Finger touch signal detection with microcontroller
The problem with this type of touch sensor is that it relies on sufficient capacitive coupling through an unknown path. A battery operated device may be too isolated to get a good response.
However you could get better results by rearranging the transistors to pull down rather than up, as this should make better use of the signal relative to ground. A complementary configuration may work even better because it only has one Base-Emitter voltage drop rather than two. For this you need one NPN and one PNP transistor. You can also increase sensitivity by using a higher value load resistor.



simulate this circuit &ndash; Schematic created using CircuitLab