Path: ...!2.eu.feeder.erje.net!feeder.erje.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: KevinJ93 Newsgroups: sci.electronics.design Subject: Re: Motor Speed Control Date: Sat, 9 Mar 2024 14:56:43 -0800 Organization: A noiseless patient Spider Lines: 72 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Sat, 9 Mar 2024 22:56:43 -0000 (UTC) Injection-Info: dont-email.me; posting-host="6cfb28f21fb317601615981d0dc03d9d"; logging-data="2699503"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX197jSwBLzW76CYb1RQZTmNZ" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:bTbKxS9JJD9FW8D6WTaGaU0/ZDs= In-Reply-To: Content-Language: en-US Bytes: 4185 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. >> The logic to drive them would have been TTL consuming significant >> amounts of power as well as expensive. > > CMOS was around and cheap. I'd first used it around 1975, and the price > fell by a factor of three as I was developing the 1975 circuit. > >> The first EPROMS that were easy to use, such as the 2708 weren't >> widely available till the late 70's. > > The stepper motor circuit that I worked on was developed in 1978. > > >