Electrical symbols are universal representations used in diagrams and schematics to show electrical components and connections clearly.
Power Supply Schematic Symbols
| Schematic Symbol | Symbol Identification | Description of Symbol |
|---|---|---|
 | Single Cell | A single DC battery cell of 0.5V |
 | DC Battery Supply | A collection of single cells forming a DC battery supply |
 | DC Voltage Source | A constant DC voltage supply of a fixed value |
 | DC Current Source | A constant DC current supply of a fixed value |
 | Controlled Voltage Source | A dependent voltage source controlled by an external voltage or current |
 | Controlled Current Source | A dependent current source controlled by an external voltage or current |
 | AC Voltage Source | A sinusoidal voltage source or generator |
Electrical Grounding Schematic Symbols
| Schematic Symbol | Symbol Identification | Description of Symbol |
|---|---|---|
 | Earth Ground | Earth ground referencing a common zero potential point |
 | Chassis Ground | Chassis ground connected to the power supplies earthing pin |
 | Digital Ground | A common digital logic circuit ground line |
Resistor Schematic Symbols
| Schematic Symbol | Symbol Identification | Description of Symbol |
|---|---|---|
 | Fixed Resistor (IEEE Design) | A fixed value resistor whose resistive value is indicated next to its schematic symbol |
 | Fixed Resistor (IEC Design) | |
 | Potentiometer (IEEE Design) | Three terminal variable resistance whose resistive value is adjustable from zero to its maximum value |
 | Potentiometer (IEC Design) | |
 | Rheostat (IEEE Design) | Two terminal fully adjustable rheostat whose resistive value varies from zero to a maximum value |
 | Rheostat (IEC Design) | |
 | Trimmer Resistor | Small variable resistors for mounting onto pcb’s |
 | Thermistor (IEEE Design) | Thermal resistor whose resistive value changes with changes in surrounding temperature |
 | Thermistor (IEC Design) |
Capacitor Schematic Symbols
| Schematic Symbol | Symbol Identification | Description of Symbol |
|---|---|---|
 | Fixed Value Capacitor | A fixed value parallel plate non-polarised AC capacitor whose capacitive value is indicated next to its schematic symbol |
 | Fixed Value Capacitor | |
 | Polarized Capacitor | A fixed value polarised DC capacitor usually an electrolytic capacitor which must be connected to the supply as indicated |
 | Variable Capacitor | An adjustable capacitor whose capacitance value can be varied by means of adjustable plates |
Inductor and Coil Schematic Symbols
| Schematic Symbol | Symbol Identification | Description of Symbol |
|---|---|---|
 | Open Inductor | An open inductor, coil or solenoid that generates a magnetic field around itself when energised |
 | Iron Core Inductor | An inductor formed by winding the coil around a solid laminated iron core indicated by solid lines |
 | Ferrite Core Inductor | An inductor formed by winding the coil around a non-solid ferrite core indicated by dashed lines |
Switch and Contact Symbols
| Schematic Symbol | Symbol Identification | Description of Symbol |
|---|---|---|
 | SPST Toggle Switch | Single-pole single-throw toggle switch used for making (ON) or breaking (OFF) a circuits current |
 | SPDT Changeover Switch | Single-pole double-throw changeover switch used for changing the direction of current flow from one terminal to another |
 | Pushbutton Switch (N.O) | Normally open contacts pushbutton switch – push to close, release to open |
 | Pushbutton Switch (N.C) | Normally closed contacts pushbutton switch – push to open, release to close |
 | SPST Relay Contacts | Electromechanical relay with internal single-pole single-throw toggle contacts |
 | SPDT Relay Contacts | Electromechanical relay with internal single-pole double-throw changeover contacts |
 | DPST Relay Contacts | Electromechanical relay with internal double-pole single-throw toggle contacts |
 | DPDT Relay Contacts | Electromechanical relay with internal double-pole double-throw changeover contacts |
 | DIP Switch Assembly | PCB mounted DIP switch with 1-to-10 toggle switches either single-pole, double-pole, rotary or with a common terminal |
Semiconductor Diode Symbols
| Schematic Symbol | Symbol Identification | Description of Symbol |
|---|---|---|
 | Semiconductor Diode | Semiconductor pn-junction diode used for rectification and high current applications |
 | Zener Diode | Zener diode used in its reverse voltage breakdown region for voltage limiting and regulation applications |
 | Schottky Diode | Schottky diode consisting of an n-type semiconductor and metal electrode junction for low voltage applications |
Transistor Symbols
| Schematic Symbol | Symbol Identification | Description of Symbol |
|---|---|---|
 | NPN Bipolar Transistor | Characterised as being a lightly doped p-type base region between two n-type emitter and collector regions with the arrow indicating direction of conventional current flow out. |
 | PNP Bipolar Transistor | Characterised as being a lightly doped n-type base region between two p-type emitter and collector regions. Arrow indicates direction of conventional current flow in. |
 | Darlington Pair Transistor | Two bipolar transistor npn or pnp connected in a series common collector configuration to increase current gain |
 | N-JFET Transistor | N-channel junction field effect transistor having an n-type semiconductive channel between source and drain with the arrow indicating direction of conventional current flow |
 | P-JFET Transistor | P-channel junction field effect transistor having a p-type semiconductive channel between source and drain with the arrow indicating direction of conventional current flow |
 | N-MOSFET Transistor | N-channel metal-oxide semiconductor field effect transistor with an insulated gate terminal which can be operated in depletion or enhancement mode |
 | P-MOSFET Transistor | P-channel metal-oxide semiconductor field effect transistor with an insulated gate terminal which can be operated in depletion or enhancement mode |
Photodevice Schematic Symbols
| Schematic Symbol | Symbol Identification | Description of Symbol |
|---|---|---|
 | Light Emitting Diode (LED) | A semiconductor diode which emits coloured light from its junction when forward biased |
 | 7-segment Display | A 7-segment display used common cathode (CC) or common anode (CA) for displaying single numbers and letters |
 | Photodiode | A semiconductor device which allows current to flow when exposed to incident light energy |
 | Solar Cell | P–N junction photovoltaic cell transducer which converts light intentsity directly into electrical energy |
 | Photoresistor | Light dependent resistor (LDR) which changes its resistive value with changes in light intensity |
 | Indicator Lamp or Light Bulb | A filament lamp, indicator or other which emits visible light when a current flows through it |
 | Opto-isolator or Optocoupler | An Opto-isolator or Optocoupler which uses photo-sensitive devices to isolate its input and output connections |
Digital Logic Symbols
| Schematic Symbol | Symbol Identification | Description of Symbol |
|---|---|---|
 | NOT Gate | Logic gate with only one input and one output and outputs a logic 1 (HIGH) when input is 0 (LOW) and outputs a 0 when input is 1 (Inverter) |
 | AND Gate | Logic gate with two or more inputs which outputs a logic 1 (HIGH) when ALL of its inputs are at logic 1 (HIGH) |
 | NAND Gate | Logic gate with two or more inputs that outputs a logic 0 (LOW) when ALL of its inputs are HIGH at logic 1 (Equivalent to NOT + AND) |
 | OR Gate | Logic gate with two or more inputs which outputs a logic 1 (HIGH) when ANY (or both) of its inputs are at logic 1 (HIGH) |
 | NOR Gate | Logic gate with two or more inputs that outputs a logic 0 (LOW) when ANY (or both) of its inputs are HIGH at logic 1 (Equivalent to NOT + OR) |
 | XOR Gate | Exclusive-OR gate with two inputs that outputs a logic 1 (HIGH) whenever its two inputs are DIFFERENT |
 | XNOR Gate | Exclusive-NOR gate with two inputs that outputs a logic 1 (HIGH) whenever its two inputs are the SAME (NOT + XOR) |
 | SR Flip-Flop | Set-Reset Flip-flop is a bistable device used to store one bit of data on its two complementary outputs |
 | JK Flip-Flop | JK (Jack Kilby) Flip-flop has the letter J for Set and the letter K for Reset (Clear) with internal feedback |
 | D-type Flip-Flop | D (Delay or Data) Flip-flop is a single input flip-flop which toggles between its two complementary outputs |
 | Data Latch | Data latch stores one data bit on its single input when EN enable pin is LOW and outputs the data bit transparently when the EN enable pin is HIGH |
 | 4-to-1 Multiplexer | A Multiplexer passes the data on one of its inputs pins to a single output line |
 | 1-to-4 Demultiplexer | A Demultiplexer passes the data on its single input pin to one of several output lines |
Here we have seen a number of basic electrical and electronics schematic symbols in graphical form used by engineers to show how a particular circuit is connected together and operates by the types of symbols used within it so that other engineers may understand.
You can download the schematic symbol from here: schematic symbol.pdf
