Mass-spring unit for generating power by applying a cyclic force to a piezoelectric member due to an acceleration of the mass-spring unit

An apparatus for generating an electrical power upon an acceleration of the apparatus, the apparatus comprising:

• a piezoelectric member having at least a portion thereof formed of a piezoelectric material;
• a mass-spring unit having a spring element attached to the piezoelectric material and configured to compress and/or elongate within a predetermined limit, the mass-spring unit further having a mass offset from the piezoelectric material;
• and
• limiting means for limiting a loading on the piezoelectric member;
• wherein the mass-spring unit is configured to vibrate within the predetermined limit upon the acceleration of the apparatus, the vibration applying a cyclic force to the piezoelectric member to generate an output power from the piezoelectric member and wherein the limiting means comprises sandwiching the piezoelectric member between the spring element and an intermediate member, wherein one of the spring element and intermediate member have a stop for contacting the other of the spring element and intermediate member where the acceleration reaches a predetermined limit.