I'm working on a monome-inspired touch-sensitive controller that uses
these:

http://www.hemomatik.se/bild_pdf/5lagesgivare/pdf/Datasheet_5673%20indd1_h.pdf

Here are pictures of the actual units I have, they're called "hot pots":

http://soundwidgets.com/uploaded_images/IMG_3951.jpg
http://soundwidgets.com/uploaded_images/IMG_3952.jpg
http://soundwidgets.com/uploaded_images/IMG_3953.jpg

The company that sells them, Spectrasymbol, requires a 25-unit minimum
order.  Since I'm only using 17 of them for my 2 prototypes I now have 8
extra "hot pots" that I don't need.  I thought I'd offer them up here
and try to recoup some of what I had to spend.

I'm offering them for $14 each, which is slightly less than my cost.  Or
you can have all 8 for $100 and save $12.  Shipping in the US will be
nominal as they will fit in a small padded envelope.  I believe this is
an extremely reasonable price - I've seen them on only one other site
and they were charging over $50 just for one.

They call them hot pots because they bake them, which is what makes them
yellow, and apparently this makes them more durable and nicer to touch.
You'll notice the color isn't entirely uniform on all of them, but this
doesn't affect their utility in any way.  They feel really nice, and you
can slide your finger on them without any stickiness.

The touch sensitive area (the center stripe) is 170mm long, which is
around 6 3/4".  They have adhesive backing.  The total dimensions of the
sticker, not including the flexible "tail", is 7 1/2".  The main body of
the sensor is somewhat flexible but I wouldn't wrap it around a sharp
corner as it seems like it would crack.  I could be wrong but decided
not to try it.  With the paper backing removed the sticker is
translucent to either side of the central active strip, so light (leds)
can shine through:

http://www.soundwidgets.com/uploaded_images/spectra_samples-008-778240.jpg

These are essentially the same as a standard linear potentiometer, or
fader, with a couple of differences.  They seem to work in 2 modes,
resistive (2 conductor) or powered (3 conductor).  They are much more
sensitive when powered by 5V, but can be used as a simple variable
resistor with no power and still work quite well.

In powered mode, you will need to add a 10Kohm pull-down resistor
between signal and ground of each pot.  This ensures the output drops to
0 volts when you're not touching it; otherwise it "floats" and stray
voltage fluctuations will give you spurious readings.  The other
important implication here is that when you're not touching the strip,
there's no signal, so you will have to make accommodations for this in
your software (e.g. save last value somewhere).  You could also add a
physical wiper (as described in the literature) and avoid this issue
altogether since that would hold the position.

I believe these could be configured to recognize 2 simultaneous touches
on one strip, e.g. a "span" gesture, using the technique described at
the bottom of this page:

http://okno.be/phys_comp_tutorial/ribbon4/ribbon4.htm

...but I haven't tried it yet.

So, for anyone interested in adding touch-sensitive strips to their
monome instead of standard pots, or if you are building your own
controller, please drop me a line.

I'd love to see what people come up with.

if someone wants all 8 to do a xenome type thing, i'll let them have it, 
but having one or two of these at the bottom of my little 4x4 would be 
pretty cool. i could probably just as easily make my own though, since i 
don't think i would use the LED shine-thru feature on this project (too 
many leds).

i also need to wait a bit though cause i'm a little bit broke right now.

I'd be interested in one?

jasanimal@aol.com

I totally don't mind selling them off piecemeal - in fact I'm really 
interested in seeing what different people do with them.

And it is of course possible to make your own ribbon controller - there 
are several sites that describe how, including the one I ref'd above: 
http://okno.be/phys_comp_tutorial/ribbon4/ribbon4.htm

What's nice about these is they are all ready to go.  Just hook 'em up.

So if people want one or two or three, probably the easiest thing is to 
send me $14 per strip by PayPal plus $1 shipping, and I'll report here 
how many are left as orders come in.  If it goes over I'll just refund 
the $.

My PayPal e-mail is ultrajosh at usa dot net.

If these turn out to be popular maybe we could do a group buy of 25 more 
in the future.

6 (six) left.

4 left.

BTW: I'm switching out the weird-looking 2-tone one for a 
regular-looking one, so no need to worry you'll get the oddball.  (3rd 
from left in this pic: 
http://soundwidgets.com/uploaded_images/IMG_3951.jpg).  Unless of course 
someone WANTS the odd one. :)

2 left.  Holy crap these are going like hotcakes.

Thanks Ultra!!!

Meoff

Check your e-mail - I just sent acknowledgments to the 4 people who've 
paid so far...

2 went to Edinburgh UK
2 went to Melbourne, Australia
1 went to NY, NY
1 went to Tuscon, AZ

Still 2 left.

Sold out!

They'll go out in tomorrow's mail.

Please post your experiments and results here for everyone's benefit.

wow those were nice … too bad I have been away from the forum… this 
would be a nice group buy in the future no?

on another note… any idea how you will mount these for you final 
product? I did a project with 5 pressure sensors once and i mounted them 
underneath a sheet of drawer liner (that sticky back material that goes 
in dressers). Actually that project is on my site here: 
http://typenerd.com/goods/?p=27

it wasnt as cosmetic as i had hope :/ its been carved up for parts since 
then.

I dunno, that woodgrain is kinda cool and retro... but I see what you 
mean.

One of the samples I got from spectrasymbol was a 1/16" stiff plastic 
piece with a touchstrip attached to the back.  So I think you can go 
pretty thick and still get good sensor feedback to come thru.  My only 
concern with that if it is too thick then it will flex as a whole and 
affect the adjacent strips.  Anyways spectrasymbol has a lot of options 
for different surfaces (when you get a custom part made).  If I ever get 
to the point of actually producing these in any quantity, I would have 
them make a plastic plate with the 8 strips built in, maybe a little 
ridge or groove along each strip to feel where you are, and then two 
clear strips to let the leds shine through.  When I talked to the 
engineer on the phone he also mentioned the possibility of embedding smd 
leds right into the plastic.  Cool idea but I bet pretty expensive.

For the prototype I'm going to experiment with different overlay 
materials.

BTW I will have 8 more (slightly used) hotpots for sale once I get the 
newest prototype working:

http://www.soundwidgets.com/uploaded_images/IMG_3944-714357.jpg

it might be interesting to try using surface mount leds which are hard 
as hell to solder but it could be worth it for embedability's sake. you 
could maybe tap really small holes on one side of a piece of transparent 
acrylic and mount the potentiometer strips to it as well.

if you can do the little diodes on a 40h kit, surface mount LEDs are 
just slightly harder.  the only difference is that you can't hold the 
soldering iron on top of the LED lens for long periods of time.

drop a dab of solder on one pad
grad the LED with tweezers
melt the dab of solder
slide one end of the LED into the melted solder blob
remove the soldering iron from the solder dab
let go with the tweezers.
solder the other end of the LED.

tone's right about surface mount leds.

i've soldered at least 1000 of them very recently.

> i've soldered at least 1000 of them very recently.
omfg, wow, that's right.  the joys of coming up with larger devices.  a 
run of 100 256 monomes is nearly the same labor of 400 40h devices, add 
to that the 128 devices.  how's the eyesight?

...this is the main reason I used multiple 10-segment bargraphs for my 
gizmo - still lots of solder joints (2600+) but at least they're already 
lined-up for me.  Check out the bottom of the new xenome/stribe proto:

http://www.soundwidgets.com/uploaded_images/IMG_3937-712971.jpg

And those are just regular solder joints, not surface mount.

we're having the new series assembled by robot, luckily. the 
hand-soldering was for prototypes.