ACKNOWLELDGEMENTThis project would not have been possible without the help, guidance and support of many individuals, I am extremely thankful to the god almighty for his blessings.I acknowledge our administrator Fr.Gigi.P.Abraham and our principal Mrs.Anu George for providing necessary lab Facilities and for their encouragement and support during the course of my study. I am also indebted to Mr.Naveen Kumar and Mr Varghese Chacko our physics teachers for their suggestions, guidance and guidance which has helped me in completing my project on time. I am also thankful to our entire lab assistant for their helps.A word of gratitude also goes for my parents and my relatives for their prayers and constant support. I also acknowledge the help, support and prayers of my lab mates, classmates and friends.
INDEX
1. Introduction32. Components used43. Component descriptiona. Capacitors6b. Resistors7c. Integrated Circuits9d. Diodes10e. Transistor12f. Thermistor154. Circuit Diagram175. Circuit Description186. Working197. Conclusion208. Bibliography21
INTRODUCTION In the fast developing world, where anything is possible in a fraction of a second, electronics has emerged as the most important branch of engineering. Electronics is simply defined as the field of engineering and science which deals with electron devices and its utilization. From the simplest calculators we use to the most sophisticated machines used for controlling the satellites in outer space, electronics has a wide range of applications.This project, temperature controlled DC fan, is based on digital electronics.The necessary theory and working are explained in the following pages.
Components Used Capacitors 100F .001 P lF Carbon Resistors 47 K 4.7K 22K IK 680 ohms Integrated Circuits IC555 Diodes IN4148 LED Transistor BC 547 DC fan Thermistor (NTC) 9V battery
COMPONENTS DESCRIPTION
CAPACITORSCapacitor is a device that stores an electrical charge or energy on it's plates. These plates (see Fig. 1), a positive and a negative plate, are placed very close together with an insulator in between to prevent the plates from touching each other. A capacitor can carry a voltage equal to the battery or input voltage. Usually a capacitor has more than two plates depending on the capacitance or dielectric type.The 'Charge' is called the amount of stored electricity on the plates, or actually the electric field between theses plates, and is proportional to the applied voltage and capacitor's 'capacitance'. The Formula to calculate the amount of capacitance is Q = C * V where: Q = Charge in Coulombs C = Capacitance in Farads V = Voltage in Volts
Capacitors have always had farad as the unit of measure, abbreviated "F". Since this is a very large unit of measure for most practical capacitors or for most uses of capacitance, you'll find that a millionth of a farad or a million-millionth of a farad are the more common units found on capacitors. Yes, these days we can find capacitors with ratings in the tens and hundreds of farads, but those are usually reserved for extremely high-current, low-voltage switching supplies or for a more frivolous use as energy-storage tanks for use with high-power automotive audio power amplifiers.This treatise is for "normal" capacitors.In scientific notation, we would write 1 millionth of a farad as 1 x 10 ^ (-6 )farad. In electronics, since we deal with so many component values and circuit values on even the smallest schematic or product, the metric prefix form is used for electronic shorthand to keep the scribbling to a minimum.
RESISTORSThere are many types of resistors, both fixed and variable. The most common type for electronics use is the carbon resistor. They are made in different physical sizes with power dissipation limits commonly from 1 watt down to 1/8 watt. The resistance value and tolerance can be determined from the standard resistor colour code.A variation on the colour code is used for precision resistors which may have five coloured bands. In that case the first three bands indicate the first three digits of the resistance value and the fourth band indicates the number of zeros. In the five band code the fifth band is gold for 1% resistors and silver for 2%.There is another scheme for resistors which have the values stamped on them. Since a decimal point is easy to miss, this code uses R instead of a decimal point. For values over 100 Q four numbers are used. The tolerance is indicated by a letter.
20 | Page
Resistor Colour Code
Resistance value, first three bands.1st band - 1st digit2nd band - 2nd digit3rd band - number of zeros.
0
1Brown
2Red
3Orange
4Yellow
5Green
6Blue
7Violet
8Gray
9White
4th band, tolerance5%Gold
10%Silver
20%No band
Different part or markings on a carbon resistor is as shown.
It is usually represented as shown below.
INTEGRATED CIRCUITAn integrated circuit (IC), sometimes called a chip or microchip, is a semiconductor wafer on which thousands or millions of tiny resistors, capacitors, and transistors are fabricated. An IC can function as an amplifier, oscillator, timer, counter, computer memory, or microprocessor. A particular IC is categorized as either linear (analog) or digital, depending on its intended application.Linear ICs have continuously variable output (theoretically capable of attaining an infinite number of states) that depends on the input signal level. As the term implies, the output signal level is a linear function of the input signal level. Ideally, when the instantaneous output is graphed against the instantaneous input, the plot appears as a straight line. Linear ICs are used as audio-frequency (AF) and radio-frequency (RF) amplifiers. The operational amplifier (op amp) is a common device in these applications.Digital ICs operate at only a few defined levels or states, rather than over a continuous range of signal amplitudes. These devices are used in computers, computer networks, modems, and frequency counters. The fundamental building blocks of digital ICs are logic gates, which work with binary data, that is, signals that have only two different states, called low (logic 0) and high (logic 1).4000 series, the CMOS counterpart to the 7400 series (logic building blocks).
DIODESA diode is a two terminal electronic component with asymmetric conductance; it has low resistance to current in one direction, and high resistance in the other. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material with a p-n junction connected to two terminals.However, diodes can have more complicated behaviour than this simple on-off action, due to their nonlinear current-voltage characteristics. Semiconductor diodes begin conducting electricity only if a certain threshold voltage or cut-in voltage is present in the forward direction (This is known as forward bias).The voltage drop across a forward-biased diode varies only a little with the current, and is a function of temperature; this effect can be used as a temperature sensor or voltage reference.Semiconductor diodes' current-voltage characteristic can be tailored by varying the semiconductor materials and doping, introducing impurities into the materials. These are exploited in special-purpose diodes that perform many different functions. For example, diodes are used to regulate voltage (Zener diodes), to protect circuits from high voltage surges (avalanche diodes), to electronically tune radio and TV receivers (varactor diodes), to generate radio frequency (tunnel diodes, Gunn diodes, IMPATT diodes), and to produce light (light emitting diodes). Tunnel diodes exhibit negative resistance, which makes them useful in some types of circuits.p-n Junction diodesA p-n junction diode is made of a crystal of semiconductor, usually silicon, but germanium and gallium arsenide are also used. Impurities are added to it to create a region on one side that contains negative charge carriers (electrons), called n-type semiconductor, and a region on the other side that contains positive charge carriers (holes), called p-type semiconductor. When two materials i.e. n-type and p-type are attached together, a momentary flow of electrons occur from n to p side resulting in a third region where no charge carriers are present. This region is called the depletion region due to the absence of charge carriers (electrons and holes in this case). The diode's terminals are attached to the n-type and p-type regions. The boundary between these two regions, called a p-n junction, is where the action of the diode takes place. The crystal allows electrons to flow from the N-type side (called the cathode) to the P-type side (called the anode), but not in the opposite direction.Zener diodesThese can be made to conduct in reverse bias (backward), and are correctly termed reverse breakdown diodes. This effect, called Zener breakdown, occurs at a precisely defined voltage, allowing the diode to be used as a precision voltage reference. The term Zener diode is colloquially applied to several types of breakdown diodes, but strictly speaking Zener diodes have a breakdown voltage of below 5 volts, while those above that value are usually avalanche diodes. In practical voltage reference circuits, Zener and switching diodes are connected in series and opposite directions to balance the temperature coefficient to near-zero. Some devices labelled as high-voltage Zener diodes are actually avalanche diodes. Two (equivalent) Zeners in series and in reverse order, in the same package, constitute a transient absorber (or Transorb, a registered trademark). The Zener diode is named for Dr. Clarence Melvin Zener inventor of the device.p-n junction diodes and Zener diode can be represented as shown below.
p-n junction diodeZener diode
TRANSISTORSA transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal.The transistor is the fundamental building block of modern electronic devices, and is ubiquitous in modern electronic systems. Following its development in 1947 by American physicists John Bardeen, Walter Brattain, and William Shockley, the transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, among other things. The inventors were jointly awarded the 1956 Nobel Prize in Physics for their achievement.The essential usefulness of a transistor comes from its ability to use a small signal applied between one pair of its terminals to control a much larger signal at another pair of terminals. This property is called gain. It can produce a stronger output signal, a voltage or current that is proportional to a weaker input signal; that is, it can act as an amplifier. Alternatively, the transistor can be used to turn current on or off in a circuit as an electrically controlled switch, where the amount of current is determined by other circuit elements.There are two types of transistors, which have slight differences in how they are used in a circuit. A bipolar transistor has terminals labeled base, collector, and emitter. 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 a field-effect transistor, the terminals are labeled gate, source, and drain, and a voltage at the gate can control a current between source and drain;
The transistor can be represented as shown above. LED (Light Emitting Diode) A light-emitting diode (LED) is a two-lead semiconductor light source. It is a basic pn-junction diode, which emits light when activated. When a fitting voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence, and the color of the light (corresponding to the energy of the photon) is determined by the energy band gap of the semiconductor.LEDs have many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. Light- emitting diodes are now used in applications as diverse as aviation lighting, automotive headlamps, advertising, general lighting, traffic signals, and camera flashes. However, LEDs powerful enough for room lighting are still relatively expensive, and require more precise current and heat management than compact fluorescent lamp sources of comparable output. On October 7, 2014, the Nobel Prize in Physics was awarded to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for "the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources" or, less formally, LED lamps.The LED consists of a chip of semiconducting material doped with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. Charge-carriers- electrons and holes- flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level and releases energy in the form of a photon.The wavelength of the light emitted, and thus its color, depends on the band gap energy of the materials forming the p-n junction. In silicon or germanium diodes, the electrons and holes usually recombine by a non-radiative transition, which produces no optical emission, because these are indirect band gap materials. The materials used for the LED have a direct band gap with energies corresponding to near-infrared, visible, or near-ultraviolet lightLEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on its surface. P-type substrates, while less common, occur as well. Many commercial LEDs, especially GaN/InGaN, also use sapphire substrate.Most materials used for LED production have very high refractive indices. This means that much light will be reflected back into the material at the material/air surface interface. Thus, light extraction in LEDs is an important aspect of LED production, subject to much research and development.
ColorWavelength range (nm)Typicalefficacy(lm/W)Typical efficiency (W/W)
Red620
