Only small loads such as an LED with a resistor or a logic input. Each pin and the board as a whole have current limits in the maker’s documentation. Motors, relay coils, long LED strips and servos need their own supply and a driver, not a pin.
A microcontroller pin is a signal, and it can only supply a small current.
Pin and board limits
The board maker publishes a maximum current per pin and a total for all pins. Exceeding either can damage the chip. The 3.3 V and 5 V pins on a board also have limits, set by its regulator and USB supply.
Loads that suit a pin
An LED with a current-limiting resistor, logic inputs of other chips, and small sensors within the board’s published limits.
Loads that need a driver
Motors, relay coils, solenoids, servos, LED strips and heaters draw more current than a pin provides. They use a transistor, MOSFET or driver board switched by the pin, and a separate supply rated for the load, with the grounds connected.
Protection
Flyback diodes across inductive loads, fuses on higher-current supplies and correct wire gauge protect both the board and the wiring.
Where the figures come from
The board maker’s documentation and the datasheets of the parts in use. For anything connected to mains power, the component makers’ ratings and instructions apply, and a hobby breadboard is not the place for it.
Questions makers ask before buying
Can a servo be powered from the board’s 5 V pin?
Small servos sometimes are in examples, but servos draw current spikes that can reset or damage a board. A separate supply with a shared ground is the common, safer arrangement for the board.
What is a flyback diode for?
Motors and relay coils generate a voltage spike when switched off. A diode across the coil gives that energy a path, protecting the transistor or driver switching it.
Last reviewed 15 September 2026