PROJECT: COLPITTS OSCILLATOR

By

Sayed Mujtaba ME-113030

Adeel Anwar ME-113039

A Project submitted to the

Electronic Department

In partial fulfillment of the requirements for the degree of

BS (MECHANICAL ENGINEERING)

Faculty of Engineering

Mohammad Ali Jinnah University

Islamabad

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ABSTRACT

This is the report of our semester final project of the Circuit lab .This

report will give the reader an overview about the steps which are involved

in the making of a Colpitt oscillator. The project is about the making of

Colpitt oscillator that will generate approximately 1 MHz frequency. In

which the following components capacitor, inductor, resistors and

transistor were used. First, the circuit is implemented on PSPICE to test

the circuit whether it giving the correct value or not. Then it was

implemented on breadboard. The frequency and waveform on

oscilloscope were accurate. For making PCB design the software PCB

wizard has been used. For testing the circuit oscilloscope was used. It

showed the output of circuit and showed the waveform of approximately

1 MHz.

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Table of Contents

Chapter 1…………………………………...

INTRODUCTION ...................................... vii

Colpitt Oscillator:....................................................................................................vii

Overview:................................................................................................................vii

1.1 Purpose of the project: ............................................................................... viii

1.2 Applications of the Project:........................................................................ viii

1.3 Theoretical bases and Organization: .......................................................... viii

Chapter 2....................................................... ix

LITERATURE REVIEW ............................ ix

2.1 Related Technologies. ................................................................................. ix

2.1.1 Metal detector: ................................................................................... ix

2.2 Related Projects: ......................................................................................... ix

Hartley Oscillator:....................................................................................... ix

2.3 Related Studies:............................................................................................ x

2.4 Summary: ..................................................................................................... x

Chapter 3....................................................... xi

TOOLS AND TECHNIQUES .................... xi

3.1 Hardware used with technical specifications: ............................................. xi

Resistor......................................................................................... xi

Capacitor ...................................................................................... xi

Transistor .................................... Error! Bookmark not defined.

Inductor ........................................................................................ xi

3.1.1 Resistors: ............................................................................................ xi

3.1.2 Capacitors: .........................................................................................xii

3.1.3 Transistor: ......................................................................................... xiii

3.1.4 Inductor: ............................................ Error! Bookmark not defined.

v

3.1.5 DMM:................................................................................................xiv

3.1.6 Oscilloscope: ..................................................................................... xv

3.1.7 Ferric chloride: .................................. Error! Bookmark not defined.

3.1.8 Kerosene oil: ..................................... Error! Bookmark not defined.

3.1.9 Driller: ............................................... Error! Bookmark not defined.

3.1.10 Solder: ............................................. Error! Bookmark not defined.

3.2 Software(s), simulation tool(s) used .......................................................... xv

3.2.1 Pispice software: ............................................................................... xv

3.2.2 Proteus software:............................................................................... xv

3.3 Summary: ...................................................................................................xvi

Chapter 4.................................................... xvii

METHODOLOGIES ................................ xvii

4.1 Design of the investigation/Algorithms/ Hardware: ................................. xvii

4.2 Analysis procedures: ................................................................................. xvii

4.3 Implementation procedure: ....................................................................... xvii

4.3.1 Details about hardware: ............................................................. xvii

4.3.2 Details about software/ algorithms: ........................................... xvii

4.4 Verification of functionalities: ................................................................. xviii

4.5 Details about simulation / mathematical modeling:................................. xviii

4.6 Summary: ................................................................................................. xviii

Chapter 5 ................................................... xix

RESULTS AND ANALYSIS ................... xix

5.1 Presentation of the findings: ......................................................................xix

5.1.1 Hardware results: ........................................................................xix

5.1.2 Software results:.......................................................................... xx

5.2 Discussion of the findings:......................................................................... xx

5.2.1 Comparison with initial GOAL: ................................................. xx

5.3 Recommendations:..................................................................................... xx

5.5 Summary: ................................................................................................... xx

vi

Chapter 6 ................................................... xxi

CONCLUSION .......................................... xxi

REFERENCES ..................................................................................................... xxii

vii

Chapter 1

INTRODUCTION

Colpitt Oscillator:

A Colpitts oscillator is a discrete LC oscillator that uses a pair of tapped

capacitors and an inductor to produce regenerative feedback.

Combination of inductor and capacitors determine frequency of

oscillator. It is type of feedback LC oscillator where feedback is supplied

capacitively. Colpitt oscillator is a device that consists of inductor and

capacitor that will generate frequency with the help of feedback signal.

The frequency is generally determined by the inductor and the two

capacitors.

Overview:

Colpitt Oscillator is a device that is used to produces the frequency. This

project gives the frequency approximately 450 kHz by using inductor of

220µH and capacitors of 102 and 103.

Circuit diagram of Colpitt Oscillator:

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1.1 Purpose of the project:

The purpose of project was base on making the Collpitt oscillator that is

use to produce frequency. A Colpitts oscillator is the electrical dual of a

Hartley oscillator.

1.2 Applications of the Project:

The Colpitt Oscillator will generate fixed frequency so this project can be

use in different appliances of electronic like metal detector and other

appliances in which frequency of 1MHZ was required. This project can

also make variable by replacing the fixed capacitor to variable capacitor.

1.3 Theoretical bases and Organization:

As Colpitt is pre-define design so that make a good feedback circuit to

attain the require frequency. Using transistor as voltage divider biased

with the resistor mention above frequency of 1MHz. In the pre define

circuit of the colpitt there is two capacitor grounded and one inductor.

The required frequency is obtained across the inductor. This is the part of

tank circuit.

Summary:

In this chapter we explain about project and the apparatus which were

used in the making of project and the applications of this project and the

theory of project and little introduction about the apparatus that was used

in this project. Also explain the some important applications of the

Colpitt Oscillator. As the colpitt oscillator is basically use to generate the

frequency so specific values of instrument was used to generate 1MHZ

frequency.

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Chapter 2

LITERATURE REVIEW

2.1 Related Technologies.

2.1.1 Metal detector:

Metal detector is a device which responds to metal that may not be

readily apparent. The simplest form of a metal detector consists of an

oscillator producing an alternating current that passes through a coil

producing an alternating magnetic field. If a piece of electrically

conductive metal is close to the coil, eddy currents will be induced in the

metal, and this produces an alternating electric field of its own. If another

coil is used to measure the electric field, the change in the magnetic field

due to the metallic object can be detected.Metal detector used colpitt

oscillator to indicate the induction of metals. It is based on beat frequency

oscillator.

2.2 Related Projects:

Hartley Oscillator:

Hartley oscillator is similar to colpitt oscillator except the phase shift

consists of two inductors and only one capacitor. The frequency can be

easily be varied by varying the inductance. It is not suitable for low

frequency because high inductance value will be required.

x

Crystal Oscillator:

A crystal oscillator is an electronic oscillator circuit that uses the

mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency. This frequency is commonly used to keep track of time (as in quartz wristwatches), to

provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers. The most common type

of piezoelectric resonator used is the quartz crystal, so oscillator circuits incorporating them became known as crystal oscillators, but other

piezoelectric materials including polycrystalline ceramics are used in similar circuits.

2.3 Related Studies:

There are different books and different websites to get maximum

application of this project and got number of application. Some important

application of this project and other related circuit of the oscillator is

mention in this report.

2.4 Summary:

In this chapter the relative study about the project and relative circuit of

colpitt was explained. Mention about the Hartley Oscillator and also draw

the basic circuit of Hartley Oscillator and the difference between the

Colpitt and Hartley Oscillator and also discussed about the application of

colpitt oscillator in different field and electronic things.

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Chapter 3

TOOLS AND TECHNIQUES 3.1 Hardware used with technical specifications:

Resistor

Capacitor

Op amp

3.1.1 Resistors:

A resistor is a passive two-terminal electrical component that implements

electrical resistance as a circuit element. The current through a resistor is

in direct proportion to the voltage across the resistor's terminals. This

relationship is represented by Ohm's law.

In this project four resistors R1, R2, and R3 are used. In which

R1=120kΩ

R2=100kΩ

R3=20kΩ

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Resistor Color Codes:

xiii

3.1.2 Capacitors:

capacitor is a passive two-terminal electrical component used to store

energy in an electric field. The forms of practical capacitors vary widely,

but all contain at least two electrical conductors separated by a dielectric.

C1 = 0.1uF

3.1.3 Op amp:

An operational amplifier (op-amp) is a DC-coupled high-gain

electronic voltage amplifier with a differential input and, usually, a

single-ended output. An op-amp produces an output voltage that is

typically hundreds of thousands of times larger than the voltage

difference between its input terminals.

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The circuit symbol for an op-amp is shown to the right, where:

V+: non-inverting input

V−: inverting input

Vout: output

VS+: positive power supply

VS−: negative power supply

The power supply pins (VS+ and VS−) can be labeled in different ways

Often these pins are left out of the diagram for clarity, and the power

configuration is described or assumed from the circuit.

3.1.5 DMM:

A multi meter is an electronic measuring instrument that combines

several measurement functions in one unit. A typical multi meter would

include basic features such as the ability to measure voltage, current,

resistance, and Diode voltage. Multi meters may use analog or digital

circuits analog multi meters (AMM) and digital multi meters. Analog

instruments are usually based on a micro ammeter whose pointer moves

over a scale calibrated for all the different measurements that can be

made; digital instruments usually display digits, but may display a bar of

a length proportional to the quantity being measured. Digital multi meters

have all but replaced analog moving coil multi meters in most situations.

Analog multi meters are still manufactured today, but only by relatively

few manufacturers.

xv

3.1.6 Oscilloscope:

An oscilloscope, previously called an oscillograph, and informally known

as a scope, CRO (for cathode-ray oscilloscope), or DSO (for the more

modern digital storage oscilloscope), is a type of electronic test

instrument that allows observation of constantly varying signal voltages,

usually as a two-dimensional graph of one or more electrical potential

differences using the vertical or y-axis, plotted as a function of time

(horizontal or x-axis). Many signals can be converted to voltages and

displayed this way. Signals are often periodic and repeat constantly, so

that multiple samples of a signal which is actually varying with time are

displayed as a steady picture. Many oscilloscopes (storage oscilloscopes)

can also capture non-repeating waveforms for a specified time, and show

a steady display of the captured segment.

3.2 Software(s), simulation tool(s) used

3.2.1 Pispice software:

Pispice is useful software for biased analysis for the circuits. Pispice is

useful to determine the voltage across each component and then compare

it with the reading that measure with the help DMM. Pispice is used to

see the output wave form.

3.2.2 Proteus software:

Proteus software is used to see and find the waveform of our circuit.

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3.3 Summary:

The details of tools used in this project explained in this chapter. The

tools are able to make this project perfect and the specific value was also

given in this chapter that was used in project. These tools help for output

of the circuit. The virtual DMM are used to see the wave. The

oscilloscope was used on which the waveform has display. So generally

the value of all tools or instrument is given and also tell about the

behavior of circuit in different from like on pispice and on proteous.

xvii

Chapter 4

METHODOLOGIES 4.1 Design of the investigation/Algorithms/ Hardware:

The colpitt is a pre define circuit so have to less work in the investigation

of the circuit and making its logic. But prefer to configure the transistor in

voltage divider biased. As knowing that transistor work and behavior in

voltage divider biased prefer this. Hardware used in project was

transistor, capacitor and resistors, which were mention in above chapter.

4.2 Analysis procedures:

Hard and difficult process of the project is analysis of the project after

making it on this hardware. As measure the current and voltage by using

DMM at different point of the circuit and by processing that analysis the

output frequency that the output of circuit was correct or not. For that

divide the circuit in different parts and measure the output of those parts

help for easy analysis.

4.3 Implementation procedure:

Implementation process made after the complete analysis of the circuit.

Draw the circuit first on the helping software make it confirm that the

circuit is 100% in working condition. Implement it by using the apparatus

mention above.

4.3.1 Details about hardware:

Hardware used in this project was transistor, resistors and capacitors

whose value is mention in the chapter 1.

4.3.2 Details about software/ algorithms:

Different software are used in this project, which are

1) Pispice software.

2) Proteus software.

3) MultiSim.

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4.4Verification of functionalities:

As the functionalities of the project was to produce the frequency of 450

KHz. So its functionalities was that the project was produced the AC

waveform across the inductor. As verify it by using the oscilloscope for

waveform and also for frequency.

4.5 Details about simulation / mathematical modeling:

As the formula

F = 1

2𝜋√𝐿𝐶

F = 1

2𝜋√𝐿(𝑐1𝑐2

𝑐1+𝑐2)

F = 1

2𝜋√220𝑢𝐻(.001𝑢𝐹×.001𝑢𝐹

.001𝑢𝐹+.001𝑢𝐹)

F = 1

2𝜋√220𝑢𝐻(1𝑢𝐹×1𝑢𝐹

1𝑢𝐹+1𝑢𝐹)

F= 454 KHz

4.6 Summary:

In this chapter methodology of the project was explained. Complete

analysis of circuit on software that was used for this project and output

analysis of the project on the oscilloscope. The expression used for the

output frequency across the inductor, which is the main part of the

project. This chapter was about the analysis and the implementation of

the project from the software to hardware and its complete methodology

and its functionalities, verification and simulation and complete

investigation.

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Chapter 5

RESULTS AND ANALYSIS

This chapter was explained the following result and the analysis of the

circuit.

Software Results

Breadboard circuit Results.

PCB circuit Results.

5.1 Presentation of the findings:

5.1.1 Hardware results:

As making project on PCB it give output frequency of 480 KHz as

the input of 5v was given to circuit. The hardware and software

values are approximately equal there was little bit difference in the

Hardware result.

Oscilloscope Results:-

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5.1.2 Software results:

As in the previous chapter explained about the software used in the

making of this project and got different values but the difference was so

small. Used proteus Software which gives the frequency at any point you

want, the result of the software was 450 KHz,

5.2 Discussion of the findings:

Finding the result obtained from the circuit by analysis and try to find the

error if it’s done.

Analysis the circuit, as 5v was given to circuit and than 2 resistors one

connected to collector and second to base and the diode configuration

was voltage divider biased, and then the main circuit which was define by

Colpitt, As 2 capacitor and inductor known as Tank Circuit come and

take output frequency across the inductor.

5.2.1 Comparison with initial GOAL:

As initially claimed was too achieved the variable frequency about 450

KHz to 1 MHz, but cannot arrange the variable capacitor of 1nF to 1uF,

so variable jacket is used in project. Using jacket it is easy to change the

capacitor value.

5.3 Recommendations:

Expert in circuit making software.

Ride over colpitts oscillator circuit.

Ride over Resonance frequency.

5.5 Summary:

This chapter is about the results and analysis of the circuit. As the main

overcome of the circuit and its output on the software and explanation

about its result on hardware and our recommendation to other about the

Colpitt Oscillator and also telling about the initial goal, comparison of

hardware and software results and limitation and recommendation.

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Chapter 6

CONCLUSION

Colpitts oscillators are similar to the shunt fed Hartley oscillator circuit

except the Colpitts oscillator, instead of having a tapped inductor, utilizes

two series capacitors in its LC circuit.

The main circuit part is two capacitors and inductor. The main problem

that was faced in this project is about the output frequency and calculated

frequency. With very hard work and team work this project are able to

take output of desire frequency. Different type of software has been used

before making the circuit on hardware to check the circuit is working or

not. After this the circuit of project was making on the breadboard. Check

its output frequency across the inductor. Trainer and DMM were used to

check the output frequency. Many problems were faced during its

making. Main problem was time issue and the time limit of the lab on

which all process has been done. As conclusion to this project, it was

good project to help us to understand of RCL circuits.

xxii

REFERENCES

1. www.seas.upenn.edu

2. www.google.com

3. onlinelibrary.wiley.com

4. wps.prenhall.com.

5. www.sbmicro.org.

6. www.allaboutcircuits.com/worksheets/oscill

7. wps.prenhall.com/chet_paynter