On Wednesday, March 16, 2011 10:19:43 PM Kirk Wallace did opine: > 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/
Not all of those 'KBIC' like controllers are scr or thyristor based. The speed controller in my micro-mill is a high frequency switched Hexfet circuit. I have already blown the el-cheapo Hexfet that it came with, and found that a Hexfet from a defunct PC's PSU was actually a higher rated bug than the OEM version. Works like a champ, I ran it for about an hour this afternoon showing peak current to the motor that occasionally pinned the 1.5 amp full scale meter I built to watch it with, and over an amp for the overall average. > 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. In either event, as you say above, the control from the computer needs to be isolated, the KBIC and look-a-likes all seem to have line voltages on the control circuitry. I use a pwm signal for speed control, feeding a PMDX-106 interface. It works exactly as it is supposed to. > 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. -- 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) <http://tinyurl.com/ddg5bz> <http://www.cantrip.org/gatto.html> When God saw how faulty was man He tried again and made woman. As to why he then stopped there are two opinions. One of them is woman's. -- DeGourmont ------------------------------------------------------------------------------ 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
