Intermediate 1 Physics
Intermediate 1 Physics
Electronics
Electronics

Input, Process and Output

Digital Logic Gates
Input, Process
and Output
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Electronic Systems
Input, Process and Output
Electronic systems can do lots of jobs.
Electronic Systems
The type of job will depend on the components used to
When something is made up of lots of parts which are put
make the system .
together to do a job, it is called a system .
A calculator is an example of an electronic system.
When the parts are electronic components the system is
Every electronic system has three main sections - called
called an electronic system.
sub-systems.
These are called the input , the process and the output.
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Subsystem - Process
Subsystem - Input
What It Does
What It Does
Changes the electrical energy from the input so
Detects some type of energy .
that the system can do its job. This is then
(for example: light, heat, sound) and changes it
passed on to the output subsystem.
to electronic energy.
This is then passed to the process
subsystem
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Block Diagrams
Subsystem - Output
What It Does
A block diagram is an easy way to draw a
system. Instead of drawing a complicated
Converts the electrical energy from the process
diagram showing all the components, we
subsystem into another type of energy which can be
draw a box or block to take the place of the
used. For example: heat , light , movement.
input , process and output subsystems.
Each block is labelled so that we know what
it is.
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Block Diagrams
Inp ut
Keyp ad
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Block Diagram Examples
Process
O utp ut
C a l c u l a t in g
Public Address System
D is p l a y
C ir c u it s
I np ut
mmicrophone
The block diagram for a calculator is shown
Process
O utp ut
lloudspeaker
aamplifier
above. Any subsystem can be further broken
down to smaller and smaller subsystems - down
to the actual components if required.
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Block Diagram Examples
Block Diagram Examples
Smoke Alarm
Intruder Lamp
P
Process
O Output
S m ok e
L og ic
S e ns or
C ir cuits
b buzzer
I
Input
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Input
H Heat
Sensor
Sensor
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Process
Logic
Circuits
Output
l
lamp
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Input Devices
Input and Output Devices
Input subsystems contain a device which changes
some form of energy into electrical energy.
Device: microphone
What it looks like:
Output subsystems contain a device which
changes electrical energy into some other form.
Circuit Symbol:
How it Works: The inside of the microphone
vibrates exactly the same way as the sound
waves. This makes identical electrical waves.
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Input Devices
Input Devices
Device: thermistor
Device: Light Dependent Resistor
What it looks like:
What it looks like:
Circuit Symbol:
Circuit Symbol:
How it Works: The resistance of the thermistor
changes as the temperature changes.
How it Works: The resistance of the LDR
decreases as the light level gets brighter .
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Input Devices
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Output Devices
Device: switch
Device: loudspeaker
What it looks like:
What it looks like:
Circuit Symbol:
Circuit Symbol:
How it Works: Moving the switch from one setting
to the other makes or breaks the circuit.
How it Works: Electrical energy -> Sound energy
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Electrical waves make vibrations inside the loudspeaker
producing sound waves
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Output Devices
Output Devices
Device: buzzer
Device: lamp
What it looks like:
What it looks like:
Circuit Symbol:
+
Circuit Symbol:
How it Works: Electrical energy -> Sound energy
How it Works: Electrical energy -> Light energy
A voltage across the buzzer makes it sound. The
buzzer just switches sound on or off.
A voltage across the lamp makes it light. The
greater the voltage, the brighter it gets.
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Output Devices
Output Devices
Device: Light emitting diode
Device: electric motor
What it looks like:
What it looks like:
Circuit Symbol:
Circuit Symbol:
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.
M
How it Works: Electrical energy -> Kinetic energy
A voltage across the motor makes it turn.
The greater the voltage, the faster it turns.
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Examples of input and output applications
Application
Output of radio
Loudspeaker The output should be
sound waves
Input of an
automatic lamp
LDR
Thermistor
Input of a
heating controller
Output of fan
Motor
Intermediate 1 Physics
Reason
Device
Electronics
The LDR will change
resistance when the
brightness changes
The thermistor will
change resistance when
the temperature
changes
Digital
Logic Gates
The motor will turn
the blades of the fan.
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Digital Signals
Digital Signals
An oscilloscope can show logic states since it
measures the high and low voltages.
Digital signals are either on or off .
An ‘off’ signal has a zero voltage (called ‘low’ ).
High voltage: Logic 1
An ‘on’ signal has a non-zero voltage(called ‘high’ ).
Oscilloscope trace showing
a digital logic
signal which is changing
from 1 to 0
several times.
The ‘off’ signal; low state is given the name ‘logic 0’
(most often just ‘0’).
The ‘on’ signal; high state is given the name ‘logic 1’
(most often just ‘ 1’).
Low voltage: Logic 0
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Logic Gates
The NOT gate
Digital logic gates are used to combine or change
digital electronic signals. There are three basic
(sometimes called an inverter ), the AND gate and
This is the simplest gate. It has one input and o
one output.
The output is always the opposite of the
the OR gate.
input.
types of logic gate called the NOT gate
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Logic Gate
Symbol
NOT gate (Inverter)
i nput
How it behaves
The NOT gate
changes the input
signal to the
opposite state.
The AND gate
output
NOT Truth table
Input
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.
Output
High
Low
(1)
(0)
Low
(0)
High
(1)
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Logic Gate
AND gate
Input B
Output
Low
(0)
Low
(0)
Low
(0)
High
Low
(0)
High
Low
Input A
Symbol
i nput A
AND Truth table
output
i nput B
How it behaves
The AND gate combines
the input signals so that
the output is only 1
when both inputs are 1.
Low
(0)
(1)
(1)
(0)
Low
(0)
High
High
(1)
High
(1)
(1)
The OR gate
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.
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Logic Gate
OR gate
Input B
Output
Low
(0)
Low
(0)
Low
(0)
Low
(0)
High
High
(1)
High
Low
Input A
Symbol
i nput A
OR Truth table
output
i nput B
How it behaves
The OR gate combines
the input signals so that
the output is 1
when either input is 1.
(1)
(1)
(0)
High
High
(1)
(1)
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Logical solutions
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.)
High
(1)
High
(1)
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How it Works
Solution System Diagram
Light
sensor
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Light Sensor
Dark
Light
low
high
Buzzer
switch
Switch
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Open
Closed
low
high
When the light is turned on, the light
sensor output is high .
This causes the OR gate output to go high
which sounds the buzzer .
When the switch under the mat is
pressed, it closes . This makes its
output high.
This causes the OR gate output to go
high which sounds the buzzer.
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Solution System Diagram
Light
sensor
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).
Buzzer
Temperature
sensor
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How it Works
Light Sensor
Dark
Light
low
high
Temperature Sensor
Cold
Warm
low
high
The buzzer can only switch on when the
output from the NOT gate is high .
Therefore the output from the OR gate
must be low .
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.
The OR gate output can only be low if
both the inputs are low.
There must be a manual switch as well.
This means it must be both dark and
cold as well.
.
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Solution System Diagram
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How it Works
Light Sensor
Light
sensor
Dark
Light
low
high
Lamp
When it is dark, the light sensor output is
low which is changed to high by the NOT
gate. This causes the OR gate output to
go high which lights the lamp.
switch
Switch
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Open
Closed
low
high
When the switch is closed, its output
is high. This causes the OR gate
output to go high which lights the
lamp.
.
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Solution System Diagram
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.
Light
sensor
Motor
Temperature
sensor
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How it Works
Light Sensor
Dark
Light
low
high
Temperature sensor
Cold
Warm
low
high
When it is steamy, it gets darker, the
light sensor output is low which is changed
to high by the NOT gate.
When it gets too hot the output from the
temperature sensor is high. .
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Intermediate 1 Physics
Electronics
End of Unit
Only when it is hot and steamy at the
same time will both inputs of the
AND gate be high to make the output
high to turn the motor.
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