Hi, Yes, the three VFD terminals of the G540 are isolated. You can use these VFD wires to connect to a VFD or DC motor controller in place of where the speed control potentiometer would go.
Engineering note 10 on this link shows a schematic of such a G540 setup. http://homanndesigns.com/store/index.php?main_page=page&id=3&chapter=0 As to the PWM base frequency required, anything above 50Hz is required. Somewhere around 1KHz would be ideal. Cheers, Peter. Kirk Wallace wrote: > On Wed, 2011-03-16 at 21:05 +0000, andy pugh wrote: >> On 16 March 2011 20:50, Michael Jones <[email protected]> wrote: >> >> > And yes, the pot is isolated as you've said. >> > >> > Does this mean that this upgrade is a "not recommended" or possibly >> > hazardous direction, or just that there's more I need to do besides >> just >> > hooking up the VFD output pins from the G540 to make it work >> > correctly/safely without breaking something? >> >> It should be fine, but you need to know how "isolated" the VFD output >> is. >> I had a KBIC speed controller and the low side of the pot was held at >> +Motor voltage (100V) >> The VFD output has it's own GND terminal, which is a good sign. >> >> http://www.cnczone.com/forums/gecko_drives/88165-g540_vfd_output_floating.html >> Has a comment from Mariss (who is Mr Gecko) saying that it will be OK. >> > > "The analog output is optically isolated from both the G540 and the PC. > - Mariss" > > This quote doesn't instill much confidence, but it seems that the G540 > terminals 7 Ground, 8 Output, 9 +10V are isolated from the Gecko circuit > and float. I am guessing these terminals are implying a potentiometer > like function in the G540. The +10V terminal is were you would connect > the +10V output from the KBIC to a potentiometer. Ground connects to the > ground from KBIC potentiometer terminal for the far end of the > potentiometer from the +10V. Then the output terminal (8) and an EMC2 > digital PWM signal go to the potentiometer wiper. > > Current > KBIC > --------------- > GND Wiper +10 > | | | > | V | > +-----------+ > Potentiometer > > New > KBIC > --------------- > GND Wiper +10 > | | | > | | | > GND OutP +10V > 7 8 9 > G540 > ^ > | > Parport 14 > > The wiper will be controlled by the EMC2 PWM on parallel port pin 14 VFD > PMW (50Hz). See here for the EMC2 HAL setup: > http://linuxcnc.org/docs/html/examples_spindle.html#r1_2 > > The PWM frequency will be determined by the thread rate that the PWM > component is loaded in - usually the servo thread or 1kHz (?). The G540 > doc hints at 50Hz, but I think it will work anyway. This is off the top > of my head, so check the above for yourself. > > I suspect you could wire the terminals directly, but there is a > possibility that current limit resistors might be needed somewhere. > -- > Kirk Wallace > http://www.wallacecompany.com/machine_shop/ > http://www.wallacecompany.com/E45/index.html > California, USA > > > ------------------------------------------------------------------------------ > Colocation vs. Managed Hosting > A question and answer guide to determining the best fit > for your organization - today and in the future. > http://p.sf.net/sfu/internap-sfd2d > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------- http://www.homanndesigns.com ------------------------------------------------------------------------------ Colocation vs. Managed Hosting A question and answer guide to determining the best fit for your organization - today and in the future. http://p.sf.net/sfu/internap-sfd2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
