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Bob Coyle

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About Bob Coyle

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  • Location
    Santa Fe
  • Interests
    Metal work and electronics

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  1. You never know with a new kiln. Best to waste some gas/electricity/clay and fire some sample pieces. Min & Sorcery are right but don't ever commit a kilns worth of pots to a firing schedule you didn't try or a kiln you are not familiar with, or a new glaze. Of course... good luck!
  2. Not sure how textured you want your castings to be but one way would be to add whatever texture you want before you use your mason stain. I have tried everything from painting the finished dry clay piece in places with shellac and sponging the clay from the areas in between. Or just using a wire brush or tool to texture the piece before the final colored slip. You can also use a sponge dipped in slip and dab it on the leather hard piece. There is no one answer. Experiment around, Lot's of things work! PS.. your castings look great to me!
  3. Sounds pretty strange that an element would have cold areas. The same current will be flowing through the entire element. I have had places where the element was thin, and glowed hotter than the rest of the coil, Maybe that is what you are seeing. It is usually isolated to a small section. The only way you can know if the element is not pulling enough current is measuring resistance of both elements. If one is way high, then there is a problem. Another place to look is the relay in the controller. If it is getting overly hot during the run, the amount of current it can pass goes down
  4. A six meter cord, if it is not the correct wire diameter, May give you a voltage drop that will cause the kiln to not get as much current to drive the elements. If the cord gets hot to the touch when you are firing, then it may be a problem. If you are running 15 amp wire for a 13 amp kiln, then 6 meters is pushing it. Ohms law i= e/r amps = line voltage/ element resistance. measure the total resistance of the kiln by unplugging it and turning on all elements to high. measure directly across the plug at the kiln if the line voltage divided by the measured res
  5. I did some checking a while back on the change in resistance of nichrome wire with temp. As far as I can remember, it was not that much at normal kiln temps, which was kind of a surprise. Probably heat loss through the kiln walls is more important. I had a wimpy 10 amp test kiln that could barely make cone 6. I put a 1 inch kaowool blanket on the top and it made a big difference.in high end delta T.
  6. Yes Tim... the old bi-metal contact switches sucked. SSR's are the way to go. They are cheap and last a long time. The way I set mine up is to put them in line with the power out of the wall and then put a female socket into the relay enclosure. I just plug the kiln into this and leave all of the switches on high. And I ALWAYS put a bar in the kiln sitter that is one cone higher than I am aiming for. Andy... The problem you are facing is not only learning some basic electronics, you also need to know a little about what basic programming is. There are hundreds of tutorials on both electro
  7. I could probably put an Arduino controller together for you for the computer end, and you could use my app to run it, but you would have to build your own solid state switch interface to the power line. As High Bridge says, that is not technically hard, but could be dangerous if you have no idea what you are doing. To build the controller part yourself, you would at least have to know how to solder.
  8. Yes Niel, you need to give those heat sinks a space to breath. Seems like a lot of the kilns just try and use a chimney effect. High Bridge... that doesn't look bad at all...less than 2C ripple will not even be noticed on a 1200 C chart..
  9. The video is interesting. High Bridge, Solid state relays are pretty cheap, so what I usually do is over spec them. I use 25 amp for a 15 amp kiln and 50 amps for a 30 amp 220. You also have to put a beefy heat sink on the back. Just attaching them to the side of an electrical box is a no-no. I also sometimes use a cooling fan I salvaged from a computer or printer to cool the heat sink if I am pulling a load close to the rated max of the SSR. Just for laughs, you should buy an Ardino UNO. They also are cheap and you could literally be up and running in 10 min, after you downloaded the Ard
  10. I am using a 5 volt digital output from the Arduino directly to the on/off switch of the solid state relay. The relays don't need much current to toggle them. Better safe than sorry, though. Better set it up through a transistor, as in your schematic. The way I code the controller is with an array of temperatures that are calculated from the ramp data that is input. I convert deg/hr to deg/min and make an array of temperature differences. This array is then used to generate the ramp plot on the graph. I have a timer set to look for a temperature reading from the Arduino every second. Thi
  11. It was a delight touring your gallery, not only artistic, but exceptional execution of the craft. Most impressive!! Bravo!!

  12. http://www.ebay.com/itm/TELEDYNE-50-Amp-solid-state-relay-ST48D50-/131683141032?hash=item1ea8ed45a8:g:FN8AAOSwHPlWekdB 5 Volt trigger ... no sweat. Works like a charm... ten bucks. simple hook up between the Arduino out and the the relay
  13. I uploaded a zip file of the stuff I have been doing code, jar files, DLL's and stuff. ... It works ok but is itself a work in progress. I will be updating the zip from time to time. You should be able to unzip it and run the jar file and pack up anything that is coming over the USB... read the readme.txt for details http://raventreestudios.com/kiln_wiz.zip
  14. Ah those ten minute fixes that turn into hours of hassle... but hey, think of how much you are learning. Lot's of electronics plus whole new combinations of cuss words! Hang in there Joel, you'll get it yet.
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