This paper deals with an optimal design of an electromagnetic energy harvesting generator for supplying wireless sensors with energy. The developed device is complex mechatronic system which generates an electrical power from an ambient low frequency mechanical vibration by use of a suitable electromagnetic generator. This device is excited by ambient mechanical vibration and electrical energy is harvested due to Faraday’s law. The design of this vibration power generator results from development cycles and the final generator can provide sufficient electrical energy for wireless sensors. The vibration power generator is tuned up to frequency of vibration 17 Hz and harvested output power depends non-linearly on level of vibration. The vibration power generator operates in level of vibration 0.1 – 1 G peak and output power is in range 2 – 25 mW.