how can I "map" potentiometer value without microcontroller? [closed]

Question

I want to make potentiometer that goes to 0 to 100% ONLY if I start to open it from 50%.
That means, if I open it to 51%, it will report as 2%. if I open it at 75%, it will report as 50%.

In Arduino, I can make it like this

int val = analogRead(0);
if (val < 50) 
{
   val = 0;   
} 
val = map(analogRead(A0,51,100,0,100);
//okay that's stupid coding for sure. 

How can I do this without arduino?

EDIT : I want to do it WITHOUT microcontroller. EDIT 2 : I want to do it as simple as possible, and if possible without using any IC.

Answer 1

If you look at map()'s documentation you will see that it's a simple scaling function:

long map(long x, long in_min, long in_max, long out_min, long out_max)
{
  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

If for whatever reason you don't have access to the Arduino standard library, you can just copy this function into your code and use it.

Answer 2

This should work.

int val = analogRead(0);
if (val < 50) 
{
  output = 0;   
} else
{
  output = ((val - 50)*2);
}