First up, sorry to those people thinking… Oh my god, yet another cool thing for MIDIBOX. Alas no, but perhaps in the near future..read on…
Driving home in the car tonight, I struck on the idea that a vertical or horizontal touchpad strip would work well as potentially a replacement of an encoder.
(Now I should stop right here and say… Using such things will still be far more expensive than using motorised faders, etc,etc, BUT, may allow for miniature 16 channel mixers to be made, perhaps entire panels of trackpad with every nanometer dedicated to some MIDI parameter, etc,etc.. and also for the “What the hell” buzz.)
Ok, let’s paint the scene, you use something like a Midibox LC except the motorised faders and the pan encoders are now little one way trackpads. You can increase and decrease the slider positions by simply dragging your finger over it. This might be useful for when say volumes (or whatever is associated with a motorised fader) are moving all over the place so quickly that the poor little motorised fader is having a hernia (does this happen in real life? Haven’t personally gotten around to using MFs). The position of the slider is shown on screen in your DAW as well as a strip of LEDS along the side much like we do for the encoders at the moment.
WHY.. because it may give you all the advantages of an encoder but with the human interface simplicity of a vertical fader strip. (and of course for the “What the Hell” trip).
(One could go on about possible uses, possible advantages, disadvantages, etc, but I will leave that to others)..
HOWDOWEDOIT
I am sure most know how trackpads work, but for the two in the corner cowering under the table, basically (very basically, I have probably even got it wrong) it uses an XY grid of tracks on a PCB and then measures the capacitance between all of these wires. Your finger has a different electrical permittivity than air, so changes the measured capacitance between the wires/PCB tracks (all non contact, your finger never touches the wires, just a protective coating, Â the flip side of the PCB, etc). From these measurements it’s possible to workout where your finger currently is, and also if you track these changes to tell where is it moving to. You can also measure the presence of a finger . (Imagine an entire control surface , flat, bare, transparent, but you move your finger over it to turn on tracks, move faders, etc, etc, and LEDS through the panel show you the status of what you pressed. WOA getting a little too Star Trekish for me.. back to reality)..
Energise.
Ok Because we are only interested in one direction, the PCB would be a heap of parallel tracks (at 90 degrees to the direction of travel. An up down slider would have tracks going left to right) because a finger is a finite size, you could also probably bridge interlacing lots of these tracks to cut down on lines you need to measure the capacitance (like, the bottom line is connected to a track 2 cm up, and then to the next one 2cm up, etc) as we are not really interested in absolute position, just state change.. You could track absolute movement and make it not only a differential control, but an absolute one.
Ok to measure capacitance… ok, probably lots of ways to do it, but any of the efficient ways will probably require their own little micro controller, or one that handles ALL of the track pads in the system. You could introduce a clock signal to alternate lines and measure the cross talk, on the ones left over. Perhaps rectify that crosstalk (after the multiplexers - see next sentence) into DC value and into an A/D. You could then have the input lines multiplexed using similar techniques we should be familiar with (i.e. A_IN module). Heaps of ways (will leave for other posts). A little processing and you could workout where you are now, and if you have moved your finger. Send this to the MIDIBOX application as an increment/decrement command (with some adjustable gain/acceleration) and you have a DIY trackpad (well it will take a little more than that, but that’s the basic principle).
So all in all,
Possible - yes
Difficult - probably
Cool- well I think so, but then I still use wax cylinders for recording
BUT.. is this a waste of time for Midibox, or could it have some actual applications?
Ideas anyone…
