Re: [ATM] Making glass blanks.

[martin.cibulski@t-online.de]

Timm, 

>>
. . . What I need to do is control the cooling process over a period of
time.  The
time needs to be over a period of days or even weeks, depending on the
size
of the piece.  It needs to cool slowly at first and then can gradually
cool
faster as the piece gets closer to room temperature.  My annealing kiln
will
be electric, so what needs to be controlled is the voltage.  I've
thought
about a high wattage dimmer switch attached via gear reduction to a
small
motor with precise gear reduction would almost be perfect, but the
wattage
is higher than 1000 watts, and the highest dimmer switch I can find is
1000
watts.  That dimmer also costs almost $50, and I'm hoping to keep the
costs
lower than that. . . .
<<

there are solid state relais available which can switch many Amperes
at high voltages. These relais can be controlled by a low voltage
signal
which could come from a computer.

Example:
http://www.crydom.com/pdf/crydom_lpcv.pdf

There is a version with a 0-5V input which would fit to a computer's
printer port. If the heater is controlled this way the computer can
switch it on and off
in variable time intervals:
100% power will be always on.
70% power will be 3.5 seconds on and 1.5 seconds off.

I assume the time constant of the temperature in the oven is long
enough so switching in intervals of some seconds will not result in
temperture changes.

Regards,
Martin Cibulski
http://martin.cibulski.bei.t-online.de
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