After more than a year of using it :
With the true drum roaster it is possible to manage the roast, much easier than with Gene Café, I used before. Very good results.
I prefered longer roasts, I couldn't say why.
E.g. Brazil 12.30-13.00 for FC was OK. With new coffee very bland. The same good results now I have with FC time 10-10.30
I have bought a cheap (~ 20$ ) Digital Grain Moisture Temperature Meter Tester from China. Now I know the reason : A humidity of new coffee is 9% , compared to old with 13%. ("old" is meant bought earlier)
The "drying phase" length must match the moisture of coffee. The rest of the roasting profile can be the same - it must match the bean an the taste target.
A lot of time is passed...
The wrong ideas can be right after some time...
I made the additional 300W air preheating, as was earlier planned.
I use higher temperatures for preheating of the roaster. The sensitive beans can last out higher temperatures, only the heat must be added at the beginning. I had small defects with brazil beans by 180C preheating and roasting time about 15 minutes, with 210C and roasting time about 11 minutes - no problems, beans without any defects.
For better repeatability of roasts was my SW solution (in console) not ideal.
But the idea of Raspberry as a part of the roaster, without connecting to PC, this was right. I made new SW, in this case in Rpi native language : PYTHON.
The functionality is now as by other usual solutions. I can now compare multiple profiles.
I can use only small numeric keyboard and operate this as "roaster component". I like this simplicity, I am tired of mouse , this is my everyday job routine.
For smaller roasts I can switch off air preheating, and in every roasts it is switched off automatically at 170C - for possibility of cooling after FC.
The key for roasting is to achieve about the same preheating values - BT,MT,MET and then is repeating very easy.
For indoors conditions I have improved air exhaust. It was necessary, I make now more coffee, about 4kg/month.
I have the same feeling, the preheating helps. I make the coffee now closer to Rao´s principles. It can be right too, a perforated drum needs shorter roasting times. The profiles above are good for coffee with minimal acidity. I like it so for espresso. I usually mix (not overly traditional blend) 75% of this brazil ,up to 222-3 C, dumped just on hint of SC or close before , with 25% of colombian or nicaraguan coffee . This is roasted to 226, 20 sec in SC. It still preserves acidity and has no oils on the surface.
I drink moka or drip only on vacancy time, where I can´t make espresso.
For this purpose, I make nearly the same coffee, I dump it about 5 degrees before. Sometime I give this coffee to a friends and they are very satisfied with it. But this is very subjective classification.
I know, when SC is about 223 C, the recommendation for non-espresso is dump about 208 - 210 C, but this works not for me.
I believe too, there is no universal profile (I´m searching for), it depends on bean, roaster and taste preferences.
My profiles now generally meet 150 at 4 to 4.30 , FC 8-9 , end on 11-12.
The roaster is now 2.5 years working, without failure and almost without maintenance. The key is to respect its properties. I am roasting now only 500g batches, for aeropress and espresso. It is easier to keep the profiles with constant load. The time has shown, the best are shorter times with higher preheating temperature. Close to Rao´s principles, but I prefer longer DTR (about 30%) for espresso. It can be caused by perforated drum and higher early RoR. Perhaps.
Your roaster and software look awesome. I'm not sure how I missed seeing your build earlier. Thanks for sharing. What is the source of your drum? Did you buy or build it?
Quest M3, IMEX digirosto 1500, various popcorn popper roasters, with TC4 logger, PIDed Rancilio Silvia espresso, Presso, Chemex, Hario, and Melitta drip, Cory and Yama vacuum/siphon, bodum french press, aeropress; Mazzer Major, Hario mini, and PeDe Dienes grinders - and a Nuova Simonelli Aurelia rebuilder in pieces
The drum is welded from 1.5mm peforated stainless.
It´s funny, the drum, vanes and heating is very similar to new chinese Dalian Amazon 1 KG Roaster, DLA721. https://www.bella...aster.html
I have by contrast insulation and more Watt/kg ratio, but not the big mass of the front plate. And my one is more ugly!
The profiles above have greater DTR, it is by low airflow in winter cold days, with "Rao" style of roasting and very low ambient temperature. In this case is the heat transfer inside the bean probably lower and it requires more developement time. In better conditions I use more airflow and smaller DTR (25%).
So that I may to roast by the same way more beans as well as in winter, I decided to add another 600W heating element. I have had to do it directly.
For better control of airflow I use pressure detection in ducting (MPXV7002DP sensor, like this solution: http://www.home-b...34759.html) and I log now fan rpm and air pressure.
(The pressure can be used for functionality control: the duct is clogged or the damper is in wrong position)