On Saturday 24 August 2019 14:46:32 John Dammeyer wrote: > Hi Gene, > > > > > Yes, that encoder will run out of bandwidth trying to get thru > > > > that bobs opto-iso circuitry. So you are out the cost of at > > > > least a 5i25 which has at least 100x more bandwidth at its > > > > encoder inputs. I've had to cut and bypass the opto crap on the > > > > bobs several times now. I am a CET, but many machinists far more > > > > capable than I at turning cranks, wouldn't feel comfortable > > > > doing such hacking. > > > > > > Actually not a problem. Especially for the spindle. > > > > Thats 10k edges per rev, and 3000 revs, that 300,000 edges a second, > > and right at or slightly beyond the bandwidth you can shove thru an > > opto-isolater. Expect problems John. > > Not really. 3000 RPM is 50 RPS. With 50 revs per second * 10,000 > edges per rev is 500K edges per second.
Yup, been bit by that rpm to rps before. I knew it didn't look right when I hit ctl+renter. > Although the Bergerda drive, > using single ended opto is, spec'd to only 200Khz pulse rate the RS422 > input format is good to 1Mhz. I've already made the motor turn at > 3000 RPM using my Agilent programmable waveform generator set to a > output 5V waveform with 1uS wide pulses and 500kHz. And if I set up > the pulse multiplier I can reduce that. > > The PMDX-126 doesn't have opto for the step/dir outputs because they > feel most drivers out there already have that. Outputs do, at the drivers input. So in the $20 bobs, you find isolated inputs, but not outputs. > And there are lots of > opto's out there now that are more than fast enough. Single-Channel: > 6N137, HCPL-2601, HCPL-2611 Dual-Channel: HCPL-2630, HCPL-2631 High > Speed-10 MBit/s Logic Gate Optocouplers Ahh, yes there are, but finding a bob that actually uses them? Or a vender smart enough to know the diff? Sorry but hens teeth are much more plentiful. > > Here on the g0704, I have a 1000 line encoder on the rear of that > > 1hp 90 volt motor. At 1500 spindle revs, the multiplier is just > > above 14000/rev, so the input to the encoder is coming in at > > 21,750,000. which should have been 362,500, much more reasonable > > Its been run thru a couple rs-485 convertors, but the > > 5i25 is not haveing problems with it. Which amazes the heck out of > > me. But mama says shes hungry, and see that famous sign. Back > > eventually. Fed us both. Got all the patches & plugs off me, but not all the tape glue. Some of that will need to wear off. Nap time and maybe a shower would improve the air around me. Heart attacks don't always wait till you've showered. > A 1000 line encoder is 4000 edges per rev in quadrature but each of > the A and B are still only 1000 pulses /second. At 25 RPS, > (1500RPM/60) that's only or 25kHz. Not really all that high. All > depends on how the hardware handles the two phased signals. > > John > > > > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
