Bill Kielb

Don’t forget switching at zero crossing, meaning his relays always wait till zero volts and fire. Elements are never subjected to startup at 170 v peak or worst case 340 v. Peak for two phase operation. As well as smoother temperature control allows the overall duty cycle of the element to match the load more practically.

Really nice project and thanks for sharing. If you ever need the PLC code created for the monitor we created ( simple ladder logic for Click PLC stuff) just drop me a message. You are welcome to it.

Nice on both fronts! I was an electrician at age 20 (some time ago) and would offer to help but the distance from Wa to IL is rather significant. I will have to cheer you on from a distance. With respect to the Rpi I was going to drop you a note that said funny, now you have some programming to perfect along with your wares. Sounds like a fun project, hope you can keep us apprised.

Old general filter was to add a small rc filter network to both legs of the thermocouple. They needed to be identical to offset the error and also needed decent capacitors. I was hoping shielded thermocouple would solve your noise issue. Hard to tell from the data you have what magnitude the noise is but likely microvolt average on a .6 to 52 millivolt signal.. Does the thermocouple board auto detect shorted and open circuit thermocouple failures? I only ask because in PLC land temperature transmitters do this for us so we need not have to worry. all still looks great BTW, under three hundred with a decent web server interface! Cool!

Looks pretty nice! I am still curious how hot the SSR gets since we have been debating on retrofitting a kiln or two with ssr replacements downstream of the existing relays. The relays would only serve as an enable during operation or a positive means of disconnect under alarm. My limited research has always indicated the use of a fairly significant heat sink install. Your SSR I believe is rated at about 12000 watts controlling approximately 10000 watts of load so not grossly over sized. At this point it looks like you could fire and be successful with about 6000 watts of power - interesting! snce this is zero crossing it should be kinder to the elements since no 177v peak starts, ever! two thoughts: do you currently have shielded cable for the thermocouple leads? did you install fuse protection for the SSR occasionally in some kilns it is possible to have an element short depending upon how much they have been allowed to crawl out and where they touch.

Relays cheap, almost always need decent heat sink and the probability that they can fail (shorted) in general requires fail safe electromechanical safety so that usually adds to the cost. A slick pseudo method has been to safety enable the existing kiln relays and feed the SSR downstream. We Often see a kiln lid switch inserted in series with this circuit as well. Everything in this loop is generally powered to be safe, interruption anywhere in the safety circuit stops the kiln and terminates the program. Manual operator reset and restart required for many errors accept maybe power outage. I think this relay is pulse width modulated and fires at zero crossing. Right now it appears he is firing 11000 cycles over about 48000 seconds or let’s say one cycle every four seconds average. This is a pretty slow thermodynamic process with a lot of thermodynamic inertia. At just short of 10,000 watts available heating I would be surprised if this does become an issue. Just a gut feeling though, his data will direct him.

Pretty nice data! I will look at noise issue, seem to remember reading type K and Rasberry Pi . Fairly small voltages so twisted pair in a shield (single end ground) might remove enough for a short run. I am not that guy though and have resisted these things in favor of PLC and temp controllers. 46% duty cycle looks nice to me. pid error looks great (is this indicatative of Pv vs Sv?) I would be curious of the temperature rise across the SSR for general heat sink sizing and if pulse width modulated, is this a zero crossing SSR? Seems minimum cycle width would be 1/2 cycle with a max freq. of 120hz. I am not an SSR guy though so most of this stuff maybe sorted out already. Finally - yes, restart for a number of reasons always addressed in almost all processes especially thermodynamic ones. This is really nice, I am pretty lazy and have utilized off the shelf controllers and have recently been looking at WiFi enable stuff for an economically viable kiln control with web interface and logging. Right now still hundreds of dollars and hard to compete with the Bartlett genesis drop in approach using existing relays and multiple zones. Looks great so far, thanks for sharing!

Really nice! It will be interesting to see a fully loaded kiln, the duty cycle of the ssr And how well the pid module performs.

Sorry about that but it did bring a wry smile to my face and memories of tools falling off a 20’ ladder near some formerly really nice finished wares.

Impressive -all! Glaze is fantastic

Great question. I was fortunate enough to take my work bench on the road to build a bench for a friend which went to sofa and sold successfully for at least four figures. Loved her art and glad it sold! Feel good about the bench as it had to support at least three hundred pounds without deflection to crack any of her tiles. Fun project and success always makes the labor part forgettable. Picture of it going to its new owner attached. December project (s) Complete a couple glaze formulations to work well over heavy underglaze on low expansion porcelain. Test are going well and should be able to publish after the first of the year. Additional December project was to get at least four basic throwing videos done for newbies in the studio. Three done so far so we will just keep plugging along. last project was to begin creating a glaze workshop for the resident artist at the studio. Just beginning this one and have outlined it. Thus far I like the direction and content.

Just a quick note. Orton cones will fall at their prescribed temperature if they fire at a certain rate within approximately the last 250 degrees of the firing. The common way to manage this is to create a cone table and reduce the speed of your firing accordingly during this period. A 108 degree per hour last segment is common but Orton produces data for 68 degree per hour through 270 degree per hour final firing rate. cones are actually glaze with a flux ratio of approximately 0.3:/0.7 rated approximately 6 cones below maturity. I believe Seeger actually developed the cone theory and Orton simply brought them to the States. the point being calculating actual accumulated heat work is pretty difficult throughout an entire firing. Most pottery wares are fired at a maximum rate to limit cracking and heating unevenly at too high of a rate for common wares. There is also a practical limit to maturing glazes and claybodys wherein they will not mature as intended unless given enough time for the silica and alumina to fully mature. Remember Silica and alumina do not melt without flux below 3000 degrees so time at a particular temperature is very relevant. the point of all this is that most computerized controllers rely on cone tables and some established rates to simplify their calculated outcomes and adjust their pid parameters according to the thermodynamic range of a particular kiln. (Thermal mass , available input power, radiation rates for a given size kiln and elements installed) at the top end of firing radiation then conduction are the main components in heating. At those temperatures the atmosphere is very thin and convection does not provide a significant path towards getting this energy to the pots. Hence when you pull a port plug at 2000 degrees, no blast of air outward is encountered in an electric kiln. Convective paths do still provide a free path for heating so offset stacking etc.... is still usually the suggested loading norm to keep zones as even as practical. Offset stacking actually provided a radiant path as well. I bring all this up because using the cone table approach and slowing your firing down in the last approximate two hours of firing is an easy way to get your kiln to end at the desired cone. I also bring this up because I encounter many folks who have intuitive ideas about kiln operation, usually good, but not always correct enough for computer control. glad to hear you have the factory timer and cone sitter in series. Neil is correct in that there can be many reasons to abort a firing for convenience and cause and stuck relays (closed), while not nearly as common as open, do happen. If you ever use a solid state relay they can fail closed (more so) as well and require another form of positive disconnect to ensure safety. Usually a main contactor for power to the kiln relays, including lid switch and manual operator reset after the safety circuit trips. Bartlett for years has produced their base V6CF controller for almost every common major kiln manufacture that you can think of rebranded by the manufacture with minor alterations in keyboard placement etc.... You might want to google their new Genesis controller and look at the firing schedules in their manual. They are extensive and include glass and other interesting schedules. A nice resource for sure. still best of luck, sounds like a boatload of fun learning about and creating something that will no doubt help you in future firings. Hopefully all my bloviating will save you some program and discovery time.

No control, only monitor for liability reasons. If we were to take control all the factory safety would remain and we would use standard linear actuators for the dampers (spring return and travel maximum limitited) and spring return rotary for the existing hand operated gas valves. We also monitor kiln pressure, gas pressure, upper and lower temperatures and oxygen. . All the temperatures are standard thermocouple (k type existing) except for the S type built into the O2 probe. All of those are standard current loop with transducers for accuracy and the distance to the monitor. We decided NOT to control the kiln for liability reasons and to force folks to learn how to properly manage their firing. The monitor is a great aid for them to learn by seeing and doing as well as recording their data or serving the screen you saw up on their IPad, Android, remote monitor etc... it truly has sped up the learning curve for all who have used it. I no longer have to show them how to calculate their rate using their smartphone timer. When I have automated large machines in the past I have always relied upon the factory operation controls provided and all the designed safety’s to avoid designing my own safety scheme. If there was a start switch I simply had the automation enable it with the existing stop and safety circuits intact and in ultimate control.. I suggest you do the same with your kiln control on your personal kiln and for sure any you might install for others. as an example, I would maintain the existing kiln sitter if present and enable through a relay. If the kiln had a safety timer this would remain in series as well else I would need to redesign and theoretically get my safety systems approved by UL, CSA , NFPA, etc..... systems that have been approved have already been thoroughly tested by these agencies to qualify. just a thought on safety and reliability. Sounds like fun though the Arduino is very attractive. A little background on me I was fortunate enough for 20 plus years to teach part time at a local junior college and even authored a couple courses in DDC ( direct digital control) in the early days of HVAC automation, so this has been a professional interest for some time. PLC stuff is old but widespread, cheap and reliable so my decision to use PLC was an easy one. best of luck with your project and stay safe.

I like your idea. Did the same for a studio in Illinois and they get great use in teaching. One thought, I created it with PLC so fairly cheap, off the shelf, web enabled, remote enabled, data storage ........ blah, blah, blah. But less time developing! I chose to make them control their kiln manually as they reduction fire and the accuracy, liability and cost for accurate feedback in an old kiln was unacceptable to me. As a teaching and learning aid I have found it vastly superior. if firing an electric, then likely no issues and knowing PID programming will likely make this very accurate. I did some research on correlation with cones and can say that the last 200- 250 degrees of firing controlled rate approach is likely the simplest in my view. Look at the Bartlett schedules, they have done this for so long they really simplified this. You might get some ideas. With respect to liability, it is a real valid concern in my view.