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-   -   A self-returning linear pot? (http://www.chiefdelphi.com/forums/showthread.php?t=46553)

Billfred 14-04-2006 11:50

A self-returning linear pot?
 
I've been tinkering with some projects in my head, and while running the board at WUSC I figured out how to control one of them: a linear pot. But to make it better for the situation, it'd be awesome to have it return to the center automagically (or at least have a detent in the middle to let the operator know it's centered).

Does any such a device exist (cheaply)?

Rick TYler 14-04-2006 12:02

Re: A self-returning linear pot?
 
I Googled on "potentiometer sliding" and found a bazillion hits. Here's a link to a manufacturer: http://www.ctscorp.com/components/Datasheets/442.pdf.

Have fun.

Edited to add: I found a number with center detents, but not self-returning. Have you considered a string pot with some sort of custom-made mechanical doohickey as the controller?

Joe Ross 14-04-2006 12:14

Re: A self-returning linear pot?
 
Would a joystick work? They tend to have a somewhat linear motion and return to center automagically.

Here are two more pots with center detents: http://bourns.com/pdfs/PTA.pdf and http://bourns.com/pdfs/PTA.pdf

Mike 14-04-2006 13:03

Re: A self-returning linear pot?
 
Quote:

Originally Posted by Rick TYler
I Googled on "potentiometer sliding" and found a bazillion hits. Here's a link to a manufacturer: http://www.ctscorp.com/components/Datasheets/442.pdf.

Have fun.

Edited to add: I found a number with center detents, but not self-returning. Have you considered a string pot with some sort of custom-made mechanical doohickey as the controller?

No doohickey needed. Just attach a spring to it. Have the shaft of the potentiometer go through the windings of the spring. As you turn it, the spring will unwind and once you stop putting force on it it will snap back to place.

Al Skierkiewicz 14-04-2006 13:51

Re: A self-returning linear pot?
 
Quote:

Originally Posted by Billfred
I've been tinkering with some projects in my head, and while running the board at WUSC I figured out how to control one of them: a linear pot. But to make it better for the situation, it'd be awesome to have it return to the center automagically (or at least have a detent in the middle to let the operator know it's centered).

Does any such a device exist (cheaply)?

Bill,
What console are you working on? Lot's of companies make detented pots. Many people don't use them because it requires another pot in series that can calibrate the detent.
Modern digital consoles can have a programmed stop stored in memory that fixes all the problems with much less expense.

Billfred 14-04-2006 14:06

Re: A self-returning linear pot?
 
Quote:

Originally Posted by Al Skierkiewicz
Bill,
What console are you working on?

The IFI OI--the idea just happened to come to me while doing my show. ;)

Al Skierkiewicz 14-04-2006 14:42

Re: A self-returning linear pot?
 
No, what audio console do you do your show on?

billbo911 14-04-2006 16:35

Re: A self-returning linear pot?
 
Quote:

Originally Posted by Billfred
The IFI OI--the idea just happened to come to me while doing my show. ;)

I think I follow what your trying to do. Make a control for some function that can attach to the OI by using a "self centering slider pot". Correct?
If so, a very cheap solution is to attach two springs of equal length, diameter, and wire size to the slider pulling in opposite directions. Make sure you stretch them equally and have enough travel on both to have the more relaxed spring still is in tension when the slider is at full travel. Now when you move the slider off center, the spring forces will pull the slider back to center when released.
Look inside a joystick, you will see a similar setup pulling the stick back to center.

colin340 14-04-2006 16:53

Re: A self-returning linear pot?
 
you may want to try an airpot i found an ad in design news it looks real cool
www.airpot.com

ECarlson 14-04-2006 22:06

Re: A self-returning linear pot?
 
Some sound and lighting boards have computer controlled presets where the board can return the pots (sliders) to any preset position. Is that the kind of board you are talking about?

I would guess that the pots have either a servo or stepper motor to return them to position. I don't know if the feedback mechanism is the pot itself (most likely, since the OI processing part of the boards are pretty much purely digital anyway), or yet another position sensor. It's also possible that the sliders are not pots at all in some of these boards, and are actually optical position sensors.


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