Re: [ATM] Making glass blanks.

["Stuart Hutchins" <stuart452@earthlink.net>]

Timm,

I'm an EE with experience designing motor controls, and have thought about
making a control for an annealing kiln for myself.  An SCR design capable of
controlling 20 amps (2400 Watts at 120Volts, or 4800Watts at 240V) is
relatively simple to make.  An analog voltage representing the temperature
setpoint and another voltage representing the measured temperature would be
the inputs to the circuit.  I don't know if you can get under $50 on the
prototype unless you really scrounge on parts.
I'm confused, though.  You mention an analog control, then you talk about
connecting to a computer and writing software.

If the goal is a standalone unit that can be programmed for any annealing
schedule over a period of many days, then the easiest to build system would
probably be based on a PIC micro controller providing an analog voltage
representing the temperature setpoint.  If you are mechanically inclined, a
clock motor with extra gearing could turn a cam, then a follower arm on the
cam could move a pot providing the setpoint for the temperature control.
Cut the cam from 1/8 inch aluminum with a jigsaw to give whatever temp
profile verses time that you want.  You will need some provision to failsafe
or recover gracefully from temporary power outages.

I'll help if I can.

Stuart


----- Original Message ----- 
From: "Timm Simpkins" <poduck@poducksworld.com>
To: <atm@atmlist.net>
Sent: Thursday, May 13, 2004 5:25 PM
Subject: [ATM] Making glass blanks.


> I have been looking for more information about actually making blanks.  I
> have experience in kiln and foundry making, and some experience in making
> glass.  What I need is someone who has experience in making electronic
> circuits.
>
> I figured that since ATMs are generally handy, and not afraid to tackle
new
> projects, maybe someone could help me figure out what I need in order to
> complete what I'm trying to do.
>
> To start out, I am not attempting this because I absolutely have to do it,
> nor am I attempting this because I think it will save me money or make me
> money.  I am trying this because I love to be able to say that I can do
> something that most people think is impossible, or are afraid to even
> attempt.  (I also love shoving it in the face of those people when I prove
> them wrong<g>.)  That's why I started making telescopes in the first
place.
>
> I have already figured out how to get and maintain the right heat for
> releasing the bubbles.  I have already tested the process, and until the
> glass shatters from not being annealed, I get perfectly clear blanks (They
> are somewhat green from the iron.).  (That is after the very tiny bubbles
> are absorbed by the glass again.)
>
> Anyway, the actual method or formulae for glass aren't what I need help
> with.  I need help designing a circuit or mechanism to control the
annealing
> process.  I would love to be able to design something that is analog and
can
> be made from freely available materials, but I believe that this process
is
> probably best done with electronics.
>
> 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.
>
> Since I'm hoping to be able to help other people do this, I also want it
to
> be simple to control.  If someone builds this, and wants to change the
> annealing time, the gearing would have to be changed, and they would have
to
> know the math behind it in order to get it right.  Another problem would
be
> speeding up the cooling process as the temperature gets lower.
>
> A fully self contained circuit would be great, but circuit that can read
the
> temperature and give it to the computer, and another circuit that would be
> able to lower the voltage to whatever voltage the computer tells it to
would
> work just as good.  I have no problem writing software.  I already have a
> temperature sensing circuit, but the circuit to control voltage eludes me.
> This is probably very simple for someone, and hopefully that someone
> subscribes to this list. <g>
>
> If someone could help me with this, or could help me make a fully self
> contained circuit with a method to set up the annealing time and
> temperatures, I would greatly appreciate it.
>
> Thank you,
>
> Timm Simpkins
>
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>


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