Northgate High School - Electronics - Revision Cards 1
Northgate High School - Electronics - Revision Cards 3
Diodes
Light Emitting Diodes LED
MECHANICAL SWITCHES
Come in a variety of different colours
Remember PANIC
Positive Anode Negative Is Cathode
SPST
SPDT
ReedSwitch
Micro Switch
Push to Make
Rocker Switch
Diodes only let current flow one
way
Electro Motive Force
or
a fool putting the battery in the
wrong way round
Tri colour and Bi
colour LED’s are also
available
Key Switch
following values - i.e. Ω ‐ K ‐ M
LDR - Light Dependent
E24 Series- 1 10, 11, 12, 13, 15, 16, 18, 20,
22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56,
62, 68, 75, 82, 91
Used to control current &
voltage in a circuit
Used to pull down or up
inputs
V
Thermistor
tors Measured in Ohms Ω
s
i
s
Available in multiplications of the
Re
Pole - the number of inputs
Throw - the number of outputs
Use switches in
parallel to create an
or setup
I R
Ohms Law
R1
Put two together to produce
a potential divider
Work out their value with a
Resistors are NOT POLARISED multimeter or the colour chart
Use switches in series to create an and setup
Northgate High School - Electronics - Revision Cards 4
Come in a variety of different sizes
CAPACITORS
Remember PANIC
Store electrical charge
Positive Anode Negative Is Cathode
Measured in Farads
To change the uf to F move the
decimal point 6 places to the left
470uf = 0.00047F
2200uf = 0.0022
Thermistors and LDR’s
As the temp and light
increase the R drops
Series Resistors
R total = R1 + R2 + R3 etc
Potentiometer
Fixed
PTM or PTB
Switch
LED’s and Diodes are POLARISED
Northgate High School - Electronics - Revision Cards 2
Variable
Toggle Switch
Remember to
consider switch
bounce when
designing
circuits
Slide Switch
Infra Red LED’s are used in
things like security lights
R2
Tilt Switch
Use them to protect components
from :
Use the Ohms law
triangle to calculate the
size of the resistor you
will need with an LED
V
I R
Push to Break
Rotary Switch
The time taken for a capacitor to charge 2/3rd full is called
the Time Constant
Time Constant = Capacitance (F) x Resistance (Ω)
The time will not be exact because of Resistor Tolerances
Used with a resistor to produce a time
delay - for example in a 555 circuit
variable time = variable resistor
Can also be used to smooth a dc
supply voltage
Electrolytic Capacitors are POLARISED
Ceramic Disc or Non-Electrolytic capacitors are NOT POLARISED
Northgate High School - Electronics - Revision Cards 5
Northgate High School - Electronics - Revision Cards 6
OPERATIONAL AMPLIFIERS
Power Supplies
Voltage differs depending on the
purpose.
Different batteries can be combined to
give different dc voltages
Voltage Regulator - used to
regulate voltage to avoid
damaging components
9V power supply
0V & 4.5V Voltage Rails
Collector
Transistor
INPUT
Base
Emitter
Northgate High School - Electronics - Revision Cards 8
Switches by
changes in light
Use with a IC to drive
buzzers, motors and
bells
MOSFET are able to
handle high currents and
usually have heat sinks
Drain
Transistors used
together to increase
the gain - create a
Darlington Pair
DP’s can be
packaged as a single
transistor
Gate
Source
Heat Sink - A piece of material
attached to a component to
disperse heat created during
operation
Turns on and
stays on when
voltage rises at
Gate
RELAY
Used as a
switch between
circuits without
electrical
connection unlike a
transistor or
MOSFET
Anode
Could be used in a
simple alarm circuit
or steady hand
game
Gate
Cathode
Relays work by magnetism
MOSFET
THYRISTOR
Works as a latch
Use with a IC to drive
buzzers, motors and
bells
Can also be used as a
comparator with a
potential divider
in a temp or light
sensing circuit for
example
OUTPUT
Photo transistor
Also called Transducer Drivers
Used to amplify current and
also as an electronic switch
Inverting input
The size of R1 and R2
determines the level of
amplification / gain
Northgate High School - Electronics - Revision Cards 7
TRANSISTORS
Non-inverting input
Used to amplify an analogue input signal
Turn the circuit off
and the Thyristor
resets
Northgate High School - Electronics - Revision Cards 9
LOGIC
Can be
used when
a circuit
requires
more than
one input
OR
NOT
A
B
Usually packaged in
a 14 pin chip
AND used when one
AND input and another are
high
OR used when one or
another inputs are
high
Truth tables are used to
show the outputs of logic
circuits for all the possible
inputs
A
B
A
NOT used when the
input is high but you
want it to be the
opposite
Northgate High School - Electronics - Revision Cards 11
MICROCONTROLLER
Microcontrollers
may need to
be connected
to a
transducer
driver to
power some
outputs
It is possible to
program microcontrollers with
programs other than
flow charts and also
with binary numbers
Output
Output
Output
A
B
0
0
Output
0
0
1
0
1
0
0
1
1
1
A
B
Output
0
0
0
0
1
1
1
0
1
1
1
1
A
Output
0
1
1
0
Logic gates respond
to DIGITAL signals
only and not
ANALOGUE
It is possible to
connect microcontrollers to
almost any type
of output device
Northgate High School - Electronics - Revision Cards 10 There are lots of different
things you can do with a
MICROCONTROLLERS
micro-controller
These are integrated circuits
that can be programmed
The oval
boxes are to
stop or start
or reset a
process
The diamond boxes are to ask questions
Is output 1 high?
Has the analogue sensor gone above 120?
Has the counter gone above 3?
The square boxes are used to make your circuit do things
You can
make OUTPUTS go high or low
make the micro-controller wait
make your circuit play a tune or make a sound
make your micro-controller count
set the counter to a certain number
call up a sub routine
Northgate High School - Electronics - Revision Cards 12
INTEGRATED CIRCUITS
DIL - Dual In Line
Some
common
IC’s are:
Pin 1 will always be on
the top left next to the
small notch and spot
8
2
Microcontrollers can
also be used
with infrared
receivers and
transmitters
Micro-controllers can be
connected to work alongside other
IC’s like 4017 decade counters
and 4026 seven segment display
drivers
SUB
ROUTINES
can be
used in
flowcharts
to repeat
processes
7
555
4017
4026
Genie
LM311
3
DIL Sockets (Chip
Holders) - Used to
ensure chips aren’t
damaged during
soldering or so chips
can be removed
Some IC’s are made
specifically for a purpose
- e.g. melody generators
found in greetings cards
and toys
Northgate High School - Electronics - Revision Cards 13
Time Constant = Capacitance (F) x Resistance (Ω)
MONOSTABLE The time will not be exact because of Resistor Tolerances
Don’t forget to change the numbers to their original values
Used as a
timer circuit
The time
can be
changed by
altering R4
and C1 in
this circuit
Northgate High School - Electronics - Revision Cards 15
Northgate High School - Electronics - Revision Cards 16
OUTPUT DEVICES
COUNTERS
OUTPUT- Mechanical
Sirens
Loudspeakers
Bells
Change the
frequency
of the
pulses by
altering the
size of the
CAPACITOR
or
RESISTORS
Changing the
size of the
RESISTORS
gives
different on
/off times (Mark Space
Ratio)
Larger the
resistor and
capacitor =
longer the
time delay.
OUTPUT - Audio
Northgate High School - Electronics - Revision Cards 14
555 Astable used to create pulses
ASTABLE (PULSE GENERATOR)
OUTPUT- Visual
Decade counters - 4017 and 4026
Simple counting chips
Lamp
ELECTRONIC SWITCHES
Solenoids
Seven
Segment
Displays
Microcontrollers
It is possible to use the following
devices as electronic switches
rather than mechanical switches
AND
Buzzers
Piezo
Sounders
LED
Output devices sometimes need attaching to drivers like - Microprocessors Decade Counters- or similar
Transistors
Logic Gates
OR
NOT
Northgate High School - Electronics - Revision Card 17s
SUSTAINABILITY
Manufacture, operation and
recycling can be dangerous Material extraction addiction - hazardous disposal
Fixing and repairing
Products are
designed so they can easily - removable
compartments
be maintained
Batteries and cells are
collected to eliminate
dangerous chemicals
from landfill sites
Some products are
designed to be
recycled
Northgate High School - Electronics - Revision Cards 18
Product Life-Cycle
Make sure you understand the following boxes
Electronic
systems produce
health and
pollution hazards
Examples What you need
to know in
in Light
Blue
Yellow
Designated
Council
collection
points
Timber is more sustainable Know how
than steel because it is
sustainable some
easier to renew and replace products are
Aluminium cans
New Cars
More electrical items
Some products are Photocopiers that use
recycled paper
designed to use
recycled materials Toilet tissue that is recycled
Council waste sites some shops. All done
to reduce electrical
and electronic waste
Know why and where the
recycling of household
electrical appliances can
be done
Northgate High School - Electronics - Revision Cards 19
Maturity stage
Declining stage
As the product develops the company experiences different sales , profit and product evolution
The more
robots can do
jobs the
fewer
employees
will be
required
Some
products are
designed to go
out of date built in
obsolescence
- this will
change the
product life
cycle duration
Microprocessors are used throughout society in almost every electronic device - advantages
and disadvantages
The development of
electronics have
social, economic and
environmental
changes
Computer game
addiction - reliance
on safety features breakdown in face to
face communications
There is extensive marketing
of products which are
labelled as fashion items and
are targeted at the
consumer - mobile phones flat screen TV’s - the latest
computer games consoles
Industry uses
electronic systems
extensively to improve
efficiency. Computer
controlled robots location tracking
devices - security
cameras.
Programming Microcontroller IC’s wouldn't
be possible without CAD
Pot Div’s are used to
control voltage in a
circuit
Also handy to use with
sensing circuits
COMPUTER AIDED MANUFACTURE - C A M
PCB Manufacture
Mould Manufacture
Casing Manufacture
PCB’s can be made with CAM
machinery
Router or Milling Machine
Masks for Photo-etching are
made with CAM machinery
CAM machinery is used to
make moulds that are then
formed over or injected into
CAM machinery is used to
make the casing for products
laser cutters & rapid
prototyping
V out is ½ Vs if
the resistors are
the same size
V out
0V
If you use a
Thermistor or LDR
with a variable
resistor you can
change the
sensitivity /
threshold
Variable
Resistor
C A D and C A M is really useful for
Stock Control
High Speed Assembly
Product Design
Automatic Production
Quality Control
Vs
The V out will
change depending
on light or
temperature if an
LDR or
Thermistor is
used with a fixed
resistor
LDR
CAD is also useful for calculating values.
POTENTIAL DIVIDER
Thermistor
Used to create designs for circuits - circuit diagrams
to make PCB track layouts
to make designs for Product Casing
Growth stage
Northgate High School - Electronics - Revision Cards 20
CAD is really useful to make sure a circuit
will work before they are made for real.
COMPUTER AIDED DESIGN - C A D
Introductory stage
Northgate High School - Electronics - Revision Cards 21
Northgate High School - Electronics - Revision Cards 22
INTERFACE DEVICES
TRANSDUCER INPUT DEVICES
Anode
All of the items in this INTERFACE
DEVICES box can be used to drive
other components or amplify
Thyristors
Gate
Cathode
Operational Amplifiers
- Op Amps
Field Effect
Transistors
Darlington
Drivers
Bi Polar
Transistors
Northgate High School - Electronics - Revision Cards 23
MATERIALS
Uses
Advantages
Disadvantages
Student Projects
Easily Shaped
High Impact
Polystyrene (HIP),
Everyday products
Hardwearing
Needs expensive
equipment to mass
produce
Low Carbon (mild)
Steel
Nuts & Bolts
Easily shaped
Can rust if not
protected
Softwood
Medium Density
Fibreboard (MDF)
Resistors that change value
depending on Light levels
Products that
change
conductivity
with the
presence of
moisture
Piezos
All of these devices
can be used in
circuits to detect
things.
Some Examples
Burglar Alarms
Household
Thermostats
Fridge Thermostats
Moisture Detectors
Outdoor Lighting
Noise Level
Monitoring
Material that
creates and small
electrical charge
when deformed
Microphones
Products that
create and
electrical input
following the
detection of
noise
Northgate High School - Electronics - Revision Cards 24
can be used for different things. Some materials that are available are: -
Acrylic
Resistors that
change
depending on
temperature
LDR - Light Dependent
Resistor
Moisture Sensors
Thermistors
Some furniture
Low cost
Dents easily
Household DIY Modelling
No grain doesn’t warp
Isn’t waterproof
OPTO ISOLATORS
Infra - red emitting diode
Interface Between two circuits
Electronic Circuit
Electronic Circuit
TESTING EQUIPMENT
Logic Probe
Multi-meter
Some materials conduct electrical current and others insulate.
Mild Steel - Copper - Aluminium Softwood - Plastic - Hardwood - Ceramics - Glass
Phototransistor
LED Tester
Quantum Tunnelling
Composite (QTC).
Northgate High School - Electronics - Revision Cards 25
SMART MATERIALS
Electro-Luminescent
Materials
These are materials that change
when an external action takes place.
They are SMART because they can
do it millions of times without any
deformation
Resistance changes
when pressure is
applied
Produce a bright
coloured light without
giving off heat
Polymer Fibre Optical Cables,
Cable that allows light to pass
down them rather than
electrical current - being used
more recently for high speed
data transfer
Nanoelectronics
Photovoltaic Cells,
is the study of manipulating
matter on an atomic and
molecular scale allowing
even smaller component
manufacture
Convert sunlight to
electrical energy
Northgate High School - Electronics - Revision Cards 26
MATERIALS
Some of the uses and
appearance of different
materials
Medium Density
Fibreboard (MDF)
High Impact
Polystyrene (HIP),
Low Carbon
(mild) Steel
Semi-conductor Material
Allows electrical current to pass
through it. The conductivity can
be changed depending on the
material makeup
Shape Memory Metals
Piezoelectric Cable
Cable that gives off a
small electrical charge
when deformed
Change shape really fast
when temperature
changes
Northgate High School - Electronics - Revision Cards 27
CIRCUIT BOARD MANUFACTURE
Routing & Milling Method
Design the circuit on a
computer
Design the circuit on a
computer
Expose the photo
sensitive board to UV
Put the board in the
developer
Etch the PCB in the
Bubble Etch Tank
Drill the holes in the PCB
Place the components and
solder them in place
Acrylic
Northgate High School - Electronics - Revision Cards 28
GOOD CIRCUIT PRACTICE
Photo-etch Method
Print the design onto
acetate
Softwood
Single Core
Multi - Core
Singe core wire - used for track jumps
and parts that will not move
Multi core wire - used for parts that
might move
Place the Copper covered
PCB in the Router
Output the design to
the router
Clean away any debris
from the routing process
Drill the holes in the PCB
Place the components and
solder them in place
Be
careful
about
the
amount
of
material
you use
Tidy wires by winding them together.
Use heat shrink or spiral wrap to tidy
wires
Colour coded insulation tape to
identify polarity
Use strain holes to secure external
components to the board to avoid
breakages.
Northgate High School - Electronics - Revision Cards 29
Northgate High School - Electronics - Revision Cards 30
PRODUCTION METHODS
ELECTRONIC SYSTEMS
Used to make products that are often very expensive - Violins
One Off
Workers are heavily involved in every stage of production
INPUT
PROCESS
OUTPUT
The method of production used to manufacture prototypes
All systems have three parts to them some have a feedback to help the
system in future
Batch
Used to make batches of products where fashion change
FEEDBACK
Workers not heavily involved in production process
Used for clothing & items where market influences change
Mass
All products should be tested
by the manufacturer to
ensure they :WORK
ARE SAFE
Used to make products that are inexpensive or where lots are needed
Workers aren’t involved in production process at all - almost
ARE RELIABLE
CAN BE RECYCLED
Used to produce things like cars or plastic bottles or nut and
Northgate High School - Electronics - Revision Cards 31
SAFETY IN THE WORKSHOP
Be
aware
of the
hazards
Tools should be always
be sharp and stored
correctly
WEAR GOGGLES
Northgate High School - Electronics - Revision Cards 32
RISK ASSESSMENTS should be
carried out - they help determine
how dangerous things are.
Users should be trained
to used tools correctly
WEAR APRONS
Immediate Risk - a
dangerous operation that
has immediate
consequences e.g. throwing a chisel
ve
ti
Risk - a
dangerous operation that
has doesn’t have
immediate
consequences e.g. Breathing in dust
Cumula
USE DUST MASKS
AND EXTRACTION
WHEN NECESSARY
Never use the 240V supply to
power your projects - always
use a transformer or batteries
INDUSTRIAL CHANGES
When a
product
goes from
prototype
to
production
there are
always
changes
made
The casing materials
will change
The PCB will be mass
or batch produced
A different finish might
be applied
The product shape may
have to be changed a
little to fit the production
process
Designers
must always
make sure
they design
products that
can be mass
produced
with ease
Northgate High School - Electronics - Revision Cards 33
Northgate High School - Electronics - Revision Cards 34
CONSTRUCTION TECHNIQUES
Temporary Construction
INDUSTRIAL MANUFACTURING
Breadboard / Prototype
Through Hole Construction
Pick and place robots are used to place
components that are too small to handle or
when work needs to be done really fast
Choose the most appropriate
method of construction
Temporary for Testing
Permanent for Production
Surface Mount Construction
ith so
PCB w
lder res
Solder Bath
ist
Pump
Vero - board
Permanent Construction
Etched PCB
Routed / Milled PCB
Molten Solder
Mass Produced PCB
Solder baths are used - run
the PCB over the molten
solder - solder sticks to the
exposed circuit board makes soldering the
components much faster
Heaters
Northgate High School - Electronics - Revision Cards 36
Northgate High School - Electronics - Revision Cards 35
PRODUCTION PROCESSES
PRODUCTION PROCESSES
Thermoplastic
Heater Bars
Line Bending
Rapid Prototyping
Very expensive but good for complicated one-off items
Line Bending
Limited to just being able to bend lines in work
Laser Cutting
Very fast and accurate - machinery is expensive
Vacuum Forming
Fast and low cost per item - limited shapes available
Injection Moulding
Very fast - high quality finish on item - v. costly to set up
Heater
Moulding
Heater
Thermoplastic
Molten
Plastic
Toggle
Clamp
Mould
Plunger
Heater
Mould
Injection Moulding
Vacuum
Pump
Vacuum
Forming