Abstract: This specification discloses a bin full detector for shredder. A bin full detector is disposed in the bottom of the shredder housing at a position not lower than the blade set of the shredder. The bin full detector includes at least one emitted for emitting an infrared beam downward to the paper chips and at least one receiver for receiving the reflected signal. The feedback signals from chips of different distances or heights are converted into different voltages and sent to a signal processing circuit. A microcontroller analyzes, computes, and compares the signals. Finally, a displaying unit shows to the user whether the paper chips in the bin need to be emptied.