Cheap or DIY String Pots?

Have a look at http://www.rino.co.uk   and http://www.ondrives.com

UK parent companies for one of our neighbours here in France, they have
mechanical bits coming out of their ears and will probably send you a
full set of catalogues if you ask

Steve

gavspav wrote:

Hello,

I am aiming to overcome my natural ineptitude and build an oversize
midi controller. Apologies for cross posting but I'm not sure where to
look for help.

See this thread:
http://groups.google.co.uk/group/rec.audio.pro/browse_thread/thread/7 ...

I am most likely going to use a 10 turn pot with a pulley attached to
the shaft.
I am thinking I will also need some kind of bearing to support the
shaft of the pot and protect it from the sideways force of the belt/
pulley arrangement.

Can anyone point me towards finding pulleys and bearings that will fit
on potentiometer shafts?

I realize this is probably a riduculous question if you are in the
know but I'm Googling round in circles (rs, cpc etc).

Thanks,

Gavin
www.digitalfunfair.co.uk

PS I was hoping to use String Pots but they seem to cost over £100
each. I only need a low res device. Are there any other alternatives?

@quokka.wn.com.au:


That's a broken link.  Can you fix the link, or provide real info?


--
Scott
Reverse name to reply

look for help.

See this thread:
http://groups.google.co.uk/group/rec.audio.pro/browse_thread/thread/7 ...


If you arrange for the actual mounting of the pot to have a little bit of
give, such as mounting it on a thin board, then the bearing could be
something you make yourself, like a piece if stainess with a hole in it just
bigger than the shaft.

gavspav wrote:

If you were in the US I'd point you to McMaster-Carr (www.mcmaster.com)
and Small Parts, Inc (www.smallparts.com).  I don't know what to suggest
for the UK.  Pulleys are so easy to turn out on a lathe that I'm not
sure you'll be able to buy them.

Pot shafts tend to come in standard sizes, like 1/4 inch or 5mm; if you
can find bearings at all you can find them to fit a pot shaft.  For
initial work I'd be inclined to just stick a pulley on the pot shaft and
see how well it works -- a 10-turn pot will cost you a lot less than the
time it would take to make a properly supported bearing.

For pulleys you may do well to traipse through a craft store looking for
bobbins, or raid the nearest kid's Tinker Toy set (do they have those in
the UK?).  Pulleys are low tech enough that if it looks like a pulley,
chances are it _is_ a pulley, even if it thinks it is something else.
Anything that has a hole that's close to your shaft size can be reamed,
shimmed, or just pressed hard to fit, so you really need to look for
something that has the right shape on the outer diameter, then go to
town with it.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google?  See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

Tim Wescott wrote:

Look through an electronics catalog for panel bushings for shafts.
Sometimes a pot with a long shaft is located far from the front panel
and the shaft is passed through a bushing at the panel.

Make your own: spring for a pot with a threaded bushing and the right
diameter shaft and break the front out of it; there's your bushing.

Most pots will sustain a fair amount of radial force if the shaft is
short enough. One is seldom warned not to press sideways on a knob.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

Thanks alot for all your suggestions.

Sorry about the broken link. This one should work:
http://groups.google.co.uk/group/rec.audio.pro/browse_thread/thread/7b941b17904fab1a/b5409ed3322eb6d2?lnk=st&q=gavspav&rnum=1&hl=en#b5409ed3322eb6d2

I have so far purchased a 10 turn pot, 2 plastic pullies and some
miniature flange bearings.
I'll get some angle iron and try to throw something together. Just one
single test slider to start with.
I'll try fishing wire for the belt.
I'm not sure about how to actually make the slider slide smoothly yet.
Any ideas for a cheap effective solution?

I'm waiting for the parts to arrive but I must admit I'm slightly
disappointed not to find a more elegant solution.
Maybe I'm just being lazy or tight! All the off the shelf solutions
were out of my price range!
The other ideas I've been toying with have been: Multiple Mice,
Infrared Movement Sensors and Optical Encoders.
I'll get there eventually.

Thanks for the help,

Gavin

to the world:


Try to find and old radio tuner. Some had pots with pulleys. Actually
they were not all pots, but variable caps and inductors.

Also you can find lots of small pulleys and bearings inside an old
copy machine.