On Monday 26 October 2020 14:56:37 Gene Heskett wrote: > On Monday 26 October 2020 14:16:55 Chris Albertson wrote: > > This is hard to follow because you are referring to pin number on a > > PCB with no schematic. How do these relate to the pins on the > > driver chip? > > Ahh, but the schematic is downloadable from the olimex site. Printed > in color on glossy photo paper its an excellent drawing. Get it from > <https://www.olimex.com> > > > Also, 10 KHz is at the limit. For initial testing better, I think > > to work near the midpoint of the acceptable range, perhaps 1KHz. > > Then after it works sneak up on the max. > > > > 20% PWM duty cycle and a 24V power supply is about 4.8 volts to the > > motor. Many DC motors will not move at 20% of rated volts. I'd not > > be surprised if it took 10 or 12 volts to overcome internal > > friction. Motion control is always the hardest to make work at the > > slow speed end. The motors all take a high voltage to "break free" > > and then run too fast so you have to slow them below the break free > > voltage so make them run slow. This is why we have PID and > > encoders and why PID tuning is hard. > > Agreed. Unforch I can't run the mesa pwmgens at different speeds, and > the other one is running the spindle. But I'll try a kilohertz just > for S&G. > > > A trick is to use a power supply that is a bunch higher than the > > motor's rated voltage and let the control logic do whatever it takes > > to drive the motor to its set-point. > > But this driver only has a 40 volt 30 amp limit. I do have higher > voltage sapplies that would foldback at the currants involved. > > > All brushed motors have brushes and hence friction. You can use > > BLDC but they cost more. (note that a stepper is a type of BLDC. > > > > What will make this work is that I doubt an index table needs to > > spin fast in both directions and start and stop with high > > accelerations. Set the speed and acceleration limits in LCNC > > way-slow. > > Thats assumed since this motor is a worm drive, 220 rpms at 24 volts. > And it will be driving the worm in a BS-1. But first it needs to move > laying on the mills table. I'll sneak up on the pid's Pgain. And it > didn't trip from following error as I've set that way up until I get > the encoder hooked up. Which has not been done just yet. > > > On Mon, Oct 26, 2020 at 10:48 AM Gene Heskett <ghesk...@shentel.net> > > wrote: > > > On Sunday 18 October 2020 22:21:11 Chris Albertson wrote: > > > > > > Advice on the OLIMEX board for a motor driver. > > > > > > I have it wired up, I think. Grounded to system ground on pin 3, > > > system logic 5 volts on pin 2. > > > > > > With complementary 5 volt dirs feeding ENA/ENB on pins 4-5 and a 5 > > > volt pwm on pin 6, the motor on its terminals and a 24 volt psu on > > > its set of terminals, pins 1-7-8 aren't connected. It will bring > > > up the leds according to the dir sigs, modulated by the % of pwm. > > > The motor is not moving at up to about a 20% pwm at 10 kilohertz, > > > and above 20%, it disables the outputs until a powerdown is done. > > > I'm switching all the motor power off with the f2 key, so 15-20 > > > seconds off to let all the switchers bleed off seems to reset it > > > ok. Pins 7-8 are sitting just a few millivolts above ground which > > > looks duff to me since they have 3.3k on-board pullups to the 5 > > > volt line. But thats how it powers up. > > No comment?
Not needed, I just uncovered a printout of the pdf, which clearly states the two diag pins must be pulled high. See the top of page 7. So that is mistake #1. There are likely more. The .hal file is 17 landscape pages long, 100% out of my ancient wet ram, and I have famously fat fingers. > > > It does warm up when the output direction leds are lit, but > > > nowhere near too hot. So I'd assume some current is flowing, just > > > not enough to move the motor. > > > > > > Obviously I'm doing something wrong, but what?. Do I need +5 volts > > > fed to pins 7-8? > > > > > > I am NOT impressed with the pushbutton terminals OLIMEX uses, they > > > do not grab a wire heavy enough to carry the expected 10+ amps of > > > currant to keep a good connection if the wire moves. And its > > > damned sure NOT a long term gas tight joint. I may yet pull them > > > out and replace them with the green screw terminal plugs. > > > Something I can put some serious torque on. > > > > > > The 150 watt audio class D can make quite an effective hand > > > massager out of this motor at 20 hz, its dc powered and doesn't > > > get warm doing it. The 430 watters need an AC supply, and don't > > > work at all with DC from this supply fed to its FW bridge power > > > input, so apparently it needs a balanced + and - supply. Either > > > would need a d/a to feed a bypass the input hf pass filter that > > > wants to protect the speakers. But other than a spinx1 that would > > > be too slow, I don't have a D/A to drive them with. But its a > > > thought and the 150 watter can seriously hammer that motor. So > > > thats a potential what if. :) > > Thanks Chris. > > Cheers, Gene Heskett 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
