![]() ![]() The layered construction is very similar to the Dynapic, but instead of a sintered piezoelectric disc, a screen printable piezoelectric lacquer with suitable electrode material is built-up using a roll-to-roll thick film deposition technique. Besides the Dynapic Wireless, Algra also manufactures flexible piezoelectric polymer composite sensor foils commercially known as Dynasim – see figure 6. This could be the case for contact (shock) loggers, say in the transportation industry. The Dynapic piezo can also be used as an energy source for small embedded systems where wireless communication is not required. More harvested energy should allow the switch to send redundant signals for increased reliability. We currently achieve a wireless transmission distance of 10 to 30m at a frequency of 2.4 GHz.Īlgra is experimenting further with high performance ceramics for the piezoelectric membrane, which could lead together with custom designed ASICs to more flexible solutions based on standard wireless protocols. It is worth mentioning that the wireless protocol used here is proprietary, designed to work with ultra-low power radio modules. This requires custom developed power management electronics that can function at extremely low currents/high impedances.įigure 5: Voltage monitoring over the storage capacitor.įor this purpose, Algra has developed a power management ASIC that includes an active bridge rectifier with a voltage conditioner drawing less than 50nA typically with a forward bias voltage under 40mV. Thus, designers must wake up the microcontroller within a short period of time and transmit a simple coded signal to the receiver using the energy generated in the order of 2-20 μJ – see figure 5. The piezo keys deliver high voltages (typically 20-50 V) at very low current with a typical time span of approximately 100ms. However, such components could not be deployed for the Dynapic piezo keys, as the energy comes in voltage busts generated by intermittent finger pressure. These do perform very well for piezo harvesters based on continuous vibrational modes, optimized for a resonant frequency. Linear Technology has recently introduced the “LTC3588-1”, which is an AC/DC converter for piezo vibrational harvesters. What’s more, most of these power management devices are developed for energy harvesters that work on continuous vibrational modes. There are several energy management ICs and voltage converters on the market but most are aimed at battery-based applications, where the voltage from a battery is reduced or boosted. The primary challenge involved in such a piezoelectric switch was to develop suitable power management devices. The energy generated by a single key stroke is sufficient to wake up a microcontroller and transmit a coded signal to a remote receiver. Algra’s latest innovation, Dynapic Wireless – as shown in figure 3, demonstrates that energy from the Dynapic piezo switch alone is sufficient to be used in self-powered wireless switching applications. A homogenous stress distribution ensures the mechanical integrity of the Dynapic piezo keys, enabling such implementations to exceed 10 million switching cycles. Figure 2 shows side by side the stress analysis of a typical cantilever bending and the Dynapic piezo key. ![]() ![]() The Dynapic technology offers an innovative solution where a discshaped piezoelectric material is bent within a controlled range from 100 to 300 µm through the use of a multi-layered sandwich construction – see figure 1. 1: Expanded view of the Dynapic technology showing the multilayer laminate construction with the piezoelectric disc.Īs early as the 1990’s, the Swiss-based company Algra demonstrated that the reliability issues of bending piezoelectric materials can be circumvented with two proprietary technologies known as Dynapic and Dynasim. ![]()
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