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Topic: Flexible DIY Potentiometer? (Read 4791 times) previous topic - next topic

Cardboard

Hi,
sometimes, when prototyping it would be extremely useful to have some sort of flexible potentiometer or actually just the variable resistor part within the potentiometer.

Resistance wire would be great but I can only find it up to 100 Ohm per meter and I´d need something in the 100 Ohm per centimeter range.

I found the instructible with the DIY paper potentiometer in which you see how to create a flexible potentiometer out of paper and the graphite of a pencil. But here the resistance is too high, in the 100 Kiloohm range.

Furthermore I found flexible membrane potentiometers which would be great but function a bit differently and are rather expensive as well as large.

So, is there a way to buy either wire, or bendable resistor metal or perhaps a resistor paste or something like that?

cjdelphi

Thinking out of the box here....

Use your paper/pencil resistor but connect it to the base of a transistor (add a 300ohm resistor in series with your paper resistor) and then have the transistor power whatever it is...

Since I have no idea what your doing, it's difficult to say...

ChilliTronix

What exactly are you trying to achieve? A variable resistor can be made by using one end pin and the middle pin of a 3 pin potentiometer.

DVDdoug

Yeah...  I think we need to know what you're trying to accomplish.   

It's not easy to make your own useful/practical resistor or pot unless you are just trying to experiment or make a demonstration project (like the pencil lead).


Cardboard

#4
Nov 30, 2014, 06:19 pm Last Edit: Nov 30, 2014, 06:23 pm by Cardboard
Thank you for your answers.

Something like this would be usefull whenever the object you are designing can not house a normal potentiometer.
Imagine a plastic doughnut cut horizontally in half for example. If you rotate the upper part you want an LED to get brighter or dimmer.
You can not install a potentiometer in the middle of the doughnut because there is hole there and the space is either needed for something else or it is wanted to be kept empty for aesthetic reasons.
Here are a couple of images that discribe what I mean (I just notied that I forgot the Power source in the drawing):






Paul__B

Funny, why didn't I think of that obvious application?

Note that you do not want a flying wire connecting to the wiper - you want two wipers moving along the sides of a "U"-shaped track.

You can use Aquadag (research it if you want its history) as the coating.

I could suggest alternative non-contact based technologies, but it is a totally ridiculous time of night here and I am off back to bed.   :smiley-grin:

Riva

Don't PM me for help as I will ignore it.

Grumpy_Mike

Try googling for the words
conductive sheet
That will give you lots of choices that apply directly to that design.

Cardboard


Cool, thank you everybody.   :D

keeper63

If I were designing something like that donut thing to move a potentiometer, I would probably use either some kind of a gear train transmission system to actuate a rotary pot, or (likely better) use a linear potentiometer, perhaps angled across the width (or even perpendicular to it), and machine or build in some fashion a cam-type mechanism to move the potentiometer in/out with rotation (for example, a spiral like on a record player - just internal to the structure).

Ultimately, it would depend on what you were ultimately doing, costs, etc - for instance, if this is for a one-off project or prototype, then some kind of specialized variable resistor might be ok, but if it were meant to be manufactured on more than a few units, then a mechanical solution coupled to a standard potentiometer might be a lower-cost solution (it would depend on the price of the components involved, and the break point in number of units, and how many you were manufacturing).
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

Cardboard

The linear potentiometer coupled with a spiral sounds like a really good idea.

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