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1John Ogilvie High School - CfE Physics
CfE Physics – SCN 4-09 b & c
Electronics Input, Process and Output
Digital Logic Gates
SCN 4-09b: By contributing to investigations into the properties of a range of electronic components, I can select and use them as input and output devices in practical electronic circuits.
SCN 4-09c:Using my knowledge of electronic components and switching devices, I can help to engineer an electronic system to provide a practical solution to a real-life situation.
2John Ogilvie High School - CfE Physics
CfE Physics SCN 4-09b
Electronics
Input, Process and Output
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Learning Intentions: State that an electronic system consists of
three parts: input, process and output. Identify from a block diagram the input, process
and output subsystems of an electronic system.
Draw a block diagram showing the input, process and output subsystems of an electronic system.
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Input, Process and Output
Electronic SystemsWhen something is made up of lots of parts which are
put together to do a job, it is called a s _ _ _ _ _ .
When the parts are electronic components the system
is called an e _ _ _ _ _ _ _ _ _ system.
system.
electronic
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Electronic Systems
Electronic systems can do lots of jobs.
The type of job will depend on the components used
to make the s _ _ _ _ _ .
A calculator is an example of an electronic system.
Every electronic system has t _ _ _ _ main sections -
called sub-systems.
These are called the i _ _ _ _ , the p _ _ _ _ _ _ and the
o_ _ _ _ _.
system.
three
input, process
output.
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Subsystem - Input
Detects some type of e _ _ _ _ _ .
(for example: light, heat, sound) and changes
it to e _ _ _ _ _ _ _ _ _ energy.
This is then passed to the p _ _ _ _ _ _
subsystem
energy.
electrical
process
What It Does
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Subsystem - Process
Changes the electrical energy from the i _ _ _
_ so that the system can do its job. This is
then passed on to the o _ _ _ _ _ subsystem.
input
What It Does
output
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Subsystem - Output
Converts the electrical e _ _ _ _ _ from the
process subsystem into another type of energy
which can be used. For example: h _ _ _ , l _ _ _ _ ,
m _ _ _ _ _ _ _
energy
heat,
movement.
What It Does
light,
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Block Diagrams
A block diagram is an easy way to draw a
system. Instead of drawing a
complicated diagram showing all the
components, we draw a box or b _ _ _ _
to take the place of the i _ _ _ _ , p _ _ _ _
_ _ and o _ _ _ _ _ subsystems.
Each block is labelled so that we k _ _ _
what it is.
block
input, process output
know
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Block Diagrams
The block diagram for a calculator is shown
above. Any subsystem can be further broken
down to smaller and smaller subsystems -
down to the actual components if required.
Keypad CalculatingCircuits
Display
I nput OutputProcess
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Block Diagram Examples
Public Address System
a l
I nput OutputProcess
mmicrophon
e
amplifier loudspeak
er
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Block Diagram Examples
Smoke Alarm
Logic Circuits
b
I OP
Smoke Sensor
buzzer
Input Process Output
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Block Diagram Examples
Intruder Lamp
Logic Circuits
l
I nput OutputProcess
HSensor
HeatSensor lamp
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Learning Intentions
State that an input device changes some form of energy into electrical energy.
State that the microphone, thermistor, LDR and switch are all examples of input device.
State that the resistance of a thermistor changes with temperature.
State that the resistance of an LDR decreases when the light on it gets brighter.
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Input subsystems contain a device which
changes some form of e _ _ _ _ _ into
electrical energy.
Output subsystems contain a device which
changes e _ _ _ _ _ _ _ _ _ e _ _ _ _ _ into some
other form.
Input and Output Devices
energy
electrical energy
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How it Works: The inside of the microphone
v_ _ _ _ _ _ _ exactly the same way as the sound waves. This makes identical electrical waves.
Device: microphone
Input Devices
What it looks like:
Circuit Symbol:
vibrates
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How it Works: The resistance of the thermistor changes as the t_ _ _ _ _ _ _ _ _ _ _ changes.
Device: thermistor
Input Devices
temperature
What it looks like:
Circuit Symbol:
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How it Works: The resistance of the LDR decreases as the light level gets b_ _ _ _ _ _ _ .
Device: Light Dependent Resistor
Input Devices
brighter.
What it looks like:
Circuit Symbol:
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How it Works: Moving the switch from one setting to the other makes or b_ _ _ _ _ the circuit.
Device: switch
Input Devices
breaks
What it looks like:
Circuit Symbol:
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Learning Intentions
State that an output device changes electrical energy into another form of energy.
State that a loudspeaker, buzzer, lamp, LED and electric motors are all forms of output devices.
State the energy conversions involved for a given output device.
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How it Works: Electrical energy -> Sound energy
Electrical waves make vibrations inside the loudspeaker producing sound waves
Device: loudspeaker
Output Devices
What it looks like:
Circuit Symbol:
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How it Works: Electrical energy -> Sound energy
A voltage across the buzzer makes it sound. The buzzer just switches sound on or off.
Device: buzzer
Output Devices
What it looks like:
Circuit Symbol:+
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How it Works: Electrical energy -> Light energy
A voltage across the lamp makes it light. The greater the voltage, the brighter it gets.
Device: lamp
Output Devices
What it looks like:
Circuit Symbol:
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How it Works: Electrical energy -> Light energy
A voltage across the LED makes it light. LEDs are used to indicate when something is on or off.
Device: Light emitting diode
Output Devices
What it looks like:
Circuit Symbol:
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How it Works: Electrical energy -> Kinetic energy A voltage across the motor makes it turn.
The greater the voltage, the faster it turns.
Device: electric motor
Output Devices
What it looks like:
Circuit Symbol: M
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Learning Intentions
Identify from a list an appropriate input device for a given job.
Identify from a list an appropriate output device for a given job.
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Examples of input and output applications
Application
Output of radio
Input of an automatic lamp
Input of a heating controller
Output of fan
Device
Loudspeaker
L _ _
Thermistor
M _ _ _ _
The output should be s _ _ _ _ _ waves
Reason
The LDR will change resistance when the brightness changes The thermistor will c_ _ _ _ _ resistance when the temperature changes
The motor will t_ _ _ the blades of the fan.
LDR
sound
change
turnMotor
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CfE Physics
Electronics
Digital Logic Gates Scn 4-09c:Using my knowledge of electronic components
and switching devices, I can help to engineer an electronic system to provide a practical solution to a real-life situation.
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Learning Intentions:
State that high voltage = logic 1. State that low voltage = logic 0. Draw and identify symbols for 2 input AND and OR gates
and a NOT gate. State that for a NOT gate the output is the opposite of the
input. State that for an AND gate both inputs must be high for
the output to be high. State that for an OR gate either of the inputs must be
high for the output to be high.
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Digital signals are either on or o _ _ .
An ‘off’ signal has a zero voltage (called ‘l _ _’ ).
An ‘on’ signal has a non-zero voltage(called ‘h _ _ _’ ).
The ‘o _ _’ signal; low state is given the name ‘logic 0’ (most often just ‘0’).
The ‘o _’ signal; high state is given the name ‘logic 1’ (most often just ‘ 1’).
Digital Signalsoff
‘low’
‘high’
‘off’
‘on’
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High voltage: Logic _
An oscilloscope can show logic states since it measures the high and low voltages.
Digital Signals
1
Low voltage: Logic _
Oscilloscope trace showing a digital logicsignal which is changing from 1 to 0several times.
0
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Digital logic gates are used to combine or
change digital electronic signals. There are
three basic types of logic gate called the N _ _
gate (sometimes called an i _ _ _ _ _ _ _ ), the A
_ _ gate and the O _ gate.
Logic Gates
NOT
inverter AND
OR
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This is the simplest gate. It has o _ _ input and o _ _ output.The output is always the opposite of the
i _ _ _ _ .
The NOT gate
input.
oneone
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The NOT gate changes the input signal to the opposite state.
Logic Gate
NOT gate (Inverter)
Symbol
How it behaves
NOT Truth table
input output
Input Output
High
Low
Low
High
(1)
(0)
(0)(1)
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The AND gate has two inputs and one output. The output of the AND gate is always at logic 0 unless both the inputs are at logic 1 when the output becomes logic 1 as well.
The AND gate
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The AND gate combines the input signals so that the output is only 1 when both inputs are 1.
Logic Gate
AND gate
Symbol
How it behaves
AND Truth table
Input A Output
High
Low Low
High
(1)
(0) (0)
(1)
Input B
Low
Low
High High
(0)
(0)
(1) (1)
Low(0)
Low(0)
High
(1)
Low(0)
input Aoutput
input B
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The OR gate has two inputs and one output. The output of the OR gate is always at logic 1 unless both the inputs are at logic 0 when the output becomes logic 0 as well.
The OR gate
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The OR gate combines the input signals so that the output is 1 when either input is 1.
Logic Gate
OR gate
Symbol
How it behaves
OR Truth table
Input A Output
High
Low Low
High
(1)
(0) (0)
(1)
Input B
Low
Low
High High
(0)
(0)
(1) (1)
Low(0)
High(1)
High
(1)
High(1)
input Aoutput
input B
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Learning Intentions
Explain how to use logic gates for control in simple situations.
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1. Donnie's dad wants to be wakened if he gets up at night. Design a system to sound a buzzer if Donnie switches on his light or if he stands on a mat. (A switch is under the mat.)
Logical solutions
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Solution System Diagram
Light sensor
switch
Buzzer
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When the light is turned on, the light sensor output is h _ _ _ . This causes the OR gate output to go high which sounds the b _ _ _ _ _ .
high.
How it Works
Light Sensor
Dark Light
low high
Switch
Open Closed
low high
When the switch under the mat is pressed, it c _ _ _ _ _ _ . This makes its output h _ _ _ .This causes the OR gate output to go h _ _ _ which sounds the buzzer.
buzzer.
closes.
high.
high
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2. A tomato grower wants to protect his delicate plants which are in his greenhouse. Design a warning system to sound a buzzer if it gets too cold during the night (dark).
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Solution System Diagram
Light sensor
Temperature sensor
Buzzer
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The buzzer can only switch on when the output from the NOT gate is h _ _ _ .Therefore the output from the OR gate must be l _ _ .
high.
How it Works
The OR gate output can only be low if b _ _ _ the inputs are low.
This means it must be both d _ _ _ and c _ _ _ as well.
.
Light Sensor
Dark Light
low high
Temperature Sensor
Cold Warm
low high
low.
both
dark
cold
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Grandad can't use the stair light switch easily since he got his walking stick.
Design a system which will switch on the stair light automatically when it gets dark.
There must be a manual switch as well.
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Solution System Diagram
Light sensor
Lamp
switch
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When it is dark, the light sensor output is low which is changed to h _ _ _ by the NOT gate. This causes the OR gate output to go high which l _ _ _ _ _ the lamp.
high
How it Works
When the switch is closed, its output is high. This causes the OR gate output to go h _ _ _ which lights the lamp.
.
Light Sensor
Dark Light
low high
Switch
Open Closed
low high
lights
high
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4. Design a system for a bathroom to switch on a fan motor when the bathroom gets so steamy, the light from the window is blocked. The fan must only come on when it is hot as well as steamy.
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Solution System Diagram
Light sensor
MotorTemperatur
e sensor
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When it is steamy, it gets darker, the light sensor output is l _ _ which is changed to high by the N _ _ gate.When it gets too h _ _ the output from the temperature sensor is h _ _ _ .
low
How it Works
Only when it is hot and steamy at the s _ _ _ time will both inputs of the AND gate be high to make the output high to t _ _ _ the motor.
.
Light Sensor
Dark Light
low high
Temperature sensor
Cold Warm
low high
NOT
high.
hot
same
turn
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CfE Physics
Electronics
End of Unit