> -----Original Message-----
> From: Roland Jollivet [mailto:roland.jolli...@gmail.com]
> > Now. Why is it not available? Two reasons. The key thing about the
> > STMBL for 3 phase AC servos was that it used single driver for all three
> > windings. Probably originally designed for washing machines. It was
> > discontinued. A different one with slightly lower power was available.
> > There are others but different pinout so board change.
> >
>
> Yes, the same style driver chip found in all the chinese drives too. A
> 27pin PDIP
> I opened a Chinese drive up and it looked to be a text-book implementation
> of one of these drivers. With very little noise suppression though.
>
There are a number of different devices out there like that. What makes them
nice to use is the current sensing for each winding is also built in so it's
easy to do all the control stuff.
But when a supplier discontinues a device it requires a change to the PC board
and possibly the software. The STMBL was created to have drivers for the
designers' machines. Add to that, as Andy mentioned, the smart-serial control
which most AC servo drives to not have, makes the STMBL a pretty special piece
of hardware.
But the designers were not in the business of creating motor drives. I got my
STMBL boards from Andy when the transitor drivers were still available. Now
the processors are back ordered. Of course a different processor, if available,
could be used. But then again someone has to modify the software and the PC
board. And be able to do all the testing to make sure it works.
This is the fundamental issue with Open Source Projects. Once the designers
are done and have their systems functional, (along with a half a dozen spares
perhaps), there's no incentive to make more or redesign. That they still
provide support is amazing and fantastic.
Look around now and it's not just MACH2 and EMC (now LinuxCNC) but there are 4
or 5 different CNC software systems out there, if not more. So the
smart-serial for a CNC system that is 20% or less of the CNC market place is a
lot of work. Probably why you don't see it on any of the Chinese drives.
And now we have closed loop stepper drivers and motors. Easy to mount on small
mills and lathes with more reliability and other than retro-fit what is the
real market for the STMBL? Especially for small milling machines and lathe
with 3 or maybe 4 axis.
So when the processor is a year or more before delivery, the driver module has
been discontinued, there is no single manufacturer making them because it's
open source, the STMBL is a great idea but not available.
In the same manner the HP_UHU DC servo, even with Henrik Olsson's microchip
processor upgrade is dead in the water unless someone does a new board run with
the latest revisions. I have the Altium CAD files and even DC motors but
nothing to mount them on that isn't already controlled with an AC servo. So
very little incentive other than just for fun to create a new HP_UHU with parts
that are available. Some of the DIP parts have been discontinued on it too so
the board layout 'tweak' isn't trivial.
John Dammeyer
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