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Posted by Daniel Rudy on October 17, 2008, 4:21 pm
At about the time of 10/17/2008 7:15 AM, Allodoxaphobia stated the
following:
> On Fri, 17 Oct 2008 04:52:13 -0700, Daniel Rudy wrote: >
>> Rotation was observed facing the motor. That last one I'm not sure
> > To observe while facing _away_ from the motor would involve a mirror, > I suppose. :-)
hehehe
Or I could look from the side, but then it would be either left hand or
right hand, which neither knows what the other is doing. :)
--
Daniel Rudy
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Posted by PeterD on October 17, 2008, 5:21 pm
wrote:
>On Fri, 17 Oct 2008 04:52:13 -0700, Daniel Rudy wrote:
>> Rotation was observed facing the motor. That last one I'm not sure
>To observe while facing _away_ from the motor would involve a mirror, >I suppose. :-)
No, my mother could have done that easily. A few of my teachers as
well. All female, so perhaps we men are left out in the cold? <g>
Posted by BobH on October 17, 2008, 8:09 pm
> There are absolutely no numbers or any other markings on this motor > besides a warning about it being hot. But from what I have been able to > scrounge up on the web. It seems that this motor was manufactured by > Magnetek and is rated at 24v. Stall current is 20. The lead wires are > only 16 AWG, so at stall, even the high temp wires would melt...the > wires are rated at 200c. >
I have a pair of these motors that I bought for a medium sized bot. They
proved not up to the job and were replaced with wheel chair motors. I
think that they were made for elevator or subway door operation, several
ads I saw a while ago indicated this. 5 years ago, they were bringing
$70 each, now I think they are about $20 each.
I am in the process of building an antenna rotator with the pair right
now. I am planning on running the field windings on a constant 12V and
PWM'ing the armature for control. I don't need a lot of torque, so I
will try 12V for the initial input power.
Good Luck,
Bob
Posted by BobH on November 6, 2008, 6:54 pm
Daniel Rudy wrote:
> Rotation was observed facing the motor. That last one I'm not sure > about...maybe I don't have enough power. But this gives me a few ideas > on power control. I'm thinking of placing a DPDT relay in series > between the armature and field windings for direction reversal, then use > a the standard PWM control from a microprocessor to control speed. > Plus, this will also protect the motor too in case any winding fails it > will open circuit.
I did some studying on controlling wound field DC motors with the
armature and the field windings in parallel and then driving the two
from a PWM source results in sort of an odd torque/speed curve that is
lacking in low speed torque. Running the field windings on a constant
voltage and controlling the armature voltage gives a flatter
torque/speed curve. Also, the adds that I remember seeing suggest that
the motor can be run on 36-48VDC.
I needed a place to attach encoders for closing the control loop and
found that the output shafts are fairly soft steel and drill and tap
very nicely. The unused side of the output shaft is exposed and flat,
making it an easy place to attach the encoders.
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