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? > > 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 -- "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
