Looking for an CNC xPro controller board

[Neale]

Seems a bit pessimistic! The AM882 claims to have TTL-compatible opto-isolated inputs, which sounds fine to drive with the ATmega chip on the Arduino board. Why put something else in between, unless it happens to make connections easier? Assuming it's a Uno board with a plugin cpu, worst that's likely to happen (and even then only as a result of a fairly significant fault elsewhere) is making the ATmega chip go pop. A 328P costs about £3, which is less than a typical breakout board!

The idea of cheap hardware plus open-source software giving better-than-PC performance for a fraction of the price of the cheapest motion controller is very attractive, and I would like to follow this one and hear how it goes.

[centurian]

OK mate
Was a bit over the top. But I'll stick with the GShield as its all I've got at present.

[Neale]

Ah, just done a bit of checking. I had assumed that the gshield was some kind of stepper driver interface. I now see that is a stepper driver card, aimed at lower voltage/power steppers than something like the AM882.

I'm not sure if your gshield is working, once the pins were straightened. If you have one of those in working order, then do you really need a whole new controller plus stepper drivers? Could you not use a cheap Arduino board to run grbl, and connect it to the gshield? I think grbl runs OK on an Arduino Uno, about £20 from Amazon. You would end up with something that's pretty well equivalent to the CNC xPRO, as far as I can see.

[centurian]

I was going to do it that way because I'd straightened the pins underneath the board so it connected to the Uno. I'll try it out on my desktop over the weekend and let you know the outcome.

Michael.

[IanS1]

Yes, only suggested the AM882 if the gShield was kaput but as it looks like it might be working OK I'd go with that.
.
The Arduino can certainly control the AM882, I think the drawback will be the speed of the 328P. I'm hopefully going to be trying it out with the GBRL firmware on a UNO this weekend. At the moment I have no intention of using this set-up in a final machine build, it's really just an experiment to see what the little Arduino can do.

[Neale]

Ian - the grbl wiki seems to suggest that even the uno (328P based?) can get up to 30KHz, which is pretty good going. Quick back-of-the-envelope sums suggest that with a 5mm pitch ballscrew and 800 microsteps, a 16KHz pulse rate would give 6m/min. That's a pretty good performance per pound out of the little 328P chip and even in terms of absolute performance is close to what I get from my LinuxCNC machine. Be interested to hear your findings.

[IanS1]

Arduino Uno with GRBL firmware controlling 3 AM882 drives with 3 NEMA 23 steppers.

It's a first test but it seems to be working very well.

Oh, I know, I know excuse the crappy wiring !!!

https://www.flickr.com/photos/43493290@N06/15837471613/