I need to calculate how much current my circuit gonna need in order to choose the right external battery to supply my arduino NANO, but I don't know how to do that so I'm wondering if somebody could help me with that.
OK, so I have 12 servo motors ( sg90 ), one ultrasonic sensor( HC-SR04 ) and a bluetooth module ( HC-05 ).
And if you wanna know, I'm actually making a Quadruped robot, it's gonna be controlled using an android app and the BT module, the US module role is to avoid any collision with something in front of the robot while walking.
The stall current of an SG90 is rated at 650mA. Your power supply needs to provide that times the number of servos that will be moving or holding a load at any time. For a quadruped robot that may be most or even all of them.
With that many servos you are going to need plenty of decoupling on the supply to stop the EMI ( Electro Magnetic Interference ) from constantly resetting your Arduino and interfering with the Bluetooth module.