Potentiometers: definitions, applications and how to choose?

Question

I've got some newbie questions about potentiometers that I can't seem to find in my reference materials.

I've been doing a lot of experimentation with potentiometers, and frequently run across linear vs. logarithmic pots. From the data sheets, I can see the graphs and understand how the output is affected by messing with the pot. My experiments have been limited to messing with what's on the parts list and swapping out linear and logarithmic pots to see what happens. I don't see it. Perhaps the difference is too subtle at the voltages or applications (changing the brightness of a blinking led or the volume of a click to a speaker) I'm working with, but it doesn't help me understand which to use.

What are some sample applications for which one would use linear vs. logarithmic, logarithmic vs. linear, and why?

Also, I sometimes see an "audio" potentiometer. Is this a third type? or is that a synonym for linear? The data sheets seem to match linear pots of the same rating more oftyen than not.

Answer 1

From the way you phrase it, it sounds like you are expecting the speed of the blinking LED to change or the frequency of the click output from the speaker to change. But I think you have the potentiometer set up in such a way where you should be looking at the brightness of the LED or the volume of the speaker. A sample schematic would be helpful.

A really simple circuit that should illustrate the difference would be to use just the potentiometer as a voltage divider and to graph the output.

Circuit from Potentiometers: what they are, how they work and how to use them with Arduino

Plot from Beginners' Guide to Potentiometers

Both links have good example circuits as well as videos (in the first case) or plots (in the second case) of what the results should be.

Answer 2

Logarithmic potentiometers are used in audio applications because our hearing has a logarithmic response to air pressure. So if you use a log pot in an amplifier you will perceive the sound volume to change linearly with knob movement. Audio potentiometer is the same as log potentiometer.