Basic Electric Symbols


Table of Electrical Symbols:


SymbolComponent NamesDescription
Electrical Wire A conductor is a device that conducts electrical current. Also known as a power line, electric line, or wire.
Connected WiresThe connection of two conductors is represented by this symbol. The intersection is indicated by a dot.
Not Connected WiresRepresents two unconnected wires/conductors.
Input Bus LineRepresents a bus for input or incoming data.
Output Bus LineRepresents a bus for output or outgoing data.
TerminalRepresents start or end point.
Bus LineA bus wire is made up of several conductors that are linked together.

Switch Symbols:

Pushbutton Switch (N.O) When the button is pressed, this switch is in the ON position; otherwise, it is in the OFF position.
Pushbutton Switch (N.C)This switch is initially turned on. When this is released, it returns to the OFF state.
DIP SwitchDIP switch is used for onboard configuration
SPST Toggle SwitchSPST stands for Single Pole Single Throw. This serves as an ON/OFF switch.
SPDT Toggle SwitchSPDT stands for single pole double throw. By altering its position, this switch permits current to flow in either of two directions.
DPST SwitchDPST stands for double pole single throw. This switch can power two circuits at the same time.
DPDT SwitchDPDT is an abbreviation for double pole double throw. By adjusting the position, you may connect the four circuits.

Ground Symbols:

Earth Ground Theoretically it is equivalent to 0V and is used as zero potential reference.
Chassis GroundIt creates a barrier between the user and the circuit, preventing electric shock.
Digital / Common Ground It serves as a reference point against which the signal is measured. Because of voltage losses in a circuit, there may be many signal grounds.

Relay Symbols:

SPST Relay SPST Stands for single-pole single-throw relay
SPDT RelaySingle Pole Double Throw Relay (SPDT). The Relay consists of a coil, 1 common terminal, 1 normally closed terminal, and one normally open terminal.
JumperClose connection by jumper insertion on pins.
Solder BridgeSolder to close connection

Resistor Symbols:

Resistor (IEEE)It is a device that is designed to opposes the flow of current in a circuit. These two symbols are used to represent fixed resistor.
Potentiometer (IEEE)Adjustable resistor – has 3 terminals.
Potentiometer (IEC)Adjustable resistor – has 3 terminals.
Variable Resistor / Rheostat (IEEE)It is a variable resistor with two terminals. They are typically used to regulate the current in a circuit. Typically used in tuning circuits and power control applications such as heaters and ovens.
Variable Resistor / Rheostat (IEC)It is a variable resistor with two terminals. They are typically used to regulate the current in a circuit. Typically used in tuning circuits and power control applications such as heaters and ovens.
Trimmer ResistorPreset resistor
ThermistorThermal resistor – change resistance when temperature changes
Photoresistor / Light dependent resistor (LDR)Photo Resistors are another name for them. LDR resistance varies with the intensity of the incident light. They are commonly seen in light detecting applications.
AttenuatorIt is a device that reduces the power of a signal. They are constructed from basic voltage dividers and so belong to the resistor family.
MemristorThe resistance of a memristor varies with the direction of charge flow. Memristors can be utilised in signal processing, logic/computation, non-volatile memory, and other applications.

Capacitor Symbols:

Non-Polarized CapacitorCapacitor is used to store electric charge. It acts as short circuit with AC and open circuit with DC.
Polarized CapacitorPolarized capacitors have a small size but a large capacitance. They are utilised in direct current circuits. They can be used to bypass or pass low frequency signals as filters.
Electrolytic capacitorAlmost all electrolytic capacitors are polarised and so used in direct current (DC) circuits.
Variable CapacitorThe variable capacitor’s capacitance can be modified by turning the knob. They are commonly used to modify the frequency, or to tune.
Feed through CapacitorFor high frequency transmissions, they provide a low impedance path to ground.

Inductor / Coil Symbols:

Iron Core InductorThese are used to replace ferrite core inductors. Ferrite core inductors have a high permeability and require an air gap to lessen it. This air gap is built into iron powdered core inductors.
Ferrite Core InductorsThe core material in these inductors is constructed of ferrite. These are generally used to reduce electromagnetic wave interference.
Center Tapped InductorThese are used in coupling of signals
Variable InductorThe most popular type of variable inductors are movable ferrite magnetic core inductors. By moving the core in and out of the coil, the inductance may be changed.

Power Supply Symbols:

Voltage SourceIt is a dependent voltage source. Usually depends on other sources (voltage or current).
Current SourceGenerates constant current.
AC Voltage SourceThis represents AC supply in the circuit.
GeneratorElectrical voltage is generated by mechanical rotation of the generator
Battery Cell (DC)This represents the DC power supply. It applies DC supply to the circuit.
BatteryCombination of multiple single cell batteries or a single large cell battery. The voltage is usually higher.
Controlled Voltage SourceGenerates voltage as a function of voltage or current of other circuit element.
Controlled Current SourceGenerates current as a function of voltage or current of other circuit element.

Meter Symbols:

Voltmeter Measures voltage. Has very high resistance. Connected in parallel.
AmmeterMeasures electric current. Has near zero resistance. Connected serially.
Ohmmeter Measures resistance
WattmeterMeasures electric power

Transformer Symbols:

TransformerThe basic element that transmits energy from one circuit to the other by electromagnetic induction is the transformer. They are commonly used in electric power applications to increase or reduce the voltage of an alternating current.
Iron Core TransformerAs a core, a piece of magnetic material is used. Iron and other ferro magnetic metals are commonly used. The magnetic field is contained by the core, which has a high permeability.
Center Tapped TransformerThe secondary winding of a center-tapped transformer is divided into two portions, each with the same number of turns. This produces two distinct output voltages across two-line ends. Rectifier circuits use this.
Step Up TransformerThe number of turns in secondary winding more than that of primary winding. The output voltage exceeds the input voltage. Inverters make extensive use of it.
Step Down TransformerThe number of turns in secondary winding is less than the number of turns in primary winding. The input voltage is greater than the output voltage. It’s common in low-power applications.

Miscellaneous Symbols:

MotorElectric motor converts electrical energy to mechanical energy
Electric bellIt is a sound producing device that rings when voltage is applied
BuzzerThis is a sound-generating device. When the voltage is applied, a buzzing sound is produced.
FuseThe fuse disconnects when current above threshold. Used to protect circuit from high currents.
FuseThe fuse disconnects when current above threshold. Used to protect circuit from high currents.
BusContains several wires. Usually for data / address.
BusContains several wires. Usually for data / address.
BusContains several wires. Usually for data / address.
Optocoupler / Opto-isolatorOptocoupler isolates connection to other board
LoudspeakerThis is also an audio device. The electrical signal is converted into sound signal here.
MicrophoneConverts sound waves to electrical signal
Operational AmplifierAmplify input signal
Schmitt TriggerOperates 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 OscillatorUsed to generate precise frequency clock signal
Direct currentDirect current is generated from constant voltage level

Table of Electronic Symbols:

Transistor Symbol:

NPN Bipolar TransistorAllows current flow when high potential at base (middle)
PNP Bipolar TransistorAllows current flow when low potential at base (middle)
Darlington TransistorMade from 2 bipolar transistors. Has total gain of the product of each gain.
JFET-N TransistorN-channel field effect transistor
JFET-P TransistorP-channel field effect transistor
NMOS TransistorN-channel MOSFET transistor
PMOS TransistorP-channel MOSFET transistor

Diode / LED Symbols:

DiodeDiode allows current flow in one direction only – left (anode) to right (cathode).
Zener DiodeAllows current flow in one direction, but also can flow in the reverse direction when above breakdown voltage
Schottky DiodeIt denotes a Schottky diode. It features a minimal forward voltage drop and switches quickly. Voltage clamping, rectifiers, reverse current, and discharge prevention are all applications for this material.
Shockley DiodeThis diode has four layers. Because of its quick switching function, it is useful in switching applications.
Varactor / Varicap DiodeVaricap or variable capacitance diode is another name for a varactor diode. The capacitance of this diode varies with the applied voltage. This is utilised in frequency regulated oscillators, frequency multipliers, and other applications.
Tunnel DiodeThis is also known as Esaki diode. It can switch quickly and operate well in the microwave frequency band. This is employed in oscillator and microwave circuits.
LED (Light Emitting Diode)The light emitting diode is similar to the PN junction diode in that it emits energy in the form of light rather than heat. These are typically utilised in lighting and indicator applications.
PhotodiodePhotodiode allows current flow when exposed to light
ThyristorIt is made up of four layers of alternating P and N materials. They function as bistable switches and are employed in circuits with high voltages and currents.
Laser DiodeThe laser diode is equivalent to the light emitting diode. In the PIN structure, the active region is produced in the intrinsic region. Laser diodes are used in laser printing, laser scanning, and other applications.
Constant Current DiodeAlso known as a current limiting or current regulating diode. It restricts the current to a set maximum value.

Antenna Symbols:

Antenna / aerialThis symbol of Aerial or Antenna. It turns electrical power into radio waves. It’s utilised in wireless communication to send and receive signals.
Loop AntennaThe loop antenna gets its name from the loop-like curvature of its wire or other electrical conductor. They are used as low-frequency reception antennas.
Dipole AntennaIt is most commonly used antenna. Mainly used in set-top TV, shortwave transmission and FM receivers.

Logic Gates Symbols:

Inverter (NOT Gate)Outputs 1 when input is 0
AND GateOutputs 1 when both inputs are 1.
NAND GateOutputs 0 when both inputs are 1. (NOT + AND)
OR GateOutputs 1 when any input is 1.
NOR GateOutputs 0 when any input is 1. (NOT + OR)
XOR GateOutputs 1 when inputs are different. (Exclusive OR)
D Flip-FlopStores one bit of data
Multiplexer / Mux 2 to 1Connects the output to selected input line.
Multiplexer / Mux 4 to 1Connects the output to selected input line.
Demultiplexer / Demux 1 to 4Connects selected output to the input line.