Cheap piezo buzzers are everywhere. They’re so cheap that they can be used in novelty birthday cards. Applying an alternating voltage across a piezo crystal makes it expand and contract, and fixing this crystal to a metal disk gives the piezo speaker its characteristic tinny sound that is anything but pleasant.

The piezoelectric effect works the other way too, and piezo elements are very useful as vibration sensors. Simply put one of your voltmeter leads on each of the piezo element’s wires and touch the element with your hand or knock it against your bench. You should see a voltage spike on your voltmeter which will change in magnitude with the amount of force you use when touching the element.

This ability to change shape when a voltage is applied and to create a voltage when they’re deformed is the basis of the piezoelectric transformer (PZT). While searching for a high voltage/low current transformer, Hackaday reader [Josh] was surprised to find a piezoelectric solution. He didn’t say whether he decided to use a PZT in his project but he did link us to a decent PDF on the subject.

In a PZT, two piezo elements sit next to each other. The primary is made up of multiple thin layers that expand horizontally and press on a single secondary piezo element. The more and the thinner the primary layers, the more force is exerted on the secondary, and the more voltage it develops. There are a few equations involved which you can check out in the PDF linked above that go over this concept in painful detail if you’re into that sort of thing.

If you have never played with piezo element you should add one to your next parts order. They are cheap and easy to experiment with. We have seen piezo elements used in DIY speakers, sonar projects, and even as the sensor for an atomic force microscope, but we have yet to see a piezoelectric transformer in a hack. Surely someone has used one in a project they worked on, leave us a link in the comments if you’re the person we’re talking about.