[Homeroast] profiling (was Re: Two QM3 roasts of Limoncillo Pacamara DP)

Allon Stern allon at radioactive.org
Thu Jan 13 23:38:24 CST 2011

On Jan 13, 2011, at 9:50 PM, sci wrote:
> I'm trying to learn how to profile beans. 

I had a thought about how to profile beans and I wanted to particularly get miKe's opinion on this....
You can watch the heat, sure, but once a profile is set in the PID, it pretty much follows that profile, but I noticed something interesting when watching a PID roast of Jimma, using miKe's profile....

with my PID unit, you can watch the % heat applied; it's interesting to watch the duty cycle of the heater at various stages in the roast. So when the roast hits a point that the beans are soaking it up, the heater works harder to hit a target temp, and when the beans are done soaking it up, the heater works less hard.

I noticed that right at the end of the profile, it was just over a hump, as it were, the duty cycle went through a peak, and had just slacked off at the end of the roast, and that got me thinking, is this one indicator of a sweet spot?

(not that all humps will indicate a sweet spot, but are all sweet spots right over a hump?)

Should be educational to set a PID to a linear roast, then graph the % heat applied vs time, alongside the temp. I'm thinking that something like this might be a good calibration roast, which you could then use to determine where to start and end each stage's ramp, as well as EOR.

Just a thought. Anyone?

(wish I had a QM3 just so I could PID it :D )

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