# building a linear slide potentiometer?

M

#### [email protected]

Jan 1, 1970
0
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...

A

#### [email protected]

Jan 1, 1970
0
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...

http://rocky.digikey.com/WebLib/Panasonic/Web Photos/New Photos/EVB-NC2P088BL.jpg

Or just buy one. Take it apart. Mail the parts to yourself and start
building it!

P

#### [email protected]

Jan 1, 1970
0
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...

APART FROM THE FACT YOU COULD BUY ONE, AND SEE HOW THEY DO IT,
YOU COULD PERHAPS USE A VERTICAL TUBE FILLED WITH WATER, AND ONE
ISOLATED WIRE WITH END STRIPPED TO THE BOTTOM,
AND A METAL WEIGHT ON AN OTHER WIRE ,THAT CONNECTS TO YOUR HORIZONTAL
OR VERTICAL SLIDER.
IN MY SCHOOL DAYS THE GUYS USED A CAPPED FLUORESCENT LIGHT THAT WAY TO
CONTROL THE SPOTS
IN THE PARTY.

KEEP CLICKING HERE FOR <drawing>

A

#### [email protected]

Jan 1, 1970
0
APART FROM THE FACT YOU COULD BUY ONE, AND SEE HOW THEY DO IT,
YOU COULD PERHAPS USE A VERTICAL TUBE FILLED WITH WATER, AND ONE
ISOLATED WIRE WITH END STRIPPED TO THE BOTTOM,
AND A METAL WEIGHT ON AN OTHER WIRE ,THAT CONNECTS TO YOUR HORIZONTAL
OR VERTICAL SLIDER.
IN MY SCHOOL DAYS THE GUYS USED A CAPPED FLUORESCENT LIGHT THAT WAY TO
CONTROL THE SPOTS
IN THE PARTY.

KEEP CLICKING HERE FOR <drawing>

MAYBE THE CHEMICALS SPILLED INTO YOUR CAPS LOCK KEY?

J

#### Jan Panteltje

Jan 1, 1970
0
MAYBE THE CHEMICALS SPILLED INTO YOUR CAPS LOCK KEY?

NO THERE IS ONLY COOKIES THERE.

M

#### [email protected]

Jan 1, 1970
0
Thanks for the tip. This probably wouldn't work for me because it's
too expensive ($47) and it's gear based (too hard to build, easy to break). I'm just wondering what materials you could use, to lay out a strip. See the drawing below (view in fixed-width type such as courier) slider wired to signal out the farther to the right it's moved, the more resistant material the signal has to travel through thus higher resistance v ___ | signal in->==================== ^ strip of resistant-but-somewhat- conducting material I would be looking for something that would be pretty durable and cheap & easy to build. Something involving liquids wouldn't work. Thanks M #### [email protected] Jan 1, 1970 0 That's not a bad idea (since it is cheap and easy) but liquid wouldn't work. What would be better would be something made out of metal or some material that is durable and wouldn't break too easily... J #### John Popelish Jan 1, 1970 0 slider wired to signal out the farther to the right it's moved, the more resistant material the signal has to travel through thus higher resistance v ___ | signal in->==================== ^ strip of resistant-but-somewhat- conducting material I would be looking for something that would be pretty durable and cheap & easy to build. Something involving liquids wouldn't work. What about liquids that become solids? Epoxy resin, roe instance. If you could come up with a mold for a strip of epoxy loaded with graphite powder, you might be able to make a slightly conductive strip. Then use plain epoxy to glue that to an insulating backing strip. A #### [email protected] Jan 1, 1970 0 NO THERE IS ONLY COOKIES THERE. SOUNDS DELICIOUS. I CAN HAS COOKIES PLZ? R #### Rich Grise Jan 1, 1970 0 Thanks for the tip. This probably wouldn't work for me because it's too expensive ($47) and it's gear based (too hard to build, easy to break).
I'm just wondering what materials you could use, to lay out a strip. See
the drawing below (view in fixed-width type such as courier) ....
___
|
signal in->====================
^
strip of resistant-but-somewhat-
conducting material

I would be looking for something that would be pretty durable and cheap
& easy to build. Something involving liquids wouldn't work.

If it's only for demonstration or education purposes, split a pencil
lengthwise.

Otherwise, find some enameled nichrome wire and a plastic stick; wind the
wire around the plastic stick; glue it in place, and sandpaper off the
enamel on one side, to contact your slider. (that's how real trimpots

Good Luck!
Rich

L

#### Lostgallifreyan

Jan 1, 1970
0
[email protected] wrote in
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...

Antistatic bags. The black ones with low resistance, cut into strips of the
length you want, and cut narrow enough to get the resistance you want.

They're soft so you want a wheel on the slider to reduce friction, so that
gentle compression keeps the wheel in contact with the plastic.

K

#### Ken Moffett

Jan 1, 1970
0
[email protected] wrote in
Thanks for the tip. This probably wouldn't work for me
because it's too expensive (\$47) and it's gear based (too
hard to build, easy to break). I'm just wondering what
materials you could use, to lay out a strip. See the
drawing below (view in fixed-width type such as courier)

slider wired to signal out
the farther to the right
it's moved, the more
resistant material the
signal has to travel through
thus higher resistance
v
___
|
signal in->====================
^
strip of resistant-but-somewhat-
conducting material

I would be looking for something that would be pretty
durable and cheap & easy to build. Something involving
liquids wouldn't work.

Thanks

I once made a long linear "pot" for a yoke for Flight
Simulator. I used an adjustable power resistor and a spring
mounted roller attached to a square slide tube (hobby brass).
It worked great for that purpose...not sure it would work for
you.

http://www.ohmite.com/cgi-bin/showpage.cgi?product=210_series

Ken

J

#### Jamie

Jan 1, 1970
0
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...
how about a ~ 3 " cross diameter shelve mounted on a shaft of a pot?
the shelve would have a mine steel or strong fishing line wrapped out
it that connects on both ends of the linear rode movement so that it
will turn the pot..
You're asking for an 8 inch travel , 8 / Pi = ~2.5 inch in width..
add a little for the fact that the pot does not do 360 degree's unless
you get a rotary pot

then there's the option of connecting a multiturn pot on the end of
the drive mechanics that is doing the traversing, Acme lead screw or
ball nut screw for example.

of course, You can do what I did once, it wasn't a linear track slide
but it could apply to you..

I got some large carpenter pencils and took the lead out or should I
say, more like carbon .. I suppose you can buy the stuff also..
I took an old screw driver handle and stuck it in a baby food jar with
turpentine and a rag wrapped around the entry point so that it wouldn't
evaporate.
After some time the old handle dissolve away from the screw driver
making a nice pliable plastic putty more or less..
Then I mixed the ground carbon power that I made into it, using a
popsicle stick as the mixer..

when you get ready to apply it in a linear track in your case for
example, poor it on and lay wax paper on top where the wiper will be.
The wax should allow it to peal away leaving a rather smooth surface
that is conductive..
p.s.
Make sure you have your end connections in the track before poring
this and the mix on the carbon has to be strong verses the potted
material you decide to use.

Btw, the dissolving of existing plastics is an old trick body shop
guys use if they are repairing a small damaged area of the plastic
interior of your car. They cut off small pieces of the same plastic so
that the color and mix will match and then use the rest of the other
tools they have for matcning up the textures and so on. I don't remember
the chemicals they used for this. I know it wasn't turpentine but
something that does the same job

J

#### John Mianowski

Jan 1, 1970
0
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...

http://www.spectrasymbol.com/linearposition.html

JM

J

#### John Popelish

Jan 1, 1970
0
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...

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

T

#### TT_Man

Jan 1, 1970
0
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...
How about a flat rack gear driving a circular gear mounted on a 10 turn pot?
Easy mechanics.... cheap solution.......

F

#### Frank Buss

Jan 1, 1970
0
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...

Not a potentiometer, but an idea for a variable capacitor. It is easier to
make a drawing for explaining it:

http://www.frank-buss.de/tmp/slider.jpg

The bright parts are wood or plastics. The dark part is metal or thin
layers of metal and is the capacitor. When moving the slider between the
metal, the capacitance of the capacitor changes. This can be measured, if
the capacitor is part of an oscillator and electronically transformed to a
resistance.

A bit more complicated to build, but good for higher capacitance changes:
Same construction, but the slider is metal, too, isolated from the metal
sides. The two metal sides are the other plate of the capacitor. Maybe use
multiple metal plates for higher capacitance changes.

Advantage: Can be built to be very long-living. Disadvantage: It could be
difficult to measure the capacitance and could be influenced by
environment, like temperature. But I don't think this is a major problem,
because old radio tuners works very precise with something like this:

J

#### Jan Panteltje

Jan 1, 1970
0
Have you considered building a string pot?
http://www.celesco.com/stringpots/index.htm

There is an other way also.
Use a LDR (Cadmium Sulfide light deopendent resistor).
Connect a piece of metal with a V sized groove to the slider knob.
Bulbs on one side (stabilized on DC), and LDR on the other side.
Or move a mirror, etc, several solutions possible.
The form of the groove sets the curve (log, lin, whatever).

D

#### default

Jan 1, 1970
0
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...

Dichotomy there - your first criteria is accurate then you mention
pencil lines?

Linear slide pot with a 10" travel? How about taking a light source
opposite a photocell and moving the pair past a triangle shaped cutout
in a light barrier?

At one end of travel light is stopped from reaching the cell by the
barrier and as the source/receptor pair move to the other end the
triangular cutout in the barrier lets more light past and the
resistance of the cell drops - any length, no contact parts to get
noisy, probably a long lifetime as long as moisture is excluded -
hermetically sealed photo cells or photo transistors.

Might work with just a light source moving closer to a photocell - no
barrier.

Downside - bound to be lots of development time tweaking in the cutout
in the barrier to compensate for non linearity in the source/detector.
Only a rheostat so it would take some electronics or a pair of
detectors (one getting more light the other less with travel)

Or drop the idea of a traditional pot and use a digital pot - then you
need a linear encoder or linear to rotary gear to get a pulse out to
set the digital pot.

Easier to just buy what you want of have it custom fabricated. Sounds
expensive, but good pots are expensive these days. They already use
them in video and sound mixing studios - so someone is making them.
--

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