Suppose one has a large metal pipe made of mild steel approximately 6-feet tall and 8-inches in diameter. Suppose this pipe has an regular pattern of perforations on its surface. Imagine the pipe is standing upright on the ground, mounted on a platform.
(Spoiler alert: I have such a pipe!)
I'd like to create a sensor or sensor network of some kind to sense when a human touches or nearly touches the pipe.
My initial inquiry went towards capacitive touch sensors and I've tried breakout boards using the MPR121 and AT42QT1010 chips, and have also tried a simple circuit like the one depicted here using the Arduino Capacitive Sensor library.
Nothing has worked.
I've connected the boards via wire directly to the pipe, and I've tried using electrodes (aluminum - about 6" square and another 2" square) insulated in a ziploc bag mounted to the inside surface of the pipe. What I've learned (I think) is that the massive amount of metal itself is such a large capacitance source (if that's the right terminology) that the differential when a human touches it is too minimal. The relative capacitance increase is too little.
- Is that right?
- Are there techniques to improve this approach?
- If this approach is futile, what are some other approaches I could use?
Bonus: If there's a way to get any level of resolution of where a person is touching the pipe, that's actually my perfect application, but I'm starting to think that's a pipe dream. (...sorry.)