On Thursday, April 12, 2012 06:35:38 AM Rolf Bredemeier did opine: > Hi all, > > I do not know if it is customary to thank here, but: > > many thnaks for the answers from so many users! Special thanks have to > Gene, the long message must be a lot of time, but also very > interresting. > > @Gene: you wrote, your wheel hast 39 slots. But when i am count out the > picture disk4.jpg from your site, i count 45 slots? And why an odd > number of slots? I think, for maths on a computer, even counts are > easier for him? Because divide/multiply can than do by shl/shr? > > Best regards, Rolf
Damn, I posted the wrong picture! Just call it a demo of what it should look like. I never thought anyone would go to the trouble of actually counting slots! The posted ngc code that carved it is I believe correct. Yes, I just checked "genes-encoder.ngc" and it is correct at 39 slots. That 39 was derived by checking the 45 slot version, finding that I couldn't push the opto units far enough sideways to get the correct timing given the .050" granularity of where you can put them in eagle, and doing a little math with a mind to moving the A/B timing into a better quadrature while also equalizing the waveforms to as close to a 50% duty cycle as I could get. That number of slots, with the hal line that enables X4 full quadrature position decoding, works well at an estimated spindle speed of 2500 rpms. This on an Intel D525MW mainboard computer running a 19.9 u-second base- thread. This 39 slots gives an update of the spindle position every 2.3 degrees of rotation, which should be more than accurate enough to cut a 1/4-28 thread, which will be in the first job I actually try to carve with it. There is a hal pin that shows the spindle speed in revs per second, and given the quantization inherent in the 19.9 u-s sampling, shows a rather noisy 41 rps with the spindle running wide open so this mobo will apparently not have any great amount of trouble keeping up. There is a lowpass function available in hal which I haven't yet wired in but which can denoise that reading by averaging it over the last X timing samples, and which should be able to smooth that for display purposes. I likely will not use it for control purposes as the mass of the chuck and motor will smooth that even if the control is wobbling about 20% in drive in any one rotation. That speed of course isn't usable in the real world as other than a bit of sandpaper polishing, I have never reached for the gear shift lever. One could I suppose actually turn metal at that speed, given another 10 hp worth of drive motor and active flood cooling. Neither of which I have of course. :( I might eventually build a mister, but its removal from the air in that small building would be an only warm weather usable item. Its a 12x16 garden shed kit, no insulation & just enough electric heat to break the chill & keep it above the dew point so stuff doesn't rust. Hindsight being 20-10 or better, I should have done 2 things when I built that building for use as a woodshop back in 1998, I should have poured a flat cement floor, this one is sagging 6" in the middle now because there is close to half a ton of stuff sitting out in the middle of the floor, and it should have been insulated from the gitgo. But since I am now 77, & diabetic, I don't want to spend the rest of my allotted time figuring out where to store those tools while I tear this one down and do it over again. I'd druther be making swarf with what I have. :) 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) My web page: <http://coyoteden.dyndns-free.com:85/gene> Harrison's Postulate: For every action, there is an equal and opposite criticism. ------------------------------------------------------------------------------ For Developers, A Lot Can Happen In A Second. Boundary is the first to Know...and Tell You. Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! http://p.sf.net/sfu/Boundary-d2dvs2 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
