View Full Version : Need expert opinions, closed-loop, configurable, SPI compatible motion-controllers?

11-14-2015, 12:52 AM
Hello everyone! I hope all is well with you. I am a student, building several machines for a multitude of intended uses. Initially, the (arguably) most important, is milling printed circuit-boards. Elsewhere, many have stated, as some might here, I am trying too hard to attain quality. However, there is a reason for this. In my quest to learn more about electronics, I need to be able to perform rapid prototyping, affordably. I can't afford to order from fab houses, deal with shipping, minimum-orders, and especially, wait a month to see that I made a simple mistake. The use of chemical-etching is a no go. It's expensive, messy, hard to dispose of, gives varied results, and isn't ideal for extremely fine traces, which I will likely have when working with micro-controllers and FPGAs.With a quality CNC machine, I have seen others do some amazing things. I would like to also. The machine will roughly cost the same as several fab orders, so for someone like me with continued need, it is a no brainer. Also, I found a company that sells boxes of double sided PCB scraps, on eBay, cheap, and by the pound. I currently have about 50 lbs., ready to be used! So I've got a lot figured out; however, there are still some things that have become increasingly muddy, about what I need to tie what I have together

Essentially, I've worked out the mechanics for the chassis, power, most electronics, and the mechanical drive for the system. As a student, I was lucky enough to be given encoder samples, the AS5048A/B, from Austria Micro Systems, and also grab a few deals on other hardware. In the course of my web research, many have said that the 5-Phase motors, used in industry, are of no use to the home CNC builder/user/tinkerer. However, after doing some rather lengthy research, I eventually started up a conversation with a gentleman that was in engineering-support for Yaskawa-America. I forgot his name, and can't find his address after I changed email providers. However, he was awesome and very knowledgeable. After a little back and forth, (much appreciated) I came to feel that the 5-Phase motors did indeed suit my purposes. While the gain is small, (depending on intended use) I think the smoother stepping, with smaller stepping angle, is going to work best for my purposes. Any gain, regardless of size, is a good thing when accuracy is concerned. Additionally, as an avid eBay-stalker, I've found many sellers hocking used 5-Phase SANYO-DENKI, VEXTA, MYCOM, and other notable brands, at a pittance compared to equivalent (or usually much less than) 2-phased motors. So perceived possible quality, and cost, are contributing factors. One mans trash... right? Anyways, moving on.

I think what most people were stating, when saying the 5-Phase motors weren't usable, is that the 5-Phase motors require specialty stepper-drivers. They never stated that; however, I want to think that they believed 5-Phase drivers to be unattainable. Luckily, last week, I was able to attain three, RORZE branded, RD-053MS, Micro-stepping drivers. These are 5-Phase, 10-wire drivers, with 1/400 micro-stepping. While the 5-Phase output is different than a 2-phase driver would be, everything that makes these motors and drivers different, appears to be handled by the motor driver. They accept standard step/dir input. I was able to get the 3 drivers, with a very nice, included, large-heatsink, for $99.00. So that seemed a good buy. From the same seller, I grabbed two, small, 12mm leadscrew-assemblies, with RORZE-motors, and various bearings and so on. I think I gave $29~ each, for the two screw assemblies. From swapping parts, I have what I need here for my Z-axis: leadscrew, nut, bearings, collets, motor, mounts (very nice mounts) and nut. The screw is 18", and appears to have a very fine pitch, probably nicer than I could have afforded otherwise, so I'm thrilled with that as well.

A few other motor-pickups proved fruitful also, so my build will have nice, RORZE-branded motors, throughout. However, being that quality is a focus for me, and learning especially is (this fascinates me like nothing else, I admit) I really want to use the AS5048A, absolute, magnetic, rotary-encoders I was given. I was even given the necessary magnets. All I have to do is make a small breakout board and I'm good. However, what I can't seem to figure out, are what my choices are, for compatible, closed-loop, controller-cards.

After a lot of research, I've come to think my only options (to use exactly what I currently have) are from the Mesa-electronics line. However, even though I emailed their sales-team, I haven't received a response for recommendations. The AS5048A uses the SPI protocol for communication. Therefore, I need a configurable, closed -loop, card-based controller, that is both compatible with SPI, and allows me to used standard step/dir output. Additionally, and preferrably, will work with LinuxCNC. A bonus would be one that works with both LinuxCNC, and Mach, so I can do comparisons.

I'm not stuck on LinuxCNC, but being a student, and getting a provem, high-quality system, at no software-cost, seems the right option. I know that the Mesa line of cards, well the several that I read about, are indeed compatible with LinuxCNC. Now what I need, is to figure out exactly which one will allow me to use what I already have, and achieve the best results.

I know that my set-up, and my peculiarities, are probably unusual; however, I need some expert advice. If anyone has any knowledge of these cards, and especially thoughts pertaining to my goals, please let me know. I appreciate your time and I'm glad to be a part of this forum. If somewhere I am mistaken, or showing ignorance, please let me know. Learning is the goal. Take care.