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High Bridge Pottery

Home Made Kiln Controller

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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.

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Bob at this point it looks like I need to aquire some skills so I don't cause a power outage on the East Coast. :) That will come since I like learning but can you suggest some basic electronics layman's texts to self teach m'self?

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I had very little knowledge going into this project. Did a little electronics back in school but that was it.

 

Lots of people out there doing videos on electronics, can't recommend a book as I learnt it all from youtube/google searches and making lots of mistakes.  

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Another thought here is to go from the normal relays in the kiln to using a thyristor/solid state relay.

This is because, when not at full whack, the normal relays generally have a maximum in.off cycle time of at least 30 seconds, which causes temperature fluctuations in the elements. According to Kanthal, this can reduce their life by as much as 20%. However this will be most noticeable as you fire closer to 1300 and have long soak times - if you just do earthenware you probably won't notice the difference.

They aren't just a straight plug-in replacement, though, and a bit more knowledge of electrics is needed to make a safe and reliable system.

I plan to do this on my kiln round about Easter this year, as I replace elements all too often with my high fired oil spot glazes, so anything that saves time and money must be good!

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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 electronics and also programming. I believe the simplest software development environment is the Arduino one which uses the "C" language. Most of what you want to do is already there in some form or other. You just go to the site and download it. There are also lots of information on basic electronics and how to hook stuff up. Once you learn a few C language commands, you can do a lot by just modifying existing code scripts. Also, The forum is very active and there are lots of people willing to help with your project.

 

Here is the link... You don't have to contribute to download at this point, you can click the just download button, but if you end up using it in your project, you might kick in a few bucks.

https://www.arduino.cc/en/Main/Donate

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Finally got round to hooking it up to my rust bucket of a kiln. It's a little hazardous with all the wires but let's call it prototyping. It will become a lot more slick and safe once I know it is working as intended.

 

Had a little battle with getting the earth hooked up to the kiln while being able to run live/neutral through the relay but I got it sorted in the end after moving it up onto the table closer to the plug. This won't be the final resting place. Also the HDMI went on my Pi so I bought another from the shops. This one still seems to have slight issues but I can at least get an output to a monitor. Once it is set up completely I will be accessing it remotely.

 

Also been opening up my old kiln controller trying to find out what went pop. Found a few suspicious looking resistors. One with the tell-tail signs of skid marks and another that seems to have fallen apart with age.

 

med_gallery_23281_1039_1506359.jpg

 

Only ran a few ramps. One going up to 100 with a hold and then another going to 200 with an hour hold. Needs a little bit of tweaking as it is overshooting the temp a bit too much and maybe not going below the set-point enough. All in all I had a lot of fun today. Need to find some time I can be around baby sitting it for a proper firing.

 

med_gallery_23281_1039_1511808.jpg

The top y-axis is 220 and the set-point is 200 so it went between 200 and 210 or there abouts.

 

Tested out my voltage and it is bang on 240v and the kiln was drawing just over 13amps. Is that good or bad on a 13amp plug socket, not too sure but I remember reading resistance decreases as temp goes up so hopefully it will pop under the 13 mark as it gets hotter. If anybody knows for sure let me know. I would hate to fuse the whole floor (managed it before from bad wiring, not drawing just over 13 amp) and have some very angry computer guys next door.

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Just checking... the angle of the picture make it look like the main power is going to the same location as the controller. And you were worried about 13A -- an amount less than a normal household socket can handle. I will also add that resistance generally increases with temperature according to hyperphysics. This means more amps are needed to flow to generate the same amount of power at a high temperature.

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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.

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Hi Joel,  I'm using the AD595 which works with a K type thermocouple, the chip is quite expensive but it is pretty accurate.   well it might seem like I know what I'm doing but I've just fudged my way through it over a few years.
 

The programmes are created in XML on the PC then sent to the controller via Bluetooth, it can hold ~500 programmes, each programme can have up to 255 segments each. It will log each successful firing into a 32k memory segment, then you can retrieve the logs via Bluetooth for display into a graph, the number of logs depends on the sample rate it's set at.
 
Everything is coded in C, the LCD, the Real Time Clock, the 64k EEPROM and also the Bluetooth UART RX / TX lines,  so all custom code and no code libraries used what-so-ever.
 
The example below is a typical programme to biscuit fire a ceramic; this particular one has 3 segments, seg 1 is 200'c at a ramp of 30'c per hr, then 600'c at 70'c, then finally 960'c at full power and it will hold for 15 mins. The XML will get compiled to a binary file then it's uploaded to the controller via a c# console app. the uC then just stuffs it into the 64k flash memory. The uC reads it back when you're selecting a firing programme via the menu of the controller.  When the controller is running it gets the time in minutes since you started, and then calculates the target setpoint based on the XML data; it also makes an initial adjustment based on the ambient temperature to skip up the curve to the correct starting place.  Regulation is just done via on/off of the SSR
<prog> <title>Biscuit</title> <short_description>Biscuit Firing</short_description> <long_description></long_description> <seg data="200,30,0"/> <seg data="600,70,0"/> <seg data="960,999,15"/></prog>

At the moment I'm in the process of re-writing all the code to work on a bigger chip  so I can add more features, but my plan is to create a nice controller that is easy to use and cheap to make, and that can perhaps be easily be maintained in the future. the idea is to keep the design all through-hole components, so perhaps it could be easily built up as a kit or repaired.

 

 

 

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At the moment I'm in the process of re-writing all the code to work on a bigger chip  so I can add more features, but my plan is to create a nice controller that is easy to use and cheap to make, and that can perhaps be easily be maintained in the future. the idea is to keep the design all through-hole components, so perhaps it could be easily built up as a kit or repaired.

 

 

Ah, so you are looking to be the Al/Grippo Megasquirt of the kiln world; not a bad idea. The only problem I see is you'd have to come in under the $219 cost of a new Bartlett V6-CF enough to make it worth while.

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At the moment I'm in the process of re-writing all the code to work on a bigger chip  so I can add more features, but my plan is to create a nice controller that is easy to use and cheap to make, and that can perhaps be easily be maintained in the future. the idea is to keep the design all through-hole components, so perhaps it could be easily built up as a kit or repaired.

 

 

Ah, so you are looking to be the Al/Grippo Megasquirt of the kiln world; not a bad idea. The only problem I see is you'd have to come in under the $219 cost of a new Bartlett V6-CF enough to make it worth while.

 

 

Lol - not sure about that ;-)   but I was thinking about £95 / $126.

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At the moment I'm in the process of re-writing all the code to work on a bigger chip  so I can add more features, but my plan is to create a nice controller that is easy to use and cheap to make, and that can perhaps be easily be maintained in the future. the idea is to keep the design all through-hole components, so perhaps it could be easily built up as a kit or repaired.

 

 

Ah, so you are looking to be the Al/Grippo Megasquirt of the kiln world; not a bad idea. The only problem I see is you'd have to come in under the $219 cost of a new Bartlett V6-CF enough to make it worth while.

 

Lol - not sure about that ;-)   but I was thinking about £95 / $126.

 

 

 

Those guys came out of a garage and changed the automotive aftermarket forever. I knew it was just a matter of time.

 

https://www.diyautotune.com/

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There's a lot more cars around than pottery kilns, even if you just take owners who want to work on them themselves, so I don't think you'll make your fortune with a kiln controller!

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Not directly part of the kiln controller, but having just had a problem with power supply to the kiln (see separate post) I'm starting work on a power monitor. At work we're doing something stuff with an ESP286 (Arduino compatible but with built-in WiFi) I was thinking of using that combined with one of the AC power monitoring ICs to do all the maths for measuring Volts, Amps etc, to an app for displaying and logging data. Although the original trigger was to just detect power failures, by doing this I can monitor V and A, plus total power consumed during a firing etc, so check what is happening in more detail.

Willing to share details when it is further developed.

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There's a lot more cars around than pottery kilns, even if you just take owners who want to work on them themselves, so I don't think you'll make your fortune with a kiln controller!

yup very true!

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Not directly part of the kiln controller, but having just had a problem with power supply to the kiln (see separate post) I'm starting work on a power monitor. At work we're doing something stuff with an ESP286 (Arduino compatible but with built-in WiFi) I was thinking of using that combined with one of the AC power monitoring ICs to do all the maths for measuring Volts, Amps etc, to an app for displaying and logging data. Although the original trigger was to just detect power failures, by doing this I can monitor V and A, plus total power consumed during a firing etc, so check what is happening in more detail.

Willing to share details when it is further developed.

"Costings" is something I've already put in the menu option for my controller but not written the code for it yet, as I think it's a handy feature.    I had thought about power monitoring but it would add extra cost and build time;  so instead you could just buy a logging clamp meter like the UNI-T UT233 instead.

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There's a lot more cars around than pottery kilns, even if you just take owners who want to work on them themselves, so I don't think you'll make your fortune with a kiln controller!

yup very true!

 

 

 

Never said nor implied but the main thing they did is change the industry forever. ;)

Tim T likes this

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Ju00Ls,

Firing costs is one aspect, and another is to combine with temperature and monitor when kiln elements are getting towards end of life.

Being out in the sticks power can be a bit dodgy - power cuts typically every couple of months - so I thought it may be useful to monitor V as well as A.

I'm using a power monitoring IC as they are cheaper than using discrete components, and the processing is all done on the IC, so less coding for me and also less load on my CPU.

Also, the intention is to build it up into monitoring temperature, and then controlling the kiln, but do one step at a time.

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Ju00Ls,

Firing costs is one aspect, and another is to combine with temperature and monitor when kiln elements are getting towards end of life.

Being out in the sticks power can be a bit dodgy - power cuts typically every couple of months - so I thought it may be useful to monitor V as well as A.

I'm using a power monitoring IC as they are cheaper than using discrete components, and the processing is all done on the IC, so less coding for me and also less load on my CPU.

Also, the intention is to build it up into monitoring temperature, and then controlling the kiln, but do one step at a time.

 

 

cool!   what chip are you using?

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