32 bit controller recommendations

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rootboy
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32 bit controller recommendations

Postby rootboy » Wed Jan 24, 2018 10:22 am

Hi guys,

What's your recommendations on a 32 bit controller? One of the things that I am interested in is modular stepper drivers, not the on-board type.

So far, I've come up with the Panucatt Devices Azteeg X5 as being a likely candidate.


Thanks!

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Xenocrates
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Re: 32 bit controller recommendations

Postby Xenocrates » Wed Jan 24, 2018 10:41 am

Is there an actual reason you want the modular drivers?
Because I can think of several to avoid it. Heat dissipation through the drivers is done through the center pad to the PCB, not through the top of the package, so heatsinks are mostly band-aids, unless the driver board is designed to have a heatsink opposite the driver chip, strictly limiting the maximum current, and making them less capable and more prone to overheating, while the best of the driver chips available are best configured using serial interfaces, and the current standard pinout for modular drivers doesn't accommodate that, meaning that you won't have the features, like dynamic step modes, or stall detection, that are actually starting to get supported enough to be useful.

Beyond that, if you just want to use external drivers, the Duet family of boards all support remapping the axis to external drivers, and you could use either gecko or modular drivers.
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rootboy
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Re: 32 bit controller recommendations

Postby rootboy » Thu Jan 25, 2018 12:32 am

Well, the idea was to future-proof it where I could change them out. Plus, if I did toast a driver, unplugging it and slapping a new one in has the appeal of simplicity. Desoldering surface-mount chips, not so much...

And I had read where one choice of driver chip on one of the newer 32 bit boards was a bit of a disaster. So I wanted to avoid that too. And I don't think that I am drawing enough amps to really get concerned about any lack of heat dissipation.

But I do want stall detection, so I'll wait a bit to see what is coming up next. Things are working well, and there is no hurry on my part.


Thanks for your input! :)

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Re: 32 bit controller recommendations

Postby dc42 » Thu Jan 25, 2018 6:21 am

The Duet WiFi and Duet Ethernet already support stall detection, see https://duet3d.com/wiki/Stall_detection ... ess_homing. However, it is of limited use on a delta printer, because motors don't produce enough back emf at low speeds for stalls to be detected. On delta printers some of the carriages move very slowly some of the time, and even reverse direction during a single move.

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Re: 32 bit controller recommendations

Postby rootboy » Thu Jan 25, 2018 11:50 pm

Oh, so not so helpful. Thanks for the info! I'll stick with the removable type boards. Has anyone tried them on a delta? How well did the anti-stall work?

Thanks again!

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Re: 32 bit controller recommendations

Postby dc42 » Fri Jan 26, 2018 3:13 am

rootboy wrote:Oh, so not so helpful. Thanks for the info! I'll stick with the removable type boards. Has anyone tried them on a delta? How well did the anti-stall work?

Thanks again!


My comments on stall detection and deltas are not specific the the Duets. The TMC2130 drivers use exactly the same StallGuard2 feature as the TMC2260 used on the Duets. The fundamental issue is that when the motors are moving very slowly, they generate very little back emf, so the difference between a motor moving properly and a stalled motor is too small to detect.

Another issue is that high inductance motors generate more back emf than low inductance motors, so high inductance motors are probably better for stall detection. But high-inductance motors limit the maximum speed you can get with a given supply voltage; so for delta printers especially, low inductance motors are preferred.

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Re: 32 bit controller recommendations

Postby rootboy » Sat Jan 27, 2018 12:08 am

Stalling isn't a huge problem for me. Probably one out of every fifty prints has a layer shift. Like I said, no hurry. I just purchased .9 degree motors, so that's the next upgrade.


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