Where to start with steppers and stepper drivers?

Using Arduino Motors, Mechanics, Power and CNC
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And look at Multistepper under the Classes tab as well.

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Bunch of motor drivers needed no matter what. How many IO pins for each one? 4?

As unipolar stepper 4 pins per motor will then lead to 120 pins ..

Defining & Configuring Motors

AccelStepper mystepper(1, pinStep, pinDirection);
A stepper motor controlled by a dedicated driver board.
AccelStepper mystepper(2, pinA, pinB);
A bipolar stepper motor controlled by an H-Bridge circuit.
AccelStepper mystepper(4, pinA1, pinA2, pinB1, pinB2);
A unipolar stepper motor, controlled by 4 transistors.

So, using bipolar steppers would cut the needed control pins by half, but 60 is still quite a number (-> port expander needed or coupling two Megas).

The simulator is just a fun project, it will probably be in my room

Would be interesting to get to know the sound level when all of the babies are humming at the same time (as I said these cheap motors are very noisy).

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scottyjr:
Perhaps these. - Scotty

Definitely those. That's exactly what they are designed for.