Hi,
I have five 28BYJ-48 and want to run them simultaneously exact the same way. Do I need to have 4 pins to each driver from the Arduino or can I address all five drivers with 4 pins in a 'bus' manner ?
It looks like you could drive all 5 motors in parallel by connecting the same wire from each one together but the resistance of each is 50 ohms so 5 in parallel will give an effective resistance of 10 ohms. 5 volts through 10 ohms is 500 milliamps so don't even think of connecting even one of the motors directly to Arduino pins, hence the need for driver(s)
You mention 5 drivers, but it would be better to use a single driver and power supply capable of delivering the required current. I have no idea how 5 separate drivers would behave with their outputs in parallel
Connecting them in parallel will also prevent synchronising their positions should (when) they get out of step
I have never done it but I suspect that connecting the 4 Arduino signal pins to the same inputs of all 4 drivers should work. It can't do any harm to try it.
I agree with @UKHeliBob that connecting the motors in parallel will prevent adjusting any individual motor.
With the usual ULN2003 drivers that are used with 28BYJ-48 motors the Arduino has to do all the work of generating the individual pulses on all 4 pins to get the motor to move. If you want a high step rate for all 5 motors it could be that a 16MHz Arduino could not work fast enough to control all 5 motors separately - especially if it also has other tasks to handle.
...R