Power to the little people
Unobstructed by corporate bulk and bureaucratic red tape the little guy seems to be consistently coming up with seriously dope shit. Take this gentleman here who was disappointed with the quality of jog wheel controllers that the current crop of dj companies with millions of dollars in development money had produced. So, as most people have been doing around here at Dj TT, he made his own- but better. Bookyakasha ninja midi master.
First, you need to see this thing in action. Yes, the video is delayed but the performance of his device is spot on.
Next, check out how the well he got the touch sensitivity to work.
To achieve this performance he wisely included a Vestax CF-PCV crossfader.
Here Dj Raseri describes his method for achieving a damn good jog wheel on his midibox page.
After considering a number of options, I settled on an optical quadrature wheel design. This consists of two photodiodes spaced slightly apart, and a wheel with a pattern of slits round the circumference. By watching the slits go past the photodiodes, you can determine the speed and direction of the turning wheel. Wikipedia has a good page on this.
Old (ball) mice use this exact technique. Which is handy, because if you have any old mice lying around, you can harvest them for optical sensors and LEDs. This is what I did. You can rig up something out of individual photodiodes and an infrared LED if you prefer.
An optical encoder wheel can be made using a transparent acetate sheet and a laser printer. Draw up a pattern using your favorite CAD program, print it onto the sheet, and cut it out.
I put the two photodiodes into two voltage dividers and wired them into pins 3 and 4 of the PIC. At the moment I just have the optical encoder wheel sitting on a spindle, with a CD mounted on top for easier grip. This is obviously a bit wobbly but it works fine for testing.