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neilestrick

Cones And Soaking Times Theory

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neil, you're right about the wearing out of elements. The closer they get to their max temp about 2385 or so, the shorter the life. I wonder about the dimishing return on longer firing at lower temp for better life span vs wearing out of relays over a prolong firing, something to consider.

Wyndham

The 40 minute hold I used to do to get from cone 6 to cone 8 did not really make the firing any longer than actually firing to cone 8. And with zone control the relays were cycling some anyway. So I don't think it hurt them much at all. Plus relays are cheaper than elements. I think the greater killer of relays is heat. I see a wide range of relay life depending on how the control boxes are designed. Some do a better job of shielding them from the heat of the kiln than others.

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Good post, Norm.

 

Too many folks do not understand the huge number of variables that are involved in each step of the pottery making process (not just firings), and then wonder why, when they THINK they did everything the same, that the results differ.  It is the variables that they do NOT control that get them... and in many cases they do not even realize that those variable are there.

 

The tools we have available help us control some of these variables. 

 

best,

 

..................john

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Pazu:

 

I have designed a kiln firing program that uses an Arduino UNO with a thermocouple module  to control a solid state relay. The user interface on the PC is based on  VB 6 . The software reports theoretical and actual heatwork, and total KW hours. It graphs the time/temp and produces a report  of the ramp and all of the above info including a printout of the graph.

 

The KW hours of the run is based on user input of volts and amps. There is no real time reading of the actual electrical params. On my  120V test kiln I get a 5 volt drop during the ON cycle and just type that value in.

 

As far as load weight is concerened, it would be easy to add some set of params to the program that set the hold time but I'm not sure it would be worth the effort of weighing each piece and kiln shelves to try to get some optimum soak.

 

If you are handy with a soldering iron, I'll send you the Arduino script and the software setup and you can have a go at it.

 

The total cost of the custom controller I put together is around $80 , but I salvaged a few of the components from an old PC.

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How are you dealing with hysteresis on the temp overshot in your code?

 

I'm not John. I have not put any logic in the code to damp overshoot.  I could but I'm not sure the gain would be worth the sweat. At lower temps I get sometimes a 10deg F or more overshoot, but when the duty cycle is more on than off it only amounts to 2-4 degreesF. I can live with that.  (the reading is with a 100 point average over 100 milliseconds)

 

Any ideas?

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The reason I chose Arduino is that there is a ton of support and add on gadgets that plug right into the board. Then all I have to do is modify the existing code for the gadget to get it to talk to my computer. It has a real simple programming development environment and the board only runs around $25.

 

you can buy clones cheaper but none of them seem to work under the dreaded WINDOWS 8!

 

The board has plenty of digital I/O and has 6 analog inputs, so you could control multiple relays. The only down side is the the A/D is only ten bits, but I think that is enough since the thermocouple reading has more slop than that.

 

Anyway, Keep us informed on how your project is going.....$60 for a kiln...some folks have all the luck.

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The Evenheat looks like it's in good, shape, although it needs a stand. For the money it's the best deal. That $65 thing is scary. Run away. The Skutt looks good, to, although the Evenheat is a lot cheaper. The Gare looks exactly like an Evenheat. I'm wondering if it si truly a Gare, or if Evenheat built them for Gare. Without seeing the inside I can't make any judgement calls on it.

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I have completely outfitted both my welding and pottery shop from craigslist this includes two kilns, a wheel, steel shelving, extruder  plasma cutter, TIG welder, drill press, vice, steel workbench etc.etc. I have gotten top-quality equipment very cheap because craigslist is a buyers market. I can't ever remember having something sold before I get there. If I spot something that I like, I usually wait a couple weeks after the posting date. By then most sellers realize that they have gotten 95+% of the traffic they're going to get on their item. At that point, I will typically, in person, offer them half of their asking price, and I have an open wallet full of hundred dollar bills clearly visible. I can usually get what I want for less than two thirds of the asking price sometimes at my original half offer.

 

After a couple of weeks they have a guy in front of them who clearly has money to spend and if they can't sell it to me they know their other use for it will be as their headstone.

 

I have gotten everything at prices that someday, when it's time to sell all of this stuff, I will lose very little money.

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I have an old kiln that has a kiln sitter. I would like to increase the amount of crystal formation in the glazes I am using, some are Steven Hill glazes and some are standard ^6 "dip" glazes. Would there be a recommendation to soak the kiln, at what setting and for how long, after the kiln sitter has turned off the kiln? I have put in cones to see how the kiln tends to fire in the past and the kiln sitter turns off the kiln but the test cones on the shelves do not indicate that a full ^6 has been reached. That said I have gotten some beautiful results, not too runny. Reading thru all these posts I think I may have made a mistake by putting a ^6 indicator cone in today! But I would still like to try out the "soak". Any guidance would be appriciated!

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