CMOS "ribbon" "synth"

DUBmatze · Posted: Sat Mar 15, 2014 2:32 pm Post subject: CMOS "ribbon" "synth"

nothing special but my kids and me have a lot of fun with it Wink

Posted Image, might have been reduced in size. Click Image to view fullscreen.

--> http://matze.reggaestriert.de/lofi-ribbon-control/

analog_backlash · Posted: Mon Mar 17, 2014 6:44 pm Post subject:

I like it DUBmatze! I've been thinking about doing a ribbon controller for my dormant Lunetta (I haven't worked on it for ages, because I've been in a really shitty mood lately). I was thinking of using a black electrically conductive bag and a length of ex guitar string as the basis for it. Perhaps I'll have go tomorrow and if I get anything useful out of it, I'll post the results. I've got to get back into building stuff again - it's the only thing that keeps me sane(ish) at the moment cyclops

Good work,

Gary

analog_backlash · Posted: Tue Mar 18, 2014 4:41 pm Post subject:

Hi DUBmatze.

I threw together a simple ribbon controller today as you will see in the attached picture. I remembered that I had some aluminium tape, so I've used that as the "wiper" and the rest of the pot was made from an old conductive bag that components had been sent in. The picture shows one assembled ribbon controller and one yet to be built, showing the materials. I used some matrix board offcuts to act as spacers. The sample is of the ribbon connected to a very simple 40106 oscillator (which I already had on a breadboard). I added a bit of Audacity reverb to make it sound better Very Happy

I was recording this "blind" (or should that be "deaf") as it was on a new laptop and I haven't worked out why it's not monitoring the input at the moment Rolling Eyes

Just thought you might like to hear it. I thought that it worked quite well considering how little effort I expended on it...

Gary

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Ribbon Controller Test.mp3

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PHOBoS · Posted: Tue Mar 18, 2014 6:48 pm Post subject:

great work,. both of you Very Happy

I've tested several different brands of VHS tape before to make a ribbon controller but never got anything that worked,
I might have some of those conductive bags though so I'll give that a try.

analog_backlash · Posted: Wed Mar 19, 2014 4:12 am Post subject:

rumblin_cynth_rampo · Posted: Wed Mar 19, 2014 5:57 am Post subject:

Thats brilliant DubMatze! Sehr toll!

Recently I have been messing about with a Softpot ribbon on an op amp oscillator (not a VCO) and was really please with the results. But your is method is so much more appealing. For some reason I didnt think of trying the Softpot ribbon with CMOS stuff. Ill have to give that a go.

PHOBoS · Posted: Wed Mar 19, 2014 7:49 am Post subject:

blue hell · Posted: Wed Mar 19, 2014 9:04 am Post subject:

Ian Fritz used to have some docs on how made a ribbon ... various types of tape to get the spacing right ... but can't find that website anymore .. there is some info here on the forums too .. googling Ian Fritz ribbon found some stuff, but not exactly what I had hoped to find back.

analog_backlash · Posted: Wed Mar 19, 2014 9:17 am Post subject:

PHOBoS · Posted: Wed Mar 19, 2014 9:42 am Post subject:

blue hell · Posted: Wed Mar 19, 2014 11:00 am Post subject:

Maybe we share some bad brain cells then Shocked

PHOBoS · Posted: Wed Mar 19, 2014 11:30 am Post subject:

I am he as you are he as you are me etc,..

I gathered some parts to give it a try.
- a piece of scrapwood that'll function as the base (I think it was part of a chair).
- two kinds of transparent plastic. one is just a thin transparent sheet that can be printed on, the other one is more sturdy probably about 0.3mm.
(I'll use the lather to cover the base since it's painted and therefor the surface isn't very smooth.)
- a couple of those conductive black bags
- double sided adhesive tape
- aluminium tape

maybe I should add a paperclip too,. just in case.

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PHOBoS · Posted: Wed Mar 19, 2014 12:24 pm Post subject:

hmm just thinking,. you could use PCB material (with copper) instead of the aluminium tape. It's also pretty sturdy so you could mount the 'ribbon' on it
and then just glue/tape the whole thing on to whatever you want. oxidation might be a problem though.

blue hell · Posted: Wed Mar 19, 2014 12:51 pm Post subject:

But then again aluminium oxidizes way faster than copper .. just looked it up, and Al₂O₃ is a bad conductor .. the layer however seems to get only 4 nm thick ... I had never noticed aluminium to not conduct, yet it always has an oxide layer.

Anyways .. I did make keys with PCB material, spacers made of PCB layout tape and then a layer of aluminium foil over it covered with a sheet of plastic ... it worked for several months at least ...

analog_backlash · Posted: Wed Mar 19, 2014 3:08 pm Post subject:

Yes the conductivity of aluminium is a bit of a paradox which I should know the answer to (from my chemistry background) but I can't fully explain it Embarassed

. As you say, aluminium is far more reactive than copper and very quickly forms a thin oxide coating (which should act as an insulator, as you say). It then stops reacting with the air because the coating effectively seals the metal off from further reaction. But, as you can easily tell with a multimeter, aluminium is a good electrical conductor (in fact, although it has a lower conductivity than copper, weight for weight you can produce lighter conductors from aluminium than copper which have similar electrical properties).

I'd have to do a bit of research on the insulating effect of Al2O3 on the metal, but practically, I've never had a problem (and I have had problems with old copper on PCBs). The only common problem which can occur is when it comes into contact with a less reactive metal (e.g. copper), but even then you'd need an electrolyte to start the corrosion off.

blue hell · Posted: Wed Mar 19, 2014 4:40 pm Post subject:

PHOBoS · Posted: Wed Mar 19, 2014 5:08 pm Post subject:

I put it all together and it seems to work Very Happy

it's mostly made up of the thicker plastic held together with double sided adhesive tape. I'll post some construction pics and more info later.
I think I also have a large piece of the conductive foam somewhere so I might give that one a try aswell.

analog_backlash · Posted: Wed Mar 19, 2014 5:26 pm Post subject:

analog_backlash · Posted: Thu Mar 20, 2014 7:39 am Post subject:

PHOBoS · Posted: Thu Mar 20, 2014 8:26 am Post subject:

PHOBoS · Posted: Thu Mar 20, 2014 9:32 am Post subject:

Some info on how I constructed my ribbon. I actually made it the other way around so the resistive track is on the bottom and the ribbon has the
aluminium conductor. I think that this way there is less change of damaging the black plastic resistivestuff and if used as the ribbon the
flexing might change the total resistance slightly. Also if the ribbon get's damaged it's easier to make a new one with aluminum tape and you'll still
have the same total resistance.

I started with putting some double sided adhesive tape (I'll refer to it as dsat) on the thicker plastic, stuck a strip of the plastic bag on to it and
then cut a 15mm wide strip from that. I put some more dsat on a larger piece of the plastic and stuck the strip on it with two strips of plastic next
to it on both sides, which I then cut to size. So that gave me two layers of plastic with the resistive strip centered on top. I made contacts by folding
some pieces of the aluminium tape in half with the sticky stuff on the inside (this side does not conduct). The resistive strip is shorter then the
bottom piece of plastic so the dsat on that holds the contacts in place.

I cut two small pieces of plastic which I stuck on both ends which act as a spacer and insulator between the contacts and the ribbon on top. They
also provide enough pressure to get a connection between the contacts and the resistive track. I cut two more strip of plastic that fitted between
the two ends and stuck them on leaving a gap that's smaller then the ribbon. This will prevent the ribbon from touching the track when not pressed.
like the black spacer on this but made up of 4 pieces:
Posted Image, might have been reduced in size. Click Image to view fullscreen.

I then put some more dsat on both ends, stuck the contact and the ribbon on it and covered it with two small pieces of plastic (one on each side).

The ribbon was made by sticking the aluminium tape on the thin plastic sheet and cutting a 15mm strip from it. I used the white border on the
side so I got a nice white ribbon Very Happy

The whole thing was then stuck to the wooden base (which I covered first with some self adhesive plastic that
has a woodprint on it) and I used thumbtacks to connect wires to the aluminium tape contacts.

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PHOBoS · Posted: Thu Mar 20, 2014 10:58 am Post subject:

So now I got a question for DUBmatze about the foam version that started the thread. Does the PCB (if that's what it is) between the two pieces of
foam have copper on one side to connect the +5V, or did you tape a wire along side of it (or through it) ?

DUBmatze · Posted: Thu Mar 20, 2014 11:45 am Post subject:

hehe,
looks a bit like ribbon is the thing ... ,) thanks for the credits.

in my version there are just 2 parts of foam ... the lower foam i just sew with a solid wire. the bright thing in the pic between the uper an lower part is just a pencil as spacer. if you put more fingers on it you get a lower resist. one foam never toch the other the conection are just the fingers. if you use more fingers or press more left or right you get other resistance. its not realy a ribbon .... its more like a tochpad.
I found a broken plastic breadboard with some glitter effect in it (not the electroc one just for cutting tomatos or bread on it). i thested this also and this is nice ..... kids playing it with a cucumber like a violin... (hint clean up after evry session this is going fast disgusting... baah)

PHOBoS · Posted: Thu Mar 20, 2014 12:23 pm Post subject:

thank you that made it perfectly clear Very Happy

cucumbers, hmm never though of that Shocked

RingMad · Posted: Sat Mar 22, 2014 4:12 am Post subject:

I might as well join in the fun. A few months ago, I had built a makeshift ribbon controller for testing out my Pulse Witch 23 box. I had found some broadcast-format videotape in the trash that's about 15K / cm. So I mounted that floating above a flat strip of copper sheet.

In this video, I wired it as a voltage divider with a power source and a pot to control the range, so as to produce a CV I could use with my box. It's not that great with this box, i.e. in terms of precise control, but that's mainly because of how I handled the CV for this particular input (it goes straight into an LED/LDR pair... so there's the slow response of the LDR that's affecting it).

James.