Re: A2 Joystick Maintenance

[pausch@saaf.se (Paul Schlyter)]

In article <H5mdnWUhguVQk77YnZ2dnUVZ_tednZ2d@comcast.com>,
Michael J. Mahon <mjmahon@aol.com> wrote:

> Linards Ticmanis wrote:
>> Michael J. Mahon wrote:
>> 
>> 
>>> A typical pot will require about 270 degrees of rotation for full
>>> resistance, but a joystick usually provides only about 30-40 degrees,
>>> necessitating use of a higher value pot.
>> 
>> It's also often helpful to connect a second, physically small, higher
>> valued pot in parallel to the main pot, to fine-tune things. Combined
>> with the usual sliders in the stick, this makes it easier to get the
>> stick into a state where the reading is really 0 at one end, 128 in the
>> middle and 255 at the other end of the scale.
> 
> To actually "fit" those two points (128 and 255) would require
> *two* adjustments, not one--but one will help get to a better
> compromise.

...and to "fit" all three points (0, 128 and 255) would require
*three* adjustments....

The 0 and 255 points are fairly easy to adjust though, by just choosing
appropriate values of the other resistors around it.  The purpose of
that pot in parallell is to get the 128 (or 127?) point right.
 
> Correcting a pot for linearity is, in general, quite hard.

Indeed - and even getting all three of the 0, 128 and 255 points right
is no guarantee that the pot then is linear.  Otoh it won't mnatter
that much, since it's just about playing games anyway - right?
 
> -michael
> 
> New, faster SUDOKU v2.0 solver for Apple II's!
> Home page:  http://members.aol.com/MJMahon/
> 
> "The wastebasket is our most important design
> tool--and it's seriously underused."

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