The iSpindel is an open source digital hydrometer and is a surprisingly easy project. Like the TILT it allows you to monitor your fermentation’s specific gravity and wort temperature remotely.
The original development, if I am not mistaken, came from universam1 and his documentation can be found here. As you scour the home brewing message boards you will find an array of builds, adaptions and various tinkerings around the same iSpindel theme. For my build I went with The Jeffrey board from opensourcedistilling. Joey Joe Joe Jr. (pictured below) has created a fantastic resource where you will find everything you need, with extremely clear instructions, that anyone without electronics experience could follow.
Mine was just a simple build (pics below), following his instructions and I used the Fermentrack for data visualisation.
The most time consuming parts of the build were waiting for the various parts to all arrive from eBay and AliExpress, then calibrating the iSpindel after the build was complete. The actual assembly and flashing (using the Fermentrack) took about 30 min. For calibration I used the instructions here. I also entered the polynomial details using the Fermentrack. Below is the output from my first fermentation with my iSpindel. There was a little anomaly at the start of fermentation but it was surprisingly accurate and it is interesting to watch the fermentation in real-time.