Urgon Posted September 20, 2009 Report Share Posted September 20, 2009 AVE...My good friend sent to me a E-mu ST 1200 service manual. We analysed its design and came with clever way to make velocity pads for any MIDIBox with at least 8 AIN ports. The basic version utilises one piezoelectric membrane as velocity/pressure sensor and 8 microswitches for AIN pin selection.Circuit diagram:It's just an amplifier/filter. RV1 is used to set pad sensitivity.Construction:Two piezoelectric membranes connected in parallel are between two metal or plastic bars, which are loosely joined together. On top are placed microswitches. Tapping one of them will send a pulse generated by membranes and amplified by circuit to one od AIN ports. This is the simple, yet working way...In more complex design you can use DIN imput(i.e. push-button 4x4 matrix) to force the Core to read data from AIN ports. Still at least one membrane must be beneath the buttons. This way you can eliminate adding contacts noise from microswitches.If you want to make a real dynamic keyboard, you must have original mechanical keyboard assembly from piano or something like that. Just replace strings with piezoelectric membranes and switches BENEATH them, so when hammer strikes any of them, you can get real velocity parameter. Switches should be connected to DIN module and write proper code for Core module...This is just concept. I wasn't able to test it, but I'm sure it will work. TLC27M4 should be replaced, since in some countries(i.e. in Poland) is impossible to find it. Probably any op-amp should work with this design... Quote Link to comment Share on other sites More sharing options...
Futureman Posted September 21, 2009 Report Share Posted September 21, 2009 The Alesis HR-16 does velocity for it's pads in pretty much the same way.. two piezo's under the 16 (?) pads. Quote Link to comment Share on other sites More sharing options...
ilmenator Posted September 21, 2009 Report Share Posted September 21, 2009 But then the HR-16 pads were a real PITA. I don't know anyone without problems with these pads, including me. They would "fire", or they would not - you could never be quite sure. This might have been an issue with the pad mechanics, though, like the pad being stuck in the bezel. I do not remember the details, I only know that I got rid of the damn thing (though the sounds were nice at its time). Quote Link to comment Share on other sites More sharing options...
Futureman Posted September 21, 2009 Report Share Posted September 21, 2009 But then the HR-16 pads were a real PITA.True, but as were the Alesis MMT'8.. and that was more of a design issue with their crappy rubber buttons they used. Quote Link to comment Share on other sites More sharing options...
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