piezo sounder

Hi, im doing a project on piezoelectric disks where I want to harvest energy from them. I have ordered some and waiting on them, I wonder if someone is familiar with working with these and could answer some questions. thanks in advance

I want to add a piezo sounder to an existing arduino project (a USB caps lock indicator - I want it to bleep when I (usually accidentally) press caps lock and peebl when I release it). In my spares box I found a 28mm enclosed piezo sounder which works very nicely driven with square waves of...