Abstract: A paper-width detecting device includes a paper guide, a conductive element, a circuit board and a control-processing unit. The paper guide is movably disposed on a paper tray for accommodating different sizes of papers. The conductive element attaching to the paper guide and moving simultaneously with the paper guide has a plurality of first conductive portions. The circuit board has a plurality of conductive wires, which is formed by a plurality of separated second conductive portions on the surface of the circuit board. An insulating region is formed between any two adjacent second conductive portions of each conductive wire. The control-processing unit is for providing an electric voltage between the conductive wires and the conductive element. When the paper guide presses against the paper, the control-processing unit generate a paper-width value corresponding to the number of current passages formed between the first conductive portions and the corresponding conductive wire thereof.

Abstract: A paper-width detecting device includes a paper guide, a conductive element, a circuit board and a control-processing unit. The paper guide is movably disposed on a paper tray for accommodating different sizes of papers. The conductive element attaching to the paper guide and moving simultaneously with the paper guide has a plurality of first conductive portions. The circuit board has a plurality of conductive wires, which is formed by a plurality of separated second conductive portions on the surface of the circuit board. An insulating region is formed between any two adjacent second conductive portions of each conductive wire. The control-processing unit is for providing an electric voltage between the conductive wires and the conductive element. When the paper guide presses against the paper, the control-processing unit generate a paper-width value corresponding to the number of current passages formed between the first conductive portions and the corresponding conductive wire thereof.