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CHAPTER ONE

INTRODUCTION

1.0 DEFINITION

Function generator is a signal source that has the capability of producing

different types of waveforms as its output signal. The most common output

waveforms are sine waves, triangular waves and square waves. The frequencies

of such waveforms may be adjusted from a fraction of a hertz to several

hundred kHz. Function Generators are one of the most important and versatile

pieces of test equipment that a Technician or Engineer can use. In both design

and troubleshooting, the circuit in question often requires a signal to simulate its

normal operation. The specific type of signal can vary widely from one circuit

to another.

Modern function generators are able to provide a very wide variety of signals,

which will meet a vast majority of these requirements. There are varieties of

function generators on the market spanning the cost range from a few tens of

dollars to tens of thousands of dollars. Some are dedicated instruments, some

are black boxes with USB interfaces and an output terminal, some are plugged

into computer or instrumentation buses, and some are software programs

(PROTUS) that run on a PC to generate waveforms on parallel port or via sound

card. There are also inexpensive kits.

In today’s electronic systems, various forms of signals are necessary, such as

sinusoidal, square, triangular, pulse, waves. Computer and control systems need

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clock pulses. In communication systems, there are a variety of waveforms

needed for modulation waveforms. Triangular waves are used for scanning an

electron beam on a CRT screen, in precise time measurements, and in time

modulation. The sine wave is the most fundamental waveform. In mathematical

sense, any other waveform can be expressed as the Fourier combination of basic

sine waves. Sine waves are used extensively in test, reference and carrier

signals. Despite its simplicity, the generation of a pure sine wave is challenging.

Sinusoidal, triangular and rectangular waveforms are generated using current

feedback operational amplifiers.

.

The software only function generators tend to be the least expensive and can be

attractive for students and hobbyists on a budget. They are also most limited in

frequency capabilities often in the audio range.

1.1 BACKGROUND OF THE PROBLEM

Educational institutions and colleges as well as test engineers need a function

generator that generates certain shapes of waveforms at a wide range of

frequency. The potential and versatility of function generation techniques have

not yet been fully realized, and in the past have been limited by the

conventional hardwired an analogue and digital circuits which were available.

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This complicates the circuit and increases the cost of the instrument. I designed

the circuit using PROTEUS (software) because it could be used for simulation.

The software used to write the program is microcode studio. The control

program that is fitted into the on-chip ROM of the microcontroller- based

system deals with interrupts to generate the required function. Since the

important feature of microcontrollers is the built-in interrupt system.

A microcontroller-based system is numerically attractive since it offers

increased flexibility, particularly in choosing the required frequency among a

wide range of frequencies. These advantages inevitably result from a reduction

in the complex control circuitry, which may be progressively replaced by

microcontroller software. Then it is possible to generate any frequency

waveform is previously assigned without altering the hardware. To reduce the

components and instrument cost a software-based system is to be designed and

built. Reducing the components and adopting software increase the reliability of

the system and flexibility of the system operation based technique.

1.2 OBJECTIVE AND OVERVIEW

The principal objective of this project is to design a low cost microcontroller

based function generator which can generate sine wave and square waveforms

and the frequency of the wave will be calculated and then displayed through

LCD.

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Function generator is a electronic equipment used to generate different types of

electrical waveforms through sine wave, square wave and triangular wave over

a wide range of frequencies. It is used in development, testing and repair of

electronic equipment.

In my project, I used 8038 IC to design the function generator circuit and PIC

16F877A as the microcontroller for the function generator. The calculated

frequency will be displayed through LCD. Here we are generating only the sine,

triangular and square waveforms.

We are well aware of the fact that a function generator is not a new concept. It

is widely used in the industry and is available in the market. But our innovation

lies in the fact that we are designing the circuit at an extreme low cost with the

output being as accurate as the costlier ones. Our project will be very useful for

lab experiments.

The project is an endeavour towards an effective design and development of

microcontroller based Function Generator. The following are the main

objectives:

1. To design hardware for the system using PIC16F877A microcontroller

2. Design and implementation of a square wave generator with minimum

distortion.

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3. Design and implementation of a triangle wave generator with minimum

distortion.

4. Design and implementation of a sine wave generator with minimum

distortion.

5. Performance and cost analysis.

1.3 SCOPE AND LIMITATION

The project-function generator is expected to have the following circuit

specification:

1. Power supply

2. Led

3. PIC16F877A 8 bit microcontroller

4. Liquid Crystal Display (LCD)

5. Sine, Square, Triangular wave generator

The major limitation of the project is the maximum frequency in which it can

execute. The maximum frequency is 300 kHz.

1.4 RELEVANCE AND SIGNIFICANCE

This project design useful in the following ways;

1. In School Laboratory, the function generator can be used to provide clock

frequency that can be used to test for modulation used in communication.

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2. The function generator can be used in ultrasonic application to generate

the frequency needed for it to operate effectively.

1.5 MOTIVATION

Though this project was the initiative of my supervisor, I embraced it with great

seriousness. However, the idea behind this project is to enhance my exposure to

the field of instrumentation as an Instrumentation Engineer. More so, the project

is meant to bridge the gap between theory and practical aspects of studies.

1.6 ORGANIZATION OF THE WORK

This project is arranged in chapters. Chapter one is on the introduction,

objective and scope of work. Chapter two is on literature review, including the

brief mention of some major components used for the design. Chapter three is

on the specific method applied in achieving the project work. Chapter four

focuses on the design analysis, calculation of components value,

implementation and testing. Conclusion and recommendations takes up chapter

five.

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CHAPTER TWO

LITERATURE REVIEW

This chapter presents and highlights the design in terms of flexibility of usage

as against previous and existing designs. It also discusses the various theories

employed in realizing the design and operational principles of the

components used in the design.

2.1 LCD

LCDs are used in digital clocks, cellular phones, desktop and laptop computers,

and some televisions and other electronic systems. They offer a decided

advantage over former display technologies, such as cathode ray tubes, in that

they are much lighter and thinner and consume a lot less power to operate. LCD

technology relies on special electrical and optical properties of a class of

materials known as liquid crystals.

2.2 RESISTORS

This are electronic components that’s use to resist or oppose the flow of

electrons through it. The symbols are shown below;

Fig 2.1: The symbol of a resistor

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Resistance are measured in ohms. 1000ohms is shown as 1Kohm, and 1000000

ohm is shown as 1M ohm.

2.2.1 Composition Type Resistors

Carbon Resistors are the most common type of Composition Resistors.

Carbon resistors are a cheap general purpose resistor used in electrical and

electronic circuits. Their resistive element is manufactured from a mixture of

finely ground carbon dust or graphite (similar to pencil lead) and a non-

conducting ceramic (clay) powder to bind it all together.

Fig 2.2: Carbon Resistor

The ratio of carbon dust to ceramic (conductor to insulator) determines the

overall resistive value of the mixture and the higher the ratio of carbon, the

lower the overall resistance. The mixture is moulded into a cylindrical shape

with metal wires or leads are attached to each end to provide the electrical

connection as shown, before being coated with an outer insulating material and

colour coded markings to denote its resistive value.

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The Carbon Composite Resistor is a low to medium type power resistor which

has a low inductance making them ideal for high frequency applications but

they can also suffer from noise and stability when hot. Carbon composite

resistors are generally prefixed with a "CR" notation (eg, CR10kΩ ).

Carbon composite resistors are very cheap to make and are therefore commonly

used in electrical circuits. However, due to their manufacturing process carbon

type resistors have very large tolerances so for more precision and high value

resistances, film type resistors are used instead.

2.2.2 Film Type Resistors

The generic term "Film Resistor" consist of Metal Film, Carbon

Film and Metal Oxide Film resistor types, which are generally made by

depositing pure metals, such as nickel, or an oxide film, such as tin-oxide, onto

an insulating ceramic rod or substrate.

Fig 2.3: Film Resistor

The resistive value of the resistor is controlled by increasing the desired

thickness of the deposited film giving them the names of either "thick-film

resistors" or "thin-film resistors". Once deposited, a laser is used to cut a high

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precision spiral helix groove type pattern into this film. The cutting of the film

has the effect of increasing the conductive or resistive path, a bit like taking a

long length of straight wire and forming it into a coil.

This method of manufacture allows for much closer tolerance resistors (1% or

less) as compared to the simpler carbon composition types. The tolerance of a

resistor is the difference between the preferred value (i.e., 100 ohms) and its

actual manufactured value i.e., 103.6 ohms, and is expressed as a percentage,

for example 5%, 10% etc, and in our example the actual tolerance is 3.6%. Film

type resistors also achieve a much higher maximum ohmic value compared to

other types and values in excess of 10MΩ (10 Million Ω´s) are available.

2.2.3 Calculating the resistance value

Fixed resistors resistances are calculated using colour codes assigned to a

numerical value. The below table shows the colours and their assigned values;

COLOUR BAND VALUE MULTIPLIER TOLERANCE

BLACK 0 1 -

BROWN 1 10 +/- 1

RED 2 100 +/- 2

ORANGE 3 1000 +/- 0.05

YELLOW 4 10000 -

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GREEN 5 100000 +/- 0.25

BLUE 6 1000000 +/- 0.1

PURPLE 7 10000000 -

GREY 8 100000000 -

WHITE 9 1000000000 -

TABLE 2.1: COLOURS AND THEIR ASSIGNED VALUES

TOLERANCE:

GOLD = +/-5%

SILVER = +/-10%

NO BAND = +/-20%

2.3 CAPACTORS:

Just like the Resistor, the Capacitor, sometimes referred to as a Condenser, is

a simple passive device. The capacitor is a component which has the ability or

"capacity" to store energy in the form of an electrical charge producing a

potential difference (Static Voltage) across its plates, much like a small

rechargeable battery. In its basic form, a capacitor consists of two or more

parallel conductive (metal) plates which are not connected or touching each

other, but is electrically separated either by air or by some form of insulating

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material such as paper, mica, ceramic or plastic and which is commonly called

the capacitors Dielectric.

Fig 2.4: A Typical Capacitor

The conductive metal plates of a capacitor can be square, circular or

rectangular, or they can be of a cylindrical or spherical shape with the general

shape, size and construction of a parallel plate capacitor depending on its

application and voltage rating.

When used in a direct current or DC circuit, a capacitor charges up to its supply

voltage but blocks the flow of current through it because the dielectric of a

capacitor is non-conductive and basically an insulator. However, when a

capacitor is connected to an alternating current or AC circuit, the flow of the

current appears to pass straight through the capacitor with little or no resistance.

If a DC voltage is applied to the capacitors conductive plates, a current is unable

to flow through the capacitor itself due to the dielectric insulation and an

electrical charge builds up on the capacitors plates with electrons producing a

positive charge on one and an equal and opposite negative charge on the other

plate.

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This flow of electrons to the plates is known as the capacitors Charging

Current which continues to flow until the voltage across both plates (and hence

the capacitor) is equal to the applied voltage Vc. At this point the capacitor is

said to be "fully charged" with electrons. The strength or rate of this charging

current is at its maximum value when the plates are fully discharged (initial

condition) and slowly reduces in value to zero as the plates charge up to a

potential difference across the capacitors plates equal to the applied supply

voltage and this is illustrated below.

2.3.1 Capacitor Construction

Fig 2.5: Parallel plate capacitor

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The parallel plate capacitor is the simplest form of capacitor. It can be

constructed using two metal or metallised foil plates at a distance parallel to

each other, with its capacitance value in Farads, being fixed by the surface area

of the conductive plates and the distance of separation between them. Altering

any two of these values alters the value of its capacitance and this forms the

basis of operation of the variable capacitors.

Also, because capacitors store the energy of the electrons in the form of an

electrical charge on the plates the larger the plates and/or smaller their

separation the greater will be the charge that the capacitor holds for any given

voltage across its plates.

By applying a voltage to a capacitor and measuring the charge on the plates, the

ratio of the charge Q to the voltage V will give the capacitance value of the

capacitor and is therefore given as: C = Q/V this equation can also be re-

arranged to give the more familiar formula for the quantity of charge on the

plates as: Q = C x V

Although we have said that the charge is stored on the plates of a capacitor, it is

more correct to say that the energy within the charge is stored in an

"electrostatic field" between the two plates. When an electric current flows into

the capacitor, charging it up, the electrostatic field becomes stronger as it stores

more energy. Likewise, as the current flows out of the capacitor, discharging it,

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the potential difference between the two plate’s decreases and the electrostatic

field decreases as the energy moves out of the plates.

The property of a capacitor to store charge on its plates in the form of an

electrostatic field is called the Capacitance of the capacitor. Not only that, but

capacitance is also the property of a capacitor which resists the change of

voltage across it.

2.3.2 The Capacitance of a Capacitor

The unit of capacitance is the Farad (abbreviated to F) named after the British

physicist Michael Faraday and is defined as a capacitor has the capacitance

of One Farad when a charge of One Coulomb is stored on the plates by a

voltage of One volt. Capacitance, C is always positive and has no negative

units. However, the Farad is a very large unit of measurement to use on its own

so sub-multiples of the Farad are generally used such as micro-farads, nano-

farads and pico-farads, for example.

2.3.3 Units of Capacitance

Microfarad (μF) 1μF = 1/1,000,000 = 0.000001 = 10-6

F

Nano-farad (nF) 1nF = 1/1,000,000,000 = 0.000000001 = 10-9

F

Pico-farad (pF) 1pF = 1/1,000,000,000,000 = 0.000000000001 = 10-12

F

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The capacitance of a parallel plate capacitor is proportional to the area, A of the

plates and inversely proportional to their distance or separation, d (i.e. the

dielectric thickness) giving us a value for capacitance of C = k (A/d) where in a

vacuum the value of the constant k is 8.84 x 10-12

F/m or 1/4.π.9 x 109, which is

the permittivity of free space. Generally, the conductive plates of a capacitor are

separated by air or some kind of insulating material or gel rather than the

vacuum of free space.

2.4 LED

Light Emitting Diodes (LEDS) is a type of Diode which emits light ray in the

form of photons when electric current is applied to it.

The die is an itty bitty cube of semiconductor, the composition of which

determines the colour of the light given off. It sits in the bottom of the die cup,

which has reflective sides to reflect the light emitted by the die toward the dome

end of the LED. The epoxy body is shaped to act as an inclusion lens and focus

the light into a beam. The distance from the die cup to the domed end of the lens

determines how tightly focused is the resulting beam of light. Some LEDs have

flat or even concave ends to disperse the light into a wide beam.

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Fig 2.6: Light Emitting Diode.

LED colours are often given in "nm", or nanometres, which is the wavelength of

the light. The wavelength given is the wavelength of the peak output - LEDs are

not perfectly monochromatic, but rather produce wavelengths over a small

region of the spectrum. The graph on the left shows colour vs. intensity for a

typical green LED - the peak is at about 565 nm, but it is emitting light over a

range of about 520 nm to 610 nm. Spectral line half-width is the width of this

curve at 50% intensity (0.5 on the Y-axis) - for this LED, it is about 30 nm - and

is a measure of the "purity" (monochromaticity) of the colour.

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Fig 2.7: The graph showing colour versus intensity for a typical green LED

Notice the temperature given in the upper right corner of the graph - LEDs emit

slightly different colours at different temperatures. They also emit different

colours at different currents, especially white LEDs which depend on phosphors

to change the colour light of the die to white light.

2.4.1 Infrared LEDs

The infrared band can be divided into Near Infrared (NIR) and Far Infrared

(IR). Far infrared is the thermal infrared used to detect hot objects or see heat

leaks in buildings, and is way beyond the range of LEDs. (NIR can be further

divided into two bands, long wave and shortwave NIR, based on how film and

CCD cameras react, which I'll get into elsewhere, else when, and else why.)

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Infrared LEDs are sometimes called IREDs (Infra-Red Emitting Diodes).

2.4.2 Ultraviolet LEDs

Ultraviolet light is divided into three bands: UV-A, which is fairly innocuous;

UV-B, which causes sunburns; and UV-C, which kills things. Most UV-B and

all UV-C from the sun is filtered out by the ozone layer, so we get very little of

it naturally. LEDs emit UV-A.

400 nm is a pretty common wavelength for UV LEDs. This is right on the

border between the violet and ultraviolet, so a significant portion of the light

emitted is visible. For this reason 400 nm UV LEDs are sometimes rated in mill

candela, even though as much as half of their energy is invisible. LEDs with

lower wavelengths, such as 380nm, are usually not rated in mill candela, but in

mill watts.

DO NOT STARE INTO AN ULTRAVIOLET LED.

2.4.3 White LEDs

White light is a mixture of all the colours. Colour Temperature is a measure of

the relative amounts of red or blue - higher colour temperatures have more blue.

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Remember that this is a measure of colour, not brightness, so don't freak out

because moonlight is "hotter" than a carbon arc! It just means that the colour is

bluer, that's all.

White LEDs have a colour temperature, but monochromatic LEDs do not.

2.4.4 LED Brightness

The total power radiated as light is radiant power or radiant flux, and is

measured in watts. How bright the object appears, however, will depend on two

additional factors:

how much radiant flux is emitted toward the observer; and

How sensitive the observer is to the wavelength(s) of the light.

Luminous flux and luminous intensity are measurements like radiant power and

radiant intensity, only adjusted for the sensitivity of the human eye. Radiant

power of a wavelength of 555 nm is multiplied by a factor of 1, but light of

higher and lower wavelengths are multiplied by lower factors, until infrared and

ultraviolet wavelengths are reached, when the radiant power is multiplied by

zero.

Luminous flux is measured in lumen, while luminous intensity is measured

in lumen per Ste radian, also called a candela

The relationship between luminous flux, luminous intensity, and beam angle

means is that focussing a given LED into a tighter beam (decreasing the beam

angle) will increase its luminous intensity (brightness) without actually

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increasing the luminous flux (amount of light) it puts out. Keep this in mind

when buying LEDs for illuminating purposes - a 2000 mcd 30° LED puts out

just as much light as am 8000 mcd LED with a 15° viewing angle. (The angle is

half in both width and height, so the beam is four times as bright.) This is one of

the reasons that ultra-bright LEDs are often "water clear", to keep the light

going in one direction and not diffuse it all over the place

The brightness of LEDs is measured in mill candela (mcd), or thousandths of a

candela. Indicator LEDs are typically in the 50 mcd range; "ultra-bright" LEDs

can reach 15,000 mcd, or higher (the 617 nm Lux on Star (part number LXHL-

NH94) can reach 825,000 mcd).

By way of comparison, a typical 100 watt incandescent bulb puts out around

1700 lumen - if that light is radiated equally in all directions, it will have a

brightness of around 135,000 mcd. Focused into a 20° beam, it will have a

brightness of around 18,000,000 mcd

2.5 PIC16F877A MICROCONTROLLER

The nominal output is taken from the potentiometer at no load condition. The

analog to digital conversion module of PIC16F877A is used to measure voltage

from potentiometer. The pulse width modulation duty cycle is calculated as per

the voltage from the potentiometer. The engine rpm is measured in capture

compare module of PIC16F877A microcontroller. The updated values of engine

rpm and the pulse width modulation duty cycle are displayed on LCD. The

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engine rpm is continuously compared with the set point and when error signal

generates it directly processed into the PID algorithm. The pulse width

modulation duty cycle is calculated from the PID algorithm and from which

PIC16F877A microcontroller moves the throttle actuator lever in such a

position where engine gets stable at the required set point.

Figure 2.8: Schematic circuit of PIC16F877A in Proteus.

The PIC16F877A microcontroller is having both analog to digital conversion

module and pulse width modulation is of 10 bit. The clock frequency of 4 MHz

is used. The Proteus software is used to do the virtual simulation before going to

real hardware. The Proteus implementation is shown in above Figure

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CHAPTER THREE

METHODOLOGY

The overall method and steps involved during the design of this project are

briefly explained here. These can be best explained using the block diagram

below.

Fig 3.1: BLOCK DAIGRAM OF THE FUNCTION GENERATOR

However, there are various methods in which function generators can be design:

i. Microcontroller based function generator.

MICROCONTROLLER FREQUENCY CLOCK

GENERATOR

DIGITAL BUTTON CONTROLS

16 X 2 LCD DISPLAY UNITS

SINE, TRIANGULAR, SQUARE WAVE

GENERATOR

5V POWER SUPPLY UNIT

LED INDICATORS

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ii. Using Operational Amplifier.

iii. Using the popular Function generator Integrated Circuit (8038).

3.1 USING OPERATIONAL AMPLIFIER

Operational amplifiers with positive feedback can be used to build oscillators.

We will explain briefly the various op-amp circuits and their respective signal

waveforms they create.

3.1.1 RELAXATION OSCILLATION

From the below circuit, there is no input signal. Nevertheless, the circuit

produces a rectangular output signal. This output is a square wave that swings

between -Vsat and +Vsat. How is this possible? Assume that the output is in

positive saturation. Because of the feedback resistor, the capacitor will charge

exponentially towards +Vsat. But this capacitor voltage never reaches +Vsat

because of the voltage across the Upper Trip Point (UTP). When this happens,

the output square wave switches to –Vsat.

With the output now in negative saturation, the capacitor starts to discharge

until it crosses the Lower Trip Point; the output square wave will switch back to

+Vsat. The cycle then repeats.

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Fig 3.2: Circuit diagram for generating rectangular wave.

Circuit analysis:

Calculating for the feedback fraction for the relaxation oscillator, we make use

of the formula;

B = R1 / R1 + R2

While the period of oscillation for the relaxation oscillator can be derived using

the formula;

T = 2RC ln 1 + B / 1 – B

3.1.2 GENERATING TRIANGULAR WAVE FROM RECTANGULAR

WAVE

By cascading a relaxation oscillator and an integrator, we get a circuit that

produces the triangular output shown in the circuit below. The rectangular wave

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out of the relaxation oscillator drives the integrator, which produces a triangular

output waveform.

Fig 3.2: Circuit diagram for generating triangular wave from rectangular

wave

3.1.3 Mathematical equations use for analysing the above circuit:

To calculate for the feedback fraction, we use the formula,

B = R1 / R1 + R2

After the feedback fraction have been calculated, we can as well calculate the

period of oscillation which is given to be,

T = 2R3C1 ln 1 + B / 1 – B

Therefore, the frequency will be,

F = 1 / T.

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3.2 USING ICL8038 INTEGRATED CIRCUIT

The ICL8038 waveform generator is a monolithic integrated circuit capable of

producing high accuracy sine, square, triangular, saw tooth and pulse

waveforms with a minimum of external components. The frequency (or

repetition rate) can be selected externally from 0.001Hz to more than 300 kHz

using either resistors or capacitors, and frequency modulation and sweeping can

be accomplished with an external voltage. The ICL8038 is fabricated with

advanced monolithic technology, using Schottky barrier diodes and thin film

resistors, and the output is stable over a wide range of temperature and supply

variations. These devices may be interfaced with phase locked loop circuitry to

reduce temperature drift to less than 250ppm/oC.

BELOW SHOWS THE ICL8038 INTEGRATED CIRCUIT PINOUT

Fig 3.4: THE ICL8038 INTEGRATED CIRCUIT PINOUT

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The below circuit shows a typical example for the test circuit of the ICL8038 as

indicated in the device datasheet.

Fig 3.5: A typical example for the test circuit of the ICL8038

For this project design, we interfaced the ICL8038 with a microcontroller

because we needed to have an LCD display unit and a digital control system

incorporated into the circuit. The Microcontroller used was the PIC16F877A,

which serves as the brain that controls the output frequency and also display the

information on an LCD Display Screen.The following are the various stages

used for the actualization of the project design.

i. Power Supply Unit

ii. The display Unit

iii. The microcontroller Control unit

iv. The square, triangular and sinusoidal generator

v. Led indicator unit.

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CHAPTER FOUR

DESIGN AND IMPLEMENTATION OF THE MODULE

4.1 POWER SUPPLY UNIT

The supply unit used for this project design was a 9V transistor battery. The

battery has a battery capacity of about 520mAhr (0.52Ahr). The reason why we

used a positive voltage regulator (7805) for the power design was because we

needed a 5V power supply for the LCD and the Microcontroller circuits.

Fig 4.1: Circuit diagram showing power supply unit.

4.2 MICROCONTROLLER CONTROL UNIT

The microcontroller is a programmable integrated circuit which has it own

central processing unit (CPU), Random Access Memory (RAM), Bus for Data

communication. The below circuit diagram shows the electronic circuit used to

interface the display, led, and digital inputs connection.

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For the program control function, we made use of C language using the

microcode studio designed by the Microchip manufactures for the purpose of

programming the Microchip Integrated Circuits.

4.3 PROGRAM FOR THE FUNCTION GENERATOR CONTROL

TRISB=%00000000

TRISD=%00011111

TRISC=%00000000

DEFINE OSC 20 '20MHZ CRYSTAL IN USE

DEFINE LCD_DREG PORTB

DEFINE LCD_DBIT 4

DEFINE LCD_RSREG PORTB

DEFINE LCD_RSBIT 2

DEFINE LCD_EREG PORTB

DEFINE LCD_EBIT 3

DEFINE LCD_BITS 4

DEFINE LCD_LINES 2

W0 VAR WORD

W1 VAR WORD

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W2 VAR WORD

WF VAR WORD

PORTB=0

PORTC=0

PORTD=0

PORTD.6=1 'RED LED INDICATOR

PAUSE 2000

CLEARALL:

W0=0

W1=0

WRITE 5,W1

PAUSE 300

START:

KHZ:

LCDOUT $FE,$01

GOSUB DISPLAY

LCDOUT $FE,$CB,"KHz"

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PAUSE 300

KHZ1:

IF PORTD.0=1 THEN GOSUB EXECUTE

IF PORTD.2=1 THEN INCRHZ

IF PORTD.3=1 THEN DECRHZ

IF PORTD.4=1 THEN CLEARALL

GOTO KHZ1

INCRKHZ:

W0=W0+1

GOSUB DISPLAY

GOSUB STORE

PAUSE 300

GOTO KHZ1

DECRKHZ:

IF W0=0 THEN KHZ1

GOSUB DISPLAY

GOSUB STORE

PAUSE 300

GOTO KHZ1

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HZ:

LCDOUT $FE,$01

GOSUB DISPLAY

LCDOUT $FE,$CC,"Hz"

PAUSE 300

HZ1:

IF PORTD.0=1 THEN GOSUB EXECUTE

IF PORTD.2=1 THEN INCRHZ

IF PORTD.3=1 THEN DECRHZ

IF PORTD.4=1 THEN CLEARALL

GOTO HZ1

INCRHZ:

GOSUB DISPLAY

GOSUB STORE

PAUSE 300

GOTO HZ1

DECRHZ:

IF W0=0 THEN HZ1

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GOSUB DISPLAY

GOSUB STORE

PAUSE 300

GOTO HZ1

DISPLAY:

LCDOUT $FE,$80,"OUTPUT FREQUENCY"

LCDOUT $FE,$C2,DEC W0," "

RETURN

STORE:

WRITE 5,W1

PAUSE 300

RETURN

EXECUTE:

IF W0=0 THEN WARNING

PORTD.5=1 'GREEN LED INDICATOR

PORTD.6=0 'RED LED INDICATOR

READ 5,W2

PAUSE 300

FREQOUT PORTD.7,60000,W2

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PAUSE 300

PORTD.5=0 'GREEN LED INDICATOR

PORTD.6=1 'RED LED INDICATOR

RETURN

WARNING:

LCDOUT $FE,$80," NO FREQUENCY "

LCDOUT $FE,$C0," VALUE SELECTED "

PAUSE 2000

GOTO START

END

4.4 LCD DISPLAY UNIT

The Display unit for this project design was designed using the Liquid Crystal

Display (LCD). We used the 16 x 2 LCD display unit for the display of

information during the operation of t.

Below picture shows a typical appearance of a Liquid Crystal Display (LCD)

module.

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Fig 4.2: 16 x 2 LCD display unit

Below table are the pin outs of a typical Liquid Crystal Display, with their

various functions.

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TABLE 4.1: PINOUTS OF AN LCD AND ITS FUNCTIONS

For any electronic device, there are always maximum ratings information that

usually accompany this devices documented by the manufacturers of this

devices. The maximum rating of any electronic device is that value in which

when exceeded causes damage to that device.

Below table information, gives the maximum rating and the electrical

characteristics when operating on safe values of the Liquid Crystal Display

Module.

38

TABLE 4.2: MAXIMUM RATING AND ELECTRICAL

CHARACTERISTICS OF LCD.

4.4.1 CONTRAST AND OPTIONAL BACKLIGHT INFORMATION

The optimal contrast for the LCD (VO) is 3.3 - 3.7V, but this may vary with

viewing angle, ambient temperature and per-LCD.

Setting the backlight up is optional, but may increase the readability of the LCD

and is pretty cool. The backlight on your LCD is one large green LED. From the

Crystalfontz documentation, the backlight requires a current-limiting resistor in

the configuration shown to the right. The formula for calculating this value is

shown below. LED Forward Voltage and Forward Current are 4.1V and .12A,

respectively, from the Crystalfontz documentation.

39

Calculating for the current limiting value of the backlight LED:

Given that, VDD = 5V, VLED = 4.1V, and the Forward Current = 0.12A,

therefore,

RLED = 5 – 4.1 / 0.12

RLED = 0.9 / 0.12

RLED = 7.5Ω

To calculate for the power dissipation of the resistor, we use the equation:

PD = I x V

PD = 0.12 x 7.5

PD = 0.9W

Choosing a closer value, we have 1W. Therefore the current limiting resistor

used for the Backlight LED was 7.5Ω/1W.

The below diagram, shows a typical circuit showing the connection of the

current limiting resistor and the Backlight LED;

40

Fig 4.3: A typical circuit showing the connection of the current limiting resistor

and the Backlight LED.

4.5 THE INTEGRATED CIRCUIT ANALYSIS

The ICM8038 function generator Integrated Circuit has an internal circuitry

like the one shown below. So I used the below circuit to illustrate how they are

analysed mathematically.

41

Fig 4.4: The circuit showing the mathematical analysis of the generation of the

various signal waveforms required for this project

The above circuit has about four basic stages which were used to achieve the

generation of the various signal waveforms required for this project.

Circuit Analysis for Stage 1:

The first stage had a non-inverting voltage gain given by,

AV = 1 + R2 / R1

42

Where R2 = 100,000. R1 = 27,000. Therefore,

AV = 1 + 100,000 / 27,000

AV = 27,000 + 100,000 / 27,000

AV = 127,000 / 27,000

AV = 4.70

Circuit Analysis for Stage 2:

The second stage had an inverting input and its voltage gain was calculated to

be,

AV = -RF / R

Where RF = 100,000Ω. R = 10,000Ω. Therefore,

AV = 100,000 / 10,000

AV = 10

The cut-off frequency for the RC circuit will be:

Using the frequency formula,

F = 1 / 2πRC

Where C = 0.1µF, R = 100,000Ω, therefore

F = 1/ 2 x 3.142 x 100,000 x 0.1 x 0.000001

F = 15.91 Hz

The non-inverting bias resistor was calculated using the formula,

Rn = RF x R / RF + R

By substitution,

Rn = 100,000 x 10,000 / 100,000 + 10,000

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Rn = 1000,000,000 / 110,000

Rn = 9090

Rn = 9.1kΩ

The value calculated is impracticable, so we choose the nearest resistance value

of 10kΩ.

Note: The third and fourth stages, appears to similar to the first and second

stages, so the same formulas are applicable.

4.6 BILL OF ENGINEERING MEASUREMENT

S/N ITEM SPECIFICATION QUANTITY UNIT

COST

TOTAL

COST

1 PIC16F877A MICROCONTROLLER 1 ₦1000 ₦1000

2 RESISTORS(fixed wire wound)

220kΩ,4.7kΩ,10kΩ,10kΩ,100Ω,1kΩ

6

₦5

₦30

3 POTENTIOMETER

10kΩ

1

₦20

₦20

4 CAPACITORS

4.7 F( Electrolytic)

1nF,1nF,3.3pF(Ceramics)

2-15pF(Variable Capacitor)

2

3

1

₦20

₦20

₦300

₦40

₦60

₦300

44

5 16 x 2 LCD DISPLAY 1 ₦1500 ₦1500

6 4 MHz CRYSTAL OSCILLATORS 1 ₦50 ₦50

7 VERO BOARD(DOTTED) 2 ₦50 ₦100

8 9 VOLTS DC BATTERY 2 ₦50 ₦100

9 FUNCTIONGENERATOR

INTEGRATED CIRCUIT

1 ₦2500 ₦2500

10 PLASTIC CASING 1 ₦1000 ₦1000

11 BATTERY CONNECTOR 1 ₦50 ₦50

12 LED INDICATOR 2 ₦5 ₦10

13 CONNECTING WIRE 2 ₦20 ₦40

14 MONOMENTARY SWITCH 5 ₦50 ₦250

15 MISCELLANEOUS - - ₦3000

TOTAL COST

₦10,005

TABLE 4.3: BILL OF ENGINEERING MEASUREMENT

45

Fig 4.5: COMPLETE CIRCUIT DIAGRAM OF THE MODULE.

46

CHAPTER FIVE

CONCLUSION

The design and construction of the function generator was sucessful carried out.

The system is effective due to its wide application in electrical/ electronics

circuits such as in communication circuits for providing signal during

modulation test, for timming circuits for providing the required time delay

(period) used for controlling events, for ultrasonic application use to provide the

required frequency for the ultrasonic transmitterswhich is about 33kHz for some

modules. This has brought about a more modernized, digitally controlled design

where every operations has been programmed using the microcontroller

integrated circuit. The system has been designed using locally available

electronic materials and the cost have been relatively minized using cost

effective circuits.

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RECOMMENDATION

The Design and implementation of the function generator was developed using

a programmable microcontroller which was the main brain for the project.

Engineers should improve in programming so that there will be a greater range

of its operation and application.

The design used for this project is essentially quite a simple one and it is this

simplicity which partly brings it down when it comes to the overall reliable

performance. The project has succeeded to a great extent, in exposing the very

basic principles involved in the generation of different wave forms. The

following recommendation was made based on the experience in doing the

project and the problem encountered in the course of the work.

Modular design should be used for analysis of each module and it should be

done cautiously.

Accurate programs should be written in order to give the required output clock

frequency.

48

REFERENCES

1. A Textbook of Electrical Technology by B.L Theraja, A.K Theraja,

S.Chand publishers India (24th

Edition)

2. Gibson, G. and Liu, Y., Microcomputers for Engineers and Scientists,

Prentice-Hall,Englewood Cliffs, NJ, 1980.

3. Herschede, R., “Microcontroller Foundations for Mechatronics Students,”

masters thesis,Colorado State University, summer 1999.