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From: Cursitor Doom <cd@notformail.com>
Newsgroups: sci.electronics.design
Subject: Re: Motor Speed Control
Date: Sun, 10 Mar 2024 08:59:30 +0000
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On Sat, 09 Mar 2024 15:13:20 -0800, John Larkin <jl@997PotHill.com>
wrote:

>On Sat, 9 Mar 2024 14:56:43 -0800, KevinJ93 <kevin_es@whitedigs.com>
>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.