There’s not much to see here. The roaster panel is how the factory made it on the surface. But you might notice the missile switch up the top. I was at Jaycar and I thought it looked pretty neat. It allows switching between automatic and manual modes. I didn’t want to have a situation where I was roasting, and the computer locked up and I would lose a batch. So, for redundancy, I put a switch here in case I need to revert back to the default mode
This is the front panel of the roaster. I placed three K type thermocouples on the front. One in the bean mass (you can see it through the glass on the front), one in the middle of the roaster (for environmental readings) and one next to the old analogue gauge. The roaster is very noisy electrically. I had these thermocouples made to specification by an engineering supplier and they work fantastically.
This is the newest control board that I've made. It uses an Arduino Nano to send information over Bluetooth to the computer. It uses some MAX31855 thermocouple amplifiers to read the temperature. It also allows electrical control of the heating element and fan speed. This allows me to turn the whole roaster over to computer control wirelessly.
I also changed out the insulation. I found I was wasting too much energy by not properly insulating the drum, I used a special grade of industrial insulation, which greatly increased the performance and energy savings of the little unit. The more head I can hold in, means the more heat that goes into the beans and the less I waste heating metal. Once this roaster gets hot, it stays that way until the days roasting is done.
I develop for Excel professionally and I wanted it use it as the basis for the computer program because I could get something together that worked relatively quickly. The program logs data, plans roasts and controls the roaster automatically. I use an algorithm I wrote to draw an ideal curve (red). The roaster uses the control software I wrote to change the element heat and fan speed to best approximate the curve. This means I can get near perfect RoRs, and really good coffee. When the batch is done, the computer saves the curve to PDF and I can start again. The spreadsheet also allows me to plan the batches ahead of time, and estimate how long it should take to complete the roasting program.