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Step 4The Arduino program code
The program to run the Arduino consist of work of others, as it include a library for the LCD display (LiquidCrystal.h) and the PID control (PID_Beta6.h) , and a protocol to communicate with the associated Arduino PID Tuning Front-end, running on Processing (same maker as the PID control library, great work from Brett Beauregard!)
The program does the following:
Display a welcome screen and waiting for you to push the button. Then it turns on the fan but not the heating coil and it allows you to set the minimal fan speed at which the beans still move a little (you can lower it during the roasting as beans get lighter). When you press the button again the heating coil is turned on and the roasting starts. The program continuously measures the temperature and adjusts the fanspeed in order to match the set point. It will lower the fan speed to increase the temperature of the beans of increase the fan speed to do the opposite. If the beans get more than 3 degrees above the set point the heating coil is switched of, which will lower the temperature directly. The set point is updated along a profile that is set into the program. First heat up to 150C and stay there for 1 minute, then slowly increase to 190C and stay there for 1 minute. Then slowly increase the temperature again until the final temperature is reached. At this point, the fan is set on max and the heating is turned down. The roaster stops when the beans are lowered to 40C.
After lots and lots of tweaking, the final program code to run the coffee roaster can be found in the file below.
The program does the following:
Display a welcome screen and waiting for you to push the button. Then it turns on the fan but not the heating coil and it allows you to set the minimal fan speed at which the beans still move a little (you can lower it during the roasting as beans get lighter). When you press the button again the heating coil is turned on and the roasting starts. The program continuously measures the temperature and adjusts the fanspeed in order to match the set point. It will lower the fan speed to increase the temperature of the beans of increase the fan speed to do the opposite. If the beans get more than 3 degrees above the set point the heating coil is switched of, which will lower the temperature directly. The set point is updated along a profile that is set into the program. First heat up to 150C and stay there for 1 minute, then slowly increase to 190C and stay there for 1 minute. Then slowly increase the temperature again until the final temperature is reached. At this point, the fan is set on max and the heating is turned down. The roaster stops when the beans are lowered to 40C.
After lots and lots of tweaking, the final program code to run the coffee roaster can be found in the file below.
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