcontroller to Port 1 while the infrared

transmitter is interfaced to Pin 0 of Port 0`.

The circuit below shows schematic representation of the Input interface.

66

FIG 4.8: Input Interface Schematic

4.4 THE OUTPUT INTERFACE DESIGN

The Output Interface of the system is a control circuit which receives

inputs from the remote control transmitter and transfers this control signal

received to their respective loads or outputs. The system uses an Infrared receiver

sensor through which the transmitted signals are received wirelessly. The signals

received by this infrared receiver is sent to the microcontroller which will

perform the processing of the signals according to the commands on the

microcontroller control program.

67

The infrared receiver is interfaced to the microcontroller on P1.0 (Port1)

The next stage of the process is the transfer of the passed signals by the

microcontroller from where the processed signals are sent to the Relay which will

perform the control operation of the loads. These signals are transferred out from

the microcontroller through P2.0-P2.4 (Pin21-Pin25) to the relays. The relays are

powered by an unregulated 12v voltage from the power supply of the transmitter.

The schematic diagram is shown below.

68

XTAL 1

XTAL 1

GND

31

40

+5v Vcc

+5v Vcc

+5v Vcc

+5v Vcc

+5v Vcc

+5v Vcc

1

ATMEL89C51

P2.4P2.3P2.2P2.1P2.021

222324252627282930

3233343536373839

30pf

30pf

16mhz

1k

1k

1k

1k

1k

2k

2k

2k

2k

2k

InfraredSensor

+5v Vcc+12v

+12v

+12v

+12v

+12v

EA/VPP

ALE/PROGPSEN

RST

RXDTXDINT0INT1

T0T1

WRRD

+5v Vcc

9

2345

Fig 4.9: Output Interface Schematic

69

4.5 SYSTEM TESTING

Testing is a vital process in the development and realization of any design,

be it hardware based, software based or both. The various components and their

circuitry has to be tested to ensure that all the components on board are certified

okay and in good working condition. The components that did not give the

required output specification where isolated and troubleshooted to determine the

nature and cause of the component failure through careful analysis, that is

examination of the working principles of the component(s).

Here also during the testing analysis, modularization and Interface design

were also tested. Each module in case of the software were tested to know

whether it performs the functions assigned to it and also to know whether each of

the module can interact as Required by transferring and returning data in form of

a signal.

4.5.0 Test Plan

The test plan specifies the steps taken in checking and testing each of the

module that constitute the whole system design. The essence of this is to check

for the functionality of the system in question for optimal performance. Some of

the steps taken are as follows:-

4.5.1 Test Data

The functionality of the system depends to some extent on the

correctness of the exact signal(s) being produced by different modules.

Here the test data includes signal that emanates from each module for

performing its intended task.

The test data are as follows: -

The signal that comes out when the sensitive switches are being

pressed or activated.

70

The signal that comes out from the power supply unit

The signal coming out from the AT89C51 microcontroller module

of the transmitter and receiver units to their respective infrared

transmitters and nfrared receiver sensors.

The signal coming out from the AT89C51 microcontroller module to the

relays.

The above-mentioned test data was used to test for the functionality

of the systems.

4.6 CHOICE OF PROGRAMING LANGUAGE

The Programming language used in programming the AT89C51

microcontroller IC is C language.

4.7 EXPECTED TEST RESULTS

The design of the microcontroller based domestic remote control for

appliances, lighting points and sockets is meant to be a system that is used to

control the powering of our domestic appliances, lighting points and sockets in

ours homes when a user presses a button on the hand held remote control

transmitter. To effectively carry out an intensive test, it is a good practice to run

or retest the project as many times as possible to make sure that the desired

design specification is met. The results that are expected is for the hand held

remote control to be able to send infrared signals which will activate the relays

and power our appliances. The expected test results where obtained as the

infrared transmitter communicated successfully with the receiver on the receiver

section of the remote control system.

The signal received was then able to activate the relay and control the

attached appliance and lighting points successfully.

71

4.8 PERFORMANCE EVALUATION

The performance of the remote control system proved satisfactory and is working

according to expectations.

72

CHAPTER FIVE

RECOMMENDATION AND CONCLUSION

5.1 PROBLEMS ENCOUNTERED

In the course of the design and implementation of this project,

Some problems were encountered. They are -

Low finance during Implementation.

Difficulty when writing programs, debugging and interfacing

Component Failures

Short Circuitry

Inadequate and epileptic power supply.

The aforementioned problems were later taken care of during the

design processes and implementation of this project.

5.2 RECOMMENDATION FOR FURTHER IMPROVEMENT

This project is a viable one in the sense that it will go a long way in making

it more convenient easier for users to easily control their appliances, lighting

points and even sockets from a central point in their home using a remote control

which has buttons for controlling each appliance connected to the system.

Because of its importance as a household need, efforts must be geared towards

designing a viable project like this one. I strongly recommend that the department

should see this project as a priceless possession and should endeavor to provide

financial assistance and more research works relating to this project to support

and encourage students embarking on this type of project so as to be used to be

used not only in homes but also in offices, schools etc.

73

5.3 CONCLUSION

In conclusion, this project is a design which should be encouraged

and put into large scale manufacturing because of its various advantages.

For a project to be executed, one has to reason out what the design is and

how the design can be carried out and also be able to implement the design in

order to achieve the aims and objectives of the project.

In the design and implementation of this project ”domestic remote control

for fans, lighting points and sockets, the 89C51 microcontroller is programmed to

coordinate the whole function of the design from the input when the button is

pressed to the processing and sending of signals to the receiver sensor from

where this signals are processed appropriately and transferred to the relay which

are connected to outputs inform of our domestic appliances, lighting points, etc.

This project is designed so as to be able to control our domestic appliances using

a central remote control.

74

REFERENCES

Horowitz, P. (1986) the art of Electronics 2nd Edition.

Schuler, A.C. (1999) Elections Principles and Application. 5th Edition.

Tokhein, R.L. (1995) Digital Electronics Principles and Application 5th

Edition.

Wiky, J. and Sons (1977) Practical Digital Design New York.

75

APPENDIXESAppendixes A

CONTROL SOFTWARE PROGRAM DESIGN

#include <at89x51.h>

unsigned char key,x,y,m,key_buff[5],z;

//delay function:

void delay(int pause)

{

while (!(pause==0))

{

pause--;

_asm; // 1ms assembly code(for 18Mhz crystal)

mov r6,#3 // adjust to crystal freqeuncy

mov r7,#215

00111$:

djnz r7,00111$

djnz r6,00111$

_endasm;

}

return;

}

unsigned char key_scan(void){

P2=0xfe;delay(50);

76

key=P0;

delay(20);

if(key==P0){

y=key;

for(x=1;x<9;x++){

if(((y>>(x-1))&0x01)==0){

return x;

}

}

}

P2=0xfd;

delay(50);

key=P0;

delay(20);

if(key==P0){

y=key;

for(x=1;x<9;x++){

if(((y>>(x-1))&0x01)==0){

return (x+8);

}

}

}

P2=0xfb;

delay(50);

key=P0;

77

delay(20);

if(key==P0){

y=key;

for(x=1;x<9;x++){

if(((y>>(x-1))&0x01)==0){

return (x+16);

}

}

}

P2=0xf7;

delay(50);

key=P0;

delay(20);

if(key==P0){

y=key;

for(x=1;x<9;x++){

if(((y>>(x-1))&0x01)==0){

return (x+24);

}

}

}

P2=0xef;

delay(50);

key=P0;

78

delay(20);

if(key==P0){

y=key;

for(x=1;x<9;x++){

if(((y>>(x-1))&0x01)==0){

return (x+32);

}

}

}

return 0;

}

void get_key(void){

P1_0=0;

for(m=0;m<5;m++){

next:

if((key_scan())==0){

goto next;}

else{

key_buff[m]=key_scan();

P1_0=1;

delay(500);

P1_0=0;

while(key_scan()){;}

}

}

}

79

void transmit(void){

for(x=0;x<3;x++){

P3=P1=0;

delay(1);

P3=P1=0xff;

delay(1);

}

}

void main(void){

key=z=0; P0=P2=0xff; P1_1=0;

while(1){

if((key_scan())==33){

while(key_scan()){;}

get_key();

P1_0=1;

}

if((key_scan())==34){

while(key_scan()){;}

// P1_1=0; delay(1000);

for(m=0;m<5;m++){

y=key_buff[m];

for(x=1;x<7;x++){

80

if(((y>>(x-1))&0x01)==0){

P1_1=P1_2=0; delay(200);

P1_1=P1_2=1; delay(500);

}

else{

P1_1=P1_2=0; delay(200);

P1_1=P1_2=1; delay(1000);

}

}

P1_1=P1_2=0;

delay(2000);

}

P1_1=1;delay(100);

P1_1=0;

}

}

81

APPENDIX B

COMPONENT COST ANALYSIS

COMPONENTS USED COST PRICES (N)

1. Vero Board(1) 150

2. 12v Transformer(1) 250

3. Bridge Rectifier(1) 100

4. 3300uf Capacitor(1) 40

5. 7805 voltage regulator(2) 300

6. 104 picofarad/0.01uf capacitor(1) 50

7. Atmel 89C51 microcontroller (2) 1500

8. 16mhz Crystal Oscillator(2) 200

9. 30pico farad (pf) capacitors(4) 120

10.10uf capacitors(3) 60

11.1 kilo ohm resistors(5) 50

12. 2 kilo ohm resistors(5) 75

13. Relays(5) 400

14. Transistors(5) 150

15. Zener Diodes(5) 25

16. LEDs(3) 15

17. 220 ohms resistor(1) 10

18. Infrared Sensors(1) 200

19. Push Buttons(5) 50

20. 9v battery(1) 100

82

21. 10 kilo ohm resistor(5) 50

22. 100 ohm resistor(1) 20

APPENDIXE C 89C51 INSTRUCTION SET Instructions that Affect Flag Settings(1)Instruction Flag Instruction Flag

C OV AC C OV AC

ADD X X X CLR C 0

ADDC X X X CPL C X

SUBB X X X ANL C,bit X

MUL 0 X ANL C,/bit X

DIV 0 X ORL C,bit X

DA X ORL C,/bit X

RRC X MOV C,bit X

RLC X CJNE X

SETB C 1

(1)Note that operations on SFR byte address 208 or bit addresses 209-215 (i.e., the PSW or

bits in the PSW) will also affect flag settings.

Notes on instruction set and addressing modes:

Rn Register R7-R0 of the currently selected Register Bank.

direct 8-bit internal data location’s address. This could be an Internal Data RAM location (0-

127) or a SFR [i.e., I/O port,

control register, status register, etc. (128-255)].

@Ri 8-bit internal data RAM location (0-255) addressed indirectly through register R1 or R0.

#data 8-bit constant included in the instruction.

#data 16 16-bit constant included in the instruction

addr 16 16-bit destination address. Used by LCALL and LJMP. A branch can be anywhere

within the 64k-byte Program

Memory address space.

addr 11 11-bit destination address. Used by ACALL and AJMP. The branch will be within

the same 2k-byte page of

program memory as the first byte of the following instruction.

83

rel Signed (two’s complement) 8-bit offset byte. Used by SJMP and all conditional jumps.

Range is –128 to +127 bytes relative to first byte of the following instruction.

bit Direct Addressed bit in Internal Data RAM or Special Function Register.

MNEMONIC DESCRIPTION BYTE OSCILLATOR PERIOD

ARITHMETIC OPERATIONS

ADD A,Rn Add register to Accumulator 1 12

ADD A,direct Add direct byte to Accumulator 2 12

ADD A,@Ri Add indirect RAM to Accumulator 1 12

ADD A,#data Add immediate data to Accumulator 2 12

ADDC A,Rn Add register to Accumulator with carry 1 12

ADDC A,direct Add direct byte to Accumulator with carry 2 12

ADDC A,@Ri Add indirect RAM to Accumulator with carry 1 12

ADDC A,#data Add immediate data to ACC with carry 2 12

SUBB A,Rn Subtract Register from ACC with borrow 1 12

SUBB A,direct Subtract direct byte from ACC with borrow 2 12

SUBB A,@Ri Subtract indirect RAM from ACC with borrow 1 12

SUBB A,#data Subtract immediate data from ACC with borrow 2 12

INC A Increment Accumulator 1 12

INC Rn Increment register 1 12

INC direct Increment direct byte 2 12

INC @Ri Increment indirect RAM 1 12

DEC A Decrement Accumulator 1 12

DEC Rn Decrement Register 1 12

DEC direct Decrement direct byte 2 12

DEC @Ri Decrement indirect RAM 1 12

INC DPTR Increment Data Pointer 1 24

MUL AB Multiply A and B 1 48

DIV AB Divide A by B 1 48

DA A Decimal Adjust Accumulator 1 12

LOGICAL OPERATIONS

ANL A,Rn AND Register to Accumulator 1 12

ANL A,direct AND direct byte to Accumulator 2 12

ANL A,@Ri AND indirect RAM to Accumulator 1 12

84

ANL A,#data AND immediate data to Accumulator 2 12

ANL direct,A AND Accumulator to direct byte 2 12

ANL direct,#data AND immediate data to direct byte 3 24

ORL A,Rn OR register to Accumulator 1 12

ORL A,direct OR direct byte to Accumulator 2 12

ORL A,@Ri OR indirect RAM to Accumulator 1 12

ORL A,#data OR immediate data to Accumulator 2 12

ORL direct,A OR Accumulator to direct byte 2 12

ORL direct,#data OR immediate data to direct byte 3 24

XRL A,Rn Exclusive-OR register to Accumulator 1 12

XRL A,direct Exclusive-OR direct byte to Accumulator 2 12

XRL A,@Ri Exclusive-OR indirect RAM to Accumulator 1 12

XRL A,#data Exclusive-OR immediate data to Accumulator 2 12

XRL direct,A Exclusive-OR Accumulator to direct byte 2 12

XRL direct,#data Exclusive-OR immediate data to direct byte 3 24

CLR A Clear Accumulator 1 12

CPL A Complement Accumulator 1 12

RL A Rotate Accumulator left 1 12

RLC A Rotate Accumulator left through the carry 1 12

RR A Rotate Accumulator right 1 12

RRC A Rotate Accumulator right through the carry 1 12

SWAP A Swap nibbles within the Accumulator 1 12

DATA TRANSFER

MOV A,Rn Move register to Accumulator 1 12

MOV A,direct Move direct byte to Accumulator 2 12

MOV A,@Ri Move indirect RAM to Accumulator 1 12

DATA TRANSFER (Continued)

MOV A,#data Move immediate data to Accumulator 2 12

MOV Rn,A Move Accumulator to register 1 12

MOV Rn,direct Move direct byte to register 2 24

MOV RN,#data Move immediate data to register 2 12

MOV direct,A Move Accumulator to direct byte 2 12

85

MOV direct,Rn Move register to direct byte 2 24

MOV direct,direct Move direct byte to direct 3 24

MOV direct,@Ri Move indirect RAM to direct byte 2 24

MOV direct,#data Move immediate data to direct byte 3 24

MOV @Ri,A Move Accumulator to indirect RAM 1 12

MOV @Ri,direct Move direct byte to indirect RAM 2 24

MOV @Ri,#data Move immediate data to indirect RAM 2 12

MOV DPTR,#data16 Load Data Pointer with a 16-bit constant 3 24

MOVC A,@A+DPTR Move Code byte relative to DPTR to ACC 1 24

MOVC A,@A+PC Move Code byte relative to PC to ACC 1 24

MOVX A,@Ri Move external RAM (8-bit addr) to ACC 1 24

MOVX A,@DPTR Move external RAM (16-bit addr) to ACC 1 24

MOVX A,@Ri,A Move ACC to external RAM (8-bit addr) 1 24

MOVX @DPTR,A Move ACC to external RAM (16-bit addr) 1 24

PUSH direct Push direct byte onto stack 2 24

POP direct Pop direct byte from stack 2 24

XCH A,Rn Exchange register with Accumulator 1 12

XCH A,direct Exchange direct byte with Accumulator 2 12

XCH A,@Ri Exchange indirect RAM with Accumulator 1 12

XCHD A,@Ri Exchange low-order digit indirect RAM with ACC 1 12

BOOLEAN VARIABLE MANIPULATION

CLR C Clear carry 1 12

CLR bit Clear direct bit 2 12

SETB C Set carry 1 12

SETB bit Set direct bit 2 12

CPL C Complement carry 1 12

CPL bit Complement direct bit 2 12

ANL C,bit AND direct bit to carry 2 24

ANL C,/bit AND complement of direct bit to carry 2 24

ORL C,bit OR direct bit to carry 2 24

ORL C,/bit OR complement of direct bit to carry 2 24

MOV C,bit Move direct bit to carry 2 12

MOV bit,C Move carry to direct bit 2 24

86

JC rel Jump if carry is set 2 24

JNC rel Jump if carry not set 2 24

JB rel Jump if direct bit is set 3 24

JNB rel Jump if direct bit is not set 3 24

JBC bit,rel Jump if direct bit is set and clear bit 3 24

PROGRAM BRANCHING

ACALL addr11 Absolute subroutine call 2 24

LCALL addr16 Long subroutine call 3 24

RET Return from subroutine 1 24

RETI Return from interrupt 1 24

AJMP addr11 Absolute jump 2 24

LJMP addr16 Long jump 3 24

SJMP rel Short jump (relative addr) 2 24

JMP @A+DPTR Jump indirect relative to the DPTR 1 24

JZ rel Jump if Accumulator is zero 2 24

JNZ rel Jump if Accumulator is not zero 2 24

CJNE A,direct,rel Compare direct byte to ACC and jump if not equal 3 24

CJNE A,#data,rel Compare immediate to ACC and jump if not equal 3 24

CJNE RN,#data,rel Compare immediate to register and jump if not equal 3 24

CJNE @Ri,#data,rel Compare immediate to indirect and jump if not equal 3 24

DJNZ Rn,rel Decrement register and jump if not zero 2 24

DJNZ direct,rel Decrement direct byte and jump if not zero 3 24

NOP No operation 1 12

87

88