Tuesday, October 14, 2014

Rebuilding a Kiln Controller: An Engineer's Story

A couple weeks ago my kiln failed right at the start of a firing.  We were getting an error message we didn't recognize.  It turns out that after 4 years of regular firing, the kiln controller needed to be replaced.  Fortunately, Colin (The Suburban Guy) is a systems engineer and his dad is an electrical engineer.  Rather than drain our account and buy a new controller, the two of them decided to build their own.

I'll let Colin take it from here...
Inside of my kiln's controller
See those white wires up at the top of the photo?  Those wires power the elements inside the kiln which generates the heat to fire Diana's work. The key to making the kiln work is to measure the temperature inside the kiln and then turn the elements on and off controlling how fast and to what temperature the kiln reaches. We fire to Cone 6 or around 1250 degrees Celsius. The work my dad and I needed to do was to replace the green board in the middle which is where the brain lives.

Testing the new controller-in-progress
The first step in the process is to make a prototype and make sure each part of the controller was doing what it's supposed to. What you are looking at here (besides a mess on the kitchen table!) is our prototype. What it does is measure the temperature of the room and then turn on and off a very high powered switch (the black box at the top left of the picture). There are a few safety parts in the way as the kiln is a VERY high powered device and I wanted to make sure we were safe (Diana runs with scissors).

Testing the controller with a lightbulb
This step was the fun part (to an engineer). To make sure the computer program I wrote worked right, the temperature probe (the part below the light bulb) was stuck by a heat source and then the new controller was given a temperature to control the probe. For our test I tried to have the controller hold the probe at 50 degrees Celsius. The result was a success and a lot of blinking on and off (the bulb not my eyes)!

Testing the new controller on the kiln
Here we have the setup outside and attached to the kiln. The original controller's box is on the floor in the back and our controller lives on the wood in the middle. This setup was a bit delicate as there is a lot of electricity which goes through the elements when the relay turns them on. My dad and I attached the computer to the controller so that we could watch the temperature go up with the program I wrote to make sure it did what was expected. The kiln was loaded with a few pieces to make sure things went right. I made a few adjustments after the first firing as it was a little too hot and heated a little long, but it was a huge success!

The brand spankin new controller

You are looking at the final package. All those crazy wires and bits and pieces wrapped up into a nice little package. The only addition to this is an SD card (the same thing that's in a digital camera) so that the program can record what it does giving us a record of each firing. It is important to know what the kiln does each time so that each batch can be compared when things go well (or not so much at times!).  I'll be installing the new controller into the old controller's box later in the week.

There it is in a nutshell. A little engineering experience and some really cool electronics and the controller for the kiln was duplicated in a weekend and a couple of glasses of wine (it's what fuels the Suburban Guy)! 

Diana P: There it is!  I have no idea how to do this stuff so I married an engineer.  Ok, that's not the ONLY reason I married him.  Thanks to Colin and my father-in-law for getting me back in business!

Happy Beading!

Diana P. & Colin "The Suburban Guy" Mellars


  1. Oh boy - not looking forward to the day my kilns pack up as i know no-one capable of kiln brain surgery. Bring your tools when you come over to visit Colin :0)

  2. This post was interesting to me. I have seen my husband do lots of similar things to cars not kilns.

  3. I LOVE this post - Really interesting! Thanks Colin for writing this up and sharing!

  4. everything that both of you do *Diana and Colin* is amazing to me! Thanks for explaining!

  5. I absolutely love the idea of an SD card that you can use to see exactly what happened during a firing - I could really use one of those for my glass cab work! Does Colin hire out?? :-)

    1. You can always shoot him a message and find out!


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