A level :: Design and Technology

A level ObjectiveThe contest task that I have finalised and undertaken for thiscoursework is to build and test a sensor. I decided to build a sensor,which would automatic bothy change the speed of a fan by using athermistor. The main objective of the experiment was to monitor andrecord the potency change as the temperature changes. Specific entirelyy, aspredicting that when the temperature increases the voltage wouldincrease and thus the fan speed would increase too, thus do acooling effect to the environment.Data InformationThermistors are thermally sensitive resistors and have, according totype, a negative (NTC), or positive (PTC) confrontation/temperaturecoefficient. A thermistor is a type of resistor whose protectionchanges importantly when its temperature changes.A negative temperature coefficient thermistor has a resistance thatdecreases with increase of temperature. This is the well-nigh common type.This is the type of resistor that I shall be evaluating and will beusi ng in my experiment.A positive temperature coefficient thermistor has a resistance thatincreases with increase of temperature. The resistance of asemiconductor generally decreases with increase of temperature.Semiconductors are therefore used to manufacture NTC thermistors.When the temperature of a semiconductor is increase, the number of weigh down carriers increases as more valence electrons gain sufficientenergy to exhibit put down from atoms to become conduction electrons. Thenumber of charge carriers increases as the temperature is increased sothe resistance of the semiconductor falls. Semiconductors are used tomake a wide range of electronic devices including electronic chips,light emitting diodes and solid-state lasers. Communications, trafficand entertainment have been revolutionised as a result ofsemiconductor devices. In electrical terms, satisfyings are classed aseither conductors or insulators or semiconductors.Semiconductors are solid materials with conductivities in between the truly high conductivity of metals and the very low conductivities ofinsulators. There are a variety of types of semiconductor, includingmetal oxides as well as elements like silicon and germanium. Ininsulators, essentially all the electrons are tightly bound to atomsor ions, and none are free to carry under an external electric field.In effect, these materials do non conduct electricity at all. Inmetallic conductors, essentially all the atoms are ionised, providingfree electrons, which move freely through the ions and can move underan external electric field. These conduction electrons glue the ionstogether, and provide non-directional bonding which holds the materialtogether. They become shared amongst all the atoms in the materialinstead of be attached to one atom.Semiconductors differ from both insulators and metallic conductors.Only a small proportion of atoms are ionised, so that although thereare conduction electrons they are relatively small in number and th e