Interesting discovery regarding a junkbox piezo element…

January 21, 2012 | electronics | By: Mark VandeWettering

I was tinkering with a small electronics project (article and video to come) and needed a sound output. Digging around in my junkbox, I found one of these piezo speakers, and decided to use it, driving it with a square wave from my Arduino:

Piezo Element 1500-3000Hz –

My initial test was supposed to be 700 Hz, but it sounded very high. I recorded a sample with Audacity and looked at the spectrum, and sure enough, it’s principle frequency was at 2100Hz. I then looked at the driving signal using my Rigol DS1102E (did I mention I got a new scope this week?) and sure enough, it was a nice 700 Hz square wave. Apparently the specifications on this little piezo element weren’t kidding: it has almost no frequency response below 1500Hz, so all you end up hearing are the third harmonic. The fifth harmonic is actually pretty weak too, so you end up with a pretty even sine wave, just at the wrong frequency.

I guess if I want higher quality sound out of this thing, I’ll need to rig a real speaker.


Comment from Eldon Brown
Time 1/21/2012 at 6:06 am


Salvage a junked PC modem card, newer cards use small 1/2 inch piezo elements which seem to work well for (some) audio. Some card use actual (very small) speakers. I used a piezo element on my previous Arduino project.

Note: Modem cards are good for all sorts of interesting project parts. I get my junked cards from RePC, a hand full for a $1.

Eldon – WA0UWH

Comment from KA7OEI
Time 1/23/2012 at 12:10 am

Those piezos don’t have enough displacement to reproduce low frequencies too well but more than that, their housings – combined with the mechanical properties of the transducer itself – resonate at the nominal operating frequency, typically 2-3 kHz.

Sweeping them with an audio generator and watching the current consumed (voltage across the resistor) will show all sorts of resonances.

Comment from Mark VandeWettering (K6HX)
Time 1/23/2012 at 9:00 am

Interesting! That might make a fun experiment too. By the way Clint, your optical communication stuff is awesome, truly inspiring. I keep nudging closer to experimenting with it myself, based in no small part on your great website. Keep up the good work!