How to determine the required power for arduino?

Question

Arduino

Hello. There is an arduino to which a relay, a motor, a radio module and a couple more sensors are connected. How to determine what voltage to apply to it so that everyone has enough? How is it connected in parallel or in series? All sensors and the motor are powered directly from the arduino.
UPD: When I power the arduino via the USB of the computer, everything works fine. And when through the charger for the iPad (5.2V, 2A), the relay goes crazy and quickly turns on and off ...

Answer 1

See InputVoltage: www.arduino.cc/en/Products.Compare
5.2 V is probably not enough.
The voltage on them will not change from the number of connected devices, but if there are a lot of them, the current may not be enough.