Lesson 7: Electronics

Technology 3 ESO bilingual

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

What is electronics?

Electronics is the part of engineering aiming to use electricity with the purpose of controlling other devices or circuits

Index

Electricity and electronics

Circuit Electric Electronic

Purpose Transporting and transforming electricity

Controlling other devices

Intensity and power

to

Resistance value

to

Index

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

Components

Fixed value resistors Variable Value resistors Condensators Semiconductors

Diodes Transistors

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

Why do we use resistors?

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)

Variable value resistors: thermistor

Thermistors are resistances which vary with temperature (PTC and NTC)

Their values raise (ptc) or fall (ntc) when temperature increases

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

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

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

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

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

States of a transistor

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Index

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

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