I spent some time yesterday documenting the build of my second-generation bean mass probe. This includes a new mounting scheme for the electronics that eliminates the need for thermocouple connectors. It also includes integration with the AdafruitIO dashboard to make accessing the data during roasting super easy. Check it out here.
Some time ago I developed a bean mass probe for the Gene Cafe coffee roaster. If you are familiar with this roaster, you will know that adding a bean mass probe is a little tricky because of the way the drum rotates. Basically, to make this work, you have to have a wireless temperature transmitter to get the data off the rotating drum and, additionally, you have to deal with the fact that the beans will not always be in contact with the thermocouple.
My first attempt at this worked pretty well using an Adafruit ProTrinket coupled with a Bluetooth board. Recently, I developed the second generation of the bean mass probe using an ESP8266 micro controller (Adafruit Huzzah) that allows me to connect directly to the roaster using WiFi and MQTT. With this I have now created a pretty slick Internet of Things Bean Mass Probe.
I’ve actually converted the entire RoastGenie system to IoT technology but that is a topic for another post.
The basic architecture of the system is shown in the figure below. I host my own MQTT server (Mosquitto) but I think you could easily use Adafruit IO as your MQTT broker. I’ve not worked with this system but it looks like it has some nice features. If you use Adafruit IO, I think you could access you live bean mass temperature data with a web browser instead of a traditional MQTT client (I use MQTT Spy). The real utility of having the bean mass probe use the MQTT protocol is that you can easily integrate the data into other systems (like the RoastGenie itself).
The bean mass probe consists of the following components: Adafruit Huzzah micro controller, MAX18255 thermocouple amplifier, and a LiPo battery. The schematic is below.
Note: A previous version of this schematic I posted had an error (the power lead to the thermocouple amplifier was shown incorrectly connected to 3Vo instead of Vin)
These components are attached to the Gene Cafe on the rotating plate on the inlet side of the roaster. The connection between the drum and the TC amplifier is done using mini K thermocouple connectors from Omega engineering to facilitate easy removal of the roasting drum. The LiPo battery is attached to the roaster with a pair of Neodymium magnets so it is very easy to remove and recharge.
The thermocouple is installed in the drum as shown in this post. This system works like a charm and is very tolerant to disruption in connections – unlike the Bluetooth version which would typically not reconnect if there was some problem (like a discharged battery). I will try to get some additional details posted about software over the next several days — in the meantime, let me know if you have any questions.
Because Sweet Maria’s does not make it easy to find tasting notes of coffees that are not currently available, I archive them here when I buy them. A bunch more is on the way!
Ethiopia Agaro -Nano Challa Cooperative
|Arrival Date||July 2015 Arrival|
|Appearance||.4 d/300gr, 16-18 Screen|
|Intensity / Prime Attribute||Medium Intensity/A concise and clean cup , bracing brightness, sweet, aromatic fruit and flowers|
|Region||Gera, Agaro Woreda, West Ethiopia|
|Roast Recommendations||City to City+ roast levels have the best sweetness and fruited notes, and a lively acidic snap. Full City roast has less fruit and sweetness, with a nice Dutch cocoa roast tone.|
|Recommended for Espresso||Yes|
The Nano Challa Cooperative is part of an initiative we have in Ethiopia to work direct at the coop level. The name Nano Challa refers to a local mythic tale about a challenge to become King of Jimma, and the coop adopted it to signify their desire to be a strong cooperative. Indeed, many coops in the West of Ethiopia have struggled to find good buyers who will pay enough for the coffee, to manage their own debts, and from internal struggles and graft. Nano Challa was formed as part of a new initiative to aid farmers in a more comprehensive way. The program is administered by a non-government organization that not only coordinates agronomists and managers for each of the coops they work with, but also has a business adviser assigned that helps the cooperative manage their debt, re-invest in quality improvements at the mill, and verifies distribution of income to all members. Nano Challa is a smaller cooperative coffee mill near Gera town in the Agaro area, Western Ethiopia. (The area also has some of the finest honey available in Ethiopia). The farms are at altitudes between 1900 to 2100 meters, planted in old regional varieties of coffee.
Nano Challa has a very refined cup character, something that will definitely strike a chord with light roast purists. Floral, sweet, clean and bright – the improvements we’ve tasted over the years are a testament to how this particular farm relationship has paid off. The dry fragrance is loaded with honey sweetness and floral jasmine hints. Caramelized sugar and toffee smells come up from the wet crust, a candy sweetness that reminds me of torrone. All of this translates to a bright and well-structured cup flavor. There is Ethiopian white honey, which is mildly fruited in flavor, and a healthy dose of ginger spice (together making for a ginger-snap cookie flavor, particularly clear in the finish). Lighter roasts have a mild citrus note, jasmine flower, and Earl Grey tea. Citrus notes are especially built up in deeper roast levels, along with a Ricola-like dark herbal aspect. Nano Challa has a lighter mouthfeel that suits it’s bright and effervescent cup flavors. Nano Challa cups OK at Full City+, but loses the intense sweetness and bouquet of fruit that is afforded at lighter roast levels.
Ethiopia Dry Process “Gey” Harar
|Arrival Date||August 2015 Arrival|
|Appearance||1 d/300gr, 15+ screen – expect to find a few broken, insect damaged, and quaker beans|
|Intensity / Prime Attribute||Medium to Bold Intensity/Rustic sweetness, dark berry, rustic notes|
|Region||Harar, Misraq Hararghe|
|Roast Recommendations||City+ to Full City+, this coffee can take a bit of heat|
|Recommended for Espresso||No|
This is our first Harar offering in quite some time. Harar is the ancient Western capital, a walled city that has been a source of intrigue for centuries. Misraq Hararghe (pronounced Harar-Gey) is the name of the greater Harar area that the city commanded, and it seems that”Gey” is a shortened name local Harari people use for the area. True Harar coffees are from the higher Eastern areas, but many coffees sold as Harar from the Western area. We try to focus only on the more traditional East coffees. Harar coffees are dry-processed out of tradition and necessity. The zone is much more arid than the Western or Southern coffee lands of Ethiopia, and there simply isn’t enough water for wet process fermentation and washing. There is a lot of competition for Harar coffees, which sadly has been a disincentive to quality; if farmers or millers know they can sell anything at a good price, why pick coffee fruit selectively? Why keep batches separate? The result can be coffee with many quakers (under-ripes) that affect the flavor and roast quality. This batch is not a farm direct lot; it was sourced through the Ethiopia Coffee Exchange and stood out because of the nice cup quality. Then we had it prepared with extra hand-picking at a mill in Addis Ababa. The resulting coffee still has all the complex wild and rustic notes of Harar, but also ample sweetness from the initial sip through the long aftertaste.
The rustic quality is expressed as earthy-sweet syrups and ripe berry notes all along the profile, from aromatics to cup flavors. The dry fragrance has a smell of strawberry and blackberry syrups, fruity and sweet, with hints of almond meal and baking spice. There’s an earthy quality too, a greenish scent of forrest floor underneath. The sweetness expands with hot water, and the steam smells of a mix of fruit reduction, rice syrup, and musky raw sugars. The cup is very sweet, mixed-berry jam and a hint of papaya, with an overlay of earth-toned sugars. A strong note of dried apple comes out as the cup cools, tart and even slightly “winey” notes that dried green apples have. Some of the more “rustic” elements include leather, and aromatic wood, flavor notes we find in coffees from Yemen, though not over bearing, and a bit more in balance with sweetness/bittersweetness (especially as you near Full City). It’s a complex brewed coffee – sweet, rustic, and with elegance to the top notes, really one of the better Harar selections we’ve tasted in a while. It’s uniquely “Harar”, a region once thought to offer the best examples of a naturally-processed coffees in all of Ethiopia.
Ethiopia Yirga Cheffe Dry Process -Aricha
|Arrival Date||August 2015 Arrival|
|Appearance||.6 d/300gr, 15-18 Screen|
|Intensity / Prime Attribute||Bold Intensity/Strongly fruited character, intense syrupy sweetness, thick body|
|Roast Recommendations||This coffee works at a wide range of levels from City to Full City+, probably even darker – the brighter jam-like fruited sweetness is going to be found with a well-developed lighter roast, around City+, and well before the coffee enters 2nd crack.|
|Recommended for Espresso||Yes|
This is our selection from one station in the Aricha kebele in the Yirga Cheffe area. There are two coffee stations in close proximity here, and Koke is just up the road, very close to Yirga Cheffe town. The great thing with Aricha is that Sweet Maria’s has first selection of coffee, and we bought a good deal of the lots offered this year. There’s other Aricha coffee (it is an area east of Yirga Cheffe town, so I suppose a lot of coffees can borrow the name), but this is from the actual Aricha station. It’s a dry-processed coffee with intense fruited character, body and sweetness, and has received extra care in preparation to exclude under-ripe coffee cherries. Dry-processing means that the coffee was not pulped (the outer skin removed) and fermented to remove the fruity mucilage layer. In dry processing, the coffee cherry is picked and laid out in raised “beds” in the sun, turning the red fruit to a deep brown color over the course of two weeks. After a storage period, the coffee seed is hulled out in one step, removing all the dried skin, fruit and parchment layers at the same time. The Aricha was prepared to the standards for Grade 1, which means removing over-ripe and under-ripe cherries that can be seen in the final green coffee as with either shiny green silverskin coating the bean, or fermenty sour beans. This extra work improves the overall cup quality and consistency in roasting.
Aricha is a very fragrant coffee, a lingering aroma of sweet berry and florals, conjuring a sort of caricature of washed Yirga Cheffe counterparts. It’s a coffee you can smell throughout the house when you grind it, and certainly not one to share the spotlight. The fragrance has strong fruit scents of tropical flowers, along with fruit jam smells, a bit like strawberry preserves. The floral aspect builds with the addition of hot water, a fresh-cut jasmine smell, along with a honey-like sweetness underneath, and intense plum and peach smells released in the steam off the break. The cup is remarkable, fruit flavors like dried strawberry, stone fruit juice, and ruby red grapefruit coming up as the cup cools. There’s a citric brightness too, an acidity often dulled in naturally-processed coffees. City+ roasts show depth of sweetness, layered raw sugar notes, and a flavor of pulpy orange juice, and those closer to Full City will see the addition of a pleasantly bittering cacao flavor on the tongue. The list of flavors we had from our test samples is too long to list; it’s a complex coffee that inspires many, many descriptors. The general groupings involved jammy fruited flavors, complex sugar-browning sweetness, some pleasantly bittering cocoa notes. It’s a fantastic brewed cup for fans of fruited dry-processed coffees.
Ethiopia Yirga Cheffe Dry Process -Gedeb Asasa
|Arrival Date||September 2015 Arrival|
|Appearance||.4 d/300gr, 15+ screen|
|Intensity / Prime Attribute||Bold Intensity/Complex unrefined sugars, bold fruits, layered chocolate|
|Region||Gedeb District, Yirga Cheffe|
|Roast Recommendations||City to Full City+; very versatile, and we personally preferred staying north of FC roast. FC to FC+ for espresso.|
|Recommended for Espresso||Yes|
Gedeb District is located in the the southern part of the Yirga Cheffe zone, and is also the name of the site where the coffee is collected and dried on elevated beds. This Gedeb site has roughly 700 local farmers who bring their coffee here for drying and hand-sorting. The farms are little more than large ‘gardens’ adjacent to homes, growing heirloom varietals native to the region. Farmers deliver their coffee as whole cherry to the station where it is graded, and then laid out on drying beds. The preparation of this coffee is Grade 1, which for dry-processed lots means a lot of hand-sorting, removing over and under-ripe coffee cherry. The coffee is again sorted after dry-milling in order to identify any additional defects that were missed at the drying beds. Naturals are milled before being transported to Addis, where, again, the coffee is sorted to improve the appearance and cup quality. Competition in the region for cherry is quite strong so farmers are paid well, especially for ripe cherry selection. This year’s price to farmers was increased from last years rates because of competition among washing stations, a win for the growers.
Gedeb Asasa is a striking example of a dry-processing done right. Out of the 200 grams of coffee I roasted, I pulled 1 full quaker, the roast showing a nice uniform color even with lighter roast development. And this consistency shows in the cup too, from one brew to the next. The aroma is intoxicating, heavy fruit smells, a strong cherry cola scent, and floral hints at City+. And Full City roast take on a strong cocoa nib smell with dark fruit jam smells not far behind. There’s a nice mingling of stone fruit flavors in the hot cup, the sweet fleshy aspects as well as a tannic, bittering quality associated with the skin. This is an extremely sweet natural, loads of complex sugar notes, counterbalancing the high level of berry and tropical fruited tones. As the cup cools, a sweet citrus flavor comes up in the profile, a bit like sweet lime (a variety of lime without the citric ‘bite’, basically a non-tart lime!), and floral Meyer lemons. But there is a bracing quality too, a level of acidity that weaves these top notes tightly together. Full City roasts develop notes of blueberry and boysenberry, mango filling, with a dark chocolate syrup flavor is well in focus. We pulled a shot too and talk about intense. Super floral aroma, tart and sweet berry notes, and an a lovely cacao-bar flavor that goes the distance in the finish.
After months of decent reliability from the Roast Genie, the SD card in the Raspberry Pi became corrupted one too many times. I am going change the architecture of the system to eliminate the Pi. Even though I had implemented a robust shutdown routine, the Pi proved not to be up to the task. I’ve seen some write-ups on RasPi applications that use a write protected SD card with a USB thumb drive for a R/W file system but frankly, I have had it with the Pi in this application.
I am now working on an alternative approach that should be considerably more robust. This system will be based on ATMEGA hardware (Arduino) that has proven to be very robust and the Adafruit Huzzah for cheap WiFi and IoT connectivity. Proof of concept is working now but it will be a while before I am posting new roast plots.
I will post details of the build later.
Buying some new coffee from Sweet Maria’s…
Colombia Cup of Antioquia -Jose Leobardo
This lot from Jose Leobardo Montoya shares much in common with our other auction coffee from Hugo Sepulveda. The fragrance and aroma boast dark-hued fruits and berry smells, and with a honey sweetness that sits on the side of raw honey-comb. Breaking the wet crust releases a very sweet scent of raisin bread with cinnamon, and a light, tart citrus note. The brewed coffee shows more-than convincing sweetness and its fair share of fruit-forward flavors. When hot, the cup pushes sweet-to-tart boysenberry and raspberry notes, a faint grape flavor, and base sugar-browning sweetness. This coffee’s body is lush, with the weight of fruit juice on the palate. As it cools, I get notes of fruit-flavored honey sticks – especially cherry, and orange – and an apple note adds to a crisp tea-like mouthfeel in the finish. Full City really bolsters deep chocolate tones, while still leaving plenty of room for fruit complexity. An espresso shot yielded a delicious mix of cherry cordial and salted caramel, loads of dark chocolate, and a citrus zing.
Yemen Dhamari Anis
Anis has a unique rustic sweetness emanating from the dry grounds, with rustic chocolate, dried banana and dried peaches. There’s a tobacco note, slightly leafy herbal quality, that also comes out in adding hot water. There are also clean earth tones, aromatic cedar, and sarsaparilla root. On the break, cola nut and clove scents are apparent, along with toasted barley malt. The cup has an intricate and complex flavor profile: It is a bit if a maze on the palate! Bittering cocoa nibs are offset by a mouthfeel of heavy, a spiced chocolate with the thickness of a mousse. There is sweetness throughout, from the first sip to the finish, but always in contrast to bittering or savory elements, spiced or wood notes. Those spice notes are heavily layered, in the key of baking spices like clove and allspice with a cinnamon-like woody accent. There is a fruited aspect in Anesi that peaks out from the City+ roast in particular, of dried Qishr tea (made from dried coffee cherry skins), muskmelon, dried fig, and dried pineapple. Whether a brewed cup or SO espresso, like all Yemeni coffee, this greatly benefits from a few days rest. 48 hours is great but we found 72 hours of post-roast rest to be best.
Ethiopia Dry Process Yirg Adado Sulula
The Adado Sulula is a classic dry-processed coffee, but prepared to the highest standards. The dry fragrance has potent with dried peach and blueberry sweetness, with a backdrop of light brown sugar and high-percentage chocolate. Adding hot water, the wet aromatics are potent with fruit and intense sweetness. There is a strong cinnamon sugar scent initially, with blueberry syrup and cocoa nibs as we break the crust of floating grounds. The cup flavors realize all the suggestions from the aromatics, and more. The blueberry notes are there with a dried fruit character, as in blueberry granola. Initial cocoa nib flavor passes into the complex sweetness of raw demerara sugar. Dried apricots assert themselves, with suggestions of mango as well. As the cup cools, I am reminded of the saturated sweetness of melted brown sugar and pineapple in a ‘pineapple upside-down cake’. Seriously. We find this coffee to really bloom in aromatics with a long post-roast rest of 2-3 days. It’s really quite a different coffee than brewing it with a short overnight degassing period. But with aromatics like this, you might not be able to wait 3 days to brew this!