Components and Circuit Symbols

To learn these symbols, use the "LOOK, COVER, WRITE, CHECK" method.

(It is fun to work in pairs when you are doing this.)

1, LOOK at the component and its symbol and try to remember it.
2, COVER up the symbol by moving the mouse over it.
3, WRITE the symbol down from memory on a small piece of paper.
4, CHECK your drawing by clicking where the symbol was and it will reappear.

 

Component Name
Type
Examples
Circuit Symbol
What it does
Battery general
  and  
Provides the e.m.f. or power to push current around an electrical/ electronic circuit.
Unconnected
Crossing
Wires
general
Shows where wires
or conductors cross
but do not make
electrical contact.
Connected
Wires
or Junction
general
The darkened electrical tracks allow current to branch off, or flow, into a different part of the circuit.The current entering a juction equals the current(s) leaving the junction.
Push to Make Switch input
Allows current to flow through it when it is pushed. It is normally OFF. (Available in many colours.)
Push to Break Switch input
Stops current flowing through it when it is pushed. It is normally ON, allowing current to flow. (Available in many colours.)
Reed Switch input
When a magnet is brought close to the case of the glass/plastic reed switch, contacts inside it close. The current can now flow through it.
Tilt Switch input
When the metal case is tilted from side to side, a contact inside is made to close and open according to the angle of the switch.
Micro S.P.D.T. Switch input

SPDT:Single Pole Double Throw. A lever operated switch that can connect its input (pole) to one of two outputs (throws).

Push S.P.D.T Switch input
SPDT:Single Pole Double Throw. A push operated switch that can connect its input (pole) to one of two outputs (throws).
LED (Light emitting diode) output
A coloured indicator that lights to show something has turned on or happened. It generally needs a protecting resistor. Also available in clear higher power types that can be used to illuminate or see with.
Lamp or Bulb output
Produces clear omni-directional light that can be used to see with or show that something is switched on.
Buzzer output
Emits an audible warning tone.
Motor output
Rotates very quickly and is usually slowed down with external gears, to provide greater torque (rotational force) when making things move.
Transistor
(npn type)
controller
Often used as an electronic switch to turn on lower-powered output devices such as LEDs. lamps etc. It is triggered by a small voltage applied to its input (base).
Integrated
Circuit
controller
These can contain many thousands/millions of electronic components housed on a square cm. wafer of silicon. A microprocessor is a larger scale version of this 8 pin d.i.l. (dual in line) device. (Note Pin 1 is shown by the black dot on the case).
Fixed
Resistor
general
Used to control current/ voltage in a circuit. Its fixed resisance is measured in Ohms () and available in a range of preferred values.
Variable
Resistor
general
Adjustable resistor - used to vary the current/ voltage in a circuit. It is measured in Ohms ()
Light Dependent
Resistor
input

Varies its resistance as the light falling on it changes.
More light produces a lower resistance.
Less light produces a higher resistance.

Thermistor input

Varies its resistance as its temperature changes.
When ntc type:
- A greater temperature produces a lower resistance.
- A lower temperature produces a higher resistance.

Non - Polarised or
Non - Electrolytic
Capacitor
general
Used to store electrical charge. Often combined with resistors to make timing circuits or used on their own to remove "noise" or interference in a circuit.
Polarised or
Electrolytic
Capacitor
general
Used to store electrical charge. They can also be combined with resistors to make timing circuits. They have polarity (+ / -) and must be connected the right way round in a circuit. Note the blue negative stripe shows the minus (-) side.

Voltmeter

(multimeter - in example set to read voltage up to 20v)

general
Measures the voltage or potential difference across two points of an electrical/electronic circuit. Connect in parallel.

Ammeter

(multimeter - in example set to read current up to 200mA)

general
Measures the current flowing through a circuit/ wire or component. Connect in series.

 

When You Are Ready...