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Intermediate 1
Physics
Electronics

Input, Process and Output

Digital Logic Gates
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Intermediate 1
Physics
Electronics
Input, Process
and Output
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Input, Process and Output
Electronic Systems
When something is made up of lots of parts which are put
together to do a job, it is called a ssystem.
_____.
When the parts are electronic components the system is
called an e _ _electronic
_ _ _ _ _ _ _ system.
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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 ssystem.
_____.
A calculator is an example of an electronic system.
Every electronic system has tthree
_ _ _ _ main sections called sub-systems.
These are called the i _input,
_ _ _ , the p _process
_ _ _ _ _ and the
o_
_ _ _ _.
output.
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Subsystem - Input
What It Does
Detects some type of eenergy.
_____.
(for example: light, heat, sound) and changes it
to e _ _electrical
_ _ _ _ _ _ _ energy.
This is then passed to the pprocess
______
subsystem
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Subsystem - Process
What It Does
Changes the electrical energy from the iinput
____
so that the system can do its job. This is then
passed on to the o _output
_ _ _ _ subsystem.
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Subsystem - Output
What It Does
Converts the electrical e _energy
_ _ _ _ from the
process subsystem into another type of energy which
can be used. For example: hheat,
_ _ _ , light,
l____,
m
_______
movement.
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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 _block
_ _ _ to take the place of
the iinput,
_ _ _ _ , process
p _ _ _ _ _ _ and ooutput
_____
subsystems.
Each block is labelled so that we kknow
___
what it is.
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Block Diagrams
Input
Process
Output
Keypad
Calculating
Circuits
Display
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.
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Block Diagram Examples
Public Address System
Input
mmicrophone
Process
aamplifier
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Output
lloudspeaker
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Block Diagram Examples
Smoke Alarm
IInput
Smoke
Sensor
P
Process
O Output
Logic
Circuits
b
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buzzer
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Block Diagram Examples
Intruder Lamp
Input
H Heat
Sensor
Sensor
Process
Output
Logic
Circuits
l
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lamp
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Input and Output Devices
Input subsystems contain a device which changes
some form of e _energy
_ _ _ _ into electrical energy.
Output subsystems contain a device which
changes e _ _electrical
_ _ _ _ _ _ _ energy
e _ _ _ _ _ into some
other form.
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Input Devices
Device: microphone
What it looks like:
Circuit Symbol:
How it Works: The inside of the microphone
v_ _vibrates
_ _ _ _ _ exactly the same way as the sound
waves. This makes identical electrical waves.
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Input Devices
Device: thermistor
What it looks like:
Circuit Symbol:
How it Works: The resistance of the thermistor
changes as the t_ _ _
_ _ _ _ _ _ _ _ changes.
temperature
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Input Devices
Device: Light Dependent Resistor
What it looks like:
Circuit Symbol:
How it Works: The resistance of the LDR
decreases as the light level gets b_
______.
brighter.
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Input Devices
Device: switch
What it looks like:
Circuit Symbol:
How it Works: Moving the switch from one setting
to the other makes or b_breaks
_ _ _ _ the circuit.
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Output Devices
Device: loudspeaker
What it looks like:
Circuit Symbol:
How it Works: Electrical energy -> Sound energy
Electrical waves make vibrations inside the
loudspeaker producing sound waves
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Output Devices
Device: buzzer
What it looks like:
Circuit Symbol:
+
How it Works: Electrical energy -> Sound energy
A voltage across the buzzer makes it sound. The
buzzer just switches sound on or off.
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Output Devices
Device: lamp
What it looks like:
Circuit Symbol:
How it Works: Electrical energy -> Light energy
A voltage across the lamp makes it light. The
greater the voltage, the brighter it gets.
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Output Devices
Device: Light emitting diode
What it looks like:
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.
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Output Devices
Device: electric motor
What it looks like:
Circuit Symbol:
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
Reason
Device
Output of radio
Loudspeaker The output should be
s _sound
_ _ _ _ waves
Input of an
automatic lamp
LLDR
_ _
Input of a heating Thermistor
controller
Output of fan
M
____
Motor
The LDR will change
resistance when the
brightness changes
The thermistor will
c_
_ _ _ _ resistance
change
when the temperature
changes
turn
The motor will t_
__
the blades of the fan.
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Intermediate 1
Physics
Electronics
Digital
Logic Gates
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Digital Signals
Digital signals are either on or off
o__.
An ‘off’ signal has a zero voltage (called ‘l‘low’
_ _’ ).
An ‘on’ signal has a non-zero voltage(called ‘h‘high’
_ _ _’ ).
The ‘o‘off’
_ _’ signal; low state is given the name ‘logic
0’ (most often just ‘0’).
The ‘o‘on’
_’ signal; high state is given the name ‘logic 1’
(most often just ‘ 1’).
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Digital Signals
An oscilloscope can show logic states since it
measures the high and low voltages.
High voltage: Logic _1
Oscilloscope trace showing
a digital logic
signal which is changing
from 1 to 0
several times.
Low voltage: Logic _
0
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Logic Gates
Digital logic gates are used to combine or change
digital electronic signals. There are three basic
types of logic gate called the N
_ _ gate
NOT
(sometimes called an i _ inverter
_ _ _ _ _ _ ), the A _
_
AND
gate and the O
_ gate.
OR
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The NOT gate
This is the simplest gate. It has oone
_ _ input and
oone
_ _ output.
The output is always the opposite of the
i _ input.
___.
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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.
output
NOT Truth table
Input
Output
High
Low
(1)
(0)
Low
(0)
High
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(1)
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The AND gate
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.
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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)
High
High
(1)
(1)
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Low
(0)
High
(1)
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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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High
(1)
High
(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.)
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Solution System Diagram
Light
sensor
Buzzer
switch
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How it Works
Light Sensor
Dark
Light
low
high
Switch
Open
Closed
low
high
When the light is turned on, the light
sensor output is hhigh.
___.
This causes the OR gate output to go high
which sounds the bbuzzer.
_____.
When the switch under the mat is
pressed, it c _ _
_ _ _ _ . This makes
closes.
its output hhigh.
___.
This causes the OR gate output to go
hhigh
_ _ _ which sounds the buzzer.
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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
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 hhigh.
___.
Therefore the output from the OR gate
must be llow.
__.
The OR gate output can only be low if
b
_ _ _ the inputs are low.
both
This means it must be both ddark
___
and c cold
_ _ _ as well.
.
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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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How it Works
Light Sensor
Dark
Light
low
high
Switch
Open
Closed
low
high
When it is dark, the light sensor output is
low which is changed to h high
_ _ _ by the
NOT gate. This causes the OR gate
output to go high which l _lights
_ _ _ _ the
lamp.
When the switch is closed, its output
is high. This causes the OR gate
output to go h high
_ _ _ which lights the
lamp.
.
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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
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 l low
_ _ which is
changed to high by the N
_ _ gate.
NOT
When it gets too hhot
_ _ the output from
the temperature sensor is hhigh.
___.
Only when it is hot and steamy at the
ssame
_ _ _ time will both inputs of the
AND gate be high to make the output
high to t turn
_ _ _ the motor.
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Intermediate 1
Physics
Electronics
End of Unit
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