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Topic: pull down resistor - linear response? (Read 1 time) previous topic - next topic

treezy

Hi,

I've finally realised how to use a pull down resistor to stop getting a floating value on my softpot variable resistor.

My question is, why does this effect the linearity of the response of the pot. It seems that lower values of the pull down compromise it more, but that there is a limit to how much a high value makes a difference?

Anyone willing to drop a little science on me?

AltairLabs

You'd get more specific info if you give more specific info.  Is this the thingy youre asking about http://www.sparkfun.com/datasheets/Sensors/Flex/SoftPot-Datasheet.pdf ?

Can you give us a schematic?  What do you n=mean by "floating value"?  Got code?

A pot with voltage on one end and grounded on the other  gives a voltage at the wiper linearly proportional to the wiper position, so long as there is no current or load..

If you add a fixed resistor from wiper to either end, then yes, the wiper voltage is no longer a linear function of position.



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