[PD] using bonk to trigger piezo sensors

Andy Farnell padawan12 at obiwannabe.co.uk
Wed Jun 27 02:47:11 CEST 2007




[bonk~] may not be the ideal unit for the job, though I am sure
it will work, it might be a bit elaborate to set up if you
are new to it. 

I made something similar once, I'm guessing the piezos are those
very thin kind, silver solder on one side and usually fixed with
a blob of epoxy, as you get in musical greetings cards (?).

They are basically mid/high frequency transducers, with a peak 
somewhere about 5kHz. I seem to remember that on a drum skin
they gave a very bouncy signal and to get them to work
I had to put a RC passive lowpass in there to settle them down
a bit and avoid multiple triggers. 

[bonk~] is quite a sophisticated object that matches brief
signal patterns. You train it with a stack of examples to
match and it does its best to identify occurances of the
same pattern in the input stream. 

For a bongo trigger I suppose you really just want a
single trigger. Something as simple as

[lop~ 400]
|
[threshold~ x]

might be all you need. Place 3 of them at 120 degrees
around the skin and you can work out where on the skin
the impact occured...a la Korg Wavedrum or Roland DP(?).






On Tue, 26 Jun 2007 13:35:13 +0200
"henrik wurster" <henrik.wurster at gmail.com> wrote:

> hello gang,
> 
> I have a project with pd using piezo sensors attached to my bongos
> underneath the skins. they actually work not too bad as microphones,
> but what I want to do is trigger the strokes being played on the bongos.
> in the end I want to trigger matching samples which I recorded previously.
> in my research how to detect small percussion instruments, I stumbled
> upon the bonk object, but don`t know how to work with it, because I am
> really new to pd...:)
> I dont expect any patching, but can anybody help me to give me an idea
> how I could start buiding the patch ? I thought about loading the samples
> into an array, but does bonk work at all checking sounds with recorded
> samples ? thanks for any piece of advice
> 
> best regards,
> - henrik
> 
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