On Monday 12 October 2009, Hubert Bahr wrote: >I measured the voltages across the potentiometers on both my X2 and X3 >they are both Harbor Freight machines. The X2 about 15 months old and >the X3 about 6 months old. The X2 had 12 volts on P1, varying >proportional to increasing speed on P2 relative to P3. The X3 had 7 >volts on P3, varying proportional to increasing speed on P2 relative to >P1. So both look like they can be controlled by the VFD outputs of the >Gecko G540. Other output pins can be used to control the direction and >power through relays. I am thinking that I might use the power relay to >also switch control from Manual to computer so I will want multiple >contacts or multiple relays working in parallel. This should not be >high duty cycle so standard coil and contacts should work. I think I >will leave the power switch in series with the new power relay so it can >be shutdown either place and the Manual switch must be engaged before >the computer can control the machine. I have never used solid state >relays, they sound interesting for higher number of switching cycles, >but that would be expensive to implement the cross switching, is it >worth it. I still need to research what I am going to do about estop. >I need to see how it is currently wired on each machine. > > Now for the feedback. What do you recommend to feed back the speed? >I would think that multiple pulses per revolution would aid faster >response. However, a single pulse per revolution would also serve as a >sync point for rigid tapping. Is this similar in character to the >recent discussion on threading? Which way is better, or do I need >both.? If multiple pulses, do they need to be 50 percent duty cycle? >I was thinking along the lines of an opto-interrupter reading cutouts on >a disk attached to the spindle pulley. I am looking to sync to speeds >over a range roughly from 50 to 6000 rpm. > >Thanks >Hubert
If threading is to be done, then emc must know the position of the spindle pretty accurately. The usual output format of a quadrature encoder, where the A and B signals are close to 50% duty cycle, and the switching edges of one phase are taking place pretty close to the centers of the stable state of the other, will give emc a pretty good idea where the spindle is. With the addition of an index pulse once per rev to tell emc when the spindle is at zero degrees, then it can do rigid threading. To drive the index pulse so it is sensitive to only one edge, one of the things discussed in that thread, one can develop a direction signal from the quadrature signals that would control the phase of the edge detector so the same physical edge of the signal is used as the index regardless of the direction its turning. Either edge of the hole could be used. As for the 6000 rpms, there was some math presented in the previous thread that would show what the limits were, given a perfectly symetrical set of signals that were also phased at 90 degrees. I currently have a wheel installed that I cut with the code I posted a day or so back, this is the code from the emc wiki page, and I note after I posted it, that I didn't adjust the comments although that code itself has been adjusted for fewer holes, on smaller circles. Cutting with a 1/16" bit, the holes are nearly round, and the index hole is actually more like a notch in the edge. There isn't enough room to get any fancier than that in a 7x12's head. It is installed between the two nuts that adjust the bearing pre-load, and I'll need smaller opto assemblies to pull it off, the LMC piece, since I'd need 3 of them, would be difficult to fit into the space available, so I'm still in the thinking out loud stage. >--------------------------------------------------------------------------- >--- 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 > -- 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> Practice yourself what you preach. -- Titus Maccius Plautus ------------------------------------------------------------------------------ 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
