-----Original Message----- From: Kirk Wallace [mailto:kwall...@wallacecompany.com] Sent: Wednesday, March 16, 2011 1:23 PM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] Spindle speed control through G540 VFD output
On Wed, 2011-03-16 at 12:29 -0700, Michael Jones wrote: > I am about to start an upgrade to my system and am wondering if anyone has > already done this and has some pointers, or better yet, a detailed how-to. > I have a mini mill that's using a G540 controller run by the current version > of EMC. For spindle control, I'm already doing spindle on/off through EMC > with a relay. I would like to add the ability to control RPM as well. My > spindle is currently controlled through a pot connected to the P1,P2,P3 > ports of the speed control board and a hard switch for direction. > > I've heard/read that the physical hook up is easy but I'm wondering about > what I have to do in EMC (Hal and such) to send the right signals to the > G540 to make it, in turn, send the right signals to the speed control board. > > I'm just starting to explore this option and any constructive input would be > greatly appreciated. > Thanks, > Michael Many mini-mills have a DC or Universal motor for the spindle, these use an SCR speed controller like a KBIC: http://www.wallacecompany.com/machine_shop/kbic/ With this type of controller, the potentiometer that sets the speed floats with the KBIC's local 'ground' which can actually be a high voltage relative to the mains or normal ground. For this type of controller the potentiometer signals need to be isolated from other circuits due to shock hazard and circuit protection. I noticed the G540 manual indicates that the speed output signal is isolated but it is unclear as to what this means. If you have an SCR based speed controller, you will need to investigate this. I suspect an e-mail message to Gecko describing your speed controller will clear this issue up. If you really have a VFD controlling your spindle motor, there should not be a high voltage speed signal ground. Usually just controlling the signal from 0 to 10, 0 to 5 or -10 to +10 Volts DC relative to the input ground is all that is needed. Often this is created by having EMC2 output a PWM signal that switches the full signal voltage on and off in a way that effectively looks like an intermediate analog voltage. If you can post what VFD, speed controller and or motor you have, we can give you better information on how to deal with it. I'm not in the shop at the moment, but looking at the link you sent, It looks just like the KBIC. The Mill is a D&M4s - basically a Sherline 5000 series in an enclosure with their standard motor. 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? Thanks, Michael ------------------------------------------------------------------------------ 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
