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Electronic Components.

Extracts from this document...

Introduction

image00.png

Electronic Components

All electronic circuits consist of combinations of electronic components. The power supply provides the electrical force (V) to 'push' current (A) around a circuit.

Electrical components can be grouped into three categories:

  1. Input transducers - senses a form of energy and converts it into an electrical signal
  2. Processors - this may amplify a current or act as an electronic switch
  3. Output transducers - changes an electrical signal into another form of energy

Basic Electronic Components

Input Components

Name

How it works

LDR

A light dependant resistor has a high resistance in the dark and a low resistance in the light.

Thermistor

This resistor reacts to temperature.  They have a low resistance when hot and a high resistance when cold.

Moisture Sensor

These sensors have a high resistance when dry and a low resistance when wet.  This is because water acts as a conductor.  It is the water that connects the metal strips.

Switch

A switch is a device that is spring loaded and will either push to connect or push to break a circuit.  They will switch on/off a single circuit only.

Resistor

Resistors decrease the amount of current in a circuit by making it more difficult for the current to flow.  Resistance is measured in ohms. Different colour bands decide the resistance.


Processors

Name

How it works

Transistor

Transistors are semiconductors and can be used as a sensitive electronic switch.

Relay

Relays are components that interface between a small voltage and current to switch on a large voltage and current.

OR gate

Electronic logic gates are digital components that have no in-between states.  In multi-input devices they decide outputs.  An OR gate gives a positive signal when either or both inputs are positive.

AND gate

An AND gate gives a positive signal when both inputs are positive.

NOT gate

A NOT gate gives a positive signal when neither input is positive.

Diode

Diodes are semi-conductor devices that allow the current to flow in one direction only.

Output Components

Name

How it works

Lamp

A lamp is a device that converts electrical energy to light as well as a little heat. This is due to the filament resisting the current flowing through the lamp.

LED

A Light Emitting Diode give out light when a current passes through it. The LED must have a protecting resistor in series with it and can be connected in the correct direction for the current flow.

Motor

A motor is a device that converts electric energy to kinetic energy. A coil carrying a current in a magnetic field will twist, this is used in a motor.

Loud speaker

This is a device that converts electric energy to sound energy. It contains a moveable coil. When current passes through the coil it makes it move and vibrates the air molecules.

...read more.

Middle

Input

The resistance can easily be changed by twisting the spindle.  Commonly known as a pot.  Resistors resist and direct the flow of electricity.  A potentiometer is a form of variable resistor with three connections.

Can be used as a potential divider.

Light Dependent Resistor

image26.png

Input

A light dependent resistor (LDR) has a high resistance in the dark and a low resistance in the light.

Can be used as a light sensor, a photographer's light meter or a 'dark-operated' burglar alarm.

Thermistor

image27.png

Input

A thermistor is a thermal resistor that reacts to temperature. They have a low resistance when hot and a high resistance when cold.

Can be used to regulate temperature, acting as a frost or fire alarm.  Also a protection device for projector lamps.

Moisture sensor

image03.png

Input

Moisture sensors have a high resistance when dry and a low resistance when wet because water acts as a conductor.  It is the water that "connects" the metal strips.

Can be used in bathrooms as a bath overflow alarm.

Microphone

image04.png

Input

Sound waves force a plate in and out in rhythm with a voice.  This in turn squeezes carbon powder so its resistance decreases which in turn alters the current flowing in the circuit.

As a noise activated switch.

Transistor

image05.png

Processor

Transistors are semiconductors which can be used as a sensitive electronic switch.

Can be used to drive relays.

Relay

image06.png

Processor

Relays are components that interface between a small voltage and current to switch on a large voltage and current (acts like a simple amplifier).

...read more.

Conclusion

Colour Code for Resistors

Black

0

Brown

1

Red

2

Orange

3

Yellow

4

Green

5

Blue

6

Violet

7

Grey

8

White

9

Resistor values are identified by four bands of colour.  Resistance is measured in ohms ().  The first ring gives the 1st number of the resistance; the second ring gives the second number of the resistance.  The third ring tells you what to multiply this number by and the fourth gives its tolerance (accuracy).  

First ring:        yellow = 4

Second ring:        purple = 7

Third ring:        red = x 100

Forth ring:        gold = 5% tolerance

So the resistor = 4700  or 4.7 k


The Diode

Diodes are processors which allow current to flow in one direction only.  This is because they have a low resistance if connected the correct way around, and a very high resistance if connected the wrong way around.  As a result, they are very useful to protect components which would easily be damaged if a power supply was connected the wrong way around.  Diodes could be used to test if a battery is connected the correct way around.

Logic Gates

Logic gates are processors which make simple decisions based on inputs. There are three main types of logic gates - AND, OR and NOT.

In a logic gate, a logic 1 means the current is above a certain value.  A current less than this value is at a logic 0.

AND gates – give an output at logic 1 if both inputs are at logic 1.

OR gates – give an output at logic 1 if either inputs are at logic 1.

NOT gates – give an output at logic 1 if the input is at logic 0.

Truth tables

Truth tables are used to show us the possible combinations of inputs and outputs for a logic gate.

AND

OR

NOT

Inputs

Output

Inputs

Output

Input

Output

A

B

C

A

B

C

0

1

0

0

0

0

0

0

1

0

0

1

0

0

1

1

1

0

0

1

0

1

1

1

1

1

1

1

        

...read more.

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