Piezo to midi

[JebemMajke]

Can someone suggest, how to change Piezo signal to midi?

I would like to make myself piezo drum kit.

[FiveseveN]

http://www.megadrum.info/
http://drummaster.digitalcave.ca/drummaster/
http://makezine.com/projects/arduino-based-midi-drum-system/
etc.

[deadastronaut]

i wanted to do this with a small 25 key midi controller keyboard as the 'brain'

but could never work out how to get 'velocity sensitive ''whacks'     ( replicating a midi key)

[Processaurus]

i wanted to do this with a small 25 key midi controller keyboard as the 'brain'

but could never work out how to get 'velocity sensitive ''whacks'     ( replicating a midi key)

The way most keyboards do velocity is that they have two separate switches that engage at different points at the key stroke, and the keyboard's processor looks at the small bit of time in between one switch closing and the other.  The faster the two switches closing is together, means the harder you struck the key.

It might be possible to design a circuit that watches the rise time of the envelope of the piezo, and generates pulses at the right time to fool the repurposed keyboard into thinking a key was struck, but my bet is it would be a) difficult to do with discrete logic, and b) glitchy, or slow. 

The low tech way would be to keep an eye out for a kids drum pad that has midi, and just wire the piezo inputs to the drum pads?  If it is to go to a computer, someone was telling me someone made a midi driver for the Rock Band drum pads, and those show up at yard sales and thrift stores.  I don't know, though, I got a beat up Drumkat off craigslist for $75 that has piezo inputs for external triggers.

If you could program a PIC, it wouldn't be outrageously complicated ("and they set sail for a 3 hour tour") to use a couple of the analog inputs, and watch them for sudden increases in voltages (a hit) and then measure the highest it went before going back down, and use a lookup table to find the appropriate 7 bit velocity number to output and then send the MIDI note on message with the right bits for velocity and note, and channel, out the UART.  Getting the right velocity feel would take work, with the curve of the values in the lookup table.

Might be able to find existing code for subroutines for sending a midi note, and doing a peak hold measurement.  Or check out the links above, FivesevenN posted.

[deadastronaut]

cheers ben, great explanation...i see the issue now.


i'll keep my eyes open for a cheapo 16 pad drum controller and experiment with that then...mini korg comes to mind

[Processaurus]

A cheap one might work better than an expensive one, I believe a lot of the MPC type controllers use FSR's under the pads, because they can be square.  A cheap one might possibly use piezo's already.