[sdiy] How do contemporary velocity sensitive midi pads work?

Declare Update declareupdate at gmail.com
Thu Aug 6 23:36:55 CEST 2015


Wow that's precisely what I'm "tambout". Sounds so cool. Are you getting parts directly from them? And what sort of materials have you tried on top of them for striking on and whatnot? Digi models of percussive and string instruments is totes why I'm interested, great to head you're having success there.
Chris

Sent from my iPhone

> On Aug 6, 2015, at 2:44 PM, nvawter <nvawter at media.mit.edu> wrote:
> 
> 
> I've been working with Sensitronics' FSRs for about a year now.
> 
> Electrically, I use a divider circuit with (IIRC) a 3k resistor.  I've found I don't need to buffer
> the electrical signal into the ADC on the STM32F4.  One really should, but really it just makes a
> different curve.  :)  I am open to experimenting with different curves such as with a logarithmic amplifer, etc.,
> if anyone has any suggestions.
> 
> I've been obsessively figuring out different ways to utilize the continuous values to emulate plucked strings, drum
> heads and pressed keys.  My goal is to be able to press lightly with one finger while striking with the other
> and have the tone come out a higher pitch/thinner and decay faster...  sort like muting a drum head or strings
> while striking it.  I've also been trying to emphasize the sound differences between a fingertip strike and
> a fingernail strike!  I know it's possible, I've recorded the electrical signal and identified different
> frequency content.  The challenge now is to transduce it into sound.  There is lots of potential here, guaranteed
> to keep you up late at night for years :)
> 
> One other interesting thing I found with them was feedback when I built a drum with them.  The speaker in the drum
> was able to induce a detectable signal in the FSR.  Not sure if that was vibration or EMI, but it can happen :)
> 
> 
> 
> 
> 
> 
> 
> 
>> On 2015-08-05 22:25, Chris McDowell wrote:
>> Howdy list,
>> I'm wondering if anyone has some experience with the design of modern
>> velocity sensitive pads (just found myself curious).
>> Controllers like the akai LPD8 don't appear to have piezos, but do
>> have concentric squares on the pcb underneath each pad. I can kind of
>> guess that these may work like the staggered switches that provide
>> velocity on a synth keybed, but it's not super clear. I've read a bit
>> about "velostat" and FSRs also, and am wondering if they're perhaps
>> doing the deed. I know older MPCs do indeed have piezos, and that
>> seems pretty straightforward. Any info is appreciated!
>> Cheers,
>> Chris
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