Originally Posted by
celemine1Gig
Just read that statement and it is plain WRONG! Don't follow this advice!!!
To correct that:
If the voltage shoots up quite badly in the lower resistance ranges with a 15k potentiometer it will even get worse with a potentiometer with higher resistance rating! Don't ever recommend things that you don't know anything about. You'll end up with people killing their hardware due to this wrong hint.
The problem is the following: Each and everey trimmer potentiometer, that I know of, gets highly non-linear resistance wise, in the lower resistance ranges. That means if you have a 15 turn 15k poti, you would expect every turn to be equal to 1k. But that is not correct. In the upper range you'll have more precision, i.e. less resistance change per turn, while in the lower range, the resistance change per turn does indeed increase.
That's why the voltage suddenly shoots up in lower resistance ranges: The resistance just drops faster --> higher voltage aand that even faster than before.
This behaviour either indicates choosing the wrong potentiometer value from the beginning (too high resistance for the desired end voltage), or just not enough precision.
The solution is either choosing a LOWER value potentiometer, which could result in quite a big default voltage bump, even when set to its max resistance.
The best solution however is to use 2 or more lower value trimmers/potentiometers, connected in series. This way you get a higher resulting resistance, but also with higher precision due to using more than one poti --> more turn per resistance change or to put it the other way round: less resistance change per turn --> higher precision.