Potentiometer Question

[evildead222]

How do I turn a 500k linear pot into a 250k linear.  Can i use a resistor.

[Gledison]

Just add. A 500k in parallel u get the 250k! 1/Rt=1/R1+1/R2
Add the resistor between lugs 1 and 3!
Cheers

[evildead222]

i connect the outer lugs with a resistor?

[Gledison]

Yep! Sorry, ive just updated my answer

[muddyfox]

yes but will it still be a linear pot?

[Gledison]

Yes!

[Gledison]

I would sugest you to get the right pot , but if you cant, try it with the resistor and see how it goes! You can always change afterwards

[evildead222]

yea it's just to test it out then i'll order the right pots

[DutchMF]

I hate to disagree with Gledison, but it's a bit more complicated than that. To start with, it depends on how the pot functions in the circuit, is it a voltage devider, variable resistance etc... This is some good reading: http://www.geofex.com/article_folders/potsecrets/potscret.htm

Getting the right pot is always preferable, but to start: a linear pot with a resistor bootstrapped over it will never remain linear.

Paul

[muddyfox]

a linear pot with a resistor bootstrapped over it will never remain linear.

Yeah I had a gut feeling about that when I asked... I really should take time and read "Life of pots"... 

[DutchMF]

It's really difficult to get your head around stuff like this, if I say so myself. I made an Excel sheet once, with some graphs linked to all the data, to visualize what happens when you start messing with pots and resistors, but I lost that one......... If I get really bored, I will give it another go, because it worked fantastic!

Paul

[Govmnt_Lacky]

Getting the right pot is always preferable, but to start: a linear pot with a resistor bootstrapped over it will never remain linear.

I agree Paul however, I would be pretty confident saying that it will get you where you want to be 

It would be close enough to a linear taper that it would work. If you want perfection.... then get the 250KB pot. If you want it to work NOW, use the 500KB pot with a 500K (or 510K) resistor strapped between Lugs 1 and 3.

A small sacrifice for having it completed now. 

[DutchMF]

Getting the right pot is always preferable, but to start: a linear pot with a resistor bootstrapped over it will never remain linear.

I agree Paul however, I would be pretty confident saying that it will get you where you want to be 

It would be close enough to a linear taper that it would work. If you want perfection.... then get the 250KB pot. If you want it to work NOW, use the 500KB pot with a 500K (or 510K) resistor strapped between Lugs 1 and 3.

A small sacrifice for having it completed now. 

Yeah, you can certainly do this to see everything works, but when the pot is used as a variable resistor, like the gain control in the Egodriver, this won't work......... Sorry for being an ass, I really only try to help. 

Paul

[midwayfair]

Getting the right pot is always preferable, but to start: a linear pot with a resistor bootstrapped over it will never remain linear.

I agree Paul however, I would be pretty confident saying that it will get you where you want to be 

It would be close enough to a linear taper that it would work. If you want perfection.... then get the 250KB pot. If you want it to work NOW, use the 500KB pot with a 500K (or 510K) resistor strapped between Lugs 1 and 3.

A small sacrifice for having it completed now. 

Yeah, you can certainly do this to see everything works, but when the pot is used as a variable resistor, like the gain control in the Egodriver, this won't work......... Sorry for being an ass, I really only try to help. 

Paul

Why do you say that? Connect lugs 2 and 3 and it's two resistors of 500K = 250K.

[DutchMF]

If you have a variable resistor pot, putting a resistor across lugs 1 and 3 wont work, was what I meant........ Or am I completely mistaken? At work at the moment, so no time to double check. If I'm wrong about this, I'm sorry and will delete the mis-information.......

Paul