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Author Topic: 10K pot without stop  (Read 2178 times)
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Anyone know if it is possible to buy a 10K pot that just keeps turning ie goes from 10K to zero as you keep turning it round and round?
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nr Bundaberg, Australia
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I haven't seen them but it's possible. However it sounds like you really need a rotary encoder.

Any particular reason for needing a pot?

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Rob
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Rob Gray aka the GRAYnomad www.robgray.com

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No it is just so easy to hook them up to the arduino and pots are cheap!  I need two devices that match, either two encoders, two pots or one of each plus two buttons.  This will be the basis of a menu driven UI for my latest device.
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I want to use a 2 line LCD with the top line as the label and the bottom as the data.  By turning a pot from full one way to full the other way you can select which data/label combination is on the screen.  Then by turning the other device you can increase or decrease the value of the data.  I have built it already on breadboard and written the software but obviously with the stops!  If you change one piece of data then change to another there might not be enough sweep left.  The other way would be to just change the value of the new variable to whatever the position of the pot is and let the user turn it back.  This would work using two pots but it isn't ideal.
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nr Bundaberg, Australia
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You can fudge an encoder with a rotary switch but probably can't tell direction, just that it was turned. They do give nice detents on the stops though.

Actually you can tell direction I think if you use a 6p2t switch and wire it correctly you would get values of 0, 1, 2 and 3 and the software could tell which direction from that. (just thinking out aloud, it may not work as I said but you might be able to figure the direction out with some thought.)

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Rob
« Last Edit: May 13, 2011, 01:50:38 am by Graynomad » Logged

Rob Gray aka the GRAYnomad www.robgray.com

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I just want a smooth rotation that has the accuracy to detect small movements like you can with a decent pot.  Using a pot also means less effort on programming.
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The pot type to look for are called servo pots and as mentioned before are not cheap. An other alternative is the helical pot or multi turn pot. These can give you up to then turns before hitting the end stop and surprisingly can be cheaper than servo pots at time.
I have used both sorts, the servo pot jumps in value as it sweeps over the wrap round point but doesn't have to be wound back like a multi turn.
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The multi-turn ones would have the same problem.  I have just found some 5K servo pots on the cheap so bought one to try out.  Thanks
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The top one looks good to me because it has a mounting thread/nut. Unfortunately it looks like it's been discontinued by Panasonic.

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Rob
 
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Maybe an old IBM PC Analog Joystick would work?
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I got some CTS 288 rotary encoders from Leo Bodnar, who, in case you don't know, sells parts for people to build racing or flight simulator cockpits. He sells them for £2.50 without a button and £3.99 with, but I'm not sure if he sells outside of the UK... Plus finding knobs for them is proving to be a pain, it has a .25" round shaft. Also decoding them is tricky if you don't know what you're doing (like me). Either way, though, the CTS 288 isn't too expensive. They do have a mounting thread, nut and washer too.

They're near the bottom of this page:
http://www.leobodnar.com/products/BU0836/.

Hope that helps!
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I have posted links to pots with no stops in the past.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P12426TR-ND

Will have a small range where no output is availalble.
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but I'm not sure if he sells outside of the UK...

At the bottom of the page it states "Worldwide shipping is £4.99 per order"
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Tke pots in hobby servos are continous rotation and rely on the gear stop to prevent over rotation. If a continous rotation pot is needed, then removing the internal stop in a cheap pot would be something to try.
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nr Bundaberg, Australia
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@Crossroads
I've not seen them before, filed for future use. You notice though that they have about 27 degrees of dead band, seems rather a lot for something that's specifically designed for this use.

@neema_t
Thanks, also filed for future use.  I love the concentric ones, I just have to think of an application now smiley

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Rob
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