Path: ...!news.mixmin.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: Thu, 7 Mar 2024 12:30:48 -0800 Organization: A noiseless patient Spider Lines: 45 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Thu, 7 Mar 2024 20:30:48 -0000 (UTC) Injection-Info: dont-email.me; posting-host="ee031d9df31d56bdb9adaa96c4b539cf"; logging-data="1305398"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+N/svRtlkDWtKWBZC+IzjC" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:3fZ+lRL0mk1yLcWz4zBYw3YmXgY= In-Reply-To: Content-Language: en-US Bytes: 3118 On 3/7/24 7:26 AM, John Larkin wrote: > On Thu, 7 Mar 2024 02:14:49 -0800, KevinJ93 .... >>> >> >> Stepper motors are much too inefficient and have too much torque ripple >> for capstan drive - not at all suitable for a battery powered device, >> they also tend to be noisy. > > Efficiency wouldn't matter for a capstain motor (they may well absorb > power!) and microstepping is easy and smooth. > Most(all?) portable cassette players used a single motor for capstan and take-up reel; it would definitely consume power and would probably be the largest item in the power budget - probably only 50-100mW allowable determined by battery life from a few C-cells or even two AA cells in later units. Microstepping is easy now - not so much even at the end of the cassette tape era 30-40 years ago when CDs started to take over >> >> 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. >> >> If stepper motors would be such a great solution how come nobody has had >> your insight and used them in the past sixty years for tape drives? > > Does anybody still make audio tape drives? Crutchfield still has a couple of tape decks being sold. I'm sure the market is very small. The only reason I've used a cassette player in the last 20-30 years is to transcribe tapes I already have into a digital format or to be able to play things in a car that has a cassette player installed. I wouldn't expect there is any significant new development being done. kw