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Topic: Connecting Piezo Elements (Read 3125 times) previous topic - next topic

Danrosey

This is a pretty simple question that I can't seem to find the answer to. 

Can you connect piezo elements together to allow for greater "knock" sensitivity?  I imagine it would be similar to the way you could connect two batteries or LEDs in series.  I am looking into building my own e-drum kit, but I am slightly concerned that one piezo element may not be efficient enough to pick up the hits for a snare drum.

Does anyone have any experience with linking piezos in series?


WizenedEE

I have never messed around with piezo, but since they're basically switches you would hook them up in parallel. I have no idea how well it would work though.

Grumpy_Mike

They are transducers so connecting them in parallel would lead to a deformation in on sensor as the other gets deformed. I can only see that as reducing the overall sensitivity. If you want to increase the sensitivity or rather area over which a knock can be detected you are best to mix the signals the same way you would with audio. That is using an op amp and mixer circuit. A simpler but less effective way would be to mix them with a resistor in series with each sensor.

Danrosey

Thanks for the input!

I may just connect them in series and see what happens--it's nice that the piezo elements are only a couple bucks USD.

raalst

#4
Feb 02, 2011, 12:11 pm Last Edit: Feb 02, 2011, 12:28 pm by raalst Reason: 1
beware that some piezo's can generate large voltages !
this can happen when they are dropped, or knocked on. 
sometimes being successful is the most dangerous ;-)
seriously, be careful what you plug the piezo's into.

In my opinion as a piezo tinkerer, if you want more
sensitivity, use a better amplifier.
I assume you know about the knock/blow/sound sensor circuit ?
this is one version, with a very nice design example spelled out :
http://www.nerdkits.com/videos/sound_meter/
another good source of piezo amplifiers for audio range is to google for "piezo pickup".
Guitarists know all about recording audio with a piezo disk.
 
the piezo disks can be seen as capacitors (with varying capacity) just like electret mics.
This explains why connecting them in series will not have much effect.
btw, those little electret capsules already have a jfet amplifier
on board. you need something comparable for your piezo.  

one other way I *believe I have understood* to increase sensitivity a bit is to pre-stress the piezo disk.
No idea how you would do that in practice though. the piezo stuff is a ceramic and brittle !
If you NEED to bend the piezo, e.g. because you want it attached to a curved surface, check out
PVDF piezo. Sparkfun has those, but they require even more amplification.

in all cases, let us know how your experiments went..

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