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About jbruce

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  1. @Ju00Ls Hi. Glad you're following and glad you're no longer just a lurker. The metal box looks scary, but it is grounded. Aluminum boxes are common for electronics projects. In this case I chose it for its thermal properties and ability to quickly absorb lots of heat and transfer it from the SSR. The high voltage/high current cable is close to the thermocouple, but I'm not getting noise from that. The noise I'm seeing comes when a client connects to the server running on the PI. I believe that connections cause a spike in the processor which draws more current which impacts the 5v
  2. Yeah @liambesaw, conservative in this regard. Mine is in my basement and I don't want to burn my house down. I guess the generally acceptable distances are: 3 ft from another kiln 12 inches from a concrete wall on a concrete floor
  3. I think a cooled solid state relay will have long life. Wear and tear on SSRs is mainly from heating (expansion) / cooling (contraction) of the components in the package. The increasing amplitude of the waveform as your kiln gets hotter is due to cooling because of the 60s cycle time. A faster cycle time would be harder on your mechanical relays, but would yield more accurate ramps / soaks. WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! running a kiln in an enclosed space is extremely dangerous. some fumes are noxious. please dont.
  4. @High Bridge Pottery With a cycle time of 2s my controller switches on about 11,000 times in a 13 hour firing. I'm not sure what "a lot" means to you. I'm not worried about the number of switching cycles - as long as I keep my SSR cool - it will have a long life. If you're switching using a mechanical relay or contactor, I would set the cycle time to at least 10s. I'm not sure about 60s... I'd have to test that. By experience, my kiln drops a F degree per second when not being heated at 2000 degrees or more. Setting a cycle time of 60s means the temp swing could be 30-40 degrees or m
  5. @High Bridge Pottery Are you deciding if you should turn the relay off or on every 2 seconds? Yes. This is a configurable parameter. The code originally made this decision every .5s and that duty cycle was too high for kilns. I have heard some folks going as high as 10s. Since it is configurable, you decide the value that works best for your kiln. How did you come up with the PID values to use? I read many articles discussing PID tuning. Some were complex algorithms, some simple. I tried to find the simplest method that could be done in a few hours. The process I used is
  6. @neilestrick The controller is a raspberry pi 3. It uses standard power supply which is 110V input, 5.1VDC 1A output. This connects to a micro usb port on pi. The power for the controller needs to be separate from kiln power. The controller is used to monitor the temperature even when the kiln is off. The power code for this currently dangles out of a gaping hole in the front of the bud box. This needs to be fixed. The load side of the relay is 48V-280V AC 50A. I believe I need another one of these to bring the controller up to snuff.
  7. Please understand that this is just an interesting project / experiment. Please note that I have no intentions of creating a product. Please understand that this hardware is not finished and is in an alpha state. I do not want defend improper practices and I am here to learn from others and improve. I love that I have found a passionate, intelligent, experienced group of people in this forum. If I had a forum with information like this when I started the project, it would have changed the course of the project. So now, I'm left to make things right with folks so they don't follow the
  8. I want to make sure I answer all of the points. First question is about using extension cords. The conductors are 12 gauge and according to https://www.powerstream.com/Wire_Size.htm for short runs / chasis wiring, a single 12 gauge conductor can handle 41 amps. I am using three conductors for each connection. Experimentally with all elements running 100% of the time, the conductors are not getting warm. Even if it can only safely handle 60A, that is 20A above the max for the kiln and 10A above the breaker it is plugged into. So is using this wire dangerous, or just messy and somet
  9. @liambesaw Here is the pic I promised. Input is a nema male plug with three conductors (2 hot, 1 neutral). I used an old extension cord for this to make sure it could handle the current. Turns out it could handle about 4 times the 40A current max, so lots of safety margin there (and free wire). One hot leg is switched by the SSR, everything else runs straight to the output on the right hand side where the female nema plug is mounted. The RPI is in a plastic case and is covered by a breadboard with all the spaghetti wiring. You can see the max31855 in there. The thermocouple is th
  10. Thanks Bill. I changed my schedule from 108F/hour to 120F/hour for that final 250F approach. We'll see if that changes the heat work a little. I expect that change will get me part of the way, but probably still a little high somewhere between cone 7 & 6.
  11. I emptied the kiln this morning after the first glaze firing and everything looked good even though the kiln was over-fired by a cone. The witness cones showed that the kiln reached cone 7... just like the kiln sitter cone did. The maximum temperature according to the thermocouple was 2221 and cone 7 is 2262 at my firing rate of 108F/hour. So I guess the thermocouple is just off by 41F. At the same time, I'm reluctant to believe this because at cone 05, the cone bends right when it should. Maybe someone with more experience with thermocouples can provide advice. It's a K type
  12. Yep. It's a small kiln, so I just have one set of witness cones. In this case, 5,6,7 on the center shelf. In past firings, I've watched these to determine when to shut down (or move on to the next part of the schedule). This time I did not get the chance because the kiln sitter flipped before I thought it would. Next time.
  13. The cone 6 glaze firing went pretty well. You can see in the image that my kiln sitter tripped just before reaching 2232. It had a cone 7 kiln sitter cone in it. I think I had a kiln shelf too close to it. No worries, I just by-passed the sitter with slow-flip and used the api to start the cooling phase. You can see I skipped the initial drying phase of this schedule. There is more error this time than previous runs because I included the initial warm up, the part of the schedule where my kiln could not keep up, and the kiln-sitter flip. It was usually within a degree F though. There were
  14. I'm excited! I'm in the middle of my first cone 6 firing using the rpi controller. I'll post stats when it's done. My kiln could not keep up with the aggressive schedule (345 F/hour) from 1880 to 1976, but it was pretty close. After 1976 it slows to 108F/hour and it caught up quickly. @liambesaw I have not forgotten I promised pics. I'll get 'em posted for ya.
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