Symbol
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Component name
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Meaning
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Wire Symbols
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Conductor of electrical current
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Connected crossing
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Wires are not connected
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Switch Symbols and Relay Symbols
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Disconnects current when open
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Selects between two connections
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Pushbutton Switch (N.O)
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Momentary switch - normally open
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Pushbutton Switch (N.C)
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Momentary switch - normally closed
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DIP switch is used for onboard configuration
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Relay open / close connection by an electromagnet
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Close connection by jumper insertion on pins.
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Solder to close connection
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Ground Symbols
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Used for zero potential reference and electrical shock protection.
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Connected to the chassis of the circuit
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Resistor Symbols
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Resistor reduces the current flow.
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Adjustable resistor - has 3 terminals.
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Adjustable resistor - has 2 terminals.
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Trimmer Resistor
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Preset resistor
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Thermistor
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Thermal resistor - change resistance when temperature changes
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Photoresistor / Light dependent resistor (LDR)
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Photo-resistor - change resistance with light intensity change
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Capacitor Symbols
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Capacitor is used to store electric charge. It acts as short circuit with AC and open circuit with DC.
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Adjustable capacitance
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Inductor / Coil Symbols
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Coil / solenoid that generates magnetic field
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Includes iron
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Power Supply Symbols
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Generates constant voltage
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Generates constant current.
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AC Voltage Source
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AC voltage source
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Electrical voltage is generated by mechanical rotation of the generator
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Generates constant voltage
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Generates constant voltage
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Generates voltage as a function of voltage or current of other circuit element.
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Generates current as a function of voltage or current of other circuit element.
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Meter Symbols
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Measures voltage. Has very high resistance. Connected in parallel.
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Measures electric current. Has near zero resistance. Connected serially.
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Measures resistance
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Measures electric power
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Lamp / Light Bulb Symbols
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Generates light when current flows through
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Lamp / light bulb
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Lamp / light bulb
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Diode / LED Symbols
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Diode allows current flow in one direction only - left (anode) to right (cathode).
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Allows current flow in one direction, but also can flow in the reverse direction when above breakdown voltage
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Schottky diode is a diode with low voltage drop
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Variable capacitance diode
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LED emits light when current flows through
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Photodiode allows current flow when exposed to light
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Transistor Symbols
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Allows current flow when high potential at base (middle)
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Allows current flow when low potential at base (middle)
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Made from 2 bipolar transistors. Has total gain of the product of each gain.
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N-channel field effect transistor
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P-channel field effect transistor
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N-channel MOSFET transistor
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P-channel MOSFET transistor
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Misc. Symbols
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Electric motor
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Change AC voltage from high to low or low to high.
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Electric bell
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Rings when activated
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Produce buzzing sound
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The fuse disconnects when current above threshold. Used to protect circuit from high currents.
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Contains several wires. Usually for data / address.
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Optocoupler isolates connection to other board
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Converts electrical signal to sound waves
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Converts sound waves to electrical signal
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Amplify input signal
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Operates with hysteresis to reduce noise.
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Converts analog signal to digital numbers
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Converts digital numbers to analog signal
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Used to generate precise frequency clock signal
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Antenna Symbols
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Transmits & receives radio waves
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Two wires simple antenna
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Logic Gates Symbols
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Outputs 1 when input is 0
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Outputs 1 when both inputs are 1.
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Outputs 0 when both inputs are 1. (NOT + AND)
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Outputs 1 when any input is 1.
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Outputs 0 when any input is 1. (NOT + OR)
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Outputs 1 when inputs are different. (Exclusive OR)
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Stores one bit of data
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Connects the output to selected input line.
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Connects selected output to the input line.
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