Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Cursitor Doom Newsgroups: sci.electronics.design Subject: Re: Motor Speed Control Date: Sun, 10 Mar 2024 08:59:30 +0000 Organization: A noiseless patient Spider Lines: 69 Message-ID: <2itquih5899b1os7fhp18k6pa5qe8hoblc@4ax.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Info: dont-email.me; posting-host="2982adc9a211c867e1a7bf94a4046e9a"; logging-data="3033589"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/kKDIwI1Unf74Z5zqmV11BbZBxPGpOTNI=" User-Agent: ForteAgent/8.00.32.1272 Cancel-Lock: sha1:PJCTjsM2c3Mb5ygoNKi00QGfP3A= Bytes: 4031 On Sat, 09 Mar 2024 15:13:20 -0800, John Larkin wrote: >On Sat, 9 Mar 2024 14:56:43 -0800, KevinJ93 >wrote: > >>On 3/8/24 8:42 PM, Bill Sloman wrote: >>> On 9/03/2024 5:49 am, KevinJ93 wrote: >>>> On 3/7/24 8:48 PM, Bill Sloman wrote: >>>>> On 8/03/2024 7:13 am, KevinJ93 wrote: >>>> ... >>>>>> >>>>>> Not in 1970. Even after that time they did not possess any advantage >>>>>> over DC motor drive with speed stabilization based on back-emf. >>>>> >>>>> Don't be silly. Back-emf depends on the strenght of the magnetic >>>>> field generating the basck-emf, and that is temperature dependent. >>>> >>>> At about 0.2% per deg the magnetic field strength stability was >>>> adequate for the speed accuracy required under the required >>>> environmental conditions. >>> >>> Motors run hotter than their environment >> >>With only 50-100mW being consumed by the motor (10's of mA at 3-6V) the >>temperature differential was small. >> >>>>> Synchronous motors rotate at a rate that reflects the stability of >>>>> the frequency source that determines the drive frequency, and >>>>> reasonably stable frequency source - watch crystals have been around >>>>> for ages. >>>> >>>>>> Even for AC powered units where power was not an issue stepper >>>>>> motors were never used. Synchronous motors with synthesized drive >>>>>> were occasionally a feature but many/most used back-emf >>>>>> stabilization with DC motors. >>>>>> >>>>>> ICs were available to integrate that circuitry: >>>>>> >>>>>> eg https://www.precisionmicrodrives.com/ab-026 >>>>>> >>>>>>>> Even implementing the discrete drive electronics would be more >>>>>>>> costly than necessary at a time where individual transistors were >>>>>>>> a significant cost; Philips' solution used two transistors - >>>>>>>> creating a divide by 4 plus driver transistors plus an oscillator >>>>>>>> would probably require about ten transistors plus numerous other >>>>>>>> components. >>>>>>> >>>>>>> Which you could could buy in an integrated circuit. Most of mine >>>>>>> were in a chunk of PROM. >>>>>> >>>>>> Not in 1970. Even by the late 70's a bipolar (P)ROM would use up all >>>>>> your power budget. >>>>> >>>>> It didn't - and it wasn't bipolar. >>>> >>>> MOS EPROMS such as the 1702 were cumbersome to use with multiple >>>> supplies required. >>> >>> It was one-time programmable, not an EPROM. >> >>If it was NMOS it was almost certainly an EPROM in a cheaper package >>without the quartz window. > > >1702 was a p-mos UV-erase part. It was called an eprom. Are EPROMs obsolete now? I assume they must be or we wouldn't have USB drives and SD cards etc.