On Saturday 15 March 2014 17:51:10 Peter C. Wallace did opine:
> On Sat, 15 Mar 2014, Philipp Burch wrote:
> > Date: Sat, 15 Mar 2014 22:27:27 +0100
> > From: Philipp Burch <[email protected]>
> > Reply-To: "Enhanced Machine Controller (EMC)"
> >
> > <[email protected]>
> >
> > To: [email protected]
> > Subject: Re: [Emc-users] I&$@)^ another C41 gone to hell.
> >
> > Hi Peter!
> >
> > On 03/15/2014 09:34 PM, Peter C. Wallace wrote:
> >> On Sat, 15 Mar 2014, Philipp Burch wrote:
> >>> Date: Sat, 15 Mar 2014 20:45:18 +0100
> >>> From: Philipp Burch <[email protected]>
> >>> Reply-To: "Enhanced Machine Controller (EMC)"
> >>>
> >>> <[email protected]>
> >>>
> >>> To: [email protected]
> >>> Subject: Re: [Emc-users] I&$@)^ another C41 gone to hell.
> >>>
> >>> Hi Gene!
> >>>
> >>> On 03/14/2014 09:23 PM, Gene Heskett wrote:
> >>>> Greetings again;
> >>>> [...]
> >>
> >> I can put the SPINX1 schematics up somewhere on Monday if it helps.
> >> Its designed for FPGA PWM (at 5 KHz) so would need larger capacitors
> >> for 100 Hz
> >>
> >> It uses a THS4281 (the TLV237x series is nice but has a pretty high
> >> output impedance so no better than ~.4V from rails with only about 2
> >> ma load)
> >
> > Good point, thanks. I didn't check that and I also do not know the
> > input impedance of the following circuit. But since it is an
> > industrial device, this should be far below 100k.
> >
> >> We get about 50 mv from the rails with a 10K load and better than 1%
> >> linearity at 5 KHz (Linearity would be a lot better at 100 Hz)
> >>
> >> Design is Fast OPTO --> pullup --> 4000 series CMOS gate for precise
> >> rail to rail PWM (OPTO is not) and CMOS has equal impedance both
> >> directions --> 2 pole filter --> THS4281 follower
> >
> > Yeah, never do the isolation in the analog part. It is so much harder
> > to compensate for all the effects of real devices if not only the
> > time domain must be concerned, but also the continuous amplitude.
> >
> > But an even better solution would be to stick to an all-digital
> > solution. Don't those/most drives have a digital setpoint input?
> >
> > Regards,
> > Philipp
>
> Sure most VFDs can use ModBus but isolated analog spindle controls are
> often used for KBIC type DC motor controllers or similar devices that
> are simple pure analog controllers. Analog (or some real time digital
> control) is also needed if its desired to close the spindle speed loop
> in linuxcnc.
>
That is already setup in my hal file Peter. Probably needs more fine
tuning for better low speed stiffness but... I never met a PID control
till LCNC. So I am a bit green, or wet behind the ears on the ultimate
tuning of the beast. That I believe IS the correct descriptive word too.
:)
> Peter Wallace
> Mesa Electronics
>
> (\__/)
> (='.'=) This is Bunny. Copy and paste bunny into your
> (")_(") signature to help him gain world domination.
>
>
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Cheers, Gene
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
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Genes Web page <http://geneslinuxbox.net:6309/gene>
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Learn Graph Databases - Download FREE O'Reilly Book
"Graph Databases" is the definitive new guide to graph databases and their
applications. Written by three acclaimed leaders in the field,
this first edition is now available. Download your free book today!
http://p.sf.net/sfu/13534_NeoTech
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