My espresso machine is customized for a quality coffee experience. Although not alone in the world of modified appliances, I think my Rancilio Silvia is unique. Her central nervous system is an Arduino microcontroller: all the switches that once flipped power to components now send requests to the Arduino. Through a set of relays, the Arduino performs the duties once assigned to the switches, making the machine entirely software-controlled. This intervention provides a platform ripe for change.
I added a precision temperature sensor and implemented a feedback algorithm to control boiler temperature. This is a scratch-built version of the popular PID mod for temperature stabilization (see MAKE, Volume 04, page 121). The Arduino’s built-in USB connection can also send temperature data to a graph on my laptop. This helps greatly in tuning the feedback loop where three values must be artfully adjusted to achieve the best temperature stability.
Because I always forget to check the water level, I installed a capacitive sensor chip and attached it to a wire that runs into the water reservoir. But water isn’t all I forget; just turning the machine on and off presents a challenge to me. As a remedy, I found a real-time clock board from SparkFun. Now Silvia starts to warm up every morning before I wake, and when I forget to shut her down before heading out to work, she goes to sleep after an hour of inactivity.
Needing some way to check all these new settings, I embedded an LCD display and attached a Wii Nunchuck game controller. I can now verify the machine’s temperature, the duration of a shot, and the time of day as I prepare the daily beverages. The WiiChuck allows me to browse a simple menu system and adjust settings.
Each morning, I wake up bleary-eyed and stumble to the kitchen. There, Silvia and I produce coffee offerings that can range from heinous to delicious. These daily failures and successes inspire changes both to my own technique and to Silvia herself. In the evening, I can return to the kitchen to tinker and tweak — efforts to help her help me. Together, we evolve toward espresso betterment.
More electronic coffee projects: arduino.cc/playground/Main/CoffeeTronics