Patent ID: 8807475

Claim:
Apparatus for dispensing sheet material from a roll including a low-material sensing system, the apparatus comprising: a sensor which generates a sensor signal indicative of sheet material roll rotation; a direct current motor having an armature, the motor producing movement of the sheet material when current is supplied to the motor; a low-material indicator; and a controller coupled to the motor, sensor and indicator and having an analog-to-digital converter, the controller being operable to: digitize a motor signal indicative of at least one of motor current and motor voltage; digitize the sensor signal; detect pulses in the digitized motor signal during motor armature rotation; measure a time between motor signal pulses which occur after the motor is de-powered and is coasting, the time being indicative of motor rotational speed; detect the digitized sensor signal during sheet material roll rotation and determine sheet material roll rotational speed therefrom; compute a ratio of the rotational speeds; and activate the indicator when the ratio reaches a threshold representative of a low-material state.