Table of Electrical Symbols Symbol Component name Meaning
Wire Symbols Electrical Wire Conductor of electrical current
Connected Wires
Connected crossing
Not connected Wires
Wires are not connected
Switch Symbols and Relay Symbols SPST Toggle Switch Disconnects current when open
SPDT Toggle Switch
Selects between two connections
Pushbutton Switch (N.O)
Momentary switch - normally open
Pushbutton Switch (N.C)
Momentary switch - normally closed
DIP Switch
DIP switch is used for onboard configuration
SPST Relay Relay open / close connection by an electromagnet SPDT Relay
Jumper
Close connection by jumper insertion on pins.
Solder Bridge
Solder to close connection
Ground Symbols Earth Ground Used for zero potential reference and electrical shock protection.
Chassis Ground
Connected to the chassis of the circuit
Digital / Common Ground
Resistor Symbols Resistor (IEEE) Resistor reduces the current flow. Resistor (IEC)
Potentiometer (IEEE) Adjustable resistor - has 3 terminals. Potentiometer (IEC)
Variable Resistor / Rheostat(IEEE) Adjustable resistor - has 2 terminals. Variable Resistor / Rheostat(IEC) Capacitor Symbols Capacitor Capacitor is used to store electric charge. It acts as short circuit with AC and open circuit with DC. Capacitor
Polarized Capacitor
Electrolytic capacitor
Polarized Capacitor
Electrolytic capacitor
Variable Capacitor
Adjustable capacitance
Inductor / Coil Symbols Inductor Coil / solenoid that generates magnetic field
Iron Core Inductor
Includes iron
Variable Inductor
Power Supply Symbols Voltage Source Generates constant voltage
Current Source
Generates constant current.
AC Voltage Source
AC voltage source
Generator
Electrical voltage is generated by mechanical rotation of the generator
Battery Cell
Generates constant voltage
Battery
Generates constant voltage
Controlled Voltage Source
Generates voltage as a function of voltage or current of other circuit element.
Controlled Current Source
Generates current as a function of voltage or current of other circuit element.
Meter Symbols Voltmeter Measures voltage. Has very high resistance. Connected in parallel.
Ammeter
Measures electric current. Has near zero resistance. Connected serially.
Ohmmeter
Measures resistance
Wattmeter
Measures electric power
Lamp / Light Bulb Symbols
Lamp / light bulb
Lamp / light bulb
Generates light when current flows through
Lamp / light bulb
Diode / LED Symbols Diode Diode allows current flow in one direction only (left to right).
Zener Diode
Allows current flow in one direction, but also can flow in the reverse direction when above breakdown voltage
Schottky Diode
Schottky diode is a diode with low voltage drop
Varactor / Varicap Diode
Variable capacitance diode
Tunnel Diode
Light Emitting Diode (LED)
LED emits light when current flows through
Photodiode
Photodiode allows current flow when exposed to light
Transistor Symbols NPN Bipolar Transistor Allows current flow when high potential at base (middle)
PNP Bipolar Transistor
Allows current flow when low potential at base (middle)
Darlington Transistor
Made from 2 bipolar transistors. Has total gain of the product of each gain.
JFET-N Transistor
N-channel field effect transistor
JFET-P Transistor
P-channel field effect transistor
NMOS Transistor
N-channel MOSFET transistor
PMOS Transistor
P-channel MOSFET transistor
Misc. Symbols Motor Electric motor
Transformer
Change AC voltage from high to low or low to high.
Electric bell
Rings when activated
Buzzer
Produce buzzing sound
Fuse The fuse disconnects when current above threshold. Used to protect circuit from high currents. Fuse
Bus
Bus
Contains several wires. Usually for data / address.
Bus
Optocoupler / Opto-isolator
Optocoupler isolates onnection to other board
Loudspeaker
Converts electrical signal to sound waves
Microphone
Converts sound waves to electrical signal
Operational Amplifier
Amplify input signal
Schmitt Trigger
Operates with hysteresis to reduce noise.
Analog-to-digital converter (ADC)
Converts analog signal to digital numbers
Digital-to-Analog converter (DAC)
Converts digital numbers to analog signal
Crystal Oscillator
Used to generate precise frequency clock signal
Antenna Symbols Antenna / aerial Transmits & receives radio waves Antenna / aerial
Dipole Antenna
Two wires simple antenna
Logic Gates Symbols NOT Gate (Inverter) Outputs 1 when input is 0
AND Gate
Outputs 1 when both inputs are 1.
NAND Gate
Outputs 0 when both inputs are 1. (NOT + AND)
OR Gate
Outputs 1 when any input is 1.
NOR Gate
Outputs 0 when any input is 1. (NOT + OR)
XOR Gate
Outputs 1 when inputs are different. (Exclusive OR)
D Flip-Flop Multiplexer / Mux 2 to 1
Stores one bit of data Connects the output to selected input line.
Multiplexer / Mux 4 to 1
Demultiplexer / Demux 1 to 4
Connects selected output to the input line.
