I am trying to solve for a reverse/inverse log taper for a potentiometer. I have a formula for a "log" output (yes, technically it is an "exponential" output but it is called a "log" in the terminology) from the following link:
http://www.geofex.com/article_folders/potsecrets/potscret.htm ... "The Secret Life of Pots" ... Copyright 1999 R.G. Keen
Hopefully the picture is large enough... otherwise, please refer to the web page above or the following text version of the formula:
1 / (((1 - a)/a) + ((1 - a)/b)) + 1
The variables:
a => 0 to 100 ... the range 0 to 100% rotation of the Potentiometer (yes, I know pots can't be rotated 100%, but theoretically)
b = 6 ... the "taper" value ... this value ranges from 0 to 6 (actually near 0 i.e. .0001 for example) ... with 0 producing a linear output to any value but with 6 as a practical limit.
This calculates perfectly and generates a graph output ... using a "b" = 0 to 6:
the ""inverse" or "reverse" log output is the mirror image of this ... simply (pictorially, at least) swapping the X and Y axis:
However, I have been unsuccessful in "reverse engineering" the "log" formula to create the "inverse log" X - Y output for each (any) of the "taper" values (1 to 6).. obviously, taper 0 is linear in each formulation.
Please ... whatever assistance anyone could provide would be enormously helpful!
http://www.geofex.com/article_folders/potsecrets/potscret.htm ... "The Secret Life of Pots" ... Copyright 1999 R.G. Keen
Hopefully the picture is large enough... otherwise, please refer to the web page above or the following text version of the formula:
1 / (((1 - a)/a) + ((1 - a)/b)) + 1
The variables:
a => 0 to 100 ... the range 0 to 100% rotation of the Potentiometer (yes, I know pots can't be rotated 100%, but theoretically)
b = 6 ... the "taper" value ... this value ranges from 0 to 6 (actually near 0 i.e. .0001 for example) ... with 0 producing a linear output to any value but with 6 as a practical limit.
This calculates perfectly and generates a graph output ... using a "b" = 0 to 6:
the ""inverse" or "reverse" log output is the mirror image of this ... simply (pictorially, at least) swapping the X and Y axis:
However, I have been unsuccessful in "reverse engineering" the "log" formula to create the "inverse log" X - Y output for each (any) of the "taper" values (1 to 6).. obviously, taper 0 is linear in each formulation.
Please ... whatever assistance anyone could provide would be enormously helpful!
