Need helt finding/making a high res. encoder

[ZiiK]

Hi!

I need to find a high resolution encoder to try some stuff out for my project. The problem I have is the ones I find are either to expensive or to tall to fit in my case.

Been thinking about making my own with photointerruptors and a code disc however it would still be hard to get the resolution I'm after.

I would like to achieve at least 1000+ klicks per revolution and if possible double that. I remember that extraclassig used the photointerruptors from an old exponent a while back and made his own code disc. Does anyone know how that turned out? Or what resolution he ended up with.

I'm a little stuck on this one, so any advice is greatly appreciated.

Been thinking about a multi level code disc, perhaps even one with absolute position to help avoiding bad readings. Let me know what you think. Could this work or is it a silly idea?

Cheers
//Joel

[derschaich]

you can easily increase the resolution of an optical encoder by adding more sensors to the circle:

i'll explain it in an easy example.
say you have a resolution of 2 klicks by now with 2 sensors (you need 2 to get the direction of the turn). if you add 2 sensors 90 degrees apart from the existing ones you can get 2 klicks per turn.

this also should work for higher resolutions than 2 klicks

be aware that the placement of the sensors has to be extremely accurate if you want some seroius output!

[ZiiK]

That should work. Would be hard to get it properly calibrated though!
Will try it once I get to that stage of the project. If it's to hard, I might get a code disc laser cut with a slight offset between each layer to get the same effect with the sensors mounted on a straight line from the center and outwards.

Thanks for your input! This could prove very useful!

Cheers

[nem0nic]

Look into gray code encoders.

http://code.google.com/p/wheel-encoder-generator/

This app gives you several variables to play with, including resolution and absolute / relative.

The great thing about using gray code is that you aren't limited by how fine you can make your photointerrupters. If you're creating a platter with injection molding, rapid prototyping equipment, etc, you're going to be hard pressed to get "teeth" finer than 2-3mm. On a small platter this can be limiting. Yes, you can use multiple sensors and quadrature, but this setup can also be fiddly to DIY.

Love this stuff - let us know how you progress!

[ZiiK]

Great stuff!
Thanks again for sharing!
If I manage to make any progress I'll post pictures for sure. This encoder project is still a couple of months away though. Going to finnish my MIDI mixer first.

Cheers
//Joel