10k or 470k potentiometer

Good Evening all,

I have hit a small problem and would like some feedback if I can, I this example http://www.youtube.com/watch?v=FKj9jJgj8Pc I am told to use a 10k potentiometer. Rather than blindly ask for an answer I have had a stab at it, could someone help correct me or validate it please.

the reason we would use a 10K potenti here is to make the servo movement responsive and fast, as there is little resistance, however if I was to swap it out and use a 470k ponenti then it would make it more accurate and fluid but slower as the resistance is higher?

Or am I so far out of the ball park I am playing a different game?

Thanks in advance

Mr C

p.s. i am sorry if these are trivial questions, but i would like to have a solid understanding of the basics before i move on :)

Hmm....I'd say no :)

In a potentiometer configuration the resistance itself is not so important for reading the analog value as is the ratio of one "side" of the potentiometer to the other (and the position of the knob determines that ratio). See here.

But the current supplied in this configuration is I=V/R (Ohm's Law) so the higher the R (potentiometer resistance), the less current will be needed. So a 10k is a very "common" value because at 5V, it only draws 0.5mA. A 10ohm potentiometer would do the same job but would draw 500mA from the power supply (way more than necessary).

So why not all the way in the other direction and use a 1000000 Ohm potentiometer and draw as little current as possible? Noise. Higher resistances lead to more noise and will also expose the non-ideal behavior of your board's A/D converter (it's supposed to draw 0 current, but in fact it draws a little bit).

I bet you'd get pretty much the same behavior with a 470k potentiometer.

Also important is that you use a linear taper pot and not a audio (log) taper pot for this kind of application.

Lefty

Thank you both for your input