Abstract: A sensor for detecting the presence of lightweight objects being conveyed on a conveyor of the type having conveyor rollers. Each conveyor roller is rotatively mounted on a shaft fixed between the conveyor side frames. A selected conveyor shaft has non-rotatively mounted thereon a pair of fulcrum bearings, each located between a conveyor side frame and the adjacent end of the roller mounted on the selected shaft. A pair of sensor arms are provided, each rockably mounted on one of the fulcrum bearings. The sensor arms are substantially identical elongated members having upper ends joined by a shaft on which a plurality of sensor rollers are rotatively mounted. The sensor arms are rockable between a normal position wherein the sensor rollers are elevated above the adjacent conveyor rollers, and a fully depressed position wherein the uppermost surface of the sensor rollers are co-planar with the uppermost surface of the adjacent conveyor rollers.