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# Lesson 7 electronics

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Basic issues on electronics

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### Lesson 7 electronics

1. 1. Lesson 7: Electronics Technology 3 ESO bilingual
2. 2. Index        Definitons. Concepts Electricity and electronics: Differences Levels in electronics Components Resistors: Fixed and variable value resistors Condensators Semiconductors: Diodes, transistors Electronic circuits Electronic devices
3. 3. What is electronics?  Electronics is the part of engineering aiming to use electricity with the purpose of controlling other devices or circuits Index
4. 4. Electricity and electronics Circuit Purpose Electric Electronic Transporting and transforming electricity Controlling other devices Intensity and power to Resistance value to Index
5. 5. Levels in electronics    Components: elements within a circuit which play a certain role over the signals Circuits: A group of components which form a circuit and performs controlling operations Devices: A circuit/group of circuits encased in a shell, which include a screen and buttons to interact with a user Index
6. 6. Components  Fixed value resistors  Variable Value resistors  Condensators  Semiconductors   Diodes Transistors
7. 7. Fixed value resistors   Fixed value resistors are used to limit the current passing through an electronic circuit. A bar code is used to indicate the value and the tolerance of a resistance
8. 8. Why do we use resistors?
9. 9. Variable value resistors: LDR   LDR: ligth dependent resistance. Based on photovoltaic effect, those resistances value diminish when ligth hits them, Their values vary between MΩ and hundreds of Ω(intense ligth)
10. 10. Variable value resistors: thermistor   Thermistors are resistances which vary with temperature (PTC and NTC) Their values raise (ptc) or fall (ntc) when temperature increases
11. 11. Variable value resistors: Potenciometer  A Potenciometer is a variable resistance which value can be fixed by a user. To do so, a bar or a wheel is moved. It displaces a movable contact of a resistance along a resistive material. Remember that R=pL/s2 Index
12. 12. Condensators    Condensators are capable of accumulating (a very small amount of) electric energy The amount of energy that they can store is called Capacity. C=Q/V Condensators are placed in parallel to other components Index
13. 13. Semiconductors    Semiconductors are metals which have a variable conductivity, which can be modified by inserting other atoms. There are two types of semiconductors: P and N The electric properties of semiconductors are extremely important for electronics. There are two main electronic components based on semiconductors: Diodes and Transistors
14. 14. Diodes       A diode is an electronic component formed by two semiconductors, one is N and other is P, joined together. Depending of the electric current sense, the diode can be directly or inversely polarized If the diode is directly polarised it acts as a closed switch. Current flows If the diode is inversely polarised it acts as an opened switch. Current stops. There is an special type of diode called LED, which emit ligth when currents flow trough them. There are many uses for diodes. One example is the conversion of AC to DC in power sources of electronic appliances Index
15. 15. Transistors  A transistor is formed by three semiconductors. They can be 2 of type n and one of type p: npn or vivecersa pnp. Each semiconductor acts as an electrode. One is called colector, other base and other emisor. The base is between the other two and is used to control the flow. Current flows from the collector to the emisor when the current coming from the base exceeds a thresold value
16. 16. States of a transistor Ib Cut Corte Conduction Saturation Vce Vcc <IT Ice 0 ~0.001mA IT<IB<IBS IB>IBS I BS V − 0.2 = CC β RC Vcc – VBE(0.2)Rc·βIB 0 ß·IB I BS = VCC − 0.2 RC Index
17. 17. Electronic circuits    An electronic circuit formed by one or more electronic components connected. Electronic circuits perform a control action using electricity, such as controlling automatic doors, a ligthmimg circuit, air conditioning Normally, electronic circuits are built over cupper film boards (integrated circuits) Index
18. 18. Electronic devices     An electronic device consists of one or several electronic circuits joined together and encased in a protective shell The operation of an electronic device is the group of tasks that its inner circuits can perform together Electronic devices normally include buttons so that the user can interact with them To provide outputs of their tasks, electronic devices often include LEDs, an screen or sound components Index