A proximity sensor circuit of a powered dispenser for dispensing individual
sheet segments from a continuous roll of sheet material includes an
antenna, an oscillator circuit and an automatic sensitivity control
circuit. The antenna has a baseline stray capacitance. The oscillator
circuit is coupled to the antenna and generates an oscillation signal
having a predetermined oscillation amplitude corresponding to the baseline
stray capacitance of the antenna. Preferably, the oscillator circuit has a
Colpitts oscillator-type topography. The oscillation amplitude of the
oscillation signal increases in response to an increase in stray
capacitance from the baseline stray capacitance of the antenna and
decreases in response to a decrease in stray capacitance from the baseline
stray capacitance of the antenna. The automatic sensitivity control
circuit is coupled to the oscillator circuit and detects a change in the
oscillation amplitude of the oscillator signal.
