Altimeter for Flight Simulator

Several options are available, with left or right knob, with one or two windows for kosslman and with barber pole indication below 10K feet or 16K feet.

I use several M3 screws and nuts. and small ones for knob, encoder and reinforcement.
A 3mm Axis and 2 brass tube, one 4 mm and the other 5 mm for the axis of the needles.
and a 2mm axis for auxliar gears.

I personally drill the holes of the gear biggers for the optical sensor, but only after mount everything. I glue the emiter an receiver of the sensor with hot-glue.

I get it from a old mouse, It is a diode and a photo-diode.

Motor is a 24BJY, it is small than 28BJY but same conections, it has 0.25 rpm and 4096 half-step by revolution. it cost more or less the same than 28BJY

You can conect to FS X via FS2Link, in this link there is the source code for the arduino:
https://github.com/alvaroalea/flightsimulator/tree/master/altimetro_v0.2