DC Power Supply For Multiple Steppers

Hello,

I'm helping my son in a project where he needs to drive 40 steppers. The steppers are 28BYJ-48, 4 phase, 5v.
Here's the data sheet:

Each motor has it's own ULN2003 driver. They are controlled by an Arduino Uno using a common signal since they
all move together, at the same time, same speed and same destination.

I can't figure out the correct DC power supply for this set up.
Appreciate your help.

This showed motor DC at .16A and .3A depending on how its driven. Supply 5V.

28BYJ-48

Regards, Dana.

That would need somewhere from 10 - 15A worst case, with every motor running.

However I'd advise doing load and speed tests on a single motor with a small 5V PSU, a wall plug type capable on anything over 1/2A.
Stepper motors tend to have quite high inductance coils and if driven from only their rated voltage, lose power dramatically as the stepping speed is increased.

The simple way around that is to use a rather higher voltage plus a resistor to limit the motor current to its rated value; eg. for those motors, a 12V supply and each motor fed via a 68 or 72 Ohm 2W resistor, to limit the current to around 100mA.

You may need a 12V supply for them to work properly, if moving at any real speed; the base speed given with 120Hz stepping (and 64 steps per turn) is only about two revolutions per second, from my interpretation of that data sheet.

(To put in in context, the motors used with 3D printers are often only rated something like 2V to 3V, but are run from 12 or 24V using motor controllers that regulate the current, as that's the only way to get reasonable performance from them).

Often stepper motors that are fed with a larger voltage, and the current is controlled using PWM. At low speeds, when the current in a winding has stabilised, the power will be turned on and off so that the average voltage will only be around the rated voltage, and the switching will be done so fast that the current changes little during each on-off cycle.

Thank you all for the info.
rjenkinsgb , already tried one and then10 motors with a bench power supply, all ok. But this will be a stand alone project so it need it's own power supply.
Yes much it is better on 12v but ULN2003 are old drivers and have no current adjustment. We could use the resistors as your suggestion but since the motors will run real slow, I think we can get away with 30W power supply, or better yet put in 2 of them to have a head room for the drivers too.

I'd aim for 10A as an absolute minimum, if you will be doing half-stepping. 6A should be OK with only full steps no more than one coil per motor at a time.

If you are not familiar with half-stepping, you power the next position coil as well as the present one for one interval, then turn off the previous and wait an interval, etc.
It gives twice the resolution without needing PWM control.

Great, I just ordered a 10A 5v .
THANK YOU.

If you require the maximum RPM from steppers, you cannot use a supply at the motor rated voltage, the inductive reactance of the motor increases rapidly as rpm increases, hence the torque rapidly drops, the modern way is to use a higher voltage than rated and use PWM in order to maintain the plate rated current of the motor. Which is important for maximum efficiency.
See such as the engineering notes on the Gecko Drives site.