Re: Encoder stuff

Arne,
Speed has nothing to do with it as long as you do not exceed the response time of the electronics. The stationary grating
should also have straight lines as the moving one. I do not know why you saw zig-zag ones, except it could have been used for
an index pulse but I really do not know.

If you take two identical gratings or encoder strips and place them on top of each other and align then perfectly, it will allow
50 % light to pass. If you move one of them half a spacing, no light will pass. If you slowly move between the two positions
the light will gradually vary between the two extremes. That is an analog output variable. It will behave identically if you
move fast but it is easier to think about the concept with the very slow movement.

Bertho
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> "Arne Chr. Jorgensen" <instel@...> wrote:
>
> Hi,
>
> Bertho, I read your answer, and I just made a simple drawing you
> can see at: http://www.metalworking.com/dropbox/encoder.gif
>
> There is a few problems: If you rotate the disk very slow, - then
> you will get something similar to square wave, and when you speed
> it up, you will reach a point where it is more of a sine wave. The
> trouble is that you need it to be a sine wave, at all speeds. So,
> when I told you about the BEI encoder, I wondered how this pattern
> worked.
>
> In the picture I have just put both patterns on the same circle, -
> just to make the drawing simple.
>
> //ARNE