Project Inverter

Home Automation with Voice Feedback

INVERTER USING 555 TIMER

A major project report submitted in partial fulfilment of the requirements for the award of degree of

BACHELOR OF TECHNOLOGY

IN

ELECTRICAL AND ELECTRONICS ENGINEERING

By:

KESHAV GARG (08814804911)

ABHISHEK GARG (09114804911)

GOPAL AGGARWAL (02914804911)

Under the Guidance of

Mrs. Neelam Kassarwani

Mrs. Shashibala Agarwal (Asst. Prof., Dept. of EEE) (Asst. Prof., Dept. of EEE)

Department of Electrical & Electronics Engineering

Maharaja Agrasen Institute of TechnologySector-22, Rohini, Delhi

May 2015

CERTIFICATEThis is to certify that the dissertation/project report entitled INVERTER USING 555 TIMER done by KESHAV GARG (08814804911), ABHISHEK GARG (09114804911) & GOPAL AGGARWAL (02914804911), is an authentic work carried out by them at MAHARAJA AGRASEN INSTITUTE OF TECHNOLOGY under our guidance. The matter embodied in this project work has not been submitted earlier for the award of any degree or diploma to the best of my knowledge and belief.

DATE: DR. RAJVEER MITTAL

(HOD OF EEE)

MRS. NEELAM KASSARWANI

(Asst. Prof, Dept. of EEE)

MRS. SHASHIBALA AGARWAL

(Asst. Prof, Dept. of EEE)

ACKNOWLEDGEMENT

We take this opportunity to express our profound sense of gratitude and respect to all those who helped us throughout the duration of this project. We wish to acknowledge the guidance and support of the Professors and our seniors in bringing up a real picture of the concept for which the report is prepared especially.

We would like to make a special mention of support, help and encouragement we received from our project guide Mrs. NEELAM KASSARWANI (Asst. Prof, Dept. of EEE) & Mrs. SHASHIBALA AGARWAL (Asst. Prof, Dept. of EEE) without whom we could not have been able to do this.

Our special thanks to Dr. RAJVEER MITTAL (HOD of EEE) & Mr. LP SINGH (Asst. Prof., Dept. of EEE) and all the staff members of MAIT for extending full support and making this whole experience enriching, informative and facilitating the successful completion of the project.

KESHAV GARG (08814804911) ABHISHEK GARG (09114804911)

GOPAL AGGARWAL (02914804911)

ABSTRACTThe human mind always seeks some portable device that can convert DC voltage to AC voltage conveniently to fulfil the needs of running small loads like CFL, tungsten filament bulb, running audio & video and Mobile Homes etc. So, keeping this in mind, Inverter which is compact and portable using 555 timer is studied and performed in real time. Although many methods have been devised earlier to convert DC into AC voltage, but many of those methods have dis-advantages like portability, compactness, power losses and requirement of high power from the source. Coming to inverter using 555 timer, all the above stated dis-advantages are absent.

Also, the demand of highly efficient and stable DC to AC inverters used in renewable energy systems to convert DC output from green energy sources into purely sinusoidal unwavering AC is on rise, due to low cost of energy generation and conversion, less complexity and environmental factors.

DC-AC inverters are electronic devices used to produce mains voltage AC power from low voltage DC energy (from a battery or solar panel). This makes them very suitable for when you need to use AC power tools or appliances but the usual AC mains power is not available.CONTENTS

LIST OF ABBREVIATION.1

LIST OF FIGURES..2 CHAPTER 1: INTRODUCTION TO INVERTER....3

CHAPTER 2: IC 555 TIMER.....8

CHAPTER 3: MOSFET........19

CHAPTER 4: TRANSFORMER..27

CHAPTER 5: TRANSISTOR.......39

CHAPTER 6: OTHER COMPONENTS..46

CHAPTER 7: WORKING OF INVERTER.....50

CHAPTER 8: DIFFERENCE OF NORMAL & 555 TIMER

INVERTER52CHAPTER 9: RESULTS & CONCLUSION...56

HARDWARE IMAGE...69

FUTURE SCOPE....60

REFERRENCES.....61

LIST OF ABBREVIATIONS DIP: Dual Inline Package GND: Ground SOP: Small Outline Package BJT: Bipolar-Junction Transistor GTO: Gate Turn Off Thyristor VCT: Volts Centre Tapped PCB: Printed Circuit Board CFL: Compact Fluorescent Lamp IC: Integrated Circuit MOSFET: Metal Oxide Semi-Conductor Field Effect TransistorLIST OF FIGURES

FIGURE 1.1: Basic Block Diagram....6FIGURE 1.2: Waveform.....6FIGURE 1.3: Circuit Diagram7FIGURE 2.1: IC 555 Timer...10FIGURE 2.2: Internal Diagram of 555 timer.10FIGURE 2.3: Astable Configuration.13FIGURE 2.4: Mono Stable Configuration.14FIGURE 2.5: Bi Stable Configuration...16FIGURE 3.1: Mosfet Structure..23FIGURE 3.2: Mosfet IRFZ4426FIGURE 4.1: Transformer Equivalent Circuit...32FIGURE 4.2: Primary& Secondary Centre Tap Transformer38FIGURE 4.3: Centre Tap Transformer...................38FIGURE 5.1: Transistor Circuit Symbol40FIGURE 5.2: Transistor as a Switch..42FIGURE 5.3: Transistor as a Amplifier..43FIGURE 5.4: BC547..44FIGURE 5.5: Physical Pin Configuration..44

FIGURE 6.1: Capacitors47FIGURE 6.2: Resistors...47FIGURE 6.3: Zero PCB..48FIGURE 6.4: CFL...48FIGURE 6.5: Battery..49FIGURE 6.6: Battery Image...59CHAPTER 1:INTRODUCTION TO INVERTERINTRODUCION TO INVERTER1.1 Project Type

Inverter using IC 555 timer with two Mosfets up to 50W and can be used upto 100W with high transformer rating.

1.2 Project DescriptionThe main objective of this project is to enable a person to convert DC into AC sine wave so that the load upto 50W can be run by applying 12Volt battery. In this, we used IC NE555 timer which worked as astable multivibrator and 12-0-12 transformer which is a center tapped transformer.

The projects have following sections:

1. Power supply (DC 12V battery)

2. IC 555 timer

3. Mosfet IRFZ44 & Transistor

4. Tranformer (12-0-12)

DC-AC inverters are electronic devices used to produce mains voltage AC power from low voltage DC energy (from a battery or solar panel). This makes them very suitable for when you need to use AC power tools or appliances but the usual AC mains power is not available. Examples include operating appliances in caravans and mobile homes, and also running audio, video and computing equipment in remote areas.

Most inverters do their job by performing two main functions: first they convert the incoming DC into AC, and then they step up the resulting AC to mains voltage level using a transformer. And the goal of the designer is to have the inverter perform these functions as efficiently as possible so that as much as possible of the energy drawn from the battery or solar panel is converted into mains voltage AC, and as little as possible is wasted as heat. Modern inverters use a basic circuit scheme like that shown in this project. Well see the DC from the battery is converted into AC very simply, by using a pair of power MOSFETs (Q1 and Q2) acting as very efficient electronic switches. The positive 12V DC from the battery is connected to the centre-tap of the transformer primary, while each MOSFET is connected between one end of the primary and earth (battery negative). So by switching on Q1, the battery current can be made to flow through the top half of the primary and to earth via Q1. Conversely by switching on Q2 instead, the current is made to flow the opposite way through the lower half of the primary and to earth. Therefore by switching the two MOSFETs on alternately, the current is made to flow first in one half of the primary and then in the other, producing an alternating magnetic flux in the transformers core. As a result a corresponding AC voltage is induced in the transformers secondary winding, and as the secondary has about 24 times the number of turns in the primary, the induced AC voltage is much higher: around 650V peak to peak.MOSFETs are used as the electronic switches, to convert the DC into AC, its because they make the most efficient high-current switches. When they are OFF they are virtually an open circuit, yet when they are ON, they are very close to a short circuit (only a few milliohms). So very little power is wasted as heat.1.3 Basic Block Diagram & Wave Form

Figure 1.1: Basic Block Diagram Figure 1.2: WaveformThe switching MOSFETs are simply being turned on and off, this type of inverter does not produce AC of the same pure sinewave type as the AC power mains. The output waveform is essentially alternating rectangular pulses, as you can see from the above figure. However the width of the pulses and the spacing between them is chosen so that the ratio between the RMS value of the output waveform and its peak-to-peak value is actually quite similar to that of a pure sinewave. The resulting waveform is usually called a modified sinewave and as the RMS voltage is close to 230V many AC tools and appliances are able to operate from such a waveform without problems.1.4 Circuit Diagram

Figure 1.3: Circuit DiagramCHAPTER 2:

IC 555 TIMER

IC 555 TIMER2.1 Description

IC 555 timeris a well-known component in the electronic circles but what is not known to most of the people is the internal circuitry of the IC and the function of various pins present there in the IC. Let me tell you afact about why 555 timer is called so, the timer got its name from the three 5 kilo-ohm resistor in series employed in the internal circuit of the IC.

IC 555 timer is a one of the most widely used IC in electronics and is used in various electronic circuits for its robust and stable properties. It works as square-wave form generator with duty cycle varying from 50% to 100%, Oscillator and can also provide time delay in circuits. The 555 timer got its name from the three 5k ohm resistor connected in a voltage-divider pattern which is shown in the figure below. A simplified diagram of the internal circuit is given below for better understanding as the full internal circuit consists of over more than 16 resistors, 20 transistors, 2 diodes, a flip-flop and many other circuit components.

The 555 timer comes as 8 pin DIP (Dual In-line Package) device. There is also a 556 dual version of 555 timer which consists of two complete 555 timers in 14 DIP and a 558 quadruple timer which is consisting of four 555 timer in one IC and is available as a 16 pin DIP in the market

Figure 2.1: IC 555 Timer2.2 Internal Diagram Of 555 Timer:

Figure 2.2: Internal Diagram of 555 Timer2.3 Functions of Different Pins:

1.Ground: This pin is used to provide a zero voltage rail to the Integrated circuit to divide the supply potential between the three resistors shown in the diagram.2.Trigger: As we can see that the voltage at the non-inverting end of the comparator is Vin/3, so if the trigger input is used to set the output of the F/F to high state by applying a voltage equal to or less than Vin/3 or any negative pulse, as the voltage at the non-inverting end of the comparator is Vin/3.

3.Output: It is the output pin of the IC, connected to the Q (Q-bar) of the F/F with an inverter in between as show in the figure.

4.Reset: This pin is used to reset the output of the F/F regardless of the initial condition of the F/F and also it is an active low Pin so it connected to high state to avoid any noise interference, unless a reset operation is required. So most of the time it is connected to the Supply voltage as shown in the figure.

`5.Control Voltage: As we can see that the pin 5 is connected to the inverting input having a voltage level of (2/3) Vin. It is used to override the inverting voltage to change the width of the output signal irrespective of the RC timing network.

6.Threshold: The pin is connected to the non-inverting input of the first comparator. The output of the comparator will be high when the threshold voltage will be more than (2/3) Vinthus resetting the output (Q) of the F/F from high to low.

7.Discharge: This pin is used to discharge the timing capacitors (capacitors involved in the external circuit to make the IC behave as a square wave generator) to ground when the output of Pin 3 is switched to low.

8.Supply: This pin is used to provide the IC with the supply voltage for the functioning and carrying of the different operations to be fulfilled with the 555 timer.2.4 Uses of 555 Timer

The IC 55 timer is used in many circuits, for example One-shot pulse generator in Monostable mode as an Oscillator in Astable Mode or in Bistable mode to produce a flip/flop type action. It is also used in many types of other circuit for achievement of various purposes for instance Pulse Amplitude Modulatin (PAM), Pulse Width Modulation (PWM) etc.

2.5 Working with Different Operating Modes

Multivibrators find their own place in many of the applications as they are one of the most widely used circuits. The application may be household (domestic), industrial, access control, communication etc anyone. The multivibrators are used in all such applications as oscillators, as digital flip-flop, as pulse generator circuit, as delay generator circuit, as a timer and many more.

There are three types of multivibrators:

1.Astable multivibrator-It has no stable state. It has two quasi stable states that automatically changes from one to another and back. So actually it changes from high to low state and low to high state without any trigger input after pre determine time.

For astable operation of IC555 we have two design equationsf = 1.44 / (R1+2*R2)*C, and% duty cycle = (R1+R2) / (R1+2*R2)Here frequency and duty cycle are the design parameters and we have to find out three unknowns R1, R2 & C. For given values of design parameters, we have to find out these three unknown

Figure 2.3 Astable Configuration2.Monostable multivibrator-it has one stable state and one quasi stable state. It jumps into quasi stable state from stable state when trigger input is applied. It comes into stable state from quasi stable state after pre determine time automatically.

Figure 2.4: Monostable ConfigurationConnections:

Instead of connecting one resistor in between threshold and discharge pin, they are shorted here as shown. One resister R is connected between Vcc pin and discharge pin. The capacitor C is connected as shown in between threshold pin and ground. External trigger is applie at trigger input pin. This pin is kept high at Vcc by connecting it to Vcc through 1K resistor. Control voltage input pin (no. 5) is connected to ground through 0.1F capacitor. The output is taken from pin no. 3. Reset input pin (no. 4) is connected to Vcc to enable internal flip-flop operation. Pin no. 8 is connected to Vcc for +Ve bias and pin no. 1 is connected to ground for Ve bias

Operation:In this mode the state of output will only change from low to high (and then back to low) if external negative trigger pulse is applied. The trigger input and the output pulse is as shown in figure.Before trigger is applied, the capacitor charges to Vcc through R1\

When it reaches to 2/3 Vcc the threshold comparator gives high output. That will set flip-flop. So output is low and discharge transistor is ON

So capacitor discharges and thats why output is low.

When negative trigger pulse is applied, the trigger comparator gives high output. This will reset the flip-flop.

So output becomes high and discharging transistor becomes off.

So again capacitor starts charging towards Vcc. When it reaches 2/3 Vcc, flip flop sets and output automatically becomes low.

So the output becomes high only when trigger is applied and remain high till capacitor charges to 2/3 Vcc.

3.Bistable multivibrator-It has both stable states. Two different trigger inputs are applied to change the state from high to low and low to high.

All these three kinds of multivibrators can be easily made using transistors. But one IC is available that can be used as astable, monostable or bistable multivibrator and that isIC555.

IC 555is the most versatile chip and it is (can be) used in all most every kind of application because of its multi functionality. Its 8 pin DIP or SOP package type chip with 200 mA direct current drive output. Its called mixed signal chip because there are analog as well as digital components inside. Its main applicationsare to generate timings, clock waveform, generate synchronizing signals, square wave oscillator, in sequential circuit and many more.

Figure 2.5: Bistable ConfigurationConnections:

Because there is no self triggering now the capacitor is excluded from the circuit. One 1K resistor is connected between threshold pin and ground as shown and another 1K resistor is connected between Vcc and trigger pin. Other connections are common and similar to astable and monostable multivibrators.

Operation:Bistable multivibrator requires two different triggers pulses as shown in figure. One positive pulse at threshold pin and second negative pulse on trigger pin.Initially the output is low. As shown in waveforms, when negative pulse (< 1/3 Vcc) is applied immediately the output becomes high. And it continues to remain high.

Then after when positive pulse (> 2/3 Vcc) is applied on threshold pin, the output becomes low and remains low afterward.

Thus the width of output pulse is determined by the time delay between two pulses.There are no any design equations or no any unknown component values to find out because entire operation depends upon external pulses.

Use of Control Input Pin:In all above modes the control input pin (no. 5) is always grounded through 0.1F capacitor. As shown in the internal diagram of IC555, this pin is connected to inverting terminal of threshold comparator (which is fixed at 2/3 Vcc). So by changing the voltage at this input will change 2/3 Vcc limit and it will change charging time of capacitor. By changing the control input voltage the charging time of capacitor can be increased or decreased. And thus the output pulse width will increase or decrease. Thus control voltage input is used to increase / decrease output pulse width.

Use of Reset Input Pin:In almost all the555 timer circuitsreset input pin is connected to Vcc. This is actually active low input that enables or disables internal flip-flop operation. As per the internal diagram this pin drives one PNP transistor that is connected to preset input of flip-flop. SoIf this pin is given low logic (connected to GND), the PNP transistor becomes ON and flip flop presets. That means the discharging transistor is ON and output is low. There is no any effect of input from threshold pin or trigger pin.If this pin is given high logic (connected to Vcc), the PNP transistor becomes OFF. There is no effect on flip-flop and output becomes high or low as per input from threshold pin or trigger pin.So the reset input pin actually works as ON / OFF switch for IC555 operation. If reset pin is ON (given high logic) the IC555 operation is ON and vice versa.CHAPTER 3:

MOSFETMOSFET3.1 Introduction

Bipolar semiconductor devices (i.e., diode, transistor, thyristor, thyristor, GTO etc) have been the front runners in the quest for an ideal power electronic switch. Ever since the invention of the transistor, the development of solid-state switches with increased power handling capability has been of interest for expending the application of these devices. The BJT and the GTO thyristor have been developed over the past 30 years to serve the need of the power electronic industry. Their primary advantage over the thyristors have been the superior switching speed and the ability to interrupt the current without reversal of the device voltage. All bipolar devices, however, suffer from a common set of disadvantages, namely, (i) limited switching speed due to considerable redistribution of minority charge carriers associated with every switching operation; (ii) relatively large control power requirement which complicates the control circuit design. Besides, bipolar devices can not be paralleled easily.

The reliance of the power electronics industry upon bipolar devices was challenged by the introduction of a new MOS gate controlled power device technology in the 1980s. The power MOS field effect transistor (MOSFET) evolved from the MOS integrated circuit technology. The new device promised extremely low input power levels and no inherent limitation to the switching speed. Thus, it opened up the possibility of increasing the operating frequency in power electronic systems resulting in reduction in size and weight. The initial claims of infinite current gain for the power MOSFET were, however, diluted by the need to design the gate drive circuit to account for the pulse currents required to charge and discharge the high input capacitance of these devices. At high frequency of operation the required gate drive power becomes substantial. MOSFETs also have comparatively higher on state resistance per unit area of the device cross section which increases with the blocking voltage rating of the device. Consequently, the use of MOSFET has been restricted to low voltage (less than about 500 volts) applications where the ON state resistance reaches acceptable values. Inherently fast switching speed of these devices can be effectively utilized to increase the switching frequency beyond several hundred kHz.

From the point of view of the operating principle a MOSFET is a voltage controlled majority carrier device. As the name suggests, movement of majority carriers in a MOSFET is controlled by the voltage applied on the control electrode (called gate) which is insulated by a thin metal oxide layer from the bulk semiconductor body. The electric field produced by the gate voltage modulate the conductivity of the semiconductor material in the region between the main current carrying terminals called the Drain (D) and the Source (S). Power MOSFETs, just like their integrated circuit counterpart, can be of two types (i) depletion type and (ii) enhancement type. Both of these can be either n- channel type or p-channel type depending on the nature of the bulk semiconductor.

3.2 Constructional Features of Mosfet

MOSFET is a device that evolved from MOS integrated circuit technology. The first attempts to develop high voltage MOSFETs were by redesigning lateral MOSFET to increase their voltage blocking capacity. The resulting technology was called lateral double diffused MOS (DMOS). However it was soon realized that much larger breakdown voltage and current ratings could be achieved by resorting to a vertically oriented structure. Since then, vertical DMOS (VDMOS) structure has been adapted by virtually all manufacturers of Power MOSFET. A power MOSFET using VDMOS technology has vertically oriented three layer structure of alternating p type and n type semiconductors as shown in Fig 6.2 (a) which is the schematic representation of a single MOSFET cell structure. A large number of such cells are connected in parallel to form a complete device. The two n+ end layers labeled Source and Drain are heavily doped to approximately the same level. The p type middle layer is termed the body (or substrate) and has moderate doping level (2 to 3 orders of magnitude lower than n+ regions on both sides). The n- drain drift region has the lowest doping density. Thickness of this region determines the breakdown voltage of the device. The gate terminal is placed over the n- and p type regions of the cell structure and is insulated from the semiconductor body be a thin layer of silicon dioxide (also called the gate oxide). The source and the drain region of all cells on a wafer are connected to the same metallic contacts to form the Source and the Drain terminals of the complete device. Similarly all gate terminals are also connected together. The source is constructed of many (thousands) small polygon shaped areas that are surrounded by the gate regions. The geometric shape of the source regions, to same extent, influences the ON state resistance of the MOSFET.

Figure 3.1: Mosfet Structure3.3 Operating Principle of Mosfet

At first glance it would appear that there is no path for any current to flow between the source and the drain terminals since at least one of the p n junctions (source body and body-Drain) will be reverse biased for either polarity of the applied voltage between the source and the drain. There is no possibility of current injection from the gate terminal either since the gate oxide is a very good insulator. However, application of a positive voltage at the gate terminal with respect to the source will covert the silicon surface beneath the gate oxide into an n type layer or channel, thus connecting the Source to the Drain as explained next. The gate region of a MOSFET which is composed of the gate metallization, the gate (silicon) oxide layer and the p-body silicon forms a high quality capacitor. When a small voltage is application to this capacitor structure with gate terminal positive with respect to the source (note that body and source are shorted) a depletion region forms at the interface between the SiO2 and the silicon as shown in the figure. The positive charge induced on the gate metallization repels the majority hole carriers from the interface region between the gate oxide and the p type body. This exposes the negatively charged acceptors and a depletion region is created.

Further increase in VGS causes the depletion layer to grow in thickness. At the same time the electric field at the oxide-silicon interface gets larger and begins to attract free electrons as shown in the figure. The immediate source of electron is electron-hole generation by thermal ionization. The holes are repelled into the semiconductor bulk ahead of the depletion region. The extra holes are neutralized by electrons from the source.

As VGS increases further the density of free electrons at the interface becomes equal to the free hole density in the bulk of the body region beyond the depletion layer. The layer of free electrons at the interface is called the inversion layer and is shown in figure. The inversion layer has all the properties of an n type semiconductor and is a conductive path or channel between the drain and the source which permits flow of current between the drain and the source. Since current conduction in this device takes place through an n- type channel created by the electric field due to gate source voltage it is called Enhancement type n-channel MOSFET. The value of VGS at which the inversion layer is considered to have formed is called the Gate Source threshold voltage VGS. As VGS is increased beyond VGS the inversion layer gets somewhat thicker and more conductive, since the density of free electrons increases further with increase in VGS. The inversion layer screens the depletion layer adjacent to it from increasing VGS. The depletion layer thickness now remains constant.3.4 Mosfet IRFZ44N

N-channel enhancement mode standard level field-effect power transistor in a plastic envelope using (trench) technology. The device features very low on-state resistance and has integral zener diodes giving ESD protection up to 2kV. It is intended for use in switched mode power supplies and general purpose switching applications. There are various advantages of this type of Mosfet those are:

Advanced Process Technology Ultra Low On-Resistance Dynamic dv/dt Rating 175C Operating Temperature Fast Switching Fully Avalanche Rated3.4 Diagram of Mosfet IRFZ44N

Figure 3.2: Mosfet IRFZ44CHAPTER 4:

TRANSFORMER

TRANSFORMER4.1 Basic DescriptionAtransformeris an electrical device that transfers energy between two or more circuits throughelectromagnetic induction.

A varying current in the transformer's primary winding creates a varyingmagnetic fluxin the core and a varying magnetic field impinging on the secondary winding. This varyingmagnetic fieldat the secondary induces a varyingelectromotive force(EMF) or voltage in the secondary winding. Making use ofFaraday's Lawin conjunction with highmagnetic permeabilitycore properties, transformers can thus be designed to efficiently changeACvoltages from one voltage level to another within power networks.

Transformers range in size fromRFtransformers less than a cubic centimeter in volume to units interconnecting thepower gridweighing hundreds of tons. A wide range of transformer designs is encountered in electronic and electric power applications. Since the invention in 1885 of the first constantpotentialtransformer, transformers have become essential for the ACtransmission,distribution, and utilization of electrical energy.

4.2 Types of Transformer According To Principle Ideal Transformer:

It is very common, for simplification or approximation purposes, to analyze the transformer as an ideal transformer model as represented in the two images. An ideal transformer is a theoretical,lineartransformer that is lossless and perfectly coupled; that is, there are noenergy lossesandfluxis completely confined within themagnetic core. Perfect coupling implies infinitely high coremagnetic permeabilityand winding inductances and zero netmagneto motive force.Avarying current in the transformer's primary winding creates a varying magnetic flux in the core and a varying magnetic field impinging on the secondary winding. This varying magnetic field at the secondary induces a varyingelectromotive force(EMF) or voltage in the secondary winding. The primary and secondary windings are wrapped around a core of infinitely high magnetic permeabilityso that all of the magnetic flux passes through both the primary and secondary windings. With avoltage source connected to the primary winding and loadimpedanceconnected to the secondary winding, the transformer currents flow in the indicated directions.According to Faraday's law of induction, since the same magnetic flux passes through both the primary and secondary windings in an ideal transformer, a voltage is induced in each winding, in the secondary winding case, in the primary winding case.The primary EMF is sometimes termedcounter EMF.This is in accordance with Lenz's law, which states that induction of EMF always opposes development of any such change in magnetic field. The transformer winding voltage ratio is thus shown to be directly proportional to the winding turns ratio.

According to the law ofConservation of Energy, any load impedance connected to the ideal transformer's secondary winding results in conservation of apparent, real and reactive power.

The ideal transformeridentityshown in is a reasonable approximation for the typical commercial transformer, with voltage ratio and winding turns ratio both being inversely proportional to the corresponding current ratio.

ByOhm's Lawand the ideal transformer identity:

The secondary circuit load impedance can be expressed as eq. (6)

The apparent load impedancereferredto the primary circuit is to be equal to the turns ratio squared times the secondary circuit load impedance. Real Transformer:The ideal transformer model neglects the following basic linear aspects in real transformers.

Core losses, collectively called magnetizing current losses, consist of

Hysteresislosses due to nonlinear application of the voltage applied in the transformer core, and

Eddy currentlosses due to joule heating in the core that are proportional to the square of the transformer's applied voltage.

Whereas windings in the ideal model have no resistances and infinite inductances, the windings in a real transformer have finite non-zero resistances and inductances associated with:

Joule lossesdue to resistance in the primary and secondary windings

Leakage flux that escapes from the core and passes through one winding only resulting in primary and secondary reactive impedance.

The ideal transformer model assumes that all flux generated by the primary winding links all the turns of every winding, including itself. In practice, some flux traverses paths that take it outside the windings. Such flux is termedleakage flux, and results inleakage inductanceinserieswith the mutually coupled transformer windings.Leakage flux results in energy being alternately stored in and discharged from the magnetic fields with each cycle of the power supply. It is not directly a power loss, but results in inferiorvoltage regulation, causing the secondary voltage not to be directly proportional to the primary voltage, particularly under heavy load. In some applications increased leakage is desired, and long magnetic paths, air gaps, or magnetic bypass shunts may deliberately be introduced in a transformer design to limit theshort-circuitcurrent it will supply.Leaky transformers may be used to supply loads that exhibitnegative resistance, such aselectric arcs,mercury vapor lamps, andneon signsor for safely handling loads that become periodically short-circuited such aselectric arc welders.Air gaps are also used to keep a transformer from saturating, especially audio-frequency transformers in circuits that have a DC component flowing in the windings.

Knowledge of leakage inductance is also useful when transformers are operated in parallel. It can be shown that if the percent impedanceand associated winding leakage reactance-to-resistance (X/R) ratio of two transformers were hypothetically exactly the same, the transformers would share power in proportion to their respective volt-ampere ratings (e.g. 500kVAunit in parallel with 1,000kVA unit, the larger unit would carry twice the current). However, the impedance tolerances of commercial transformers are significant. Also, the Z impedance and X/R ratio of different capacity transformers tends to vary, corresponding 1,000kVA and 500kVA units' values being, to illustrate, respectively,Z 5.75%,X/R 3.75 andZ 5%,X/R 4.75.

Figure 4.1: Transformer Equivalent Circuit

4.3 Basic Transformer Parameters

Effect Of FrequencyBy Faraday's Law of induction transformer EMFs vary according to the derivative of flux with respect to time.The ideal transformer's core behaves linearly with time for any non-zero frequency.Flux in a real transformer's core behaves non-linearly in relation to magnetization current as the instantaneous flux increases beyond a finite linear range resulting inmagnetic saturationassociated with increasingly large magnetizing current, which eventually leads to transformer overheating.

The EMF of a transformer at a given flux density increases with frequency.By operating at higher frequencies, transformers can be physically more compact because a given core is able to transfer more power without reaching saturation and fewer turns are needed to achieve the same impedance. However, properties such as core loss and conductorskin effectalso increase with frequency. Aircraft and military equipment employ 400Hz power supplies which reduce core and winding weight.Conversely, frequencies used for somerailway electrification systemswere much lower (e.g. 16.7Hz and 25Hz) than normal utility frequencies (5060Hz) for historical reasons concerned mainly with the limitations of earlyelectric traction motors. As such, the transformers used to step-down the high over-head line voltages (e.g. 15kV) were much heavier for the same power rating than those designed only for the higher frequencies.

Operation of a transformer at its designed voltage but at a higher frequency than intended will lead to reduced magnetizing current. At a lower frequency, the magnetizing current will increase. Operation of a transformer at other than its design frequency may require assessment of voltages, losses, and cooling to establish if safe operation is practical. For example, transformers may need to be equipped with 'volts per hertz' over-excitationrelaysto protect the transformer from overvoltage at higher than rated frequency.

One example is in traction transformers used forelectric multiple unitandhigh-speedtrain service operating across regions with different electrical standards. The converter equipment and traction transformers have to accommodate different input frequencies and voltage (ranging from as high as 50Hz down to 16.7Hz and rated up to 25kV) while being suitable for multiple AC asynchronous motor and DC converters and motors with varying harmonics mitigation filtering requirements.

Large power transformers are vulnerable to insulation failure due to transient voltages with high-frequency components, such as caused in switching or by lightning. Energy LossesReal transformer energy losses are dominated by winding resistance joule and core losses. Transformers' efficiency tends to improve with increasing transformer capacity. The efficiency of typical distribution transformers is between about 98 and 99 percent. As transformer losses vary with load, it is often useful to express these losses in terms of no-load loss, full-load loss, half-load loss, and so on.Hysteresisandeddy currentlosses are constant at all load levels and dominate overwhelmingly without load, while variable windingjoule lossesdominating increasingly as load increases. The no-load loss can be significant, so that even an idle transformer constitutes a drain on the electrical supply. Designingenergy efficient transformersfor lower loss requires a larger core, good-quality silicon steel, or evenamorphous steelfor the core and thicker wire, increasing initial cost. The choice of construction represents atrade-offbetween initial cost and operating cost.

Transformer losses arise from:Winding joule lossesCurrent flowing through a winding's conductor causesjoule heating. As frequency increases, skin effect andproximity effectcauses the winding's resistance and, hence, losses to increase. Hysteresis losses

Each time the magnetic field is reversed, a small amount of energy is lost due tohysteresiswithin the core. According to Steinmetz's formula, the heat energy due to hysteresis is given by

, and,

Hysteresis loss is thus given by

where,fis the frequency,is the hysteresis coefficient andmaxis the maximum flux density, the empirical exponent of which varies from about 1.4 to 1.8 but is often given as 1.6 for iron. Eddy current losses

Ferromagneticmaterials are also goodconductorsand a core made from such a material also constitutes a single short-circuited turn throughout its entire length.Eddy currentstherefore circulate within the core in a plane normal to the flux, and are responsible forresistive heatingof the core material. The eddy current loss is a complex function of the square of supply frequency and Inverse Square of the material thickness.Eddy current losses can be reduced by making the core of a stack of plates electrically insulated from each other, rather than a solid block; all transformers operating at low frequencies use laminated or similar cores.

Magnetostriction related transformer hum

Magnetic flux in a ferromagnetic material, such as the core, causes it to physically expand and contract slightly with each cycle of the magnetic field, an effect known as magnetostriction, the frictional energy of which produces an audible noise known asmains humortransformer hum.This transformer hum is especially objectionable in transformers supplied atpower frequenciesand inhigh-frequencyflyback transformersassociated with PAL systemCRTs.

Stray losses

Leakage inductance is by itself largely lossless, since energy supplied to its magnetic fields is returned to the supply with the next half-cycle. However, any leakage flux that intercepts nearby conductive materials such as the transformer's support structure will give rise to eddy currents and be converted to heat.There are also radiative losses due to the oscillating magnetic field but these are usually small.

4.4 Transformer Used In Project

Center Tapped Transformer:In electronics, acenter tap(CT) is a contact made to a point halfway along a winding of atransformerorinductor, or along the element of aresistoror apotentiometer. Taps are sometimes used on inductors for the coupling of signals, and may not necessarily be at the half-way point, but rather, closer to one end. A common application of this is in theHartley oscillator. Inductors with taps also permit the transformation of the amplitude ofalternating current(AC)voltagesfor the purpose of power conversion, in which case, they are referred to asautotransformers, since there is only one winding. An example of an autotransformer is anautomobileignition coil. Potentiometer tapping provides one or more connections along the device's element, along with the usual connections at each of the two ends of the element, and the slider connection. Potentiometer taps allow for circuit functions that would otherwise not be available with the usual construction of just the two end connections and one slider connection.

Volts Center Tapped(12-0-12):Volts center tapped (VCT) describes the voltage output of a center tapped transformer. For example: A 24 VCT transformer will measure 24 VAC across the outer two taps (winding as a whole), and 12 VAC from each outer tap to the center-tap (half winding). These two 12 VAC supplies are 180 degrees out of phase with each other, thus making it easy to derive positive and negative 12 volt DC power supplies from them. Figure 4.2: Primary and Secondary of Center Tapped Transformer4.5 Diagram of a Center Tapped Transformer

Figure 4.3 Centre Tap TransformerCHAPTER 5:

TRANSISTOR

TRANSISTOR

5.1 Description:

Transistorsamplify current, for example they can be used to amplify the small output current from a logic chip so that it can operate a lamp, relay or other high current device. In many circuits aresistoris used to convert the changing current to a changing voltage, so the transistor is being used toamplify voltage.A transistor may be used as aswitch(either fully on with maximum current, or fully off with no current) and as anamplifier(always partly on).The amount of current amplification is called thecurrent gain, symbol hFE.

5.2 Types of TransistorsTransistorsamplify current, for example they can be used to amplify the small output current from a logic chip so that it can operate a lamp, relay or other high current device. In many circuits aresistoris used to convert the changing current to a changing voltage, so the transistor is being used toamplify voltage.A transistor may be used as aswitch(either fully on with maximum current, or fully off with no current) and as anamplifier(always partly on).The amount of current amplification is called thecurrent gain, symbol hFE. Figure 5.1: Transistor circuit symbol5.3 Operation:There are two types of transistors, which have slight differences in how they are used in a circuit. Abipolar transistorhas terminals labeled base,collector, andemitter. A small current at the base terminal (that is, flowing between the base and the emitter) can control or switch a much larger current between the collector and emitter terminals. For afield-effect transistor, the terminals are labeledgate,source, anddrain, and a voltage at the gate can control a current between source and drain.The image to the right represents a typical bipolar transistor in a circuit. Charge will flow between emitter and collector terminals depending on the current in the base. Because internally the base and emitter connections behave like a semiconductor diode, a voltage drop develops between base and emitter while the base current exists. The amount of this voltage depends on the material the transistor is made from, and is referred to asVBE.

5.3.1 Transistor as a switchTransistors are commonly used as electronic switches, both for high-power applications such as switched-mode power suppliesand for low-power applications such as logic gates.

In a grounded-emitter transistor circuit, such as the light-switch circuit shown, as the base voltage rises, the emitter and collector currents rise exponentially. The collector voltage drops because of reduced resistance from collector to emitter. If the voltage difference between the collector and emitter were zero (or near zero), the collector current would be limited only by the load resistance (light bulb) and the supply voltage. This is called saturationbecause current is flowing from collector to emitter freely. When saturated, the switch is said to beon.

Figure 5.2: Transistor as a SwitchProviding sufficient base drive current is a key problem in the use of bipolar transistors as switches. The transistor provides current gain, allowing a relatively large current in the collector to be switched by a much smaller current into the base terminal. The ratio of these currents varies depending on the type of transistor, and even for a particular type, varies depending on the collector current. In the example light-switch circuit shown, the resistor is chosen to provide enough base current to ensure the transistor will be saturated.In any switching circuit, values of input voltage would be chosen such that the output is either completely off,or completely on. The transistor is acting as a switch, and this type of operation is common in digital circuitswhere only "on" and "off" values are relevant.5.3.2 Transistor as an amplifierThe common-emitter amplifier is designed so that a small change in voltage (Vin) changes the small current through the base of the transistor; the transistor's current amplification combined with the properties of the circuit mean that small swings inVinproduce large changes inVout.

Various configurations of single transistor amplifier are possible, with some providing current gain, some voltage gain, and some both.

From mobile phones to televisions, vast numbers of products include amplifiers for sound reproduction, radio transmission, and signal processing. The first discrete-transistor audio amplifiers barely supplied a few hundred milliwatts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved.

Modern transistor audio amplifiers of up to a few hundred wattsare common and relatively inexpensive. Figure 5.3: Transistor as an amplifier5.4 BC 547 TransistorIn our inverter, we use BC 547 transistor. Basically, A BC547transistoris a negative-positive-negative (NPN) transistor that is used for many purposes. Together with other electronic components, such as resistors, coils, and capacitors, it can be used as the active component for switches and amplifiers. Like all other NPN transistors, this type has anemitterterminal, a base or control terminal, and a collector terminal. In a typical configuration, the current flowing from the base to the emitter controls the collector current. A short vertical line, which is the base, can indicate the transistor schematic for anNPN transistor, and the emitter, which is a diagonal line connecting to the base, is an arrowhead pointing away from the base.

Figure 5.4: BC547There are various types of transistors, and the BC547 is a bipolar junction transistor (BJT). There are also transistors that have one junction, such as the junction field-effect transistor, or no junctions at all, such as the metal oxide field-effect transistor (MOSFET). During the design and manufacture of transistors, the characteristics can be predefined and achieved. The negative (N)-type material inside an NPN transistor has an excess of electrons, while the positive (P)-type material has a lack of electrons, both due to a contamination process called doping.

Figure 5.5: Physical TransistorThe BC547 transistor comes in one package. When several are placed in a single package, it is usually referred to as atransistor array. Arrays are commonly used in digital switching. Eight transistors may be placed in one package to make layout much easier.To make use of a transistor as an audio preamplifier, a direct current (DC) source is needed, such as a 12-volt (V)power supply. In a common emitter configuration, the negative side of the power supply is alternating current (AC)-coupled to the emitter via acapacitor. There is also a small resistance connecting the power supply to the emitter. The power supply is then connected to the collector via aresistor, which may be referred to as a limiting resistor. When the collector-to-emitter current flows, there will be avoltage dropin the limiting resistor, and in the idle state, the collector voltage is typically 6 V.

Transistor circuit design requires a thorough understanding of current-voltage ratings of various components, such as transistors and resistors. One goal is to keep the components from burning up, while another is to make the circuit work. Saving electricity is also important, such as in the case of battery-operated devices.

CHAPTER 6:

OTHER COMPONENTS

OTHER COMPONENTS

Besides components like IC 555 timer, mosfets, transformer and transistor, the following other components are also used in this project.

6.1 Capacitors

Standard electrolytic capacitors of various ratings are used in this project. The role of the capacitors is to absorb the spike energy or can be used to correct the power factor.

Figure 6.1: Capacitors6.2 Resistors

Standard carbon resistors of various values and 0.25W rating are used in this project. Figure 6.2: Resistors6.3 Zero PCB

Zero Printed circuit board is used in this project to design this circuit. The manual soldering connections are done through the multi strand wire.

Figure 6.3: Zero PCB6.4 CFL

CFL 5W (Compact Fluorescent Lamp) is used to test the output of the circuit. It is connected directly connected to the transformer secondary as shown in the practical diagram

Figure 6.4: CFL6.5 Connecting Wires

In this project, mainly multi-strand wire is used, as the operating voltage is 12V, Single strand can also be used but for using it with Mosfets, multi strand is more preferable.

6.6 Battery

Battery is the most important part of this project. The 12V, 7mah battery is used in this project. It must be accurately charged upto 12V or more than that. So, the rechargeable battery is mostly preferred. If the voltage of the battery is less than the rated voltage that is required for the operation to be performed then the CFL will not glow. In this projects these type of batteries are used as battery banks. These are mobile battery as they can easily be carried for the use anywhere.

Figure 6.5: BatteryCHAPTER 7:

WORKING OF INVERTER

WORKING OF INVERTERIn this project basically DC voltage is converted to AC voltage hence the name given to this project is Inverter as conversion from DC to AC is the work of an inverter. In this firstly a 12V DC voltage is taken from a battery of rating 12V and 7.5 Ah and then it is given to IC-NE555 timer which is a square wave frequency generator output of 50Hz and can be used as the driver in PWM technique for the Mosfets. The frequency is determined from resistor and capacitor which we have set to 50Hz output. Then we use both N-type Mosfet IRF Z44N (Q2, Q3) as to drive the transformer coil (primary winding).These two MOSFETS are arranged in such a way that one of the Mosfet is directly connected to the 555 Timer IC and another is connected to the 555 Timer IC via Transistor .Here the Mosfets will function like Transistors only as Mosfet also has three terminals i.e. Gate, Source and Drain. The positive pulse coming from 555 Timer IC drives the Mosfet which is directly connected to it and during the negative pulse first Mosfet will be OFF and second Mosfet will conduct. Now the current of Pin 3 of IC1 will flow two ways, first through R3 to gate of Q2 and, second ways will flow to Q1-transistor BC547 as inverter logic form to reverse signal difference first ways. Next current flow to gate of Q3 to also drive the transformer. Then because of this AC voltage of 220V is achieved at the output.CHAPTER 8:

DIFFERENCE OF NORMAL

&

555 TIMER INVERTER

DIFFERENCE OF NORMAL & 555 TIMER INVERTER8.1 Difference Between regular inverter and inverter using 555 timer

A home UPS/inverter system has a system of inverter and batteries that is connected to the home power connection. When the power is coming from the grid, the UPS/inverter system charges the batteries using the power coming from the grid. When the power is off, the inverter takes the DC power from the batteries and converts it into AC used by appliances. There is an automated switch in the system that senses if the grid is not supplying power and switches the UPS into battery mode.

This type of inverter is quite bulky, costly, not portable, and also require large space for installation.

But inverter using 555 timer is cheap, less bulky, small in size, portable and require small space for installation. Due to these features, now a days requirement of this type of inverter increases and according to the required load capacity can be increased. The efficiency of this type of inverter is also high.

It has also advantages because of transisitor, earlier vaccum tubes were used which are bulky and less efficient.8.2 Advantages

No power consumption by a cathode heater; the characteristic orange glow of vacuum tubes is due to a simple electrical heating element, much like a light bulb filament.

Small size and minimal weight, allowing the development of miniaturized electronic devices.

Low operating voltages compatible with batteries of only a few cells.

No warm-up period for cathode heaters required after power application.

Lower power dissipation and generally greater energy efficiency.

Higher reliability and greater physical ruggedness.

Extremely long life. Some transistorized devices have been in service for more than 50 years.

Complementary devices available, facilitating the design of complementary-symmtery circuits, something not possible with vacuum tubes.

Greatly reduced sensitivity to mechanical shock and vibration, thus reducing the problem of microphonicsin sensitive applications, such as audio.

8.3 Limitations

Silicon transistors can age and fail.

High-power, high-frequency operation, such as that used in over-the-air television broadcasting, is better achieved in vacuum tubes due to improved electron mobilityin a vacuum.

Solid-state devices are more vulnerable to electrostatic dischargein handling and operation

A vacuum tube momentarily overloaded will just get a little hotter; solid-state devices have less mass to absorb the heat due to overloads, in proportion to their rating

Sensitivity to radiation and cosmic rays (special radiation-hardened chips are used for spacecraft devices).

Vacuum tubes create a distortion, the so-called tube sound, which some people find to be more tolerable to the ear.

CHAPTER 9:

RESULTS & CONCLUSION

9.1 RESULTS

The Inverter using 555 timer IC is performed successfully on the zero printed circuit board. It is practically performed & run in real time. Proper working of inverter is studied and observed.

In this hardware, basically the output is shown by the Compact Fluorescent Lamp (CFL) i.e. 5 watt rating. The Supply is given through the DC 12V battery which is a rechargeable battery and can easily be carried to the remote location. This particular hardware can take the load upto 20-25watt but not higher than that as the transformer used in this has the maximum output of the 25W.

Yes, we can say that higher rating load upto 100 Watt can be carried by the same circuit as shown in this project, if we replace the transformer by higher ratings. The output waveform is partially sinusoidal & partially rectangular, it do contains harmonics in the waveform, but it easily carry the low load without any hindrance or glitches.There is a finite possibility that the circuit may not run in the case if the voltage of the DC 12V battery even slightly drop down from 11.7V. So it is highly preferable and recommended that one should be having rechargeable battery and it should be charged properly time to time. Refer Fig for the picture of the tested circuit.

9.2 CONCLUSION

This report presents a method to convert DC to AC using 555 timer and Mosfets, when the user connects the specified load where AC supply is not accessible, the user can easily run that load using this circuit as DC supply through 12V battery is converted to 220V AC which is the main requirement for the load to run.We learned a lot in the process of doing this project and writing this report and we hope it will encourage many of you to consider this type of mobile inverter for running low rating loads. I admit the dis-advantage that if battery is slightly discharged or less than 11.7V volt, the load will not run and it is not appropriate of the high rating loads.

The main advantage of this project in day to day life is that it is very handy and can be carried to the remote location for use. Another, it is efficient way to covert the power with very minimum loses. HARDWARE IMAGE

Figure 7: Hardware ImageFUTURE SCOPE

There are mainly following future scope which can extensively be used:

This project can further be extended by using solar panel which is used to charge the battery and can be the source of renewable energy. This is further extended to meet the requirements to run heavy loads with high transformer rating.

REFERNCES

BOOKS & RESEARCH PAPERS:

1. P.S. Bimbhra, Power Electronics, 4th Edition, Khanna Publishers.

2. MD Singh & KB Khanchandani, Power Electronics, 3rd Edition, Tata McGraw-Hill Publishing Company Limited.

3. PC Sen, Power Electronics, 30th Edition, Tata McGraw-Hill Publishing Company Limited.

.

4. Zeeshan Shahid, Sheroz Khan, AHM Zahirul Alam and Musse Muhamod Ahmed, LM555 Timer Based Inverter Low Power Pure Sinusoidal AC Output, World Applied Sciences Journal 30, IDOSI Publications, 2014.

5. Himani Goyal, Understanding of IC 555 Timer and IC 555 Timer Tester, International Journal of Inventive Engineering and Sciences, Blue Eyes Intelligence Engineering & Sciences Publication Pvt. Ltd.

WEBSITES: http://www.engineersgarage.com

http://www.engineering.electrical-equipment.org

http://www.eleccircuit.com

http://www.datasheetcatalog.com

http://www.electusdistribution.com.au http://circuitstoday.comPAGE