I found that it works better if you put some kind of peak detector
op-amp circuit between the piezo and the arduino.
See the peak detector circuit in here:
http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/part8/Page3.html
The diode rectifies the signal and the capacitor stretches it out so the
arduino has time to measure it, the resistor drains the capacitor so it
doesn't hold the peak forever.
Putting weights on top of the piezos increases their output, as does
gluing them to a resonant object.
Martin
On 2011-06-17 08:53, Roman Haefeli wrote:
Hi Pierre
Actually, I wouldn't connect the piezos to an arduino, but to a sound
card, because the piezos will likely give very very short spikes and the
sampling rate of the analogIns of the arduino is quite low (don't know
the exact value) compared to the sampling rate of a common sound card.
Also, you have more control in Pd to build a trigger detection filter
then on the arduino. Also you would likely get much lower latency with a
good audio setup than with the atmega->ftdi->usb->comport path. Also
when using the soundcard, the latency is constant, while you would have
glitches with the arduino.
I'd be glad to hear other opinions, though, since my thoughts are purely
theoretical. I haven't implemented a piezo-based trigger, neither with
sound card nor arduino.
Roman
On Fri, 2011-06-17 at 14:27 +0200, Pierre Massat wrote:
Dear List,
This is yet another question about Arduino. Sorry about that.
I want to use piezos to trigger samples using my arduino board. I want
the trigger to be sensitive, and a quick google search seems to show
that piezo is the way to go.
Does anybody have any experience with piezo triggers (what type of
piezo, isolating each piezo, etc.)? I will hit the piezos with my bare
fingers (no drumsticks or anything like that), but i guess it doesn't
really matter since i can control the threshold within Pd.
This last sentence is just to make sure that everyone knows i'm
talking about piezos in case there wasn't enough occurences of the
word in my message.
Cheers!
Pierre
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