The picture is of the CRF-150, the prototype of an interesting new project in Korea. It is designed for about 50 to 200 grams of raw coffee (I suspect from the name that should be 150 grams, but anyway it is capable of 200). It is a fully automatic roaster with ceramic heating elements, and a ceramic afterburner which burns up all the waste gases. It is rated at 1kW.
It is a part of a project to produce a machine that automatically roasts raw coffee and makes a pot from the freshly roasted beans, but this machine here only does the roasting.
I have one of the prototypes here for testing, and over the coming weeks when I can find the time I shall give some more photos and information on it.
Basically: a lady from the company behind the project came to our roasters meeting where we had one of these machines to try out. I asked her about the ceramic heating elements (thinking of my Hottop - I've long been wondering about replacing the element with ceramic) - and then she said, well you know, we need people to test it, maybe we can give you one to test?
Sorry I haven't managed to find time to put in a detailed report and photos yet! I hope to find the time to do so next month.
Just a quick preview:
The ceramic heaters work very well, although I'd like to see a bit more juice;
the ceramic afterburner also works well, burning off the smoke and smells in the exhaust gases;
the built-in roast profiles are a dead loss;
the cooling cycle is very problematic;
there seems to be some problems with the design of the electronics, especially the power supply.
I've managed to tap into the digital signals controlling the roaster and can now control heater, fan, motor and afterburner all manually with the TC4 connected, and have managed to get some much better roasts as a result. My biggest problem at the moment is that the bean temperatures I am getting are massively lower than I am used to - eg first crack at 175 Centigrade!! That is with the same thermocouples and TC4 that I have used on my other roasters, where I always get first crack in the range 200 to 210 Centigrade (c. 204 to 210 for most coffees).
Does anyone have any idea what is causing the temperature to read so low? I know a number of larger drum roasters (Diederich for example) also get very low readings for bean mass compared to what I am used to, and I always suspected it was related to the sensors and/or electronics, but here I am using exactly the same measurement equipment and sensors as I use on my Hottop and HotPot. What could be responsible for this difference?
I have a 1.5 mm steel sheathed thermocouple poking into the roast chamber from below, with the tip covered by the beans. The ceramic heating elements are above, and heat by purely radient energy. Interestingly, I originally had the tip a bit too high so that it was not always covered, and then it also gave readings a bit too low, eg first crack 194 to 198 Centigrade. Since the heating works by infra-red I could "understand" it being a bit low on the basis of poor IR absorption and expected temperatures to rise when I adjusted it to the proper height - instead the reverse happened! Recorded first crack went right down to 175 Centigrade, so that all the temperature measurements are pretty hard to interpret! At 200 Centigrade on my first roast I even got a small fire!
One possibility that does occur to me is earthing problems, because the thermocouple is in electrical contact with the body of the roast chamber, and there does seem to be a difference between the ground levels of the TC4 and the roaster. There is a special terminal on the electronics card for a ground wire, but there is no ground wire installed! However as far as I can see the card should be grounded by the mounting screws anyway. Could there be some problem of differences between the digital ground (on the roaster) and the mains ground, and could that explain why the earth wire is not installed? And if that is so, could there be any dangers in trying to ground the TC4 to the roaster chamber?
Not sure what could be causing the weird read at 1C.
A couple of thoughts on the roaster. From your description it seems similar to the design of the Korean Unimax 2000 which was an overhead IR design with a small spring loaded stirring arm at the bottom. It too suffered from woefully inadequate cooling and sometimes went into and continued in 2C for 15 seconds into the cooling cycle. It's controls were pretty crude, a thermistor sensor strapped to the side of the vertical RC can feeding a simple electronic stat that had a dial you could set for ending the roast and starting the terrible cooling cycle.
No matter where you set the dial you never knew where it would end the roast so you just set it to max and ended the roast manually.
The roaster used two 350 watt quartz tubes with coiled nichrome inside and could stop heating fairly rapidly.
A potential problem with your ceramic IR heaters is the high thermal inertia and resulting slow reaction to control changes.
Does this roaster use programmed time/power level steps or real PID time/temp steps?
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana