Re: Treadmill motors as Servos

John,

After looking at your motors from the link you posted, I noticed
they are the same ones that I purchased through Surplus Center. From
my experience these do not work well with Gecko servo drives, at
least on the set-up I have. The motors seem to have too much torque
ripple to be used as a servo. I am in the process to find a suitable
motor to replace them. I might have to change drivers.

Regards,

Protman16

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "kz1927" <kz1927@...> wrote:
>
>
> Thanks Les,
>
> I was pretty sure that was you. Thank you for answering.
>
> I put some pictures of the motors here...
> http://www.flickr.com/photos/26361144@N00/
>
> I didn't have a D cell put it turns smoothly on a single AA
> Duracell, I guess thats a good sign.
>
> No more lost steps??? I can't believe it!!!
>
> Is that the same encoder you used?
> How does it connect in all of this?
>
> Is your mill still running with the treadmills or did you upgrade?
> I think your old post is from a year or so ago on this topic.
>
> I have nearly $1000. tied up in G202's and 600 oz Nema 34's
> and it's not even as reliable as any of my 3 Hobbycnc boards.
> It's likely something I'm doing wrong, but I just expected
> better. When it goes off course on a $20.00 block of plastic, I
just
> shut it down and mill by handwheel. And it's done that 75% of the
> time. I've changed the voltages, changed computers, adjusted the
> trimpots, use Mach3 and CNCPro ,I need something that works.
>
> I got the treadmills for making a spincaster later down the road
> and was sifting thru old posts for refs on how to control them.
> That's when I came upon some of your old posts.
>
> So someone could have a working servo system where the motors &
> encoders are a little more than $100.?
>
> Naturally I've got to pay for more drives, but if it's reliable
> enough to leave the room while it's running then it'd be worth it.
>
> Which drives do you like?
>
> Again, Thanks Les, for helping with this.
>
> John
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Leslie Newell <lesnewell@>
> wrote:
> >
> > Hi John,
> >
> > That was me. The encoder on those motors comes as two parts - a
slotted
> > metal disc and a plastic pickup. The disc is pressed onto the
shaft and
> > is fairly easy to remove. You must be a bit careful pulling the
disc
> off
> > as I had one fly across the workshop. It took me ages to find
it.
> > afterwards. The encoders are only 200 line, giving 800
pulses/rev.
> This
> > is a bit low but it seems to be OK on my mill.
> >
> > I used a slightly different motor to the one you show. Mine had
a
> > convenient shaft sticking out the back that I ground down to fit
the
> > encoder. Also check that the brushes are at right angles to the
> > commutator. Some are angled and this can cause problems. Surplus
Center
> > are very helpful and if you email them, they will have a look at
the
> > motor and check the brushes for you. If you already have motors,
a good
> > test is to connect them up to a 1.5V D cell. The motor should
turn
> > fairly smoothly. If it doesn't turn or if it seems to turn in a
series
> > of steps then it won't be brilliant as a servo. If I remember
correctly
> > I used 200V rated motors. The higher voltage motors have a higher
> torque
> > constant (more torque per amp) and turn slower on 80V. You don't
really
> > want a servo spinning at 6000RPM.
> >
> > You can't get nearly as much power out of them as you would
think. The
> > ratings are for full speed running and fan cooled. They are also
only
> > rated for intermittent use. On my Bridgeport I use about a 4:1
> reduction
> > ratio between the motors and the screws. This works well, giving
me a
> > top speed of about 100IPM with enough torque to snap a short
10mm
> > carbide cutter without even noticing. Normally they run just
slightly
> > warm to the touch.
> >
> > Apart from the motors and encoders you need Gecko or Rutex
drives. If
> > you are already using steppers with Geckos then use Gecko servo
drives
> > as they are the same size and hole spacing. I would never go
back to
> > steppers. Lost steps? What are they? The only time you lose
position is
> > if a drive faults (overload or trying to move too fast) or you
hit
> > Emergency stop. Link the drive resets together so if one drive
faults
> > they all stop.
> >
> > Les
> >
> >
> > kz1927 wrote:
> > > Thanks Rich!
> > >
> > > That's a good starting point. I saw(think I saw) where someone
> > > used this encoder
> > >
> > >
> http://www.surpluscenter.com/item.asp?UID=2006110919282545&item=10-
1834&catname=electric%3E
> > >
> > > and this motor
> > >
> > >
> http://www.surpluscenter.com/item.asp?UID=2006110919282545&item=10-
1783&catname=electric
> > >
> > > but I wasn't clear on how you make it work.
> > > I think it was Les Newell on a bridgeport, so it MUST work well
> > > if he says it does.
> > >
> > > Is that all one needs (besides some Gecko's)??
> > >
> > > Thank you for any help on this.
> > >
> > >
> > > John
> > >
> >
>