variable frequency device

TRIAC

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Dissertation submitted in partial fulfillment of the Btech. course.

Variable Frequency Device

Under the Guidence of

HOD electrical

Submitted By

Abhishek Kaushik

SG-119836.

Table of Contents

  1. Acknowledgements.

  2. Certificate.

  3. Introduction to the Project.

  4. Circuit Diagram.

  5. Component List.

  6. Hardware

    1. Power Supply for the circuit.

    2. Integrated Circuits.

    3. Transistors.

    4. Diode.

    5. Relays.

    6. Transformer.

    7. Resistors.

    8. Capacitors.

  1. Project Working.

  2. Project Synopsis.

  3. Bibliography.

INTRODUCTION:

In this project, we are controlling DC motor timer. When we give the voltage frequency variations timer, we can control the our DC MOTOR.

This PROJECT is divided into following part:

  1. Power supply

  2. H bridge circuit

  3. Circuit

We are using one h bridges circuits for motor. We are using +12v DC motor for movement. We are using two types of transistors:

  1. Pnp

  2. Npn

By using these transistors we made H bridge circuit. We will use resistances for voltage drop.

About Timer

COMPONENT DESCRIPTION

TRANSISTOR (BC558)

A transistor is semi conductor device consisting of three regions separated by two P-N junctions. The three regions are Base, Emitter & Collector.

The base may be of N- type or P- type. The emitter and collector have same impurities but different from that of base. Thus if base is of N- type then emitter and collector are of P- type then transistor is called P-N-P transistor and vice versa transistor is called N-P-N transistor.

The base is made thin and number density of majority carriers is always less than emitter and collector. The base provides junction for proper interaction between emitter and collector.

Electrons are majority charge carriers in N- region and in P-region, holes are the majority charge carriers. Thus two types of charge carriers are involved in current flow through N-P-N or P-N-P transistor.

SYMBOLS FOR TRANSISTORS :

In schematic symbols, the emitter is always represented by an arrow indicating the direction of conventional current in the device.

In case of N-P-N transistor arrow points away from base and in case of P-N-P transistor it points towards base.

When transistor is used in circuit, emitter – base junction is always forward biased while base – collector junction is always reverse biased.

Fig. Structure and symbol of P-N-P transistor

BIASING OF TRANSISTOR :

The two junctions can be biased in four different ways:

  • Both junctions may be forward biased. It causes large current to flow across junctions. Transistor is to be operated in “SATURATION REGION”.

  • Both junctions may be reversed biased. It causes very small current to flow across junctions. Transistor is to be operated in “CUT OFF REGION”.

  • E-B junction is forward biased and C-B junction is reverse biased. The transistor is said to be operated in “ACTIVE REGION”. Most of the transistors work in this region.

  • E-B junction is reversed biased and C-B junction is forward biased. The transistor is said to be operated in “INVERTED MODE”.

Fig. (a) P-N-P transistor biasing (b) N-P-N transistor biasing

CIRCUIT CONFIGURATIONS :

There are three possible ways in which a transistor can be connected in the circuit which are following :

  • Common Base Configuration : Base is made common in this configuration.

  • Common Emitter Configuration : Emitter is made common in this configuration.

  • C

    ommon Collector Configuration : Collector is made common in this configuration.

Fig. PNP Common Base Configuration

 

CIRCUIT DIAGRAM

Block Diagram

Timer

NE55

Variable

Resistors

Current and voltage amplifier

 

DC Motor

 

SOLDERING

Soldering is the process of joining two metallic conductors the joint where two metal conductors are to be joined or fused is heated with a device called soldering iron and then as allow of tin and lead called solder is applied which melts and converse the joint. The solder cools and solidifies quickly to ensure is good and durable connection between the jointed metal converting the joint solder also present oxidation.

SOLDERING & DESOLDERING TECHNIQUES :

There are basically two soldering techniques:

  1. Manual soldering with iron.

  2. Mass soldering.

The iron consist of an insulated handle connected via a metal shank to the bit the function of bit is to

    1. Stare host & convey it to the component

    2. To store and deliver molten solder 7 flux.

    3. To remove surplus solder from joints.

Soldering bit are made of copper because it has good heat capacity & thermal conductivity. It may erode after long term use to avoid it coating of nickel or tin is used.

SOLDERING WITH IRON :

The surface to be soldered must be cleaned & fluxed. The soldering iron switched on & bellowed to attain soldering temperature. The solder in form of wire is allied hear the component to be soldered &b heated with iron. The surface to be soldered is filled, iron is removed & the joint is cold without disturbing.

component

qty

rate

Timer 555

1

20

Diodes in4001,

4

1

IC 7805

1

15

Optocoupler PC817

4

12

Tr548

4

3

Tr 558

4

3

Motors 12v

2

250

IC base 20 pin

1

10

Crystal 12 Mhz

1

25

Resiatncec 10k

4

.25

4k

4

.25

Cap 10µf

1

5

Connecting wires

1

20

  • Software:-

Keil compiler or UMPS for programming

Window xp

RESISTORS

The flow of charge (or current) through any material, encounters an opposing force similar in many respect to mechanical friction. This opposing force is called resistance of the material. It is measured in ohms. In some electric circuits resistance is deliberately introduced in the form of the resistor.

Resistors are of following types:

  1. Wire wound resistors.

  2. Carbon resistors.

  3. Metal film resistors.

Wire Wound Resistors:

Wire wound resistors are made from a long (usually Ni-Chromium) wound on a ceramic core. Longer the length of the wire, higher is the resistance. So depending on the value of resistor required in a circuit, the wire is cut and wound on a ceramic core. This entire assembly is coated with a ceramic metal. Such resistors are generally available in power of 2 watts to several hundred watts and resistance values from 1ohm to 100k ohms. Thus wire wound resistors are used for high currents.

Carbon Resistors:

Carbon resistors are divided into three types:

  1. Carbon composition resistors are made by mixing carbon grains with

binding material (glue) and moduled in the form of rods. Wire leads

are inserted at the two ends. After this an insulating material seals the

resistor. Resistors are available in power ratings of 1/10, 1/8, 1/4 ,

1/2 , 1.2 watts and values from 1 ohm to 20 ohms.

  1. Carbon film resistors are made by deposition carbon film on a ceramic

rod. They are cheaper than carbon composition resistors.

  1. Cement film resistors are made of thin carbon coating fired onto a

solid ceramic substrate. The main purpose is to have more precise

resistance values and greater stability with heat. They are made in a

small square with leads.

Metal Film Resistors:

They are also called thin film resistors. They are made of a thin metal coating deposited on a cylindrical insulating support. The high resistance values are not precise in value; however, such resistors are free of inductance effect that is common in wire wound resistors at high frequency.

Variable Resistors:

Potentiometer is a resistor where values can be set depending on the requirement. Potentiometer is widely used in electronics systems. Examples are volume control, tons control, brightness and contrast control of radio or T.V. sets.

Fusible Resistors:

These resistors are wire wound type and are used in T.V. circuits for protection. They have resistance of less than 15 ohms. Their function is similar to a fuse made to blow off whenever current in the circuit exceeds the limit.

Resistance of a wire is directly proportional to its length and inversely proportional to its thickness.

R L

R 1/A

RESISTOR COLOR CODE

Example: 1k or 1000 ohms

1st 2nd 3rd 4th

Band1

Band 2

Band 3

Band 4

COLOUR CODES

COLOUR

NUMBER

MULTIPLIER

COLOUR

TOLERANCE

Black

Brown

Red

Orange

Yellow

Green

Blue

Violet

Grey

White

Gold

Silver

0

1

2

3

4

5

6

7

8

9

100

101

102

103

104

105

106

107

108

109

10-1

10-2

Gold

Silver

No colour

5%

10%

20%

CAPACITORS

A capacitor can store charge, and its capacity to store charge is called capacitance. Capacitors consist of two conducting plates, separated by an insulating material (known as dielectric). The two plates are joined with two leads. The dielectric could be air, mica, paper, ceramic, polyester, polystyrene, etc. This dielectric gives name to the capacitor. Like paper capacitor, mica capacitor etc.

Types of capacitors:

Capacitor

 

Fixed capacitor

Variable capacitor

 

Electrolytic

Non-Electrolytic

Gang condenser

Trimmer

 

Mica

Paper

Ceramic

 

Capacitors can be broadly classified in two categories, i.e., Electrolytic capacitors and Non-Electrolytic capacitors as shown if the figure above.

Electrolytic Capacitor:

Electrolytic capacitors have an electrolyte as a dielectric. When such an electrolyte is charged, chemical changes takes place in the electrolyte. If its one plate is charged positively, same plate must be charged positively in future. We call such capacitors as polarized. Normally we see electrolytic capacitor as polarized capacitors and the leads are marked with positive or negative on the can. Non-electrolyte capacitors have dielectric material such as paper, mica or ceramic. Therefore, depending upon the dielectric, these capacitors are classified.

Mica Capacitor:

It is sandwich of several thin metal plates separated by thin sheets of mica. Alternate plates are connected together and leads attached for outside connections. The total assembly is encased in a plastic capsule or Bakelite case. Such capacitors have small capacitance value (50 to 500pf) and high working voltage (500V and above). The mica capacitors have excellent characteristics under stress of temperature variation and high voltage application. These capacitors are now replaced by ceramic capacitors.

Ceramic Capacitor:

Such capacitors have disc or hollow tabular shaped dielectric made of ceramic material such as titanium dioxide and barium titanate. Thin coating of silver compounds is deposited on both sides of dielectric disc, which acts as capacitor plates. Leads are attached to each sides of the dielectric disc and whole unit is encapsulated in a moisture proof coating. Disc type capacitors have very high value up to 0.001uf. Their working voltages range from 3V to 60000V. These capacitors have very low leakage current. Breakdown voltage is very high.

Paper Capacitor:

It consists of thin foils, which are separated by thin paper or waxed paper. The sandwich of foil and paper is then rolled into a cylindrical shape and enclosed in a paper tube or encased in a plastic capsules. The lead at each end of the capacitor is internally attached to the metal foil. Paper capacitors have capacitance ranging from 0.0001uf to 2.0uf and working voltage rating as high as 2000V.

THE DIODE

Diodes are polarized, which means that they must be inserted into the PCB the correct way round. This is because an electric current will only flow through them in one direction (like air will only flow one way trough a tyre valve). Diodes have two connections, an anode and a cathode. The cathode is always identified by a dot, ring or some other mark.

+

 

The PCB is often marked with a +sign for the cathode end. Diodes come in all shapes and sizes. They are often marked with a type number. Detailed characteristics of a diode can be found by looking up the type number in a data book. If you know how to measure resistance with a meter then test some diodes. A good one has low resistance in one direction and high in other. They are specialized types of diode available such as the zener and light emitting diode (LED).

SYMBOLS OF DIFFERENT DIODES

anode cathode

simple diode zener diode

IC

IC (Integrated Circuit) means that all the components of the circuit are fabricated on same chip. Digital ICs are a collection of resistors, diodes, and transistors fabricated on a single piece of semiconductor, usually silicon called a substrate, which is commonly referred to as ‘wafer’. The chip is enclosed in a protective plastic or ceramic package from which pins extend out connecting the IC to other device. Suffix N or P stands for dual-in-line (plastic package (DIP)) while suffix J or I stands for dual-in-lime ceramic package. Also the suffix for W stands for flat ceramic package.

The pins are numbered counter clockwise when viewed from the top of the package with respect to an identity notch or dot at one end of the chip.The manufacturer’s name can usually be guessed from its logo that is printed on the IC. The IC type number also indicates the manufacturer’s code. For e.g. DM 408 N SN 7404 indicates National Semiconductor and Texas Instruments.

Other examples are:

Fair Child : UA, UAF

National Semiconductor : DM, LM, LH, LF, and TA.

Motorola : MC, MFC.

Sprague : UKN, ULS, ULX.

Signetic : N/s, NE/SE, and SU.

Burr-Brown : BB.

Texas Instruments : SN.

The middle portion i.e. the IC type number tells about the IC function and also the family, which the particular IC belongs to.IC’s that belongs to standard TTL series have an identification number that starts with 74; for e.g. 7402, 74LS04, 74S04 etc. IC’s that belongs to standard CMOS family their number starts with 4, like 4000, 451B, 4724B, 1400. The 74C, 74HC, 74AC & 74ACT series are newer CMOS series.

Various series with TTL logic family are:-

Standard TTL 74.

Schottky TTL 74s.

Low power Schottky 74LS.

Advance Schottky 74AS.

Advanced Low Power Schottky 74ALs.

Also there are various series with CMOS logic family as metal state CMOS 40 or 140.

Power Supply

For TTL circuits, the power supply pin is labeled Vcc and its nominal value.

For CMOS ICs, the power supply pin is labeled as VDD & its nominal value range from T3 to 18V.

Unconnected Inputs

An unconnected input is called “floating input”. The floating TTL input acts as logic 1. High level is applied to it. This characteristic is often used when

testing a TTL circuit. A floating TTL input will measure a DC level between 1.4V to 1.8V when checked with VOM as oscilloscope. If a CMOS input is left floating, it may have disastrous results. The IC may become overheated and eventually destroy itself. For this reason, all inputs to CMOS circuit must be connected to a LOW or HIGH level or to the output of another IC.

 

 

Temperature sensors

A temperature-sensitive resistor is called a thermistor. There are several different types:

 

The resistance of most common types of thermistor decreases as the temperature rises. They are called negative temperature coefficient, or ntc, thermistors. Note the -t° next to the circuit symbol. A typical ntc thermistor is made using semiconductor metal oxide materials. (Semiconductors have resistance properties midway between those of conductors and insulators.) As the temperature rises, more charge carriers become available and the resistance falls.

Although less often used, it is possible to manufacture positive temperature coefficient, or ptc, thermistors. These are made of different materials and show an increase in resistance with temperature.

How could you make a sensor circuit for use in a fire alarm? You want a circuit which will deliver a HIGH voltage when hot conditions are detected. You need a voltage divider with the ntc thermistor in the Rtop position:

 

 

How could you make a sensor circuit to detect temperatures less than 4°C to warn motorists that there may be ice on the road? You want a circuit which will give a HIGH voltage in cold conditions. You need a voltage divider with the thermistor in place of Rbottom :

 

This last application raises an important question: How do you know what value of Vout you are going to get at 4°C?

Key point: The biggest change in Vout from a voltage divider is obtained when Rtop and Rbottom are equal in value

Advantages

Reliable

Low cost

Easy to use

Portable

Components available in the market

BIBILIOGRAPHY

1. HAND BOOK OF ELECTRONICS A.K. MAINI.

2.HAND BOOK OF ELECTRONICS GUPTA & KUMAR.

3.LET US C YASHWANT KANITKAR.

4.SHYAM SERIES TATA MC GRILL.

5.DIGITAL SYSTEMS PRINCIPLES AND APPLICATION RONALD LTOCCI.

(Sixth addition)

6.ELECTRONICS FOR YOU (MARCH 1998).

7.DIGITAL DESIGN MORIS MANO.

(Second addition)

8.RELAYS AND ITS APPLICATION SHARMA, MC.

(Bpb-publishers)

9.MODERN ALL ABOUT MOTHERBOARD LOTHIA, M.

(Bpb-publishers)

10.POWER SUPPLY FOR ALL OCCASION SHARMA, MC.

(Bpb-publishers)

11.CMOS DATA BOOK (74SERIES) ECA.

(Bpb-publishers)

12.PRACTICAL VALUE AND TRANSISTOR DATA POPE.

(Bpb-publishers)

13.PRACTICAL TRANSFORMER DESIGN HAND BOOK LABON. E.

(Bpb-publishers)

14 MODERN IC MANAHAR LOTIA.

(DATA AND SUBSTITUTIONAL MANUAL)

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