Minimum Viable Arduino Project: Aeropress Timer

Summary

Okay, okay. I admit. This isn’t the minimum viable Arduino project. That’s the blinkey-light demo. But this comes pretty close. It’s the minimum viable Arduino project that is actually useful. This project stems from two things: First, these super sweet aluminum buttons I picked up a few weeks ago. Second, the fact that the Aeropress coffee maker needs to be plunged after 30 seconds, and it’s really annoying and error-prone to set a 30-second timer. Oops, I’m tired and I hit zero too many times. That’s a 3-minute (3:00) timer. I typed in 3-0 correctly, but hitting the start button didn’t quite register. Siri misheard. Siri took 10 seconds to respond about a 30 second timer. So I went extra. I designed and built a dedicated 30-second timer around the Adafruit Trinket M0. This is basically an inexpensive Arduino-alike (it also can do Circuit Python if that’s your thing). It has a handful of GPIO pins, some of which can be PWM analog outputs. The electronic design of this timer is dead-simple. It’s a button wired to ground on Pin 0 (using an internal pull-up resistor) and a piezoelectric buzzer wired to Pin 1. I’d hoped to do interesting things with the buzzer by feeding it PWM-powered analog-ish power, but it seems to behave in a very binary fashion. Either it has enough power to get over the threshold to make noise, or it doesn’t. A pictographic schematic looks a bit like this: At first, I’d planned to put it in a small laser-cut wooden box. My Glowforge broke after cutting a cardboard prototype, so I shelved that idea. (I’ve since fixed it!) I instead drafted something quick on OpenSCAD to print on the Ultimaker (scad file, stl file). I think this worked out a little better because of the integrated clip for the buzzer, plus it’s a single unibody piece and not glued-together panes of wood or acrylic. The Trinket board has a USB connector. In both designs, the board is flush with the side opening, exposing the USB, for power. This has a side effect in that the light ...