[sdiy] MIDI VOL PEDAL with no micro??

[Roman Sowa]

Get any parallel output 8-bit ADC, feed its output to the inputs of 
serial shift register, like HC597, then add a few more HC597 to set the 
rest of the message.
Next thing is clock source - either crystal one, or piezo resonator, or 
even plain RC clock, as you need clock stability of about 3%.
Next step - simple movement detection circuit made with opamps (you
asked for them) - gain of about 20, then integrator, and 2 comparators
to detect +/- 0.5V crossing. Pot movement detected this way latches the 
shift registers and triggers  clock burst to the chain of HC597. You may 
also use digial comparator and latches for last sent value, but that's 
quite a few chips more.

You need to send this sequence, including start/stop bits:

0 1 0 1 1 0 0 0 0 1 0 0 0 0 0 0 1 1 1 1 0 0 <7 MSB from ADC> 1
which in human hex language means "B0 07 <pot>", this is channel volume 
in channel 1.

30 bits total, so 4x HC597

A lot more complex circuitry than any example with uC, but also a lot 
bigger chance to learn something while building it, and pure fun of 
making it without any firmware.

Roman

W dniu 2014-02-08 20:16, Dan Snazelle pisze:
> is it possible to create a MIDI volume pedal with nothing but an
> optocoupler, opamps, cmos and passives?
>
>
> i ask because i have a friend who wants to make one himself
>
> id just use an AVR with an opto and a pot based pedal.... but i
> thought it might be fun to go the other route
>
>
> are CC messages complex? i wouldnt dare try this with SYSEX but i
> thought a CC pedal might be within the realm of possibility!
>
>
> thanks
>
>
> Sent from my iPhone _______________________________________________
> Synth-diy mailing list Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>