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Stacking multiple stepper bonnets on PI
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Stacking multiple stepper bonnets on PI

by gjpetryk on Wed Dec 01, 2021 4:17 pm

I need to stack 3 stepper bonnets to run 6 stepper motors. But the bonnets I received have sockets soldered in place and no through holes for the stacking header pins to pass through. How am I suppose to stack the headers? Do I have to remove the 40 pin socket from the bonnet first? How am I suppose to remove it and replace with stacking header?
From the Ada-Fruit Bonnet page: "In fact, you can even stack multiple Motor Bonnets, up to 32 of them, for controlling up to 64 stepper motors or 128 DC motors (or a mix of the two) - just remember to purchase 2x20 stacking headers."

Please help ASAP.

Thanks

Greg, of Systems Exclusive, Inc.

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Re: Stacking multiple stepper bonnets on PI

by adafruit_support_bill on Wed Dec 01, 2021 5:02 pm

To stack them, you would need to remove the existing headers and install stacking headers. Removal is easiest done with a hot-air station. Another approach is to just clip off the legs of the existing header.

An alternative to physical stacking is to connect them with jumpers. You would need to connect just GND, 3.3v, SDA and SCL.

What do you plan to do with the 6 steppers? One limitation of stacking many boards is that the combined step rate of all the motors will be constrained by the i2c bus speed (and Python communication overhead). If you need to move multiple motors concurrently at high speeds, there are better options.

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Re: Stacking multiple stepper bonnets on PI

by gjpetryk on Wed Dec 01, 2021 5:56 pm

Thank you for the reply and the information is helpful.

And yes, after my initial tests with one bonnet, stepper speed was degraded using python to move the motors.
I need to move qty 6 "Nema 8" motors, all together as they are used for positioning of the attached mechanical devices.
Would I be closer to my goal of "6 simultaneous steppers at highest speed possible" using individual stepper controllers connected to the GPIO ports?

Thank you also for the quick response! That was unexpected and I love it :)

Greg Petryk
Systems Exclusive, Inc.

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Re: Stacking multiple stepper bonnets on PI

by adafruit_support_bill on Wed Dec 01, 2021 9:34 pm

For high-speed operation, a step & direction stepper controller would give better performance. And if step timing (i.e. consistent speed control) is critical, then you would want to minimize your reliance on Linux & Python. The TIC controllers from www.pololu.com would be my choice in that case.

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