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From: rbowman <bowman@montana.com>
Newsgroups: alt.folklore.computers,comp.os.linux.misc
Subject: Re: The joy of FORTRAN
Date: 9 Mar 2025 06:35:27 GMT
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On Sat, 8 Mar 2025 22:57:22 -0500, c186282 wrote:

>    A good question ... are 'solid state' relays always "better" ?
>    Admittedly no contacts to wear out and quicker. DID encounter a
>    situation once where the delay was a GOOD thing, made it possible to
>    test a critical condition before the entire relay chain was engaged.
>    Maybe not the best design strategy, but what was, was.

We used a lot of octal base 120 VAC ice cubes. One problem as solid state 
devices started to appear was the voltages and currents involved looked 
like dry circuits as far as the ice cubes were concerned. 

https://www.trafficsignalmuseum.com/pages/ef15.html

There are photos of a stepper toward the bottom of the page. They were 
popular for industrial controls. Later models had pieces that you could 
snap onto the cams rather than breaking pieces off that saved 
disassembling the entire thing to replace a cam if you screwed up. 

Anyway hitting a limit switch would actuate the solenoid lifting the 
massive lead weight which would then drop rotating the drum one position 
bringing you to the next state. 

The company I worked for at the time went to a new design of vertical 
hydraulic press where the ram was in free fall until it hit a limit 
switch, closing a pilot operated check valve. Then the ram would be pumped 
down at a slow speed. In theory. It worked fine in our shop. When we set 
it up at the GE plant they filled it with hydraulic fluid that resembled 
squirrel piss. On the trial run the ram hit the limit switch, the stepper 
barely twitched, and the mold closed at full speed. Not good.

I added a relay that was fast enough to react to the limit switch and 
would then actuate the stepper. After that fiasco we went entirely to 
relay logic and skipped the stepper.

Footnote: years later and at another company we had a contract to build 
the controllers for the sequenced runway landing lights and I got to meet 
the stepper again. Since the GAO recently said the FAA is years behind 
modernizing I'm thinking those 50 year old steppers are still thunking 
away.