Patent ID: 8882102

Claim:
An image forming apparatus comprising: a paper feed cassette with a lift plate; a moving device configured to move up the lift plate with an associated motor; a changing device configured to mechanically change a resistance value of a variable resistor depending upon a position of the lift plate; a mechanical switch configured to mechanically detect that an upper end of one or more paper sheets placed on the lift plate or an upper end of the lift plate has reached a predetermined uppermost position in the paper feed cassette; a connecting device configured to apply a predetermined DC voltage to the variable resistor when the upper end of the one or more paper sheets placed on the lift plate or the upper end of the lift plate has reached the predetermined uppermost position in the paper feed cassette; a calculating device configured to calculate a remaining amount of paper sheets placed on the lift plate as a function of a DC voltage value output from the variable resistor; and a stopping device configured to stop upward movement of the lift plate using the DC voltage value output from the variable resistor.