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Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail 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 Organization: A noiseless patient Spider Lines: 36 Message-ID: <usgoo4$255sp$6@dont-email.me> References: <qak4ti1ncqfkmihf9dvfsh5fv16l505t9s@4ax.com> <us3u77$95n9$1@gonzo.revmaps.no-ip.org> <us5vgf$3egni$4@dont-email.me> <us7puf$3te18$1@dont-email.me> <us8i7u$2673$1@dont-email.me> <usad4b$ibi5$1@dont-email.me> <usbeed$s81p$1@dont-email.me> <usc42q$104da$1@dont-email.me> <uschnp$135ah$1@dont-email.me> <usd767$17qpn$1@dont-email.me> <qf0luipimeqekgch0lh67241ilkvid9ip5@4ax.com> <usflfg$1rk9q$1@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Sat, 9 Mar 2024 04:32:04 -0000 (UTC) Injection-Info: dont-email.me; posting-host="8999cc58ca815e678928e469e899534b"; logging-data="2267033"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18oeepMJLCZBvCTOKPL9/7fSpcudKe5Cow=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:qIxZAc8oVKqmEFBnZ5jI2Tnh08Q= Content-Language: en-US In-Reply-To: <usflfg$1rk9q$1@dont-email.me> Bytes: 2474 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