Midé Technology Corporation makes the Volture line of piezoelectric energy harvesters. Each Volture product uses a resonant beam of piezoelectric material that is clamped at one end and tuned to the resonant frequency of the vibration source for maximum output [9]. While output depends heavily on both the intensity and frequency of the vibrations, a Volture V25W tuned to 40 Hz with a 15.6 gram tip mass on the cantilever and a 1 G vibration source achieves an output voltage of 9 V and output power of 9.2 mW. While that is a peak value, a steady output of 2 to 3 mW should be enough to help power most wireless nodes for a considerable amount of time. Figure 2 shows how Volture can be used to power a wireless sensor node [15].