On Sunday 11 October 2009, Steve Blackmore wrote: >On Sat, 10 Oct 2009 23:02:59 -0500, you wrote: >> The SX3 or Super X3 sold by Grizzley (G0619) does use the digital >>control. The X3 sold by Harbor Freight and also Grizzley (G0463) use a >>speed potentiometer. > >All are suitable for connection to an analogue input to control speed, >we've done it in testing. > >The problem is there are several different control boards, and motor >types. Certainly the early X1, X2, X3 types with DC motors had the pot >referenced to mains neutral. The later models with Brushless AC motors >have a VFD, and the additional board that is connected via a ribbon >cable is isolated. It still accepts a 0-10V analogue signal, from the >other board at the back of the up/down speed buttons and LCD readout. > >Whether isolated or not, it would be foolish to supply anything other >than signal from an isolated board like the following, for example > >http://www.cnc4pc.com/Store/osc/product_info.php?cPath=25&products_id=58 > >Steve Blackmore
That also would work nicely, however I think that VFD would be a miss-use of the 'lingo'. Those drive controllers are not feeding a variable Frequency to the motors at all. In the one that I'm using, I have always called it a VSD rather than a VFD because its frequency is semi-fixed and not related to how fast the motor is running. It functions as a switch, but uses a big hexfet to do the switching (I know, I blew mine and replaced it with an even better rated unit scavenged from an old PC power supply) so it is not married to the powerline frequency in order to turn off the SCR or Thyristor. Mine seems to run at a middle audio rate that is not synchronous with the line frequency at all, and does the speed control using a pulse width modulated scheme to turn the hexfet on and off. I suspect the X3 unit is pretty similar, with a better output stage. So in short, it should be called a VSD, not a VFD. A VFD would need a 3 phase motor, and made to run synchronous if it is to have usable torque at low speeds. Minor nit picking to be sure but there is a world of difference in the actual hardware. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) The NRA is offering FREE Associate memberships to anyone who wants them. <https://www.nrahq.org/nrabonus/accept-membership.asp> Bore, n.: A guy who wraps up a two-minute idea in a two-hour vocabulary. -- Walter Winchell ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
