Gravity Monitor for Beer Brewing

I started this project out of curiosity for how a motion sensor is working and since I like to brew beer this was the result. This software can be used with iSpindle hardware and utilizes the same hardware configuration. No part of this software has been copied from that project.

Functionallity

I have made a few differnt design decision compared to the standard iSpindle software.

All configuration options have been moved to a web gui and is accesible without using the double reset function. You only need to use this for changing the WIFI configuration. The web gui can be accessed when either the device is laying flat on a surface (90 degress) or it's beeing charged. The benefits is that it's easier to change settings and also read the angle/tilt when doing calibration. You can also change the forumla and directly see the new calculated result.
The software also has built in OTA support so new versions can be downloaded from a local webserver (when connected to power)
Temperature calibration of DS18B20 sensor so you can adjust the temperature sensor readings.
Automatic temperature gravity calculation to adjust for a lower temperature in the fermentation vessels. Useful if you are fermenting at lower temperatures. It's possible to build this into the normal gravity formula but this is an easier option. Just make sure that the calibration is done at 20°C.
The software will read the motion sensor 50 times and use the average to calculate the angle. If the readings show that the device is moving it will wait a few seconds and retry the operation again to make sure that no invalid angles should be reported. The downside is that the device will remain running if it's moving and draw more power. For normal fermentation this should not be an issue.

Integrations / Sending data

In this version the software supports sending data to standad HTTP endpoint and Brewfather. These are the ones I use so more can be added on request.

Configuration

Configuration is accessed by entering the URL for the device, this will be the mDNS name device.local or the IP adress.

Index page

http://gravmon.local/

The main page shows the device readings; gravity, angle, temperature and battery charge. If the checkbox is active then the device will never go into sleep mode. This is useful if you are collecting angle/tilt for calibration. If this is unchecked the device will go into sleep mode and the web UI is no longer accesible.

Device page

http://gravmon.local/device.htm

The device page shows the device settings and software versions.

Config page

http://gravmon.local/config.htm

This page is divided into several categories of settings. The first one contains device settings, mDNS name, temperature format, and gyro calibration data. Calibration needs to be done or the device will not work correctly. Place the device flat on a surface with gyro up and press the calibrate button when it's stable.

The second section contains the push settings, two URL's for http sending and one for Brewfather. The interval setting is the amount of time the device will be in sleep mode between readings (interval is in seconds).

This is the format used for standard http posts.

{ 
   "name" : "gravmon",      // mDNS name
   "ID": "gravmon",         // mDNS name
   "token" : "gravmon",
   "interval": 900,     
   "temperature": 20.5,
   "temp-units": "C",
   "gravity": 1.0050,
   "angle": 45.34,
   "battery": 3.67,
   "rssi": -12,
   "run-time": 2.30,        // Runtime for this reading
}

The third section contains the gravity options, formlua and option for temperature correcting gravity.

Gravity formula is compatible with standard iSpindle formulas so any existing calculation option can be used. I use the tool fermentrack for controlling my fermentation and I use this tool for calculating gravity.

The fouth section contains the hardware options, voltage factor for calculating the battery charge, temperature sensor adjustment and OTA base URL.

For the OTA to work, place the following files (version.json + firmware.bin) at the location that you pointed out in OTA URL. If the version number in the json file is newer than in the code the update will be done during startup.

Example; OTA URL (don't forget trailing dash), the name of the file should be firmware.bin

http://192.168.1.1/firmware/gravmon/

Contents version.json

{ "project":"gravmon", "version":"0.3.0" }

Compiling the software

I recommend that VSCODE with PlatformIO and Minfy extensions are used. Minify is used to reduce the size of the HTML files which are embedded into the firmware or uploaded to the file system. When using minify on a file, for example index.htm the output will be called index.min.htm. This is the file that will be used when buildning the image.

By default the html files are embedded but there are options to upload them to the file system to reduce the size of the image if the size becomes to large for OTA.

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