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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: Motor Speed Control
Date: Sat, 9 Mar 2024 15:31:49 +1100
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On 9/03/2024 5:30 am, KevinJ93 wrote:
> On 3/7/24 7:18 PM, John Larkin wrote:
>> On Thu, 7 Mar 2024 12:13:59 -0800, KevinJ93 <kevin_es@whitedigs.com>
>> wrote:
>>
> ...
>>>
>>> Stepper motors are invariably of the reluctance type. With simple
>>> drivers they have a great deal of cogging, which is undesirable in a
>>> capstan drive motor.
>>
>> There are two types, PM and VR. PM steppers use bipolar coil drive and
>> have a strong unpowered detent. And can act as generators.
> 
> Yes, I was wrong.
> 
>> Both can microstep nicely, for smooth motion.
> 
> Given appropriate driving circuitry that would have been expensive and 
> power consuming in 1970.

Nonsense. The cheap way of making an approximation to a sine wave is 
pulse width modulation.

https://www.tinaja.com/glib/sinquest.pdf

That document is from 1997, but the idea has been around for a lot 
longer. I used it in 1975 - if not to make sine waves - and it is cheap 
and efficient. The "modified square wave" - which has no third harmonic 
content - is equally old.

<snip>

-- 
Bill Sloman, Sydney