The ICT in Schools’ Initiative of the Department of Education and Science

Basic Electronics

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Electric Circuit

Components are connected together with electrical wire to form a closed loop.

Components are represented by symbols

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Electric Circuit

•Electrical wire used to connect components is a conductor.•A conductor allows electric current to flow through it easily.•Good conductors include: copper, gold, silver, tin •Copper wire is generally used as it is most cost effective.

•All electrical wires have a plastic cover. •Plastic is an insulator.•An insulator does not allow current to flow through it.•Avoids electric shock.•Insulators include: plastic, glass, wood

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Electric CircuitElectric Current is the flow of electrons around a circuit.

Electrons have a negative charge

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Electric Circuit•Electric current is measured with an Ammeter•The ammeter is placed into the circuit (in series)•Unit of measurement is the Ampere or ‘amp’•Represented by the letter I

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Electric Circuit•EMF (electromotive force) is the force that makes electrons flow around a circuit.

•EMF is often called Voltage and is provided by the battery.•Higher voltage = more current

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Electric Circuit•Voltage is measured using a Voltmeter.•The voltmeter is placed across a component (in parallel)•Unit of measurement is the Volt.•Represented by letter V.

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Electric Circuit•Resistance is the opposition to the flow of electric current.•All components have resistance.•Electrical wire has resistance.•Unit of measurement is the Ohm (Ω)•Represented by the letter R

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Electric CircuitResistance is the opposition to the flow of electric current.

All components have resistance.

Electrical wire has resistance.

Unit of measurement is the Ohm (Ω)

Represented by the letter R

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Ohm’s Law

Voltage , Current & Resistance are calculated using Ohm’s Law

IxRV

V

I RR

VI

I

VR

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Series Circuit•Components are connected one after the other•There is only one path for current to flow around

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Series Circuit•The current at all points in a series circuit is equal

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Series CircuitThe voltage is shared between the components in a series circuit.

•Components of equal resistance – voltage is shared equally

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Series CircuitThe voltage is shared between the components in a series circuit.

•Components of unequal resistance – voltage is shared proportionally

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Parallel Circuit•Components are connected side by side•There is more than one path for current to flow around

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Parallel CircuitThe voltage across each path is always the same as the applied voltage

• When component resistance in each path is the same

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Parallel CircuitThe voltage across each path is always the same as the applied voltage

• When component resistance in each path is different

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Parallel CircuitThe voltage across each path is always the same as the applied voltage

• When there is more than one component in a path

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Parallel Circuit•The current is divided between the paths proportionally (Ohm’s Law)

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Motor ControlSPST Switch:

Polarity connection determines direction of rotation

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Motor ControlDPDT Switch:

• Forward and reverse control of motor

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Motor ControlDPDT Switch

+V

C3

C4

C1

0V

C2

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Motor ControlDPDT Switch: Wiring Diagram

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Motor ControlDPDT Switch: Wiring Diagram

The ICT in Schools’ Initiative of the Department of Education and Science

Motor ControlDPDT Switch: Wiring Diagram

The ICT in Schools’ Initiative of the Department of Education and Science

Motor ControlDPDT Switch: Wiring Diagram

+V

0V

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Motor ControlForward and reverse control of motor with limit switches

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Motor ControlForward and reverse control of motor with limit switches

Wiring Diagram

+V

0V

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Motor ControlForward and reverse control of motor with limit switches

The ICT in Schools’ Initiative of the Department of Education and Science

Motor ControlForward and reverse control of motor with limit switches

Wiring Diagram

+V

0V

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Motor ControlWill SW1 and SW2 act as limit switches in this circuit?

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SensorsLight Dependent Resistor (LDR)

• Resistance increases as darkness increases

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SensorsThermistor

• Resistance decreases as the temperature increases

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TransistorActs as a switch

Voltage > 0.6V-0.7V between the base and emitter transistor is on

Collector EmitterBase

BFY51

Collector

BFY51

EmitterBaseCollector

BFY51

Collector Base

BFY51

Collector Base EmitterBase

E

B

C

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TransistorVoltage Divider circuit is used to create the turn on voltage between the base and emitter.

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LDR Transistor Circuit An LDR changes the voltage according to light levels

Dark = LED on

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Relay A relay is a switch used to turn other circuits on and off

DPDT switch

Coil terminals are part of controlling circuit

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Relay

Position A

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Relay

Position A

P1NC1 NO2

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Relay

Position B

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Relay

Position B

P2NC2

NO2

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Relay