On Tuesday 22 October 2019 17:17:09 andy pugh wrote:

> On Tue, 22 Oct 2019 at 21:47, Gene Heskett <[email protected]> 
wrote:
> > > Steppers are good for driving things slowly. What are you pumping?
> >
> > Koolmist to a misting nozzle. Pretty close to plain water.=
>
> That sounds like a dosing rather than pumping application, so I would
> definitely be looking at steppers.

Unforch, the pumps motor is a 12 volt brushed pmdc motor. And while I 
have a quartet of tb6550's I took out of the 6040 because they, and the 
psu were way too puny.  So the pwm seems the best choice.  And its 10% 
of the size of any stepper motor I have.  Weight is maybe 2oz, so it can 
ride the z carriage if it had to but I'm considering changing that motor 
for one with 4x the muscle due to the weight of the 1hp spindle motor it 
has to lift, making 30 ipm the best it can do running up the pole, where 
xy can do 200 ipm with 28 volts feeding 2M542 drivers.

But I'll likely put this in a hose clamp near the bottle, which moves 
with the gantry's y motion. Separate project from changing the z motor.
So it looks like a single mosfet and a free wheeling diode to protect the 
mosfet. I can drive it direct from a cmos rail to rail logic signal.  
I'm amazed I can't buy that on fleabay. For a $10 bill for a 5 pack. 
Litterally a relay driver.  And I may have found one, 4 channel, so I 
sent the vendor a couple questions.

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>


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