So I’ve played around with the PID settings. I haven’t officially sat down and tried to do a “real” tuning since the processing app I’m using right now lets you play with different numbers and feed it back to the Arduino to tweak it. As a result I came up with a few numbers that flattened out a lot more than it did previously.
First roast with crudely adjusted PID
Next I will need to take it more seriously I wipe out the configurations, dump some junk beans in, and fire up the roaster and calibrate until I can’t stand it anymore and then roast some coffee again.
In regards to the button controller I have figured out a layout that I will likely use but I’m trying to keep this accurate on the schematic system I’m working with to build a real PCB later. For whatever reason the part in the system appears to not match every other part I’ve seen out there and what I’m currently working with. I also need to go back to radioshack and buy a resistor I’m going to need because the big multi-pack I have doesn’t include that one resistor that I need to make the math work.
The last couple roasts with this new controller turned out decent enough. After 3-4 days rest they had extremely good smells (but tasted only “pretty good”.) Today’s two tests are MUCH closer to ideal roasting the way they worked out and the smells (and the smoke detector) agreed at the right times. I’ve got two batches waiting that will get consumed over the next several days and we’ll see how it’s going as they rest. I’ve got a single serve coffee brewer that’s working out better than some of the other ones so it will take me some time to work through all of the beans.
For this roast session the first one (where I was playing with random tunings throughout) came out acceptable with some good flavor but generally lacked any sort of really stand out flavors that made it noteworthy. The second roast pictured in the screen shot, however, was a lot more solid in terms of tracking the roast curve. It had a lot of flavor to it than the first roast and it seems to be going the right direction. I know I’ve gotten more flavor out of these particular beans (I’ve got about 20 lbs of them to work with) but for the most part they’ve never been very repeatable. There are absolutely certain qualities that seem to be coming out roast after roast with the Arduino controlled roaster now but I still need to get the heat control more reliable and less “wild” by tuning properly.