building a linear slide potentiometer?

[default]

Can anyone explain how to (or where to find instructions) build an
accurate linear slide potentiometer of 100k, 150k or 1M ohm? I am
looking to make one with a physical length would be from 2" to 10". I
have seen little exercises where you can draw a pencil line on paper
and connect electrodes to it, and it acts as a resistor, so I am
thinking that building a slide pot might be possible with the right
materials. Any info appreciated...

Take a pot with a 3" travel and use a lever and pivot to change the
range required to move the pot 3 inches . . .
--

 

[Spehro Pefhany]

Can anyone explain how to (or where to find instructions) build an
accurate linear slide potentiometer of 100k, 150k or 1M ohm? I am
looking to make one with a physical length would be from 2" to 10". I
have seen little exercises where you can draw a pencil line on paper
and connect electrodes to it, and it acts as a resistor, so I am
thinking that building a slide pot might be possible with the right
materials. Any info appreciated...

I've seen it done (as a servo feedback sensor) with a single length of
resistance wire, but of course it's nothing like even 100K; more like
< 100 ohms.


Best regards,
Spehro Pefhany

 

[Bob Masta]

Have you considered building a string pot?
http://www.celesco.com/stringpots/index.htm

I'll second this recommendation. Many years ago in an alternate
universe far, far away I was an automotive engineer for GM, and
we used string pots a lot for long-travel measurements. One
application in particular was monitoring the motion of suspension
parts during travel down various roads. String pots were more
accurate than (say) tricks with multiple accelerometers (which we
also used in abundance) when you wanted displacement.

As I recall, the stringpots were basically 10-turn rotary pots with
a return-spring mechanism that tried to keep them at one end of the
travel. A string around the shaft pulled against the spring to
advance the pot. Stringpots with stronger springs handled higher
accelerations.

Depending on your application, you might not need this return-spring
at all... use an old-time radio dial arrangement that turns a pot
instead of the tuning cap.

Best regards,


Bob Masta

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