how do midi keyboard keys work?...and how to replicate a keys function.

[deadastronaut]

i know its off subject for pedals..but.

ive been searching around for info on how an actual midi key works and how it is velocity sensitive etc...

and alas have found very little info..(surprisingly)..

what i am trying to say is i want to REPLICATE A MIDI KEY IN A BOX....obviously wired to the internal connections

of the keyboards key(which is assigned a note/drum etc.....get me?..

i want it to act as a bass kick pedal.....or bass note etc...or even pads wired to several keys to form a kit..hmmmm..theres an idea..

.i know i can put just 2 connections to turn on off a note/key..but how could i get it to be velocity sensitive too......?

sorry for the off subject thing but im curious to see what you guys think..............

how do midi keys work?......and how to replicate it......?

rob.

[Processaurus]

They have two rubber buttons under each key, that are different height.  A microprocessor reads the time in between the two switch's closing, to know how fast (hard) the key was struck.  I've fixed a couple keyboards that had stuck velocity on some notes from dirty pads under one of the two switches.

[deadastronaut]

cheers..but how would i replicate the black grid circuit part that they hit..?...

and how does that work?....is it 2 grids inner and outer...?..how does it work with a  piece of rubber hitting it..?

hmmm...rob.

[potul]

If you only need one button in a box (like a bass kick, or similar), you could go into the approach of using a piezo sensor. The harder you kick, the higher the voltage peak. It can be easily fed into a mC, take a look at the multiple e-drum projects out there and see how they read velocity out of a piezo.

Potul

[deadastronaut]

If you only need one button in a box (like a bass kick, or similar), you could go into the approach of using a piezo sensor. The harder you kick, the higher the voltage peak. It can be easily fed into a mC, take a look at the multiple e-drum projects out there and see how they read velocity out of a piezo.

Potul

cheers potul...yeah ive got some piezos. thats what i originally thought.......but what is mc by the way?......

...all i want to do is trigger my key but be velocity sensitive...could i just attach a piezo to my key?...in some way...?


anyone got a diagram of how the circuit pressure pad works...so i can build one...


aha...just found out they are called 'force sensing resistors'......the bit i want to make.....

just found a link to a diy force sensing resistor...looks like it could be usefull for pedals too.....wah etc...

dont know how id wire it to my midi keyboard for sensitivity still though.....

not the same as a piezo either?...

massive link...lol.

http://www.google.co.uk/imgres?imgurl=http://www.circuit-projects.com/dimg4/building-a-force-sensitive-resistor-FSR.jpg&imgrefurl=http://www.circuit-projects.com/miscellaneous-circuits/building-a-force-sensitive-resistor-fsr.html&usg=__PxIpi-etTANzjDXUfyaAO64DDP0=&h=290&w=400&sz=52&hl=en&start=22&um=1&itbs=1&tbnid=EXMh-Ef5qSPfUM:&tbnh=90&tbnw=124&prev=/images%3Fq%3Ddiy%2Bforce%2Bsensing%2Bresistor%26start%3D20%26um%3D1%26hl%3Den%26safe%3Doff%26sa%3DN%26ndsp%3D20%26tbs%3Disch:1

[potul]

Sorry, I was not clear in my message. By mC I was trying to say "microcontroller" (a PIC, AVR or similar).

What do you plan to do with the signal? This would help having an idea of what can and what cannot be done with the piezo setup.

Potul

[potul]

Oh, I think I understand now... So you have an actual midi keyboard and you want to somehow get a cable out of it going to a box, and have a footswitch to act like a key in the keyboard. Is this it?

Potul

[deadastronaut]

yep thats it exactly...

i did it to a non sensitive keyboard (kids toy) years ago...and just soldered wire onto the key points..

but i want this to be velocity sensitive...cheers potul...

i think this thread may turn out to be useful to many...........

[potul]

I'm affraid there's no easy solution for what you want to do. Whatever solution based on  piezo will require some sort of microcontroller to somehow sense the force applied to the piezo and transform it into a velocity.

The only way to plug a stomp thing into your existing keyboard is really to "replicate" what the key does... and this is something probably will depend highly on your keyboard. Are you sure your keyboard is using an FSR?

I was thinking on something more like a standalone box with a stomp that would connect via MIDI somewhere. But this would be a project involving microcontrollers and MIDI programming... probably something you don't want to get into.

Potul

[deadastronaut]

hi yes i dont want to have to go down the micro/pic route...when i have the sound and controller already..

i thought all keyboards had fsr's in them...that little grid circuit that the rubber hits?..

i was wondering if i could add another to it...and use externally...

cheers rob.

[frank_p]

I wonder if the M-Audio midi controllers have those rubber pads...  They are already not too pricey and maybe you can find one used to hack it.  I've been thinking about that too.

Note that there are foot MIDI controllers too (like on organs)...

[deadastronaut]

I wonder if the M-Audio midi controllers have those rubber pads...  They are already not too pricey and maybe you can find one used to hack it.  I've been thinking about that too.

Note that there are foot MIDI controllers too (like on organs)...

cheers frank. yeah i think the pad controllers are exactly the same...not sure totally, but would think so...

im looking at the cheapest way possible to do it...triggering the key is no problem on/ off..its the velocity part thats
a bit elusive....wothout having to have a module/pic/micro controllers etc...

midi foot pedals are pricey too...nice though..
rob.

edit: just been reading on how to make an fsr...nice n easy to make..just need to know if it would work.


i gather the fsr is the same in theory as a piezo..they put out a certain voltage when hit...

then this goes to the controller.processor...i could be wrong though...


edit: i suppose if i measure the resistance of th key being hit soft and hard...and then adjusted the piezo
to match it may work.....but then it might not..lol..

[DougH]

Why ask why? It's a miracle: http://www.youtube.com/watch?v=FGbdomlBnJM



Seriously, maybe look into the other kind of stompbox: http://en.wikipedia.org/wiki/Stomp_box

[deadastronaut]

Why ask why? It's a miracle: http://www.youtube.com/watch?v=FGbdomlBnJM



Seriously, maybe look into the other kind of stompbox: http://en.wikipedia.org/wiki/Stomp_box

wtf?..lol..

anyway..i saw them ages ago..but im greedy i want it to trigger more than a boom..lol..

drum/sample/loop...it would be well handy/footy to use...


edit: ha ha i just contacted emu about my midi keys and whether they are in fact fsr's?....
cant wait for the reply...(they'll prob tell me to go fish ha ha.......funny though!..cheeky ...b****d eh?..
worth a try....lol..

[deadastronaut]

yep . i was right..they me gave me a brush off..saying they had no idea how they worked..

as they only deal with warranties/problems/repairs...how do they repair em then?...ha ha ha ha...

anyway anyone have else have any ideas on how to replicate a midi key?...

[newfish]

Additional band member and a long stick.

It would work.  Bit 'old skool' though...

[ashcat_lt]

It would be a lot easier to find yourself a drum brain.  Something with at least a single trigger input.  Then you can use the piezo and let the brain do the rest.  Use a MIDI cable to connect to whatever sound source you want.

[deadastronaut]

It would be a lot easier to find yourself a drum brain.  Something with at least a single trigger input.  Then you can use the piezo and let the brain do the rest.  Use a MIDI cable to connect to whatever sound source you want.

yeah i know...but i dont want to pay £100 plus just to trrigger one key....lol..

im trying to do this without a module etc...i just want to connect to the key itself...

the sound is there, the trigger is there..so i 'll carry on...if i can eventually do it i'll post results.

still open to ideas though!...

[Gurner]

I know you're trying to avoid it, but this one totally screams out for a £1 PIC and a signal chain like thus...

Analogue input 'trigger' (piezo pickup, mic - whatever you want)->simple preamp ->tiny bit of filtering (one resistor and cap!) ->PIC->  midi sound unit.

The PIC AtoDs the analogue input - 8 bit  sensitivity (256 levels), then spits out  the simple serial midi data on its output pin

About 10 components in total...and a total cost of no more than £5.

To do want you're after using discreet & logic would be *much* more involved (mainly the midi data aspect),  but with a PIC it's a piece of the proverbial.

[deadastronaut]

cheers gurner..

would i be able to trigger more than one too?...using that method....

be nice to have a few triggers if  attempting to go down that path.....

dont suppose you have schematic or dare i say layout for that idea? as ive never dealt with pic's.......

sounds like a greeat idea though...and simple-ish...
thanks man..rob.