Piezoelectric device operating as sensor and harvester to drive switching circuit in LED shoes

The power generated by the designed piezoelectric energy harvester replaces the standby power that is constantly used in sensors and driving circuits in commercial LED shoes; the harvester thus reduces battery consumption. LED shoes incorporating a piezoelectric energy harvester are designed for night workers who work near roads. The piezoelectric energy harvester, composed of a piezoelectric device (PZT ceramic), which is inserted under the insoles of shoes, converts mechanical energy generated by motion of user into electrical energy. The designed harvester has an area of 6 × 4 mm and height of 3 mm (pressed state); it weighs 14 g. Because of its small size and light weight, device is suitable for real workers’ shoes. This piezoelectric energy harvester produces 800 μW at a resistive matching point of 400 kΩ; it is used as a sensor to control an LED switching circuit, allowing the LEDs to blink based on user movements. By applying the piezoelectric energy harvester to LED shoes, battery usage time can be doubled compared to LED shoes that are turned on continuously.