Hi what's up. So basically my goal is to detect if someone drew a path on a piece of paper between two points in pencil. Although the graphite is conductive, unless you press down really hard, the max length I want to be able to draw appears to have a resistance in the 100s of M Ohm to GOhm range.
I had to make the pencil line significantly thicker between the two points (about 6 inches apart) to even get a resistance reading on the multimeter of 100MOhm.
Also when applying a voltage of 30v and measuring it in series with the pencil line, even though 30v should still be measured on the output theoretically, I only measured 1V (I suspect due to the internal resistance of the multimeter, which is usually negligible but not with such a massive resistance of the pencil line).
So suppose point A is connected to V+, point a to point b thru the pencil line drawn, point b to some circuit, and that circuit connects to ground.
The goal will be to integrate this with an arduino. However an arduino does not seem like it can be directly used as pins cannot be left floating and the internal resistances might be enough to get in the way.
So my idea is basically I gotta make some circuit that can tell when points A and B are connected thru this high resistance path. However since the resistance is so large accounting for the resistance of everything and noise becomes important.
So is there maybe an op Amp or 555 circuit for this? Or maybe the arduino adc could work?
Whats everyone's ideas?
I had to make the pencil line significantly thicker between the two points (about 6 inches apart) to even get a resistance reading on the multimeter of 100MOhm.
Also when applying a voltage of 30v and measuring it in series with the pencil line, even though 30v should still be measured on the output theoretically, I only measured 1V (I suspect due to the internal resistance of the multimeter, which is usually negligible but not with such a massive resistance of the pencil line).
So suppose point A is connected to V+, point a to point b thru the pencil line drawn, point b to some circuit, and that circuit connects to ground.
The goal will be to integrate this with an arduino. However an arduino does not seem like it can be directly used as pins cannot be left floating and the internal resistances might be enough to get in the way.
So my idea is basically I gotta make some circuit that can tell when points A and B are connected thru this high resistance path. However since the resistance is so large accounting for the resistance of everything and noise becomes important.
So is there maybe an op Amp or 555 circuit for this? Or maybe the arduino adc could work?
Whats everyone's ideas?