ESP32 Coffee Grinder Upgrade

A coffee grinder is great for... grinding coffee, but what if you wanted to produce a certain amount of ground coffee automatically? The Eureka Mignon Libra device is capable of such an operation, but creator Tech Dregs (TD) had only a Eureka Mignon Crono that lacks – or lacked – this functionality. Now, with the addition of a Seeed Studio XIAO ESP32C3 board and a load cell, coffee grinding is fully automated, and features a smartphone Bluetooth interface.

The project started off with TD sourcing a cheap scale off of Amazon to use for its load cell, but found that the IC inside was inconveniently epoxied-over. He then ordered an HX711 load cell from SparkFun, which was of course much easier to use, and he proceeded to interface it with the XIAO ESP32C3 that forms the brains of the device.

From there, interfacing with the coffee grinder motor control was relatively straightforward. They provide a nice pin header that facilitates this operation, to allow for interchangeable parts between models. TD used a 2N9304 transistor to convert between the XIAO’s 3V3 output and the Eureka’s 5V input.

The device includes an onboard OLED screen, but the main user interface is via a smartphone app created using MIT’s App Inventor program. As seen in the video below, the grinder does a good job of dispensing ground coffee, though as with most any project there are a few small issues that could be improved upon. Code is on GitHub if you’d like to give this type of project a shot!