Vibration Energy Harvesting System - Energy Harvesting Autonomous Sensor Systems - page 123

FIGURE 4.13
A basic set of a LightningSwitch with one transmitter (left) and one receiver (right).

suffers from two more drawbacks: (1) high input force is required to release
the hammer of the push-button mechanism and (2) high output voltage and
low output current of a few kilovolts and microamperes are generated due to
the piezoelectric stack structure. Because of that, the design and implemen-
tation of the power management circuit become complicated.
To overcome these drawbacks associated with the piezoelectric igniter sys-
tem, another type of impact-based 31-mode piezoelectric generator, operating
in mechanical nonresonance, has been explored to harvest impact or impulse
forces from human pressing. There are several types of impact-based piezo-
electric generators described in the literature [104-106], and there are also
some companies like LightningSwitch [115] that apply this piezoelectricity
technology on commercial products like a wireless control switch. The self-
powered wireless control switch with energy harvesting capability has two
significant advantages: (1) flexibility in positioning the power electronic de-
vices at any part of the deployment area that is within the RF communica-
tion zone and (2) elimination of the high manpower and material costs in
laying wiring cables between the switches and the devices. A basic set of
LightningSwitch, consisting of one transmitter and one receiver, is shown in
Figure 4.13 . Inside the transmitter (see Figure 4.14 ) , LightningSwitch employs

Human
Pressing
Force

Translated
Mechanical
Force

Cantilevered
Piezoelectric
Material

FIGURE 4.14
Internal design of a LightningSwitch transmitter.