“The extraction of the complex aromatic and flavor characteristics of a coffee bean is dictated by a roaster’s ability to control a variety of variables that act on a green coffee bean while it is roasting,” Brenn10 explained in an Instructables post.
“Not only must one understand certain audible and visual cues from the beans during the course of the roast, but the roasting apparatus must also react to changes to the fan speed and heater power in order to change the temperature inside of the roasting chamber.”
Concurrently, the roast logging software should display a graphical summary of the temperature in the chamber versus time – also known as the roasting profile.
Enter the upcycled controllable coffee roaster. As Brenn10 notes, a modified popcorn popper is capable of rivaling the functionality of a high-end programmable roaster – if properly equipped with internal temperature sensors, a reactive control system and an intuitive UI programmed to save multiple roasting profiles.
“The modified popcorn popper will [also] automatically control the temperature and total roast time based on industry roasting profiles,” Brenn10 continued.
“Component costs [should] remain under $360; [with] a taste comparison between beans roasted in a modified and unmodified roaster completed by an experienced coffee taster.”
Indeed, Brenn10’s upcylced roaster controls both the power to the heater coil and the speed of the universal AC/DC motor tasked with blowing air over the heating coil. More specifically, the air is directed into the roasting chamber where thermocouples relay temperature information to a microcontroller interfaced with a roast logging software known as Artisan.
“This roast logging software displays the temperature versus time inside of the roasting chamber, while also providing functionality to the roaster user to adjust the percentage of power going to the heater coil and the percentage of speed that the fan is spinning,” Brenn10 added.
- Crydom D2425-10 Solid State Relay
- K-Type Thermocouple – Glass Braided
- K-Type Thermocouple – Flexible Probe
- TC4 Roasting Thermocouple Shield – (Kit or Pre-Built)
- Zero Cross Detector Terminal Block – 8 Total Connections
- 12” jumper wires
- Wooden Project Box
- Antique Glass Chimney
Interested in learning more? You can check out the project’s official Instructables here for a detailed, step-by-step tutorial on how to transform a standard air popcorn popper into a controllable coffee roaster.