Can I Power a Motor or Servo From the Arduino 5V Pin?

Short answer: usually no. The Arduino 5V pin is meant for small sensors and logic, not motors or servos.

Small sensors: OK
Single tiny servo at low load: Sometimes, but risky
DC motors or multiple servos: No

Why this is a problem

Motors and servos draw big spikes of current when they start or stall. The Arduino regulator and USB port cannot supply those spikes, so the board browns out or resets.

Safe rule of thumb

Rule

If it spins or moves, power it from a separate supply.

How to power a servo safely

Use a dedicated 5V supply for the servo.
Connect the servo ground to Arduino ground.
Connect only the servo signal wire to the Arduino pin.

That shared ground is critical. Without it, the signal has no reference and the servo will behave randomly.

How to power a DC motor safely

Use a motor driver or transistor, not a direct Arduino pin.
Power the motor from its own supply.
Add a flyback diode across the motor leads.

How much current can the 5V pin supply?

It depends on how you power the board:

USB power: limited by USB, often 500mA total for the whole board
Barrel jack or VIN: regulator gets hot quickly, practical current is much lower

Those numbers are for the entire board, not just your motor.

Bottom line

Use the Arduino 5V pin for sensors and logic. Use a separate supply for motors and servos, and tie the grounds together.