This week I came across an interesting new product from Linear Technology: the LTC3588 energy harvesting power supply intended for powering remote microcontroller systems. According to the product description this chip is a complete energy harvesting solution optimized for low energy sources, including piezoelectric transducers.
The LTC3588 datasheet does mention some manufacturers of piezoelectric transducers that can be used with the chip. I looked one up: the T220-A4-503X from Piezo Systems. As I allready suspected, it is not really a buzzer. It is also more expensive than a buzzer: $125. You can buy a lot of batteries for that money, but it is probably cheaper than to send out a maintenance engineer to replace a dead battery. This particular transducer can deliver 5.4 mW RMS when it vibrates ±1.57 mm at 80 Hz. It comes as a 0.5 mm thick card of 31.8 x 63.5 mm (1.25" x 2.5") that has to be soldered with special solder (the transducer has nickel electrodes).
OK, so this kind of piezoelectric transducers is probably not for me, but the LTC3588 datasheet shows other ways of using the chip: with a solar panel or a thermoelectric transducer or as an electric field harvester.
I like the last one. It uses two 30 x 60 cm (12" x 24") sheets of copper at about 15 cm (6") from a 60 x 120 cm (2' x 4') fluorescent light fixture. At such a short distance you might as well wire the chip directly to the light fixture supply, right? Luckily the datasheet also shows you how to do that.
Yet the LTC3588 seems like a pretty interesting chip and I ordered some samples. I will let you know if I get them and if I did, what I managed to do with them.
A nice introduction to piezoelectric transducers