Cheap or DIY String Pots?

Have a look at

and 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:

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:

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

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?

See this thread:

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.

"Bruce Varley" wrote in news:45e7eecf$1 @quokka.wn.com.au:

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

If you were in the US I'd point you to McMaster-Carr

and Small Parts, Inc 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.

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

Thanks alot for all your suggestions.

Sorry about the broken link. This one should work:

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

On 1 Mar 2007 02:26:38 -0800, "gavspav" proclaimed 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.