[sdiy] ribbon controller schematics

[nicolas]

I have tested quite a few video/audio/computer-backup tapes and found that pro-grade tapes that are at least 20 years old are the most likely to be suitable (amongst older pro-grade tapes I found I needed to test about a dozen tapes to find two or three suitable ones).  Consumer grade VHS is not so likely to be suitable.  I think you want somewhere between 10K and 100K per 10cm of tape.  Most tapes are more like 1M or more over that distance which is too high to be useful.  I have found one oddball that was about 3K per 10cm.  

One thing to note is that the contact resistance can be quite high.  For example if you get a reading of 100K over 10cm, 25K of that might be the probe to tape contact resistances.  So 1cm would read about 30K.  This doesn't usually matter with three wire voltage divider type circuits, but does affect two wire variable resistor type circuits.

I have some quarter inch tape from a computer backup cartridge and some half inch tape from professional TV betacam that both give me a reading of just under 100K per 10cm.  Both work well with 25-30cm of tape set up as a voltage divider with a guitar string stretched over top of them as the wiper.  I stick the tape down with double sided sticky tape.  I am using a simpler circuit than the one you linked to, which gives an approximately exponential voltage output because my synth is V/Hz.

You only need to find one tape that works and it will supply you and everyone you know with ribbon controllers for the rest of your life including regular replacements of the ribbon if necessary.  So if there is anyone in Christchurch, New Zealand who needs some suitable tape, feel free to contact me.

Cheers,
Nicolas

--- On Sat, 29/11/08, Heitor Alves <theatomlabspt at gmail.com> wrote:

> From: Heitor Alves <theatomlabspt at gmail.com>
> Subject: Re: [sdiy] ribbon controller schematics
> To: elektrodwarf at yahoo.se, Synth-diy at dropmix.xs4all.nl
> Received: Saturday, 29 November, 2008, 6:42 AM
> You mean... a VHS tape would do? I've tryed that aproach
> also, but the ones i've tryed never got any result ...
> i've found a membrane potentiometer from spectra symbol
> that works great, but the price is a little high and limited
> in size.
> 
> :)
> 
> ----- Original Message ----- From: "Karl Ekdahl"
> <elektrodwarf at yahoo.se>
> To: <Synth-diy at dropmix.xs4all.nl>; "Heitor
> Alves" <theatomlabspt at gmail.com>
> Sent: Friday, November 28, 2008 4:21 PM
> Subject: Re: [sdiy] ribbon controller schematics
> 
> 
> > too bad the ribbons are always too expensive or too
> hard to
> > find (at least here in portugal). The antistatic bags
> are a
> > solution, but i've had at least 100 of them tested
> and
> > no luck yet :( Still looking for the one...hehehehehe
> 
> There's an easier and cheaper way - 80's video
> tape! I too couldn't find any antistatic bags that
> worked, so i brought my DMM with me to a thrift store and
> measured all their tapes until i found one that worked!
> Since the tapes are very long you can make many many
> controllers from only one find, it's worked perfectly
> for me!
> 
> Karl
> 
> > regards and thanks for the link alf :)
> > 
> > heitor
> > 
> > ----- Original Message ----- From: "alf
> holm"
> > <solution at netcabo.pt>
> > To: <Synth-diy at dropmix.xs4all.nl>
> > Sent: Friday, November 28, 2008 8:13 AM
> > Subject: [sdiy] ribbon controller schematics
> > 
> > 
> > >
> http://www.paia.com/ProdArticles/dual-ribbon-howto.htm
> > > _______________________________________________
> > > Synth-diy mailing list
> > > Synth-diy at dropmix.xs4all.nl
> > >
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> > 
> > _______________________________________________
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> 
>     
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