On Fri, 30 Sep 2011, Karl Cunningham wrote: > Date: Fri, 30 Sep 2011 10:24:49 -0700 > From: Karl Cunningham <ka...@keckec.com> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] VFD Speed Input > > On 09/30/2011 09:27 AM, Kirk Wallace wrote: > [snip] >> The only reason I was thinking about a push-pull (half bridge) is >> because it would incorporate the common terminal. >> >> I haven't connected my oscilloscope to the VFD terminals yet, this may >> shed some light on how the input works. I suspect for an SCR speed >> controller, the input provides a voltage level for triggering the SCR, >> but for a VFD it may be a PLL or "Maybe it's something really cool that >> I don't even know about" (tree of trust). > > Kirk, > > You might try a pull-down resistor between the analog input and common > of the VFD. Is there an input resistance (impedance) spec on the VFD? Of > you could put an op-amp voltage follower in between the opto and the > VFD. You'd have to use a pull-down resistor on the input of the op-amp. > Only trouble is if you don't have a -15V supply to run the op-amp, you > have to use one that can drive to the negative rail and tie it's -Vps to > ground. > > Karl
Thats basically what our 7I47S analog spindle output circuit is like: Fast OPTO with pullup --> 4000 series gate so we accurate full scale V- V+ swing with push-pull drive --> 2 pole filter --> rail-rail OP amp buffer all powered from V- and V+ (pot ends) > > ------------------------------------------------------------------------------ > All of the data generated in your IT infrastructure is seriously valuable. > Why? It contains a definitive record of application performance, security > threats, fraudulent activity, and more. Splunk takes this data and makes > sense of it. IT sense. And common sense. > http://p.sf.net/sfu/splunk-d2dcopy2 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ All of the data generated in your IT infrastructure is seriously valuable. Why? It contains a definitive record of application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-d2dcopy2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
