Maths for converting between lin, log, and reverse log

[egasimus]

I can't quite figure it out - slept through most of math class since the 2nd term of 9th grade Let's say you have a potentiometer acting as a voltage divider. If you know the output voltage and the pot taper, what calculations should you make in order to determine what the output voltage would be if the pot was one of the other two common tapers instead?

I'm trying to do some very useful magic here, so stay tuned.

[slacker]

I don't know if it's any help, but this http://www.geofex.com/article_folders/potsecrets/pottaper.gif from R.G.'s Secret life of pots article shows the voltage divider ratio versus pot rotation for lin, log and reverse log.

[frequencycentral]

http://www.diystompboxes.com/smfforum/index.php?topic=70732.0

[egasimus]

^ great, thanks

I've been thinking about this. It's about the speed pot of univibes, in my case the tri-vibe. Picture this - I want to be able to use any expression or volume pedal with the univibe. This, in my book, involves a LED/LDR (0 light, 500k dark), and using the pedal as a (buffered) voltage divider. I would, however, like to accommodate for different tapers - ideally have a on-off-on which toggles between two tapering resistor configurations for lin and log pedals, and none if an actual rev log pedal is used.

So, how do I taper a log pot to become a reverse-log (without turning it around) if I'm only using it to pass DC?

I almost over-engineered my way around this (which refered to that "very useful magic", which I now realize isn't the best solution, but I might probably build what I have in mind anyway).

[egasimus]

So, how do I taper a log pot to become a reverse-log (without turning it around) if I'm only using it to pass DC?

Bump

[panterafanatic]

There are other pictures in that thread including reverse log, scroll down.

[egasimus]

Yes, but, from what I understood, it's all about tapering linear pots.
Has anyone had the crazy idea of tapering a log pot to become a reverse log?

[alfio]

I suggest to create an MS Excel sheet, insert a pair of column for a Resistance vs slider position with a log formulation, define a series/parallel combination for tapering and plot what happen in a graph.