Double axis expression pedal for controlling LFO depth and speed

[spectraljulian]

I've been thinking about chorus and modulation in general.  I love keyboard modulation in that you have the mod wheel so you can change the depth from 0 to a lot.  So you can hold a chord or a note and quickly or slowly bring in the modulation.  I'm thinking a chorus that has default 0 depth and the lowest possible speed and then with one foot be able to modify either the depth, speed, or both at the same time but at possibly different rates would be really amazing and useful. 

I've got this idea in my head of building the ultimate chorus, and this is what it started with.  I know a lot of people make joystick controllers for bended pedals, but I want something I can use my foot with.  A joystick like assembly in metal with a square footplate on top with more resistance (something that wouldn't move as soon as I tap it, but something that needs to be slowly and gently pushed, a plus would be that it would spring back to 0, which I might sort of like)  or a big trackball for the foot would be really cool too if it was sensitive enough and there was a simple way to implement it (I think it would be fairly complicated to get it to work in the way you'd want.)

So here are my ideas for my crazy chorus/vibrato:
Rate and depth controlled by a dual axis expession pedal of some sorts. 
Feedback controlled by a pot on the side (can self oscillate)
Tone control pot
mix control pot
vib/chorus switch
true bypass (of course)

to simplify it, I think I might by a clone theory and mod it and house it under the expression system.  I'm a decent modder, but I've never took on building a whole pedal from scratch. 

Any ideas of how to implement a dual axis expression pedal that isn't awkward
and any ideas of mods I could do to the chorus circuit to make things a bit more interesting

[tomp]

Some Hammond organ volume pedals have little side pedals towards the toe end of the pedal.  With the one I have, these left and right toe switches lead to simple buttons or toggles, but perhaps a mechanism like this would work. 

[spectraljulian]

Well, I think that could be implementable, but it would make the depth rise and fall at a given speed, and not one controlled by the foot, which would be the optimum. 

[StephenGiles]

Find an old Fender or DeArmond Tone Pedal.

[spectraljulian]

Eek, those are expensive. 

I'm looking more to make my own mechanical system or modify something on the cheap. 

[orgaqualia]

I did this by turning a joystick upside down. They all use pots so you can do it with any stick. of course you may have to modify the values of the pots and  you might not get all the range you want but it does work. if you use the microsoft sidewinder you can even use a third axis! (they spin from side to side).

[spectraljulian]

Oooh, that is a good point, I could use the 3rd control to control feedback.  Could you post pictures of the one you did? 

Do all sidewinders have a 3rd degree of rotation?  I'm trying to figure out which model I should look for.  I want something less boxy and cumbersome looking.  Also, do they have rubber bands to spring them back?  How exactly do the mechanics work?  If I wanted more phyisical resistance could I had some extra rubber bands, or would I have to worry about it popping back to center too fast and stripping the gear or whatever turns the pots? 

[spectraljulian]

Do joysticks use pots that are easily replaceable?

[sfr]

Besides Ebay, Happ Controls (and several other places) sell trackballs, as well as interfaces for them.  Several places make USB or PS/2 (the computer standard, not the videogame) adaptors for standard arcade trackballs that let them operate as a mouse.   This might get you going in a good direction if you wanted to try a larger arcade trackball. 

I've got an arcade trackball at the house, (built a MAME cabinet a long while ago) and a couple of different interface boards.  No promises, but if I can find where I put the boards (the trackball is in the cabinet, but not hooked up right now) I'll see if there's a blantantly obvious way to get a controllable resistance out of it, or at least what the heck it's putting out of the wire harness. 

The folks at some of the message boards online where they build arcade cabinets for playing MAME, etc., can probably help you out real well with joystick/trackball related questions.  If you were going to go the joystick route, I'd suggest picking up something meant for an arcade, simply for the durability of it, since it sounds like you're going to be using your foot.  I know I've seen at Happ and a few places a sturdy analog arcade joystick that would probably work real well for foot control. 

[spectraljulian]

That's a good idea, I definitely don't want something that will break on me.  I think I'm definitely going the joystick route, as that method would be hopefully easier.

I made a post on experimentalist's anonymous too, because I thought someone there probably knows a bit more about it than I do
http://experimentalistsanonymous.com/board/viewtopic.php?t=767

Basically to get it to work the way I want, I believe I'd want to have the X and Y send out V +/- CV.  So I'd send V+ to one side of the pot and V- to the other, and try to set it so that when the joystick is centered it is at 0V.  Then just figure out the best way to get a positive CV out of both the V+ and V-, and also have the V- perhaps trigger a switch for self oscillation. 

[orgaqualia]

The post are rather standard in the sidewinder and most of the models I have seen do have the third axis.
The durability isn't an issue for me but the innard of the stick could give you some ideas. I have also fooled around with the idea of using LDRs. they are lots more flexable than post mechanically( I hear).

[orgaqualia]

The guts are spring loaded and not easliy modded. A couple of years ago I threw together a two axis version out of wood and plumbimg for a friend to use with his ringmod moogerfoger thingy and as far as I know it's still going. If you intend to perform with it lots you might want to consider this option. If you want to tinker for ideas go to goodwill every day, they almost always have joysticks that cost about a dollar.
All you really need is something that pivots on the axis's(sp?) and thats pretty simple, you could even use door hinges.
I found that my initial ldea was a bit impractical as my foot dosen't realy tilt inward that easily so I ended up with half of the side to side range unusable  until I redesigned it so that "off" for the side to side part was flat and "on" was angeld down to the right. Sounds kinda confusing but I think that you will know what I mean if you try it..
I don't have any photos cause I don't have any of them around anymore. If I build another one (which this thread has me itching to do) I'll post some

[spectraljulian]

Yeah, I think the main thing is just picking up a couple of joysticks and trying to mod them.  I have one plastic joystick with suction cups that I'll mod for dual axis expression and be able to attach to any guitar.  Then I'll make a little strap that attaches to my hand so that I can manipulate 1 axis while playing by moving my strumming hand up towards the neck.  Then I think I'll get a mame joystick (they don't look too hard to mod, the pots look pretty easy to replace) and I'll try to mod that into a footpedal.