BeerBoi 2.0

BeerBoi is a digital hydrometer intended for home brewers, a project to kill some time during the pandemic of 2020 and continuing into 2021.

BeerBoi 2.0 is here! The original BeerBoi was intended to be mounted on the fermenter and take regular readings of the specific gravity so the fermentation process could be tracked. While this is certainly useful, it is also very useful to be able to just dip the BeerBoi into the fermenter and get a reading on the spot. BeerBoi 2.0 introduces an oled screen to support this on-the-spot reading capability.

A BeerBoi 1.0 looks like this:

It provides a web page like this:

It can be used as either a hand-held instant read hydrometer or mounted to the fermenter to track fermentation over time. As a hand-held hydrometer, it requires no separate sample, just dip the boi into the fermenter and read the specific gravity. As a mounted digital hydrometer, it records the specific gravity of the fermenting wort over the length of the fermentation cycle and provides a web page with a graph showing the trend.

As a fermenter-mounted unit, an external power supply is recommended as it is intended to run several days unattended. As a hand-held unit, a battery can be used to promote portabiltiy.

Design goals:

Low cost, about $20 for parts
Hand assembly from off-the-shelf parts, no 3D printing or CRC cutting involved
'Commodity' parts, as in electronic components and whatever, meaning I can find them all at Amazon or my local hardware store
Relatively easy to put together, does require decent soldering skill
Easy calibration
No outside service required, contained completely within the local network(*)
No internet access required
OTA firmware updates

(*) Beerboi doesn't need to connect to the internet, but your browser does. Several javascript and stylesheet files are loaded from beerboi.org. This is done for performance reasons, the ESP-12 webserver is low powered and it's actually much faster for your browser to load files from beerboi.org than from the ESP-12.

BeerBoi consists of a small circuit board hosting a stress gauge and an ESP-12 wifi-enabled microcontroller. The ESP-12 runs a web server, so it's just a matter of pointing a browser to it to control it and see the gravity readings. It has an outstanding range, it should measure specific gravity from 0.000 to 1.750 with an accuracy of +/- 0.001.

How It Works

A hydrometer measures the specific gravity of a liquid. Specific gravity is the ratio of the density of the wort compared to the density of water. For beer, when the wort is first put in the fermenter, it starts out as a fairly heavy syrup, so things float higher. Another way to look at it is that things weigh less, relatively speaking. As fermentation continues, alcohol is produced. Alcohol has a lower density than water, so the alcohol dilutes the solution and reduces the density. A hydrometer is calibrated to measure how much it floats or sinks, which is a good indication of when fermentation is done and the percentage of alcohol. Awesome beer coaster picture:

So when the hydrometer sinks, it's "heavier" and when it floats higher, it's "lighter". This digital hydrometer does the same, but rather than measure how far it sinks, it lowers a known mass into the wort and calculates how much it weighs. Initially, the boi will weigh less because the wort is thick with sugars, then as fermentation goes on and alcohol is produced, it will become "heavier". The stress sensor measures that weight difference, and calculates the current specific gravity.

This project is all about making one of these.