I built a liquid level sensor on my Uno based on this Instructable that I found: http://www.instructables.com/id/Building-a-Capacitive-Liquid-Sensor/
It works great. I used a 1M resistor. However, it is really sensitive to my hand near it, etc... I also understand temperature could skew the reading. I did it just like the instructable, used two tin foil strips, running up the side of a plastic bottle (across from each other). Soldered wire to each strip. One to ground and the other to DI2. Then I ran the 1M resistor from DI2 to DI3. I used the capSense code I found here. One thing I am going to do is switch to copper tape instead of the foil. However, to make it more robust (filter out noise and smooth the readings, handle temperature) I have the following thoughts. Can somebody provide their opinions or feedback on these thoughts? Thanks!
- Since temperature could change the result, I was wondering if a temperature sensor was implemented, could this keep it calibrated? I assume the liquid temperature would be most important. I was thinking a temperature sensor attached to the water bottle at the lowest point.
- Would shielded cable would work better. Would you put the shield to the ground piece of foil and the center wire to the other foil (sense)? I did notice that the results we jumpy and that my hand would throw it off. I wonder if the shielded cable would help the result be more consistent and prevent the noise (from my hand).
- I see in the image of the instructable of the water bottle that the wire is soldered to the foil and then wrapped around the bottle a few times. It also appears that the lead back is also twisted. I wonder if these are important steps? Would they help with the noise? Would they be required if you are using shielded wire?
I also saw another writeup on this method and it mentions using an insulator over the foil and then another layer all the way around that is a ground plane.