A portable electronic device comprises a main body and a battery cover. Each PDU has a motor, at least one driver roller element coupled to said motor, a light source, a light detector, and a processor. Rotation of the rod stopping for a period of time at a stop position in which a removed ice cube can rest atop the harvesting assembly to refreeze the melted portion. Elongation of the stepchain is also reduced as there is a reduction in the number of interfaces. The method is useful in the manufacturing of food products, feed products or useful metabolite products.