Hello , i am planning to create an open door project using arduino ,5 servos and 5 ir sensors , it seems my arduino mega cant provide enough current for all my 5 sg 90 servos , in this case should i use an external source for them and what parameters (voltage, current)should it have?
You must use an external source.
According to a data sheet 4.8 to 6.0 volts.
And from my experience a minimum of 1A per servo, so 5A.
Don't forget to connect the external power supply Gnd, and the Servo Gnd, to the Mega Gnd.