On Thursday 30 November 2017 13:29:05 Gene Heskett wrote: > On Thursday 30 November 2017 10:27:39 andy pugh wrote: > > On 30 November 2017 at 14:13, Gene Heskett <[email protected]> > > wrote: > > > Yes, and its math I should have explored, but I had no clue that > > > there was that big a geardown in the head, even in high gear, > > > before I ordered that 1000 line encoder. That says the motor, > > > running wide open, is turning about 20 k rpms. > > > > There is something very wrong with your maths still, I think. > > > > Your 7000:1 gear ratio is simply wrong. I think you divided > > revolutions by counts (I recall you saying that encoder resolution > > didn't matter, but you were using rawcounts, so it most certainly > > does). > > So, a 1000:1 error there. (There isn't _room_ in the head for a > > 7000:1 gear ratio) > > > > Also, you keep confusing RPM and Revs Per Second. > > That too, but I have a new problem now, and need an answer to 2 > questions. > > 1. is the feedback signal in phase or out of phase with the command? > 2. and this is for Jon. > > I have a fixed gain scale setting that prevents the pwm from exceeding > a 98% duty cycle. The pwmgen is running at 20 kilkohertz, and when the > pid is outputting 46 something it is up against this limit, with a > 1.06 u-sec recharge time. The data that you get from the Pico site > says half a microsecond is needed to recharge the gate drivers. So > this should be enough. The 12 volts is nominally 11.6. > > BUT, its sitting out there right now at that minimum of 1.06 > microsecnds off time, with the spindle turning about .8 rps. It ought > to be at 3 grand. > > Clicking fwd, no reaction, add a + button click and it hits that 3 > grand in about 1/2 a second. 30 seconds later it starts to slow, and > in another minute its down to about .8 rps and running steadily. Motor > is seeing a noisy 2 volts, and it has almost zero torque. > > While this is "percolating", I'm going to reduce that scale, wideing > the off time to see what effect it might have. > > Cheers, Gene Heskett
Now this is weird. Reducing the drive to hm2_5i25.0.pwmgen.00.value, widening the low portion of the waveform, actually increases the speed very slightly. Put a halmeter on that pin, it starts out from a cold stop, getting fed a value of nominally .14. That spindle starts wide open, and actually slows slightly when the input from the pid has caused the value to exceed 5. So I think I've putzed around and blown the pwmservo's input somehow. I haven't looked to see what chip that may be yet. Probably best if I get Jon to fix it anyway. But lets see what John thinks before I unbolt it... Maybe he has something else to test. 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
