Idea & Research

A project log for Peppermint

A flag-themed blinky countdown memento for time spent apart, with capacitive touch switch.

Benjamin BroceBenjamin Broce 09/15/2018 at 19:100 Comments

I've wanted to build something for the square inch project since the original challenge announcement, but most of my ideas have involved the ESP8266 or ESP32, and were a bit too grandiose for my first foray into PCB design. So with a few weeks left, I thought I'd build a blinky memento for my upcoming mission trip. The basic idea is a square inch flag-themed LED grid with 1 LED for each month I'll be gone.

My wish list after that includes:

I considered several options for how to achieve the functionality I was going for, including consolidating processing and low-power capacitive touch interrupts with the ATmega328PB, but this didn't seem to be well-supported in the Arduino environment, and required a Windows-based proprietary tool to setup the touch sensing.

Instead, I decided to use a plain-old ATmega328P and an AT42QT1010 momentary capacitive touch sensor - the board was starting to look a little tight! For 3.3V power from a 3V CR2032 coin cell, I decided to use an MCP1625 boost regulator. Things look to be coming together!