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From: KevinJ93 <kevin_es@whitedigs.com>
Newsgroups: sci.electronics.design
Subject: Re: Motor Speed Control
Date: Thu, 7 Mar 2024 12:30:48 -0800
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On 3/7/24 7:26 AM, John Larkin wrote:
> On Thu, 7 Mar 2024 02:14:49 -0800, KevinJ93 <kevin_es@whitedigs.com>
....
>>>
>>
>> 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