The sensors have takes a lot of time for this project… We’ve experimented a lot and learned a few things along the way. The biggest issue is that we have no real ground as reference, since the cups are carried around. We’re actually using the “wrong” method for measuring capacitance, but we’ve managed to get it to work anyway 🙂

Our first problem was the the signal cables from our sensors were interfering with each other, which messed up the readings. Touching one sensor would affect all the others. We solved this by using wires with isloation, and connected the isolation to ground. In the final circuit only we managed to only have a few millimeters of wire/solder between the sensor cable and the arduino pin.

We had no way of solving the ground problem. Instead we found a work-around. By restarting the program within relatively short intervals (0.5-2 minutes) we could reset the ground reference value. I do now have the knowledge to understand exactly why this workes, but it does. We improved the readings by putting grounded strips of copper behind our copper sensors. We have some idea of why this works, but not a full understanding of it… Mostly we’ve just been trying stuff, either by reading what others have done, or just experimenting.

Lastly we moved the sensors closer to the surface to get better readings.

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