Optical Encoder Resolution Based on IR Pair Position

[airman00]

Lets say I have an optical encoder, it resembles this:


You see how the IR emitter detector pair is placed looking at the center of the encoder? Would there be any difference in resolution if I moved the pair upwards so that it is looking at the top portion of the encoder or if I moved in downwards so its looking at teh bottom of encoder?

Basically I am asking, would where the IR pair is positioned affect the accuracy of the encoder. Like if I put the IR pair more towards the center of the encoder , would I have a different encoder resolution then if I put the IR pair towards the edge of the encoder? Or is it only the number of "clicks" the encoder has that sets resolution?

[szhang]

It is the number of clicks that determines resolution.  The encoder works by counting the number of pulses, and that number is the same per revolution of the wheel no matter where on the disk you point your IR detector at.

[Ro-Bot-X]

If you put it closer to the top, your encoder will work better with high speeds, since it has more time between clicks so it doesn't skip them. To modify the resolution you need to make a different disc, with more or less stripes. If you look at the CD-bot tutorial, I have a postscript file that generates encoder discs.

[airman00]

so generally speaking anywhere I position it , I will get the same resolution . Right?

[Ro-Bot-X]

Right.

[Soeren]

Hi,

If you put it closer to the top, [...] it has more time between clicks

Wrong!
No matter where it is placed, the time between each transition will be the same at a given speed!