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How to connect 20 stepper motors to Raspberry Pi 3b+ ?

Posted: Tue Dec 18, 2018 9:52 pm
by bluebit87
I want to be able to control 20 stepper motors with a keypad connected to a Raspberry Pi 3b+ and an LCD Display connected to the same raspberry as well. When #1 is pressed on the keypad, motor 1 spins, #2 on keypad is pressed, motor #2 spins, etc. I don't need to control all or multiple motors at the same time, only 1 motor at a time according to each button pressed on the keypad. Since the Raspberry Pi 3 B+ doesn't have enough ports to control 20 stepper motors, what part or parts do I need to do this?

Re: How to connect 20 stepper motors to Raspberry Pi 3b+ ?

Posted: Tue Jan 01, 2019 12:52 am
by rzusman
You could use something like this: https://www.pololu.com/product/2971

And then connect the enable pin to a serial-in, parallel out shift register, or a port expander.

Re: How to connect 20 stepper motors to Raspberry Pi 3b+ ?

Posted: Wed Jan 02, 2019 7:02 pm
by ghp
In the datasheet DRV8880 the Enable pin is described to disable H-Bridge (which I assume will remove power from the motor, no hold torque available). Whereas step counter will remain active. So Enable pin is not perfect to 'cut off the chip from control signals'.
A demultiplexer like a 74HC154 could be used to deliver the signals to controllers.
What are the requirements for your motors ? Perhaps continuous rotation servo controlled by a PWM device like PCA9685 could help you ?