x/y touchpad controller

[audiocommander]

On a side note, the 'rotary' pots look sweet. They look like they would act just like the control on an Ipod. I could imagine a several of these circles used to make a totally 'flat' midi controller.

Yeah, but they're not good to use. I have two samples and both of them require so much fingerpressure, that you can't follow the rounded form anymore... (you get hot and queeky fingertips ;D )

Maybe they have other ones, too... but I'm not really convinced about these 360° soft-pots samples I got

;) Michael

[stryd_one]

Bogus :( Are the x-y pads the same? I would imagine so .....

[audiocommander]

I don't know, unfortunately I don't own an x-y pad  :-\

But to cheer you up: I have also some linear softpots which require a lot less pressure... and in contrast to the round ones, it's not that hard moving the finger up and down, but you got to try this:

move your fingertip in a circle, have noticeable pressure, do it on a plastic underground (sqeeee) and try to get a smoth movement (eg for controlling a fadeout)... :)  This is nearly impossible with the 360° pots I have.

I'm sure, they tested it only with wooden gloves for usage in laboratories and not with sweaty fingers in a nightclub ;D

[stryd_one]

Yeh they should have more realistic tests, like, half of the musicians also have sticky ganja residue on their fingers ;)

[audiocommander]

;D ;D

LMAO...

[DrBunsen]

Wooow swirly, lookit go round and round and round and round ...

[stryd_one]

"Lookit go round and round....It's like it's changing the music man"

"Dude, it IS changing the music"

"Wow, cool maaan. I love this song too, who's it by?"

"You, you're on stage man...."

"Wow coool. Look this thing go round and round....It's like it's changing the music man...."

[Wisefire]

rofl..

[audiocommander]

"Look man! How cool is that?! :o – a ganjaPot"

"Yeah! Let's Rub'n'Roll" ;D

[stryd_one]

LOL Just picture a box of ganjaPot going through customs ;)

[MRE]

yah, I got my samples friday. It looks like they would be a bit of a biatch to make work. A sample and hold circuit for 30 pots might be a bit excessive and contrary to the whole "Midibox philosophy" anyway.

I was considering perhaps using the straight linear for a modulation wheel, but it just all sounds too complicated since its not mechanical.. (with an unknown point contact when you dont hit it right dead center to start..)

Ohh well.. they were a sweet dream for a moment.

Now, I also got some nice button pads. Those I plan on using for the menu buttons. and, worst case scenario, I can chop them up and re-arrange the button layout.

[tos]

You can always program a linear touchsurface to work as an encoder.

[stryd_one]

You're gonna get an exponential curve out of that setup  :-\

There are some other threads around with info on this, probably within a couple of months old I think. I'm not sure where, but that should help with the search.

[AndAway]

It's been a long time...

I'vean idea about touchpad. You can use ADC-> latch -> DAC, so it can remember last 'position'.

I'll assembly a simple circuit next week. I'm not sure if to use CMOS or TTL...

[tos]

??? I'm not sure it will work, What about the situation when you release the touchpad and it gets back to (0,0) Latch will pick that up too.

The real way is to use another layer of some conductive surface (eg. Al foil) and connect it as a touchsensor. That way you can detect touch and start recording the values to PICs RAM.

[Wilba]

I think you can just use an opamp to detect whether it's being touched or not.

This circuit here:

http://www.paia.com/LabNotes/index.htm

does a lot of fancy things like detecting two contacts, but if you look at IC2C, that's what is used to trigger sampling of the ribbon, i.e. if there is a touch on the ribbon, it will turn on the switch at IC1C and get sampled at IC3B, when there's no touch, IC3B holds that voltage.

You could simplify this because you've got a PIC doing ADC so just use a logic level input (DIN pin) to detect when there is touch and only do new ADC when it is high.

[AndAway]

So I should use only the 'CVLo' part of the schematics?

[AndAway]

So maybe I can use another PIC to control touchpad/ribbon?

I thought of a sub-menu 'touchpad' where you would have:

1) Callibration - just like the callibration of a joystick - move your finger around touchpad for a few times. PIC should remember the maximal and the minimal values and create some kind of 'virtual scale' and convert it to midi values 0..127 (touchpads at x=0 y=0 point have some resistance, not 0)

2) Kind of 'mode' of work. The first can be 'relative' - PIC only add or subtract values, the pressing point doesn't matter, only the direction of movement. The second - the values sent depend on the place touched.

Is it possible to add these features to the existing mhbp or I should use other PIC for handling menu/display and/or other for calculating and remembering those things?

What do you guys think about it?

[audiocommander]

Hey AndAway and ToS,

I don't have no touchPad, but a few of these touchPots (so I may be totally wrong) - but I don't really understand the problem. You have to write your own app anyway, so if the pot snaps back to 0, you just have to ignore 0!

I am reading a 10bit value (while sending a 7bit value!), so just ignore the values 0..24 => then 25 is the 7-bit value '0' ... see? No difficult circuits, no additional foils or stuff...

...although I think Wilba's circuit seems very promising if you want to build a MB-Pro  8)

Cheers, ;)

Michael

[tos]

Three cheers for audiocommander, the smoothest solution [ever, I think].

[AndAway]

The only problem is that when you don't touch the ribbon you dont have value 0 but it's like suspending the signal cable of potentiometer in midair - so you will get flickering...

[Wilba]

You can fix that problem by using bits of that circuit I posted earlier.

You can get a gate/trigger output from the ribbon using an opamp that sense touched vs. not touched. Look at the circuit between the ribbon and the "Gate Out" output.

Again, I have to say I haven't actually built this circuit yet... and pay attention to the power symbols, which aren't too common. My guess is that the + input of opamp IC3C is tied to VEE (negative rail) via a 10M resistor. Any touch of the ribbon is going to bring the + input above ground.

[goule]

Getting back to the subject of XY pad : did anyone suceed in finding those FFC connectors ? Or did anyone find any other method that works without that connector ?

Thanx all

[stryd_one]

http://www.switchesplus.com.au/catalogues/sp/2005-6/Connectors/0379%20Conn%20sect%20p203.pdf

That mob are wicked... If they don't ship international, let me know, and I'll order them and send them to you.

[goule]

Wow  :D thanks man ! I went to their web site and filled an information product request, I checked the "sample for eval" box ... let's see if they send me one. If not I would be very interrested by your offer !

By the way, did you succeed in using the pad for the midibox ?