piezo transducer to adc ?

[Giulio]

Greetings all...

I need to interface one of those cheap piezo disc transducer thingies to a pic via an adc pin - the sort of thing you can get in Maplins for 10p or whatever.

Last time I remember playing with one on the 'scope, it produced wildly varying output depending on how hard you hit it - as is its nature (!).

Is it possible to tame and scale this output to receive a value twixt 0-255 or should I be looking at a different kind of sensor?

I need something that responds to being hit !

Any thoughts?


Giulio

[Melanie]

If you put a scope on a piezo, you'll see that it certainly responds to being hit... this application is used in some Burglar Alarm Sensors to detect doors and windows being smashed and with amplification to detect drilling and masonry demolition. Sadly the days of digging into your favourite Bank vault from the sewers (as perfected in France) is long gone... the technology may not have reached rural areas of Bolivia and Peru yet, but the currency isn't exactly changeable at the local wine mart...

Perhaps if you elaborate on your application, (there's different kinds of hits... raindrop and freight train tend to be two ends of the scale that spring to mind) there might be a few better suggestions.

[Giulio]

Haha! Thanks for the reply. There goes my evil plan to appropriate wheelbarrows full of Peruvian banknotes...

Ok, I intend to mount this sensor in (or under) a silicon rubber membrane (think syn-drum) and, hopefully, send the resultant data via USB to a PC, which will then play a sound sample corresponding to the number received.

I simple look-up table at the PC end should suffice, e.g. receive values 0-20 = play little sound, receive values 21-50 = play LoUdEr SoUnD, receive values 51 - 100 = PLAY VERY BIG SOUND, etc...

These values are arbitrary, of course. I don't suppose it's realistic to expect to be able to discern 255 discreet values from this type of sensor, but you get the idea.

As far as the raindrop/freight train analogy goes, there's the rub (and quite prescient of you...). Some drummers I know play exactly like Hinakuluiau, others as though a freight train had passed over one's skull...

I did have a look at these entirely nifty QTC pills, but there seem to be few resources on the Internet regarding them.

That's the (half-baked) plan!

[rossfree]

My son has taken Radio Shack piezos and made his own drum pads which he has wired into a sound module/amp. Fairly impressive... I suspect you could get a minimum ten sound levels with these things. Not too bad. Love to hear how things turn out for you.

Ross

[mister_e]

Usually drum pads use Piezo or more than often cheap(and ooh the most cheapest and nifty) unidirectional microphone.

Run the signal of the the microphone to a high-pass filter avoid to have 'false trigger' comming from the rumble or low frequency sound generated by the FOH or musician monitor amplifier system.

Most drum-pad system have the ability to adjust the trigger level for the same reason as above.

HTH