Objective of the present work is to present the design and the laboratory tests of Wireless Sensor Nodes (WSNs) equipped with three different on-board energy production systems, to be installed on freight trains for condition monitoring and structural diagnosis of the railway vehicle. The three sensor nodes are designed to be completely energetically autonomous, exploiting three different energy sources easily available on a moving train: Solar, Wind and Mechanical vibration power. a PCB board hosts different ICs, able to convert the uncontrolled and unregulated power sources in order to properly feed all the on-board components and possibly to charge the battery. The electronics for the acquisition, elaboration and wireless transmission of data, is presented and analyzed in terms of performances and consumptions. The three WSNs, based on the different energy sources, are designed and compared in terms of fatigue behavior and performances by means of laboratory tests.