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AIn with other values than 0 to 10K ...


gillesdeshays

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Either some software solution (you best ask for that @ MIOS topic or directly to TK - who isn´t here @moment).

Or a hardware solution:

With some OPAmps you can change any voltage to some other voltage (e.g. get the voltage with one OPAmp down by 1.2 Volt and with a second OPAmp factorize it to fit the 5V maximum).

Greetz!

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Guest Mark420

I have a similar Question,

I have some Alps 200k pots and wondered how I get them to work on the ain.

Maybe its just a question of adding resistors? so that when the 200k pot is on full deflection the resistance=10k not 200k

Or is it a Mios trick?

Any feedback greatly appreciated!! ;))

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i'm making a new control glove .. using 10k pot but without the full course ( i mean nothe full rotation ...)

the midi values are from 05 to 119 instead of 01 to 127 ...

so i need a software trick to have the full 127 values ....

i'm looking in the mios code .. without any result from now ...

for mark420 i think you can cheat with different voltage ... ( resistor ..  post edited ...)

MIOS need 0 to 5v ... put another voltage ( instead of 5V) and check what you can have on thepot pins ... but DO NOT PUT more than 5V on AIN !!

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@mark:

It doesn´t matter what the max resistance is so much, cause you use those pots as voltage dividers. You use them to go from 0 Volt up to 5 Volt.

So the only thing what could happen is jittering. As in 10 k Pots there is a current of appr. 0,5 mA running, there won´t be so much jitter anyhow. But with 200 k´s you only got 0,025 mA (25 uA!!). That´s a little low, this will only work with a very good shielding (which the ALPS faders perhaps have).

I would give it a try, but if it jitters, you got problems...

Greetz!

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Guest Mark420

Ok guys I understand a bit better now.

Well I have to wait a couple of weeks before I can try this out (waiting for parts;(() but I will cross my fingers and hope the noise isnt too bad..

On a related point...The midibox I am making is going to be made from a converted audio mixer u see (hence the good quality pots and faders) and the pots and buttons on the mixer are mounted onto a pcb then mounted with pillars under the face plate.Theres soo much room inside the mixer to fit a core and modules.

I dont want to destroy the audio mixer so i was thinking...if I wire the core's PSU to the mixers pcb and then take only one wire per pot back to the Ain module by soldering on the pcb cos +5 and 0v would be from the board, and its got a great ground plane!.

Same with the switches on the mixer-its got i think 6 mometry switches and i think 6 latch switches wich i hope i can make into layer buttons to add more switches.

Like the pots i hope to be able to solder the switch wires from the back of the mixers pcb.

I think this would help stop "jitters" thro ground problems?

And also maybe when I get it all working I "maybe" get it to work both as a midibox and then with a throw of a switch it goes back to being a standard (very high quality) audio mixer.

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Well, if the pots are from an audio mixer, they are probably logarthmic, and mios should have linear pots.

I think log pots will work but the values you get will not be equally spaced. as for swapping between audio mixer and midibox, i am not sure that this is possible, and if it is it is probably not easy.  I think I would keep your very high quality audio mixer as is, and build a seperate MidiBox. If I had a very high quality audio mixer, I wouldn't go mucking around inside and adding things to its pristine circuitry, but I have never had the pleasure of owning such a mixer. Maybe you could look for a broken mixer on ebay.

Just my thoughts, anyone else got a comment?

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oki Gilles it seems to be a very intersting project!! :D

I wanted to make some Virtual Reality stuff some times ago, a glove is a good start :) I still plan to make something in opengl... (and I want to build a hemlet too hehe).

Well, the adc of the pic is 10bits max, so you can scale the pot easily I think, need to make some pic asm (or C code ;))

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Guest Mark420

well im kinda lucky...its surplus to requirements (i have two of the same model u see) and very easy to take apart and theres soo much room inside for midibox circuits.

Its also has rackmount brackets so I can make a nice flight case solution so that I can lug it around to clubs etc..

I have found out the model number etc of the pots and heres a link to the data sheets.

http://www3.alps.co.jp/pdf/2004pdf/pdf_e/Potentiometer/Insulated/14_insulated.pdf

I cant see anywhere if they are Log or Lin pots and the part number doesnt suggest anything.

I know for sure that the faders are 10k Linear cos I have crossref them with the Alps site and i can see them there.

I am using it only for Traktor (normally I use the mixer like a traditional mixer with Traktor coming in on two line in channs, I would much preffer to use the mixer as a midi controller because then i can cut down a LOT of mouse and kb activity and you can get a more precise control of parameters with a pot than a kb key..Also its going to help a lot when i am recording demo mixes for promoters/clubs etc.

Mark;)

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So? Just measure it out!  ;)

Just use some Ohmmeter and put it to the lower end and to the middle pin. If you now move your fader to appr. the middle it should show 100 k (half of 200 k). If it does not and shows something like 60 k or so (less) it´s logarithmic (you can also recognize that if you move the fader - at the beginning the increments are very low and to the end it will be something like 20k or more per millimeter).

Greetz!

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