DIY potentiometer, Voltage division?

[Alkex]

Hello,

I would like to make a midi instrument out of an old guitar,

I want to use the fretboard as a kind of potentiometer With

5V at top of neck, and a resistor between each fret downwards.

I could then use the string to "read" the voltage at the touching fret.

The main question, being a complete clueless sod in electronics and electricity is:

What resistors do I need to divide 5V into 22 more or less equal frets (sections)?

Is there a formula I can use maybe?

Thanks in advance,

Alex

[illogik]

Hi,

nice idea!

i think that when u use resistors of the same value you automatically get equal sections. (every resistor has the same value>>the same voltage accross it)

To keep it in the midibox range (10klin for pots) i would divide 10k trough 22= 455 ohm or something in that range.

would be even nicer if you could make it with some kind of ribbon controllers so you get full pitch range instead of notes (but would be much much more work+money ofcourse)

good luck, marcel

[istephen]

You'd need to consider what happens when the string hits more than one fret - it's gonna happen sooner or later. In the worst case - hitting the first and last frets simulaneously, you would more or less short out the resistor ladder with the string. This would be bad. To solve the immediate problem of causing damage to the 5v surply, you could add a 10K resistor, so that even then the ladder is totally shorted, it's still not drawing more current than is acceptable.

Ian

[MyCo]

You could solve it digitaly. Just use the string as ground and connect the frets to DIN... then you only need the firmware...

[levon]

though you would have to tell it to only use the highest note.... cause when you fret a note you are tentioning the string between 2 frets. for say a A note on the low E string, the string hits fret 4 and fret 5. another thing is that when you are playing arpegeios you keep your fingers in position, and pick the notes in time, so you might have to come up with soem sort of 'picking' digitizer.

[Alkex]

Hi all!

Thanks for your feedback,

believe it or not, this system is quite reliable in analog mode.

I just mesured the (noisy) voltage ranges for each fret and used a "IF VOLTS>LAST FRET, THEN" etc

Now to sort out a nice triggering system...

Alkex

[Jaco-]

Hello!

I am interested in building something similar to MIDIfy an electric bass guitar using part of a MIDIBox but there's something I don't know how to do.

I think the resistor ladder is a good idea which will use only one analog input per string, but if I use an analog input of the MIDIBox to send Note On events, the analog value is taken as a Velocity value and not a Note value. I think that this is something that could be managed with some software changes but unfortunately I have no experience in coding. I would need to assign different note values for different voltage ranges of an analog input.

Does anyone know how to do such a thing?  A hint about how to deal with the code would be of great help!

thanks in advance!

[Alkex]

Hi!

Happy to hear you like my idea,

My guitar has been put on hold for the moment, leaving place for a all in one "sid midi keyboard" but here is how I handle notes with resistor laders:

Yes, you would have to change the code, but fear not, I am Hopless at coding and ended up with a more or less reliable system.

I stored each analog value in a register and continuously compared the live value to the previously stored one,

any passage from and to 0v then sends NOTE ON or OFF respectively.

As for the actual Notes, I just transpose up and up towards the read voltage.

this must sound confusing but its a simple thing to do:

example (where X is voltage (.4 volts in this example):

Is X > 0 then NOTE=C

else goto send_note

IsX > .3 then note=D

else goto send_note

Is X > .4 then note =E

else goto send_note

Is X > .5 then note = F

hope this clarifies things....

Alkex