On Sunday 22 September 2013 18:52:16 Gregg Eshelman did opine:
> On Sun, 9/22/13, Claude Froidevaux <men...@bluewin.ch> wrote:
>
> Subject: Re: [Emc-users] Very weird thing with my stepper motors. They
> don't like to be moved while running. To: "Enhanced Machine Controller
> (EMC)" <emc-users@lists.sourceforge.net> Date: Sunday, September 22,
> 2013, 6:20 AM
>
> Le 22.09.2013 06:54, Gregg Eshelman a écrit :
> > That's not the weird thing. What is effed up is that
>
> when the motor is running if I pick it up or move it, it
> stops running. Doesn't matter if it's laying down or
> standing on its back end, if it's picked straight up or
> allowed to rotate around its shaft axis it locks up and
> squeals. Tried two of the three, both do the same thing.
>
> That let me thing you may have miss-connect the motor. 1
> phase must be
> connected between A+ and A- (you shall measure low impedance
> on motor
> motor side). I have got theses strange result once when I
> wired a phase
> between A and B output of the driver.
>
> Claude
>
> I've checked to make sure one coil is connected to a+ and a- and the
> other to b+ and b- Disconnecting the enable line allows it to run both
> directions instead of just counterclockwise. Still has a low and slow
> pulsing harmonic vibration. I tried reversing one coil and that made it
> worse so I switched it back. I've also swapped pair A and B locations.
> Always has this vibration. I also disconnected both ends of the enable
> wire and moved the ground to dir - with a jumper to pul -
>
> Here's a video
> http://www.youtube.com/watch?v=uL9tzYGSVhY&feature=youtu.be
>
> Have to get rid of that vibration and the sensitivity to motion. They're
> over 1,000 oz-in torque, should be plenty of rotor inertia that one
> could stick the motor on the end of a baseball bat and wave it around
> without bothering it.
>
> That's something I've noticed in every Youtube video of people showing
> stepper motors running. Nobody ever picks up or otherwise moves them
> except for when they're firmly mounted to something like the head on an
> X-Y gantry.
Generally that is because the motors 'step' is pretty violent, so it has to
be held down or bolted down it you don't want it to walk off the table.
1. Which ever way it runs both directions is probably the correct enable
line status. I suspect you'll find lots more torque available then, if
thats the problem. Also, to this old CET, the fact that its running one
direction only tells me that BOB hasn't enough output muscle to drive it
solidly off. Cut your loses, its new, better BOB time in that event.
2. Just in case the optos in those drivers really are slow, set the parport
reset time up to 10000 ns. Same for dir setup and dir hold, eg for
testing, make it longer than any sane driver will ever need. All you'll
lose is top speed but that will at least prove it works.
3. What are you using for motor power? I have seen switch mode supplies
that, because the driver recirculates current back into the supply in the
course of the drivers current regulation, which can drive a poorly designed
switching supply out of its alleged mind, so its pulsing on & off.
4. An oscilloscope to see whats going on can be very enlightening. But it
needs to be a decent one, most hobbiest scopes are toys that belong in the
bin at the curb. It must have calibrated gain down to DC, and to really
look at these signals, will need good response to at least 35 mhz, 100 mhz
is even better, as is dual trace.
5. BOB's can be funny at times. The one I have used 2 of now, is the C1G
from cnc4pc, which can source or sink 24 milli-amps on any output, driving
it to within 50 millivolts of which ever rail its supposed to be at. I am
driving 6 of the 2M542 drivers and have never had to invert or otherwise
play with a signal to make it work, it just does. One of its big
advantages is that every input and every output has an led on it, so you
can instantly determine the signals state. And they are _bright_, see them
plumb across the shop.
Cheers, Gene
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
It is the quality rather than the quantity that matters.
-- Lucius Annaeus Seneca (4 B.C. - A.D. 65)
A pen in the hand of this president is far more
dangerous than 200 million guns in the hands of
law-abiding citizens.
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