Download Circuit Symbols You must learn to recognise each of these circuit

You must learn to recognise each of these circuit symbols below, and be able to draw them too
Component
Cell
Symbol
Control
System
Definition
generates
reaction.
electrical
Battery
Two or more cells.
Resistor
Slows down
components.
current
energy
and
via
a
chemical
protects
(delicate)
process
(input)
Variable resistor
A resistor whose value can be adjusted.
process
(input)
Potentiometer
A resistor whose value can be changed, with a third
adjustable leg.
Thermistor
A resistor which changes resistance as temperature
changes. As temperature decreases (gets colder)
its resistance increases.
input
Light
Dependent
Resistor (LDR)
A resistor which changes resistance as ambient light
changes. When it gets darker the resistance
increases.
A transducer which converts brightness (light) to
resistance (an electrical property).
input
VLE > D&T > KS4 > GCSE Electronic Products - Cohort 2013 - 2015
process
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Definition
Control
System
Light Emitting
Diode (LED)
A diode that only allows current to flow in one
direction only and lights up when it does.
output
Flashing Light
Emitting Diode
A diode that only allows current to flow in one
direction only and flashed on and off when it does.
output
Bi-colour Light
Emitting Diode
This is two LEDs which are wired back to back so it
glows in one colour for current in one direction and
glows another colour for current in the opposite
direction.
output
Tri-colour Light
Emitting Diode
This is a combination of two LEDs with three leads
(legs). There are three colours, either one or the
other, or a combination of both. A popular
example is red and green, which combine to give
yellow.
output
Photo transistor
A light-sensitive transistor (see transistor below).
process
Opto-isolator
This is a semiconductor device which allows
electrical signals to be transferred between circuits,
devices, or systems, while maintaining electrical
isolation between them.
process
Ammeter
A meter that measures the flow of electrical current
in amperes.
Push to make
switch (PTM)
A push switch allows current to flow only when the
button is pressed. This is the switch used to operate
a doorbell.
Component
Symbol
VLE > D&T > KS4 > GCSE Electronic Products - Cohort 2013 - 2015
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input
Component
Symbol
Control
System
Definition
Push to break
switch (PTB)
This type of push switch is normally closed (on), it is
open (off) only when the button is pressed. This is
commonly found in a fridge.
input
Single Pole
Single Throw
switch (SPST)
An on-off switch allows current to flow only when it
is in the closed (on) position.
input
Single Pole
Double Throw
switch (SPDT)
A 2-way changeover switch directs the flow of
current to one of two routes according to its
position. Some SPDT switches have a central off
position and are described as 'on-off-on'
input
Capacitor
A capacitor stores electric charge. A capacitor is
used with a resistor in a timing circuit. It can also be
used as a filter, to block DC signals but pass AC
signals
process
Electrolytic
Capacitor
A capacitor stores electric charge. This type must
be connected the correct way round. A capacitor
is used with a resistor in a timing circuit. It can also
be used as a filter, to block DC signals but pass AC
signals.
process
Piezo crystal
oscillator
A transducer which converts electrical energy to
sound.
Diode
A device which only allows current to flow in one
direction.
process
An electronic latching switch
process
Thyristor
VLE > D&T > KS4 > GCSE Electronic Products - Cohort 2013 - 2015
output
(input)
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Definition
Control
System
NPN transistor
A transistor amplifies current. It can be used with
other components to make an amplifier or
switching circuit.
process
Field Effect
Transistor (FET)
Similar to a transistor, however, needs only a minute
amount of current to switch/amplify e.g. used in a
touch switch/sensor.
process
AND gate
An AND gate can have two or more inputs. The
output of an AND gate is true when all its inputs are
true.
process
OR gate
An OR gate can have two or more inputs. The
output of an OR gate is true when at least one of its
inputs is true.
process
NOT gate
A NOT gate can only have one input. The 'o' on the
output means 'not'. The output of a NOT gate is the
inverse (opposite) of its input, so the output is true
when the input is false. A NOT gate is also called an
inverter.
process
Bell
A transducer which converts electrical energy to
sound.
output
Microphone
A transducer which converts sound to electrical
energy.
input
Buzzer
A transducer which converts electrical energy to
sound.
output
Component
Symbol
VLE > D&T > KS4 > GCSE Electronic Products - Cohort 2013 - 2015
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Definition
Control
System
Loudspeaker
A transducer which converts electrical energy to
sound.
output
Lamp
A transducer which converts electrical energy to
light. This symbol is used for a lamp which is an
indicator, for example a warning light on a car
dashboard.
output
Motor
A transducer which converts electrical energy to
kinetic energy (motion).
output
Component
Voltmeter
Voltage rails
Symbol
A voltmeter is used to measure voltage.
The proper name for voltage is 'potential difference', but most
people prefer to say voltage!
A power supply
Earth
A connection to earth. For many electronic circuits
this is the 0V (zero volts) of the power supply, but for
mains electricity and some radio circuits it really
means the earth. It is also known as ground.
555 timer IC
Used in circuits to produce monostable (timer,
delay) effects as well as astable (pulse generator)
effects.
process
Operational
Amplifier (OpAmp)
Acts as a comparator; and Analogue to Digital
Convertor (ADC); also acts as an amplifier; can be
used as an extremely sensitive [sensor] switch.
process
VLE > D&T > KS4 > GCSE Electronic Products - Cohort 2013 - 2015
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Definition
Control
System
Voltage
Regulator
A device that controls or maintains the voltage of
an electrical circuit.
process
crossing of
conductors
This is indicates where wires cross over each other
(without joining) – sometimes called a bridge
joined
conductors
This indicates where wires are joined. You should
make sure your draw the ‘blob’ so that it is quite
distinct.
Component
Symbol
VLE > D&T > KS4 > GCSE Electronic Products - Cohort 2013 - 2015
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You will NOT be required to draw these symbols, however, you should be aware of them as some of
these appear in the specification and you are required to know their functions
Definition
Control
System
NAND gate
A NAND gate can have two or more inputs. The 'o'
on the output means 'not' showing that it is a Not
AND gate. The output of a NAND gate is true unless
all its inputs are true.
Although not required for AQA specification, it is
useful to know, that from this gate, all others can be
made.
process
NOR gate
this is the opposite of an OR gate; only when both
inputs are low / 0 the output is high / 1
process
XOR gate
similar to an OR gate, output is high / 1 only when
one of the inputs are high / 1 (not both)
process
moisture sensor
(probe)
a sensor component that reacts to something
become wet (NOT changes in moisture) – used for
plant watering monitors, fuel level sensors, flood
alarms
7 segment
display
displays numerals in a decimal fashion (dot-matrix
displays are a more complex version) used in digital
clocks, some modern car dashboards
output
solenoid
a coil of wire around an iron core; becomes a
magnet when current passes through the coil e.g.
fire alarm bells, timed locks on bank vaults
output
terminal
a contact on an electrical device or circuit
Component
Symbol
ac supply
an electric current that reverses direction sinusoidally
50 times per second (50 Hertz (Hz))
double pole
double throw
switch DPDT
used to reverse the direction of a motor e.g. an
electric drill
relay
an electrical switch operated by current flowing
throw it e.g. switching on an mains operated heater
using an Op-Amp temperature sensor circuit
VLE > D&T > KS4 > GCSE Electronic Products - Cohort 2013 - 2015
input
input
Input
process
output
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