A device for converting mechanical energy to electrical energy that include a mechanical device comprising a seismic mass flexibly connected to a base by at least one spring, a mechano-electric transducer that is associated with the mechanical device for converting mechanical energy of the seismic mass to electric energy, and an electric circuit that is connected to the mechano-electric transducer in a way that electric current is generated in the electric circuit when the seismic mass moves relative to the base. The mechano-electric transducer is designed to adjust a force that the mechano-electric transducer can exert on the mechanical device and by that to control the conversion level of the mechanical energy to the electrical energy.