At 11:49 29/04/2003 +0200, Jan-erik Soderholm (QAC) wrote:
>Hi.
>I just scraped an old mouse (a Logitech wheel mouse)
>to see what optical components they used.
>I noticed that the wheel had one LED (IR?) and one
>3 pin "receiver" mounted. Now, the wheel just have a row
>of spokes, but someway, the unit must not only detect
>spoke/nospoke, but also the direction the wheel is turning.
>Anyone know how these receivers work ?

There are actually two sensors on each of those receivers.
These will receive the same signal but with a phase shift.
e.g.:

"Forward" movement:

sensor 1 - 1111000011110000111100001111
sensor 2 - 0011110000111100001111000011

"Backwards" movement:

sensor 1 - 0011110000111100001111000011
sensor 2 - 1111000011110000111100001111

By looking at the phase shift you can find out the direction
the wheel is turning.

G.

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