Anyone used a String Potentimeter

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06-22-2009, 11:23 PM
mattford1

Anyone used a String Potentimeter

Hi Guys-

Looks like one of my slide pots is going out and am toying with the idea of using string potentiometers. Anyone used one?

Thanks,
Matt
06-23-2009, 07:14 AM
Matt Olieman

Re: Anyone used a String Potentimeter

Matt, there's been discussion here regarding string pots and where to buy them. Even how to make them :)

Keep lighting the world Matt, you do a good job of it :) :) :)

Matt Olieman
06-23-2009, 08:15 AM
Rodney

Re: Anyone used a String Potentimeter

Matt here is a short thread on mine;http://www.mycockpit.org/forums/show...ght=string+pot And Gallie (Mike) also built a set. I think John Combs has a commercial set.
06-23-2009, 08:38 AM
mauriceb

1 Attachment(s)

Re: Anyone used a String Potentimeter

Here is my poor man version of a string potentiometer. Not really how a string potentiometer functions since real ones use transducers, but worked quite well in my setup.

Maurice
06-23-2009, 09:03 AM
mattford1

Re: Anyone used a String Potentimeter

Thanks for the info guys. The thing I've found in my 737 quadrant is due to the movement of the arm, the travel is not linear at the end, ie the rate of change decreases towards the end of throw of the throttle arm. A string pot would fix it, but MAN those are expensive. I'm very torn about it :-).
06-23-2009, 09:47 AM
mauriceb

Re: Anyone used a String Potentimeter

Quote:

Originally Posted by mattford1

Thanks for the info guys. The thing I've found in my 737 quadrant is due to the movement of the arm, the travel is not linear at the end, ie the rate of change decreases towards the end of throw of the throttle arm. A string pot would fix it, but MAN those are expensive. I'm very torn about it :-).

I'm sure you already know that, but are you sure you are using a linear potentiometer rather than an audio taper potentiometer?

Maurice
ps Sorry if this insults your intelligence :D
06-23-2009, 10:15 AM
Rodney

Re: Anyone used a String Potentimeter

Quote:

Originally Posted by mattford1

Thanks for the info guys. The thing I've found in my 737 quadrant is due to the movement of the arm, the travel is not linear at the end, ie the rate of change decreases towards the end of throw of the throttle arm. A string pot would fix it, but MAN those are expensive. I'm very torn about it :-).

Make your own for less than $20. I choked at the commercial versions too. Just couldn't see $450+ for that function.
06-23-2009, 10:17 AM
mattford1

Re: Anyone used a String Potentimeter

Rodney-
There are no such thing as stupid questions and that's actually a very astute one! Yes they are linear but thanks for the reply!

Matt
06-23-2009, 10:33 AM
mauriceb

Re: Anyone used a String Potentimeter

Quote:

Originally Posted by mattford1

Rodney-
There are no such thing as stupid questions and that's actually a very astute one! Yes they are linear but thanks for the reply!

Matt

Actually, it wasn't Rodney who asked the 'stupid' question :-). It was me, but what I actually meant is whether you checked with an ohmmeter whether the pot is actually linear. I once ordered & received some 'linear' pots which turned out to be audio taper instead, so the only sure way to know is to check them yourself. Just a long shot ;)

Maurice
06-23-2009, 10:43 AM
mattford1

Re: Anyone used a String Potentimeter

It looks linear, it's just very dirty/jumpy and i wouldn't mind changing them out (pulled the quadrant out anyway). The thing has been in there almost 10 years now. Does anyone have a good lead on 100mm linear pots? Seems everywhere I look they are audio taper.

Thanks!
Matt
06-23-2009, 10:57 AM
mauriceb

Re: Anyone used a String Potentimeter

I ordered mine from http://ca.mouser.com/Home.aspx (very good service). They have a good selection but I could not find any 100K linear slide potentiometers at that time, so I got 10K pots instead and they work fine. They probably have a much bigger selection of rotary pots though if you can use those.

Maurice
06-23-2009, 11:02 AM
mattford1

Re: Anyone used a String Potentimeter

Was yours a 100mm pot? I didn't see any there that are linear taper.

Matt
06-23-2009, 11:06 AM
mauriceb

Re: Anyone used a String Potentimeter

Quote:

Originally Posted by mattford1

Was yours a 100mm pot? I didn't see any there that are linear taper.

Matt

Yes they were. Here is the part number I ordered from Mouser:
688-RSA0N11S9002 . If you are looking for more 'beefy' construction (& more expensive as well), here is a source that I found:

http://www.familygate24.com/alps/pot...ice/index.html

Maurice
06-23-2009, 04:57 PM
mattford1

Re: Anyone used a String Potentimeter

Maurice-
Looking at that mouser part number it looks as if you have an audio taper as opposed to linear.

Matt
06-23-2009, 06:13 PM
mauriceb

Re: Anyone used a String Potentimeter

Quote:

Originally Posted by mattford1

Maurice-
Looking at that mouser part number it looks as if you have an audio taper as opposed to linear.

Matt

I thought exactly the same thing too and I fired an e-mail to them when I received the shipment notice but they assured me they were linear pots. When I received them, I checked them and they were indeed linear & not audio. I think the description or the type of taper is misleading or wrong but for sure the ones I received were linear.

Maurice
06-23-2009, 06:23 PM
mauriceb

Re: Anyone used a String Potentimeter

Quote:

Originally Posted by mattford1

Maurice-
Looking at that mouser part number it looks as if you have an audio taper as opposed to linear.

Matt

One more thing; here is my e-mail to them and their answer:

There seems to be a discrepancy between what I ordered and what was shipped. The data sheet (Page 494) in your website for 688-RSA0N11S9002 (see insert below) shows that this item has a Linear taper (which is what I wanted) and the item you shipped shows a D Taper on the order form below. Can you please check into this and let me know what is it exactly that you shipped and if this wasn't what I wanted, how can I go about exchanging the items and getting the right ones I needed?

And their answer:

Page 494 of the catalog shows that part number as a linear taper. Thank You - Brian

To which I answered:
Yes, I mentioned Page 494 as well, but I was questioning the order details below which show a D Taper, whatever that is.

4 688-RSA0N11S9002 4 7.000 28.00
ALPS Slide Potentiom
10K OHM D TAPER Is this description wrong then?

And they answered:

There is more than one type of linear taper - I think you have what you need. Thanks _ Brian

So, not very re-assuring & very confusing but they were the right type after all :)

Maurice
06-24-2009, 05:59 AM
Prof Bill

Re: Anyone used a String Potentimeter

Quote:

Originally Posted by mauriceb

Here is my poor man version of a string potentiometer. Not really how a string potentiometer functions since real ones use transducers, but worked quite well in my setup.

Maurice

Hi Maurice,

This is a really neat solution that helps sort out a control mechanism that we have built on an experimental rig here!
Nothing to do with Flight Simulation

Many thanks indeed,

Bill.
06-24-2009, 06:15 AM
riche543

Re: Anyone used a String Potentimeter

Hey Guys what do ya reckon of hall effect sensors havnt tried myself but heres a Attached pdf we found interesting , I think they could be worth tryin out , Has anyone ever used this method Cheers Riche..