Symbols Used to Represent Common Components

I/O board pin

This symbol represents an I/O board pin. If it is a specific pin it must include the pin number or specification if it is a binary, pwm or analog input pin.


This symbol represents a power supply, showing the positive and negative terminals.


This symbol represents a cell battery, like thos 9V batteries used in electronic devices or toys. Batteries can be found with different voltages, sizes and duration depending on the application or use.


This symbol represents a ground connection. It is used to show that whatever is connected is attached to the ground terminal of the power supply.


This symbol represents a resistor. It resists the flow of electricity on both directions. Resistance is measured in Ohms, usually its value is next to the symbol.


This symbol represents a capacitor. It is a device that temporarily stores electric charge. Capacitance is maesured in Farads, which is a big unit, usually micro-farads (uF) or pico-farads (pF) are used. They also indicates tha maximum voltage the circuit can run at.


This symbol represents a generic lamp like those found in flashlights. Lamps have different ranges of voltages at which they work properly.


This symbol represents a diode, which is a semiconductor device that conducts electricity in only one direction.

Light-Emitting diode (LED)

This symbol represents a Light-Emtting diode, know as LED, it is a special kind of diode that emmits light when electricity flows in the direction indicated. They are offered in a variety of colors and forms and are the most common indicator in electronics. It has a very low resistance in its conducting direction, so a small resistor (between 100-470 ohms) is needed to connect it to a 5V power supply.


This symbol represents a push button or pulse switch. It is normally open and it is closed when the user presses it.


This symbol represents a contact switch. It has a ON and OFF position to close and open the circuit.


This symbol represents a potentiometer, which is resistor that can change it's resistance value from zero to the maximum specified in Ohms. It is also called a voltage divider.


This symbol represents a photoresistor. It is a special resistor that changes its resistance value according to how much light is received by its surface, it is also known as light sensor.


This symbol represents a transistor which is a switching device. The one shown in the diagram with the arrow going out is a NPN transistor, if the arrow is going in it is a PNP transistor.


This symbol represents a metal-oxide silicon field-effect transistor (MOSFET) which is s special kind of transistor switch, used to handle higher loads than the microcontroller can by itself. Logic-level MOSFETs can be connected directly to a I/O board output pin.


This symbol represents a coil, relay, a pneumatic or hydraulic valve or solenoid. When power is applied to it, it generates an electro-magnetic field which atracts some metal part to generate different effects.


This symbol represents a generic DC motor. It is very important to consider factors like voltage, power consumption, torque before deciding which motor to use. Motors can not be connected directly to a I/O pin, the need to be interfaced with a MOSFET or with a special motor driver chip.