FET's, Field Effect Transistors

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FET’S:

FET’S is Field-effect transistors. It’s a voltage control electronics device. It has 3 terminals.

1: Gate        2: Drain        3: Source

It’s has 2 configurations’ 

1: N-channel

2: P-channel

N-channel FET when we give negative (-) signal or pulse in Gate then it’s working as forward biased Gate to drain, Gate to source reveries biased. when get output from Darin…  

P-channel FET when we give positive (+) signal or pulse in Gate then it’s working as forward biased Gate to drain, Gate to source reveries biased. We get output from Darin…  

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Applications:

FET’s use as Amplification.

FET’s use for switching.

JFET:

JFET is junction field-effect transistors. This type of transistor is operating current limiting . JFET operate as forward biased and reversed biased …

When P-channel Gate have Positive (+) signal then its work Gate to Drain forward biased and Gate to Source reversed biased.

When N-channel Gate have Negative (-) signal then its work Gate to Drain forward biased and Gate to Source reversed biased.

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Oscilloscope

Definition of Oscilloscope :

Oscilloscope is an electrical Instrument through which we can observe and measure the different wave forms and graphically behavior of Electrical Circuits.There are two types of Oscilloscope one is Analog and second is Digital.In Analog Oscilloscope we need to perform mathematical calculations to measure the actual values of Wave form.In Digital Oscilloscope we no need to perform any Mathematical calculation to measure the actual values of wave form.Today I will tell you the detail usage of Analog Oscilloscope.

PIC OF Oscilloscope   

Basics of Oscilloscope:

Oscilloscope shows the 2-Dimensional graphical view. For                                   2-Dimensional graphical view there are two axis in Oscilloscope one is X-axis and other is Y-axis. we can adjust the position of wave on X & Y axis by vertical and horizontal position probes.

X-axis shows the time period of the current wave form as Time per Division.

Y-axis shows the Amplitude of voltage of current wave form as Volt per Division.

There are commonly two basic channels in Oscilloscope. From two different channels we can observe two different wave forms from two different input sources. For both channels Time axis is same but Volt axis for both channels are different. The reason is that time on time per division for both wave is same but the voltage’s amplitude can be different of both waves. 

It will continue in next lecture………………

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PART3

Bootstrap Capacitor Design:

From the application notes of the HIP4081, we studied that the bootstrap capacitor must be greater than the ten times of the gate to source capacitance of the MOSFET used in the bridge.

Qgs = 12.3 nC 

Vgs(min)= 2volt 

Cgs = Qgs/Vgs = 12.3/2 = 6.15 nF

 So bootstrap capacitor > 61.5 nF 

We used a value of 200 nF.

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part2

block diagram of UPS 

AC TO DC CONVERSION

Type of chargers:

i). Ferro-Resonant Charger

They are very bulky because of low frequency magnetic control system in it. They are slowly recharged. Their magnetic field may disturb other components of the equipment.

ii). Linear Charger

They also use low frequency transformer in it to reduce the level of the ac voltage, then a combination of bleeding resistor, series resistor and a capacitor is used to control the current and voltage level of dc output.

iii). Switch Mode Charger

It is a newly technique, it directly rectify ac input, then this dc input is switched with high frequency through transistors and with the help of high frequency transformer, its level is lowered and rectified to desired dc output level

A/H Ratting of the Battery

Before designing the charger stage of the battery, we must see the A/H ratting of the battery, which determines the charger time as well as the backup time with respect to the charging current. The ampere-hour ratting ( A/H ratting ) is the indication of battery energy capacity, it is given by the relation:

A battery with a capacity of 10 amp-hour should be able to continuously supply a current of 10 amp to a load for exactly 1 hour, or 20 amps for 1/2 hour, or 1/3 amp for 30 hours, etc., before becoming completely discharged.


Typical A/H Rating of Some Batteries:
 Typical automotive battery: 70 amp-hours @ 3.5 A (secondary cell)
 D-size carbon-zinc battery: 4.5 amp-hours @ 100 mA (primary cell)
 9 volt carbon-zinc battery: 400 milliamp-hours @ 8 mA (primary cell)
The most common type of battery available is lead acid battery. A lead-acid cell generates around 2 volts. Small batteries contain 6 cells in a container which add together to give 12 volts at the terminals.

Battery Charger Selection:

 The steps to calculate the charger requirement for a battery are
 i) Determine the suitable A/H ratting of the battery required according to the load and Backup as well as the charging time required
ii) Determine the recharge time required.
 iii).To get the charging current, divide the A/H rating by that time.
iv). Add 20% to allow for the battery inefficiency.
v). If there is any additional battery load current during its charging like control circuit, add it also to the charging current.
vi).Select the next biggest charger in the range

  Calculations:

Battery Voltage = 12
Volts Load Required = 700
Watt Efficiency Required = 90%
Total Battery Current = (700/0.9)/12 = 70 Amp
 Estimated Additional Current = 1 Amp
 Total Battery Output Current = 71 Amp
Battery Charging Current = 0.1 * 71 = 7.1 Amp
 Backup Time Required= 2 Hour
A/H Ratting Of Battery = 2 * 71 = 141 A/H



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HIGH FREQUENCY SINE WAVE UPS

In conventional inverters which are now a day’s commonly used in Pakistan,
consumer faces many problems relating to their performance. The foremost problem is
their efficiency which is in between 85% to 90%. The efficiency mainly depends upon
the switching frequency of the transformer which is used in DC/AC inverter.
The large size of transformer also make the U.P.S very bulky. It also occupies a
large area which is also not good from the point of view of the customer.
The E.M.F induced in the transformer given by the formula relating its
frequency, area, number of turns and magnetic field to each other is

CLASSIFICATION OF INVERTERS:

Introduction OF INVERTER :

Inverter is device that converts the DC Power into AC power. The voltage and the frequency of the converted AC power can be set to required level depending upon the selection of the transformers and control circuit. AC main is converted into DC through a rectifier circuit and battery is charged than the DC from the battery is converted to AC by an inverter circuitry

Types Of Inverter:

Inverter available in the market are usually provide three types of output

•  Square wave
•  Modified square wave
•  Pure sine wave

Square Wave:

Inverters are first invented using a square wave as the output. Square wave has a large number of problems related to the functionality of the devices as these devices are usually designed to operate for the sine wave. Due to the harsh corner of the square wave it is very harmful for the electrical equipments. Harmonic content of the square is very high that result in the overheat of the electrical equipment. So the inverter use the square wave technology tends to produce a lot of heat due to power loss. Efficiency of the square wave inverter is less. The price of these inverter define the efficiency of the inverter.

Modified Square Wave:

Some alterations made on the hardware of the inverter in order to remove the harsh corner of the square wave. Some time the supplier of the modified square wave inverter use the term modified sine wave in order to increase the demand of the that inverter but in reality it is only the modified square wave . It has better characteristics than the square wave. But the overheat factor is still present that result in the reliability of the equipments. So here is a need to make of sine wave inverter

Pure Sine Wave:

All the home appliances and electrical devices are designed to operate for the sine wave. So there is a need to design a inverter that gives output very close or similar to the sine wave. Our project is also to make a sine wave inverter. It also reduce the noise interferences associated with other inverters. With the pure sine wave inverter our project fully assures that sensitive loads will be powered correctly with no noise interference. Depending upon the switching frequency inverter can be classified as

 Low Frequency Inverters

 High Frequency Inverters

Switching frequency related to the rate at which the DC is converted to the AC. Low frequency inverter oscillates a DC voltage at 50Hz. The voltage of that inverter is then step up to desire level using a large and heavy transformer. The transformers are iron core shown below

Iron core transformer

High frequency inverter on the other hand use small size transformer. Such high frequency inverter may have large harmonic content near the range of the switching frequency. But the advantage is that these harmonics are high in order than the fundamental frequency 50HZ. So in order to separate these harmonics a low pass filter is use. High frequency inverter use ferrite core transformer shown below

Ferrite core transformer

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CONTROLLED SPY VEHICLE

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CONTROLLED SPY VEHICLE

The project is designed for spy purpose. A wireless audio/video camera is used to transmit the audio/video signal on computer. The camera is mounted on a vehicle, vehicle moves in accordance with the command from the computer. The vehicle can also be moved from a remote control. In world of today high security deployment is required, and this project will give an idea in acquiring a protected environment. In future warfare these types of intelligence devices played a very vital role to achieve their desired targets. A clear of this is the current spy drones operation of US in Pakistan and Afghanistan. 

          We have also used the GPS to get the co-ordinates from the satellite and GSM through which the GPS co-ordinates will receives on the LCD as well as on the mobile.

Introduction

The security or defend of any person, object or any asset is very essential. Throughout the history steps and measurements are taken for the betterment of security and to make it as useful and as protective and efficient as possible.

In modern era sophisticated equipments and tools are used for the defense in face of spying. Different robots, vehicles, a few nanometer cameras, drones and other type come into widespread use.

Pakistan is the only Islamic Nuclear state and there are great threats to its nuclear and other military assets.

Keeping in view this background we have designed a spy vehicle, which is a step forward, and a minute try to spy some targets and to save some precious life where the spy at that particular (congested) area is difficult.

RF: Radio frequency (RF) technology is commonly used to transmit and receive information without wires. A wide variety of electronic devices such as television, radio, and wireless telephone use radio frequency technology to transmit or receive information. RF can be used in helping one’s business track inventory and equipment.

1.1      Aim

The purpose of this project is spying of any place or surrounding and sending audio and video signals to the computer where they can be analyzed.

The aim of the project is to design a multipurpose R/C robot. This project will produce utility for the user to remotely monitor enemy activities, the destructed buildings and such places where it is hard for a human being to make a view point. After making a view point action can be taken accordingly.

Although we have applied this system to monitor and control some basic functions more complex functions can be added according to the requirement.

1.2      Features

·        Patrol the surrounding with sharp camera–eye.

·        Send video and data captured to the server wirelessly.

·        Easy control by a computer Wireless media.

·        Mobile in all directions with miniature size.

·        Conceal in camouflage without attracting attention.

·        Can take appropriate action when needed.

1.3      Applications

·        Typical applications of the project include.

·        Military reconnaissance mission.

·        Wireless security and surveillance in hot spots.

·        Search and rescue operation.

·        Manoeuvring in hazardous environment.

·        R/C soldier.

·        Home security.

1.4      Requirements

·        Design of robotic car.

·        Receiver circuitry.

·        Transmitter circuitry.

·        Tuning of wireless video camera.

·        Wireless transmission of video and control instructions.

·        Remotely control the direction and position of the robot and perform the specific action.

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