Update on the milowidget
Here are a couple of plots from weekend testing of the milowidget on the hottop. All I am doing right now is turning heat on and off once per second depending on the bean temp vs the profile.... simplest method so far.
The 1st plot is of the first roast with 250 grams of green. Note how good the ramp is and how closely the bean temp followed the profile, once it caught up with the curve.
The 2nd plot is of a roast of about ~75 grams of green. I want to be able to control the curve no matter the green I put in (within reason of course). With the smaller bean mass there is temperature overshoot both directions. Also not how extreme the environment temp goes up and down too. This is where the PID control will come in... now just to implement that in code..... that and a few small glitches in code here and there.... safety code (so the thing doesn't burn up)...
Also found out that once the hottop warms up, it's more difficult to keep it on temp... odd, but I think that's because it's hard to cool it off quickly. I'll need to tinker also with the fan and see how that affects the curves too.
If only I didn't have a day job to distract me from my work
On a side note, my temp swing (see plots from a few posts earlier), I found out, is coming from serial port noise on my interface board..when my laptop is plugged in... unplugged the reading is stable (note difference from plots a week ago). I
may need more shielding on the interface board or may have to move the thermocouple connector away from the serial port terminals. Also the temp spikes are real readings also probably some sort of interference. The thermocouple voltages are very very small so any higher voltage near them can cause spikes. Looks like I'll need to enlarge my ground plane near the thermocouple inputs to the amplifiers.