Subject:
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Re: More torque
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Wed, 12 Apr 2000 06:12:02 GMT
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Original-From:
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Chuck McManis <cmcmanis@mcmanis.com^Spamcake^>
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Viewed:
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1191 times
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One word "Chopper"
Nearly every commercial stepper motor driver I have ever seen uses a
chopper circuit. This is because torque is related to current (actually its
related to magnetic flux but that's related to current :-). The operation
of a chopper is pretty simple, you slam a "huge" voltage on your motor with
a circuit the measures the current through the motor, (voltage comparator
across a .1 ohm resistor is good for this) and then when it gets to the max
current you "chop" the voltage off. (usually by turning off a MOSFET) When
the current gets a bit below where you want it you turn the voltage back
on. (this provides "holding" torque) It is all a simple feedback circuit
and requires no software at all.
--Chuck
At 11:31 PM 4/11/00 -0600, Sean Verret wrote:
> Is there an easy way to get more torque out of a stepper motor? Upping the
> voltage is not an option at this time. I've already decreased the width of
> the pulses enough (so that it has enough torque to start on its own without
> a push) that it goes rather slow. Speeding up the pulses doesn't allow it
> to start - maybe my wheels are too slippery? Maybe putting some sort of
> grip on them.... I'm just throwing out some ideas here - please throw out
> some more if you've tried anything like this before... oh yeah - setting up
> a gear box is most likely out of the option due to my current time
> constraints.
>
> Thanks in advance for all your help.
>
> Sean Verret
> B.Sc. Electrical Engineering 2000
> University of Alberta
> mailto:verret@ee.ualberta.ca
> http://www.ee.ualberta.ca/~verret/
> Phone: (780) 439-0329
> Fax: (206) 493-2713
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