On Fri, 2011-09-30 at 10:17 +0100, andy pugh wrote: ... snip > I am not clear what you have here. Are you connecting the Opto output > direct to the speed control pin? Or do you have an RC network that you > haven't mentioned?
I have a direct connection. See attachment. I figured the VFD has it's own input filter. > Is the VFD designed for PWM input? No, the manual only shows a potentiometer on the analog input. > If not you may be using an input > filter cap as a PWM integrator. (and a series resistor on the input > might stretch the range for you, probably at the expense of > linearity). An input series resistor seemed to lower the range as if there were already an internal resistor to common, forming a voltage divider. > I designed a dual-opto push-pull circuit for PWM to (isolated) voltage > but as I have never tried to use it yet I am reluctant to show it > again. 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 Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA
<<attachment: VFD_speed_in-1a.png>>
------------------------------------------------------------------------------ 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
