Re: [ATM] Making glass blanks

[Michael Lindner <mikell@optonline.net>]

On Sunday 16 May 2004 01:01 pm, Martin Cibulski wrote:
> I would do everything in the computer without an external controller.

I wouldn't. This is a system that's supposed to run over a period of days or 
even weeks, continuously. What happens if there's a power hit? What happens 
if a disk crashes? Will the element stay on continuously, and melt the glass 
(and perhaps start a fire)? Will the element turn off completely (and perhaps 
crack the blank from thermal stress)?

Much better to have a dedicated controller that handles those issues (either 
electronically or mechanically), and use the computer (if you need one) to 
set the annealing schedule. For instance, there are digital variable 
resistors that have step-up and step-down pins, and remember their setting if 
power is lost. Compare the voltage across one to the output of a 
thermocouple, with 3 comparators (one to control the heating element, and one 
each for "too far over" and "too far under", to warn of impending doom). 
Alternately you could rig up some thermocouples with comparators for alarms 
at various setpoints, but that would be about as complicated as a control box 
anyway.

I'm just a belt-and-suspenders kind of guy...

Clear skies.
-- 
Michael Lindner
http://www.starastronomy.org *** http://home.att.net/~mikel
http://www.atmsite.org *** http://www.atmlist.net

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