# Interesting controler



## 8ntsane (Apr 21, 2013)

Interesting controller for stepper motors

http://www.pc-control.co.uk/stepperbee_info.htm

Anyone here have any experiance with this product?
Looks like it would have uses on a motorized rotary table, or ?


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## DMS (Apr 21, 2013)

Looks like an interesting idea, but I would have a few reservations  in using in a CNC machine

1) Not much power output, max current is 500mA. Maybe for a 4th axis it would be enough. I would be happier with something closer to 2, better yet 3A.
2) It's USB definitely not going to work with LinuxCNC
3) Has a custom programming interface, maybe somebody has written a driver for Mach3? I didn't see anything about that though.


If you can't find a driver for Mach, you're either going to be be writing your own driver, or writing your own controller, neither sound fun to me. Prices aren't bad though.


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## JohnAspinall (Apr 22, 2013)

*LinuxCNC realtime vs non-realtime [was: Interesting controler]*

Warning: thread drift ahead.



DMS said:


> Looks like an interesting idea, but I would have a few reservations  in using in a CNC machine
> ...
> 2) It's USB definitely not going to work with LinuxCNC
> ...



So I got curious about this restriction (no USB with LinuxCNC), and read more about it here:
http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Emc2HardwareDesign .

That prompts the following question:  Can the realtime parts of LinuxCNC be separated from the non-realtime parts?
It seems like LinuxCNC has some nice parts that do not require realtime service.  (_E.g._ the basic G-code interpreter, trajectory planning, ....)
Suppose you've got a nice machine controller that implements the control loops internally?  Can LinuxCNC be configured with much more "relaxed" realtime requirements?
(I won't say no realtime requirements, but let's say orders of magnitude slower.)


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## DMS (Apr 22, 2013)

There have read some speculation about whether this is possible or not. The hard part (as I understand it) is that you need a real time driver for whatever you want to control in a real time fashion. USB was never designed to be a real time interface. Mesa has a card that works over ethernet, which may solve a lot of the issues that typically drive people to USB. 

I hear a lot of people on either side of the Mach/LinuxCNC debate (might I call it a "holy war") say Mach is superior because it can use USB, or Linux is superior because it uses a hard real time kernel, and USB is crap. Ultimately they are  two very different pieces of software designed in totally different ways to do approximately the same thing. Keep that in mind. For example, SmoothStepper doesn't work with LinuxCNC, which is a gripe, but if you have a smoothstepper, use Mach; it's what the SmoothStepper was designed around. If you want to use LinuxCNC, then don't buy a smoothstepper, for hardware acceleration on LinuxCNC, Mesa cards are a better choice (I recently upgraded, and couldn't be happier). 

As far as getting USB support in LinuxCNC, maybe it's possible. Would performance be good enough to make it worthwhile? I don't know. I have a feeling somebody has done it, even if it is not in the official version. 

I still think these little cards are too underpowered for  a mill or lathe, though they might be interesting for a 3d printer or hot wire cutter.


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