Pot that you can turn for ever: do they exist?

I am building a intervalometer (openmoco dot org) and am wanting to use something like a pot to dial up the interval. What I want it to do is to allow you to keep turning it clockwise to increase a value for ever, or anti-clockwise to decrease and stop at zero. I have no issue programming it, but wonder what to look for in terms of hardware. Is there a pot of some kind that will allow you to keep turning it?

Cheers.

A rotary encoder is perfect for what you want/need.

A pot can’t increase forever. You can get pots without stops but after
so many turns the pot will be back at zero ohms. You can also get
10 turn pots but all of the ones I have seen have stops.

The rotary encoder that was suggested could be a good option.

(* jcl *)


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There are servo pots that don't have a stop on them so you can turn that forever. Every 360 degrees they jump from their maximum resistance to zero. They are however quite expensive.

The true engineers here will shudder, but the true hobbyists will leap for joy....

You could bust open an old fashioned ball mouse and tap into one of the two roller sensors... it is a rotary encoder, just like what you could buy if you were more sensible than penny-wise, pound-foolish me.

Whether you buy or bust, the encoder has a disc with radial slots which make TWO sensors go low/ high/ low/ high... as the disc rotates. The really clever bit is how you know which way the disk is rotating....

See the "Incremental encoder" part of....

http://en.wikipedia.org/wiki/Rotary_encoder#Incremental_rotary_encoder

... or, (the things I found before finding the above!)

http://www.ubasics.com/adam/electronics/doc/rotryenc.shtml

... or...

http://hades.mech.northwestern.edu/index.php/Rotary_Encoder

(jump down to the "incremental encoder" section.)

Hi Uber - yes, what you're looking for is a rotary encoder, not a pot. Are you using this as a control for a UI?

!c

Of course, the difference between a rotary pot and a rotary (quadrature) encoder is that the pot is an absolute device - it has a defined maximum and minimum position (very adjacent!) and effectively a positional memory, whereas the encoder only knows how far it has been turned. This may or may not be important to the application.