Frankenstein design questions???

[3rdordertrauma]

Hello everyone I'm new here. My first post... (sorry for the long one)

I've been thinking about building my own midi box for a long time now but just haven't had the balls to take the leap as of yet. My biggest reason for wanting to build my own (which I'm sure is obviously the case for most of you) is most the midi boxes available today are cool and cheap but just don't provide ALL the right features for my particular use (not that its an obscure one). Not to mention most of them lack the more interactive forms of control, such as multiple joysticks, keypads, touch pads, optical sensors, Etc.. Many of them do but I'm not really the kind of person who wants to page through a menu to select the track and then the parameter I want to tweak before I start tweaking. I want to reach for a control that is always there and does the same thing, usually track specific or independent.

I'm a long time electronic music producer and audio engineer. I'm also good with my hands and an accomplished craftsman, instrument builder and so on. So putting together a professional looking, properly laid out box would be the easy part for me. But when it comes to source codes and din's, pic's, ain's, dout's, jdm's, shx8's and all that, I have NO idea whats what.

Basically what I'm thinking of trying to do is Frankenstein a box together using buttons and knobs from old electronics, gaming controllers and telephones, in conjunction with new control surface elements. Would really want the unit to have touch sensitive motorfaders, pots for the EQ controls and encoders for most of everything else. This would be a dedicated Ableton Live controller for live performance. I know there are many out there and I've read some great things here already which have given me a lot of great ideas. My focus with the Frankenstein parts would not be to save money but to add some unique controls to the unit.

So my question is this: How possible is it to use things like telephone or calculator keypads & buttons, pots & encoders from old electronics, joysticks from gaming controllers, track balls from mice and so on for some of the control elements in the Midibox systems? I'm assuming there is a difference between a pot used on a analog modeling synth (for example) and a pot on a midi controller? Or are they similar or the same? Or say a fader used on a audio console vs. a midi controller? So when I'm sourcing (scrounging) parts, what specs am I after?

Also the links I'm finding for parts in the US are somewhat lacking in the area of non-detent encoders, joysticks, touch pads and such.

Any ideas, suggestions, info, links... whatever would be much appreciated.

[Therezin]

Welcome to the forum!

Buttons and such: The main thing is that they're a normally-open contact. You'll find that a lot of calculators, phones etc (probably most of them in fact) use a scanning matrix rather than individually connecting the buttons, and this might cause a problem... or it might not. YMMV.

Pots/Faders: The big issue here is whether the pot/fader (they're essentially the same thing but a different shape) uses a linear or logarithmic taper. Linear taper means the resistance increases in a linear fashion, while logarithmic taper means the resistance increases by a larger amount the higher up the scale you go. MIDI wants linear, while volume controls and the like tend to be logarithmic (because the human hearing is logarithmic).

Joysticks: Basically 2 pots controlled with one stick. They tend to be linear.

Mice: Use 2 encoders the same way that a joystick is 2 pots.

[Wilba]

Yes, calculators and many other things with buttons will use a scanning matrix, but that's not too big a problem... most consumer electronics have buttons that are the button part with a conductive pad that bridges across contacts on the PCB... so you can cut the tracks on the PCB to make them individual switches. This might be an easier solution for you, and using the existing MIOS apps, than writing custom PIC code to handle a scanning matrix.

As for specs, the suggested value for pots/faders on a MIDIbox is 10K, any higher and the current going into the PIC is not good for the analog to digital conversion. This is also a widely used value too. If you happen to find pots that are less than 10K then they'll still work fine, just use more current, you probably wouldn't want to use anything less than 1K.

Gaming controllers are cool, something like a PlayStation Dual Shock controller has two analog joysticks which are perfect, and some of the buttons are even pressure sensitive too, but you'll need to adapt them a bit to suit MIDIbox as they're like a pot without a wiper, the harder you press, the lower the resistance. So to make any use of that, you need to convert that into a voltage range.

[DrBunsen]

If it's just the look of old knobs, buttons and faders you like, you can always mount them on new components.  ie take the knob off an old analogue pot or dial and fix it to a new encoder.

[3rdordertrauma]

Thank you guys so much for the input and help. I've been away from the forum for awhile and forgot I even asked this question. This is some good stuff to know. Thank you guys!

I'll do some more research and I'm sure I'll be back with more questions.

Cheers!