Science Buddies: "Ask an Expert"

Hey guys! I just wanna ask really quick about contact microphones. Is there any way to calculate the electric signal that comes out from the mechanical stress? Sorry if my question is weird and very naive. Help would be greatly accepted.

Calculate - as in predict? or measure? The specification sheet from the manufacturer will tell you what to expect for both voltage output and frequency response. In general, a piezo microphone is similar to a standard microphone and can be used with standard mic preamps and such. If you want to measure the output and/or see the waveforms, an oscilloscope is definitely the right tool for the job.

You can easily expect a 1V peak output from a contact mic. If you have a DIY or cheap version, a strong mechanical shock might give you a spike of 20 to 30V. As a precaution, it's always a good idea to use a commercial contact mic, or build a buffer into a DIY solution to protect whatever you're plugging it into.

Thanks for the input! And I'm more of a software guy than hardware, what kind of buffer would work well with a DIY one?

It depends on the actual element, but lots of circuits are all over the web. The bad part is that you may have to build one from scratch - I don't see that there are a lot of kits. You may be able to buy one in a music store though, as contact mics are pretty common for guitars, brass instruments and drums.

I thought this video was pretty nice: https://www.youtube.com/watch?v=aOJuCYgmPPE . It discusses why you need one and shows how he built his own. There are countless more articles and videos out there as well. You'll have to do a bit of research on this, pick one to try and give it a go.

HowardE wrote:It depends on the actual element, but lots of circuits are all over the web. The bad part is that you may have to build one from scratch - I don't see that there are a lot of kits. You may be able to buy one in a music store though, as contact mics are pretty common for guitars, brass instruments and drums.

I thought this video was pretty nice: https://www.youtube.com/watch?v=aOJuCYgmPPE . It discusses why you need one and shows how he built his own. There are countless more articles and videos out there as well. You'll have to do a bit of research on this, pick one to try and give it a go.

Thank you! I'll go look around then.