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A pedestrian floor tile energy harvesting system (PFEH) capable of accommodating harvesters of variable widths (20, 30, and 40 mm) is designed for operating Internet of Things (IoT) sensors. The electrical characteristics of the piezoelectric energy harvesters (PEHs) were measured using an impedance analyzer. The PEHs in the PFEH are displaced following a cantilever mechanism, over a distance of 4 mm. Finite element simulations using the ANSYS tool reveal similar stress distributions for various widths at the same displacement (d = 4 mm). The 40 mm PEH group (six 40 mm wide PEHs) produced the highest output power of 1.01 mWmax under identical impedance conditions (RL = 105 kΩ). The PFEH containing the 40 mm PEH group turns on a small LED display board (comprising 30 LEDs) for 2 s through an undervoltage-lockout (UVLO) module. The proposed pedestrian floor tile energy harvesting system can be employed as a power source for IoT sensors.

We propose a piezoelectric energy harvesting technology installed in a roadway speed bump. We have installed a module that can charge mobile phones utilizing a speed bump piezoelectric harvester (SBPH), which is easy to apply to roads. A highly integrated module with 40 piezo-generators was fixed and installed at the center of the speed bump. When a medium-sized vehicle passed the module at a speed of 30 km/h, an output voltage of 144 Vmax, output current of 45.2 mAmax, and output power of 4086.08 mWmax (6.81 W/m2) were measured at a load resistance of 2 kΩ. When the vehicle passed over the SBPH nine times, it charged a capacitor (10,000 μF) to provide 6 V for about 200 s, and the charged electrical energy was enough to operate a cellphone. The self-controlled battery charging system via electricity generated by the piezoelectric module could be applied to a speed bump installed on an actual road.

Piezoelectric devices previously studied usually generated a single voltage to power an electronic device. However, depending on the user’s purpose, the electronic device may need dual power supply. Here, we report a self-powered bipolar voltage generator using a piezoelectric energy harvester with two piezoelectric devices. When a force is applied to the piezoelectric energy harvester, the two piezoelectric devices separately supply positive and negative voltages to the operational amplifier that requires dual power supply to amplify an AC signal that have positive and negative polarity. At the same time, the harvester supplies additional power to an electronic device through a DC-to-DC converter with an output voltage of 3.3 V. This technique proves the feasibility of applying the piezoelectric energy harvester to operational amplifying systems in the field of sound, earthquake, and sonar that require both bipolar and single voltages without external power sources.