Electronic Design and Simulation Module 1 Resistors PDF

ELECTRONIC DESIGN AND SIMULATION  COURSE OUTCOMES CO 1: Identify and test various electronic components. (Understand Level) CO 2: Simulate simple circuits using LT Spice. (Understand Level) CO 3: Design first order RC circuits. (Understand Level) CO 4: Perform testing of simple electro...

ELECTRONIC DESIGN AND SIMULATION  COURSE OUTCOMES CO 1: Identify and test various electronic components. (Understand Level) CO 2: Simulate simple circuits using LT Spice. (Understand Level) CO 3: Design first order RC circuits. (Understand Level) CO 4: Perform testing of simple electronic circuits.(Apply Level) COURSE STRUCTURE  SYLLABUS MODULE I : Electronic Components & Measuring Instruments. Power Supply: AC, DC, Variable supply. Parameters of Voltage and Current: Peak, RMS, Average value. Measuring Instruments: Voltmeter, Ammeter, Multimeter. Block diagram of Function Generator, CRO and DSO. Electronic components: Resistor, Capacitor, LED, LDR, Relay  MODULE II : Electronic Simulation Simulation Environments: LT Spice, Proteus. Diode – Characteristics simulation, equivalent model. Design and Simulation of simple circuits using LED, Resistor and switch.  MODULE III : Electronic Circuits Clipping and Clamping Circuits: Working and simulation. Basic DC power supply with waveforms, SMPS and its comparison with linear power supply.  MODULE IV : First order RC Circuits RC Time Constant and its derivation. Working and Simulation: RC Integrator, Differentiator, High Pass filter, Low Pass filter and its frequency response.  MODULE V : Printed Circuit Boards (1 hour) PCB Chemical etching and PCB milling. Soldering – De soldering. Project using simple components: Design, Simulation and Prototyping.  INTRODUCTION Electronics is a branch of science which deals with the flow of electrons and their effects in materials like vacuum, gas and semiconductors. Electronics deals with low range of voltages current and power but it has capability to control high voltage current and power devices. The word ‘electronics’ is derived from electron mechanics, which means the study of the behavior of an electron under different conditions of externally applied fields. PASSIVE ELECTRONIC COMPONENTS RESISTORS CAPACITORS INDUCTORS ELECTRONIC COMPONENTS  PASSIVE COMPONENTS These components by themselves are not capable of amplifying or processing signals. They are linear elements which control or modify the output of electronic circuits without playing an active role in its performance. They cannot increase the power of any signal applied to them and will almost cause the power to be lost. But without the use of these components we cannot design and implement any electronic circuit. Eg: Resistors, Capacitors, Inductors RESISTORS  Device which provides a force opposing the charge-flow (or current) in a circuit. This opposing force is called resistance (R). Measured in ohms (symbol is Ω). Resistors are the materials which opposes the flow of electric current. Resistor Symbol SPECIFICATIONS OF A RESISTOR Resistance value Power Rating Tolerance Temperature Coefficient of Resistance Voltage Rating RESISTANCE VALUE It gives the value of resistor R in ohms. Its value is either printed or colour coded over the body depending upon the type of resistor. In general resistors may vary from 1ohm to Mega ohms. RESISTOR COLOUR CODING The colour bands are printed at one end of the resistor and are read from left to right. The first colour indicates first digit, 2nd colour the second digit, 3rd colour gives the multiplier and the fourth colour indicates the tolerance value. Four band resistor colour coding.  Resistance of a conductor depends on: The resistance of a conductor depends upon the resistivity, length and cross-sectional area of the conductor which is given by the relation R=ρl/A It does also depend on other physical factors like temperature etc. POWER RATING It is the maximum power that a resistor can withstand without raising the temperature too high. It is expressed in Watts. The power rating depends on the size of the resistor. Common standard power ratings are ¼ W, ½ W,1W and 2W. When current flows through a resistor of resistance R ,heat is produced (Joules Heat).This heat when in excess can damage the resistor. P=I2R TOLERANCE The tolerance of the resistor is an important parameter of the resistor, which tells us about the amount by which the resistance of the resistor may vary from its specified value during the operation. A 100Ω resistor with 10% tolerance ,means its value can be between 90Ω and 110Ω. TEMPERATURE COEFFICIENT OF RESISTANCE Change in resistance with temperature If resistance increases with increase in temp- Positive temp coeff. of resistance Eg: Cu, Al, Tungsten If resistance increases with decrease in temp- Negative temp coeff. of resistance Eg: Semiconductors Alloys like Magnanin, Constantan etc. shows zero temperature coefficient of resistance VOLTAGE RATING Maximum voltage that can be applied across a resistor without causing damage to it (V). CLASSIFICATION OF RESISTORS FIXED RESISTORS Resistors, whose ohmic values remain fixed at a constant value, are known as fixed resistors. 1. CARBON RESISTORS Carbon resistors are made of carbon. These are of two types: (i) Carbon-composition resistors (ii) Carbon film or cracked carbon or pyrolytic resistors. I. Carbon-composition Resistors The carbon-composition resistors are made of finely divided carbon or graphite mixed with a resin binder in suitable proportion needed for the desired resistance value. II. Carbon Film Resistors Carbon film resistors are manufactured by depositing very thin film of carbon on to a substrate of ceramic or glass tube. Depending on the thickness of the film we have thin film (< 5 μm) resistors and thick-film (> 5 μm) resistors. Groves are made on the carbon film to get the precise values  III. WIRE WOUND RESISTORS Wire wound resistors are constructed from a long fine wire (usually nickel-chromium wire) wound on a ceramic core. A wirewound resistor is an electrical passive device that limits or restricts current flow in a circuit.  IV. METAL FILM RESISTOR Metal film resistors are axial resistors with a thin metal film as the resistive element. The thin film is usually deposited on a ceramic body. VARIABLE RESISTORS Variableresistors are resistors whose resistance value can be varied. In certain electrical/ electronic circuits sometimes it is necessary to change the values of currents and voltages. Forexample it is often necessary to change the volume of sound and brightness in T.V, volume of sound and tone in radios and to regulate the speed of a fan. Such adjustments can be done by using variable resistors. POTENTIOMETERS A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. They are commonly used to control electrical devices such as volume controls on audio equipment. It is a three terminal variable resistor. The arrow indicates the movable contact on the resistive element. The position of the movable contact determines the resistance value in the circuit. Based on the material used for construction, potentiometers are classified into two types, 1. Carbon potentiometers  I. Carbon Potentiometers Resistive material is deposited on a non-conducting base. Stationary contacts are connected to each end of the resistive material. Finally, a moving contact or wiper is constructed to move along the resistive material and tap off the desired resistance. The two ends are solder lugs forming the end terminals. The middle lug is connected to the variable arm which in turn connected to a metal spring wiper. As the shaft is rotated, the variable arm moves the wiper to make contact at different points. Carbon Potentiometer II. Wire Wound Potentiometers Wire is used as the resistive element in wire wound potentiometers. Generally Nichrome wire is wound on flat strip of insulating former. This strip is bent into a round shape. There is a rotating shaft at the center of the core. The shaft moves an arm and a contact which moves on winding wire. This unit is covered with a protective container by taking three terminals outside. The two outer terminals are taken from the two ends of the wire and the middle terminal is taken from the rotating arm. The position of the rotating contact decides the resistance value the potentiometer in the circuit. Resistance range from 0.1kΩ to 50kΩ and power rating is from 2W to 4W RHEOSTATS Rheostat is a big size variable resistor used to vary big values of current. The position of the terminal 2 determines the resistance offered by a rheostat. Usually rheostats are variable resistors use to control of currents in low resistance circuits for a.c power applications. Rheostats in their construction, a resistance wire is wounded on a ceramic or cement former. This wire is coated with vitreous enamel. It is provided with a Rheostat