I bought a Masterbuilt 23013314 Butterball Indoor XL Fryer from Amazon when it was the deal of the day recently. I ran some tests and it was holding temperatures reasonably well maybe with +5 degrees. But I wanted finer control so I can use it brew small batch beer. I took the main heating bit apart. Some pictures here https://goo.gl/photos/6SSZS5LTRwqzmu9X9 I was surprised to find no active control that I recognized. Just a potentiometer and two of those round silver things and a mechanical limit switch.
So now I'm thinking I will put a solid state relay in there and connect it to an arduino. Is there any reason I can't just drive the heating element straight from those ebay ssr 24-360VAC 25A? Also how hot can the arduino get? Maybe I should mount it externally and blow a pc fan across it. Since I will be boiling water temps could be near 100c.
You probably already plan to do this but just in case I highly recommend leaving the original control system intact and just set it a bit higher than the highest temperature your system will go to under control of the Arduino. This way if there is a bug in your program or hardware you have a backup temperature limiting system that will prevent any serious mishap(other than possibly ruining your brew).
Yeah I already ripped out the two funny round things it had. I'm guessing they were thermostats. I plan to work on it more later tonight. I left most of the wiring in place which looks like high temp fiberglass.
I pulled out everything in the removal controller/heater unit that I didn't understand; including the lights. I left the limit switch which seemed to be serving a useful function. Then I just dremeled in a hole for the ssr. I connected the dc inputs of the ssr to a female pigtail and after giving 3v from a breadboard I successfully heated up some water.
Next I think I will build the temperature sensing circuit.
