.
   Thanks, Kathy and Russell.

   I don't like much the optical idea, because of dusty air.
Linear Hall sensors seems to be good-enough solution.
But, as I recall from my student years (I've done about
a hundred lab jobs on phisics with real research apparatus)
Hall effect gves relatively small voltage, so thermo-stability
of amplification may arise into serious issue, resulting in
differential scheme and voltage to frequency conversion
with following getting frequency difference by heterodyne.
I'll check datasheets and prices anyway.
   Using two variable capacitors, as I posted, we already
have two frequencies, and getting the difference is only
a question of programming technique.
   Moreover, capacitor plates may be made in overall design,
since one capacitor plate of PIC oscillator is Ground.

   Mike.
-------



Kathy Quinlan wrote:

>>      Hi, PICfighters!
>>    I'am thinking about building a sort of simple but reliable
joystick
>> with maximum endurance.
>
>Hi all,
>
>For this sort of an application you should look at commercial
Joysticks, the
>ones used in arcade games are very reliable, and ones for industrial
use are
>about the same, they all use the same idea, micro switches. they have 4
>switches, one on each end of travel, and allow either left right, up
down,
>left right and up down, or 8 direction travel ie up right.

Russell McMahon wrote:

>Agree. An alternative if starting anew is to look at optically
interrupted
>beams or magnets and Hall sensors. With a linear Hall sensor you can
even
>get linear response (with processing) with no moving parts apart from
the
>joystick mechanism proper.

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