Recommendations for pressure transducers

[Ben-jammin]

I’m interested in playing around with velocity control of midi through a differential pressure transducer. Ideally it would be a 0-5 volt analog device and was wondering anybody had a recommendation for a sensor part number that would have the required range of positive pressure and vacuum to work in an accordion. A 4/20ma device would also work out.

 

[Ventura]

i don't understand your query

differential pressure would be a ramping up of the value,
like a bellows sensor, which cannot give a reference to
determine speed or relative force because it is continuous

velocity control is based on two different events in time,
and the relative speed of those two linked events for a
specific note/gate, which is then analyzed-and a value is
output that controls (through MIDI) controller 7 or controller 11,
or in a Synth above MIDI possibly the opening of an envelope
related to resonance or some other filter that allows for a variable
in sound intensity or saturation, which is applied to the attack.

so the ideal sensor for MIDI velocity is simply 2 linked switches,
(limited/enhanced by the quality of the software analyzing the delta)
or in equipment beyond the MIDI spec, perhaps 4 or more linked sensors..

or what did you mean ?

 

[Ben-jammin]

Maybe I misspoke when I referred to velocity. I am looking to control instantaneous midi volume with the bellows pressure.

For my application I am looking for pressure differential in the sense that it would compare the difference in pressure between the atmosphere outside of the bellows vs the pressure inside the bellows. It would provide an instantaneous value that would likely need to be filtered to generate a midi volume reference for any notes that are active at that time.

 

[Ventura]

the ORLA reedless accordion used that method, the bellows
only routed to controller 7, volume, rather than both velocity
and (11) intensity as did the other reedless models coming out
at that time, and as currently used in the industry

so if that would fit the bill for you, might run into one somewhere
and do your experiments without having to build something from scratch

but if you are attempting to craft a bellows sensor that you can
overlay onto an existing (older type MIDI) accordion, yes there are
pressure sensors out there, and by now i imagine some that can
sense both positive and negative pressure, so you would only need
one sensor for push and pull.. so electronically/digitally controlled
"volume pedal" you could merge into the MIDI note datastream

cool

when i was looking, the sensors were only one way.. i did pick a couple
up but never got around to doing anything with them.. but yes they
just have an enclosed diaphram with a tube and 2 contacts to read
the variable resistance.. simple devices really.. and back then they were
all pretty large.. i imagine now there are miniature versions just as sensitive
or even better.. mine might have been picked up as automotive parts surplus !
a lot of stuff on your car is controlled by variable vacuum sensors

good luck with your project

 

[Ben-jammin]

I found the part# used in the Sem Ciao accordion and ordered one. It’s a Wheatstone bridge design so will require amplification but should be suitable with an operational amplifier

 

[Ventura]

plus Wheatstone is a famous/legendary name in Concertina's
so you are staying in the accordion family