Opto Report

8/3/2019 Opto Report

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Preface

Gratitude to ALLAH ALMIGHTY (Azza-wa-Jal) by the grace of which we achieve

success in every field of life. Second our teachers and some classmates who helped us

understanding the things which we find difficult.

Acknowledgement

In the name of ALLAH the ALMIGHTY who enabled us to

complete this report successfully and helped us in the difficult moments during the

development of this report. The project is compiled on a student level on the behalf of

possible technical data arranged from internet and from course book.



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Contents

Preface ............................................................................................................................................. 1

Acknowledgement ........................................................................................................................... 1

Introduction ..................................................................................................................................... 3

Block Diagram .................................................................................................................................. 3

Working ............................................................................................................................................ 4

Configurations: ............................................................................................................................ 4

Significance ................................................................................................................................. 5

Circuit Diagram ................................................................................................................................ 6

Component List ................................................................................................................................ 6

Microcontroller: ........................................................................................................................... 6

DC Motor:.................................................................................................................................... 6

Diode:........................................................................................................................................... 7

Transistor: .................................................................................................................................... 7

Coding .............................................................................................................................................. 7

Conclusion ........................................................................................................................................ 8



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Introduction

Our project is to design and implement a circuit which

operates a DC motor controlled by the microcontroller using an Optocoupler for the

isolation between the two circuits. Electronic equipment and signal and power

transmission lines can be subjected to voltage surges induced by lightning, electrostatic

discharge, radio frequency transmissions, switching pulses (spikes) in power supply. A

circuit can also incorporate high voltages by design, in which case it needs safe, reliable

means of interfacing its high-voltage components with low-voltage ones.

The main function of an opto-isolator is to block such high voltages and voltage

transients, so that a surge in one part of the system will not disrupt or destroy the other

parts.

Block Diagram



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Working

The working of the project is very simple. A controller has been

used for the operation of the dc motor, programming of the controller is done in assembly

language. The dc motor is derived into one direction only. For the isolation of two

circuits (i.e. controller and dc motor) an optocoupler has been used.

In electronics, an opto-isolator (or optical isolator, optocoupler, photocoupler, or

photoMOS) is a device that uses a short optical transmission path to transfer a signal

between elements of a circuit, typically a transmitter and a receiver, while keeping themelectrically isolated, since the signal goes from an electrical signal to an optical signal

back to an electrical signal, electrical contact along the path is broken.

Configurations:

A common implementation involves a LED and a phototransistor, separated so that light

may travel across a barrier but electrical current may not. When an electrical signal is

applied to the input of the opto-isolator, its LED lights, its light sensor then activates, and

a corresponding electrical signal is generated at the output. Unlike a transformer, the

opto-isolator allows for DC coupling and generally provides significant protection from

serious overvoltage conditions in one circuit affecting the other. It uses a beam of light to



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transfer energy from one circuit element to another, and it can handle incoming voltages

of up to 7500V.

With a photodiode as the detector, the output current is proportional to the amount of

incident light supplied by the emitter. The diode can be used in a photovoltaic mode or aphotoconductive mode.

In photovoltaic mode, the diode acts like a current source in parallel with a forward-

biased diode. The output current and voltage are dependent on the load impedance and

light intensity.

In photoconductive mode, the diode is connected to a supply voltage, and the magnitude

of the current conducted is directly proportional to the intensity of light.

An opto-isolator can also be constructed using a small incandescent lamp in place of the

LED; such a device, because the lamp has a much slower response time than an LED,

will filter out noise or half-wave power in the input signal. In so doing, it will also filter

out any audio- or higher-frequency signals in the input. It has the further disadvantage, of

course, (an overwhelming disadvantage in most applications) that incandescent lamps

have finite life spans. Thus, such an unconventional device is of extremely limited

usefulness, suitable only for applications such as science projects.

The optical path may be air or a dielectric waveguide. The transmitting and receiving

elements of an optical isolator may be contained within a single compact module, for

mounting, for example, on a circuit board; in this case, the module is often called an

optoisolator or opto-isolator. The photo sensor may be a photocell, phototransistor, or an

optically triggered SCR or Triac. Occasionally, this device will in turn operate a power

relay or contactor.

SignificanceThe main purpose of an opto-isolator is "to prevent high voltages or rapidly changing

voltages on one side of the circuit from damaging components or distorting transmissions

on the other side. Optocouplers are most often used to separate two circuit elements that

are operating on extremely different voltages. This prevents damage to the part working



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at a lower voltage. They also work to keep the two elements from being damaged by

reverse voltage or power surges. Because of this trait, optocouplers are best utilized in

associated with on/off switches and the transfer of digital data. They are commonly found

between a transmitter and a receiver in an electric circuit.

Circuit Diagram

Component List

Microcontroller: 89S51

128KB RAM

4K ROM

32 I/O pins

DC Motor: 12 V



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Diode: 1N4007

1 directional current flow

Transistor: TIP120 Darlington

Increases the gain

Codingorg 00h

here:setb p2.0

mov r0,#50

call delay

clr p2.0

mov r0,#50

call delay

sjmp here

delay:mov r1,#20

dl1:mov r2,#100

djnz r2,$

djnz r1,dl1

ret

end



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Conclusion

Optocoupler play integral roles in many common household items, such as telephones,

cellular phones, computer circuits, internet modems and even the entire house electrical

circuit. Optocoupler have also become essential to modern televisions as the technology

and complexity of digital components has grown. They are used extensively to separate

the parts of the circuit that manage the cable receiver, screen performance and screen

settings.

Opto Report

Documents

Transcript of Opto Report