Re: Motor Speed Control

On 3/7/24 7:26 AM, John Larkin wrote:

On Thu, 7 Mar 2024 02:14:49 -0800, KevinJ93 <kevin_es@whitedigs.com>

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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

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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.
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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