Old 04-18-2019, 04:51 AM   #1
5/4
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Default Creating contact mics and others.

Hello all,
I understand this might get more traction on other more specialised message boards but this forum is the only one I currently have an account on and as Reaper users tend to be an inquisitive and technologically minded bunch I felt I could probably still garner an interesting response here.

Anyway as the title suggests I'm interested in picking up some piezo transducers in order to make some toys to mess around with. When looking through the selection at https://www.mouser.de I see a large range of different options all with varying resistances and sizes so I was just looking to see if anyone had any experience with these various parts and could shed some insight into what I should and shouldn't worry about when picking them up .

Thanks for any and all help on the subject!

Also as a side note if anyone has any projects related to homemade transducers piezo or otherwise I would love to hear about them or if anyone thinks I should really be posting these kinds of questions on another board then please let me know of any other good communities that would garner good discussions on this subject.

many thanks and have a good day all!
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Old 04-19-2019, 07:53 AM   #2
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Originally Posted by 5/4 View Post
Hello all,
I understand this might get more traction on other more specialised message boards but this forum is the only one I currently have an account on and as Reaper users tend to be an inquisitive and technologically minded bunch I felt I could probably still garner an interesting response here.

Anyway as the title suggests I'm interested in picking up some piezo transducers in order to make some toys to mess around with. When looking through the selection at https://www.mouser.de I see a large range of different options all with varying resistances and sizes so I was just looking to see if anyone had any experience with these various parts and could shed some insight into what I should and shouldn't worry about when picking them up .

Thanks for any and all help on the subject!

Also as a side note if anyone has any projects related to homemade transducers piezo or otherwise I would love to hear about them or if anyone thinks I should really be posting these kinds of questions on another board then please let me know of any other good communities that would garner good discussions on this subject.

many thanks and have a good day all!
I love screwing around with cheap transducers I don't really have any useful wisdom to impart, but I have some good bookmarks saved to remind me to get back to it. Have you seen "Music Of Sound"s site? They're a New Zealand sound fx company with some very extensive releases of audio recorded with contact mics. They post blogs occasionally with details about new releases and their page about contact mics is pretty informative, especially in the comments.

http://www.musicofsound.co.nz/blog/t...ntact-mic-club
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Old 04-19-2019, 08:19 AM   #3
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I'd recommend checking out piezo film tabs. They sound much more natural and don't have the strong resonant peak that rigid piezo discs have. They are relatively hard to work with (e.g. very easy to destroy when soldering) and they need to be shielded to avoid hum.
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Old 04-19-2019, 09:44 AM   #4
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I'll second Clepsy's hint. I had some leftovers from an industrial project and they are much more real mics than some piezos.

You can also get shielded film, helps get rid of the hum. Mine were destined for vibration measurements in machines, so the low-end is rather present. Other piezos often lack low-end.

In the end, any piezo will do, if you take into account that they need to see a high impedance on the preamp. So use an instrument pre, or find a second hand measurement preamp. These have an impedance of 10 Mohms, or higher, where the instrument preamp usually is only 1 Mohm. Higher impedance yields better linearity, more headroom and less distortion.

I've even used piezos from musical "happy anniversary" cards...
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Old 04-19-2019, 11:49 AM   #5
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You can also get shielded film, helps get rid of the hum.
Nice -- hadn't seen that. The shielding can be an issue with the unshielded variety, as you need to figure some way to encompass them in metal without trashing the frequency response, so it's good to hear that the shielded option exists.
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Old 04-19-2019, 01:57 PM   #6
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It's just an extra sheet of alu foil in the film, of course with an extra contact surface.

There's thousands of these vibration sensor films around. Some combined with other sensors. Some extremely expensive, for all kinds of environments.

Most of these aren't simple crystals, but polymers. Here's an interesting blog post from Element 14 about one:

https://www.element14.com/community/...-piezo-sensors

These cost just a few bucks. You can get them from the usual suspects, like Element 14, Farnell Seeedstudio, or Sparkfun. Here's an interesting kit from Seeed:

https://www.seeedstudio.com/Grove-Pi...or-p-1411.html

Note: these are new to me. I'm a bit puzzled by the fact that they have a stated source impedance of 100 to 300 Ohms. And I've never tested these.

An example of a shielded one that I have tried and that works very well for audio:

https://www.newark.com/sensor-soluti...or/dp/03AC2025

A bit more expensive, around 25$. Ready to stick in place. No electronics. Same technology.
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Old 04-21-2019, 10:23 AM   #7
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I have a friend who grows his own piezo crystals. He said he learned how from Youtube. He uses sections of copper pipe for making bridges, and grows the crystals inside the pipe sections.
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Old 04-22-2019, 04:58 AM   #8
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thanks so much for the responses guys lots of good info
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