On Wednesday 02 October 2019 23:41:38 Brent Loschen wrote: > On 10/2/2019 7:18 AM, Gene Heskett wrote: > > On Wednesday 02 October 2019 00:36:41 Brent Loschen wrote: > >> <https://www.ebay.com/itm/Mini-Peristaltic-Pump-Head-With-Tube-Smal > >>l-F > >> low-Stepper-Motor-OEM-Package/273419600046?hash=item3fa91400ae:g:h1 > >>MAAO SwMdZbe77a> > > > > I sorta went crazy, ordered two kits of telescoping brass tubing to > > help make better, smaller nozzles. I can solder up a 1/16 od, and > > redrill it at #80 to get an even smaller tip. Then off this link, > > which takes a short nema 42 motor with a 10mm shaft (no way do I > > have a motor that big), but I did find a 12 volt rated peristaltic > > that looked usable at $6.32/copy. So since even the silicon tubeing > > has a limited lifespan in service of only a year or so, I bought 4 > > of those. But they're in china, so a Nov 1 estimated delivery date. > > Spit. > > If you check out the mechanical drawing of the pump in the link above > (last thumbnail to the right), it appears to have both 31mm and 47mm > c-c mounting holes which match NEMA 17 and 23 steppers respectively.
The only mech specs are at the bottom of the page, and say a nema 42 with a 10mm shaft to drive it. But thats usually a smaller nema 34, the two 34's I have have 15mm shafts, but are 960 and 1600 oz-in motors, and still way too big physically, adding considerable weight to the gantry if mounted there. I think I can pwm over at least a 10/1 ratio using the ones I've bought. SW is cheap, even a nema 23 is 35+ bucks, and weighs 10x what these do. I may be wrong, have been before, but you'll see it here when I am. > Not sure why they reference a 42 motor which has a larger bolt pattern > (89) than the overall dimensions of the pump (57)! > Although it would be nice to have adjustable spring tension on the > pinch arm to accommodate a wide range of pump tubing, it's hard to > beat the price ($13 delivered) for a 6 roller pump. Precise speed > control of a stepper should be a lot simpler than to PWM a DC motor. > Would it be possible to treat that pump/stepper as a joint and set the > RPM via feedrate in Gcode? Yes and no. We can name the signal anything that doesn't clash with LCNC, and set its speed in gcode, but I suspect it would involve some pyvcp to set the speed if we want to vary it from the gui. By useing one of the motion.analog i/o's to get it into hal. Set up an on cycle just long enough to move the pump 2 or 3 degrees, and leave it off for a pyvcp interval. With a hard enough bang, the on time needn't be more that 2ms I'd think. 10 such pulses a second ought to be smoothed somewhat by the hose to the mister, giving a reasonably continuous mist at the nozzle. I have some power fets to do the switching with as that cycle speed would destroy a relay in short order. Need more wet, bang it 100 times a second. Using a stepper driver in a mesa card, ought to simplify it somewhat. I can imagine 2 or 3 ways to skin this cat using these itty bitty pumps. The biggest problem is over coming the drag to get it moving. But I've got 12 volts at 5 amps to play with. I'm useing some, maybe 1.5 amps now with the air valve and 3 other relays, should be enough left to move the motor. hal code is not a problem, I just have to write it, but banging the motor hard enough for 2 or 3 mili-secs is. These particular pumps have silicon hoses, so ought to last a couple years, maybe more at a 5 seconds per full rotation speed. And that might actually be fast for this. From the bubble speed I'm seeing creeping thru the hose with the current lashup, I'd guess a rev in 20 secs. Thanks for the feedback. But what I'd like to see in a short nema 23 driving a pump about this size. That I could probably use. > Brent > > > Now if I can write hal code to allow enabling a PWM module to drive > > this for speed control, at the same time the m7 is on, and some more > > pyvcp to dial the speed via controlling the pulse width, I should be > > set better than I am right now. Enough air pressure to keep the work > > area clear, and just enough fluid to cool things without soaking the > > neighborhood. > > > > The stepper drive is a nice idea, and I may yet pull one of the > > 225's off the remains of the hf and put it on this 6040's z drive. > > OTOH, unless I start doing a lot of 3d woodworking, this is fast > > enough. Famous last words... > > ========== > > Speaking of PWM, is it possible we (meaning LCNC) have a means to > > detect the rise in back emf as the motor starts to turn, effectively > > pulsing the motor so it has enough power to overcome roller > > friction, but would them turn it off after 2-10 degrees of rotation? > > Should make a much more controllable low flow speed control. > > > > Somehow, I doubt we could turn it off and sample the back EMF with > > one of a 7i76's 12 bit A/D's fast enough to make that work, and the > > docs don't say how long to a valid reading, but can you tell me, > > Andy or Peter? > > > > That way I could use a solid 12 volts to bang it with, detect that > > the motor is moving, extending the pwm's off time for speed/flow > > control and that should allow flows that hardly wet a finger. Or > > have I let my imagination out to play w/o a chaperone again? > > > > Won't be the first time, and I hope not the last. :) > > > > Thanks. > > > > Cheers, Gene Heskett > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
