Re: Which shaft encoder to use?
 

It's rated for human hand turning speed. You can't spin the encoder shaft very fast.
So the question becomes how fast (rpm) do you plan on gearing it?

Re: Which shaft encoder to use?
 

Jeff,
Go to the Grayhill site to be sure, but many of these encoders are not continuous rotation. The flag for me was the spec that an operational cycle was a full rotation through all positions and a return to zero. Since one application is for frequency set on a radio this may be only a 250-270 degree rotation with 32 detents. When checking devices be sure to find the spec on the maximum allowable rotational speed as well.

Re: Which shaft encoder to use?
 

Check out BG micro. They have a surpluss assemble that includes 2 encoders.
Real cheap. I don't think i would use these for a competition bot but, for some summer experimentation they would be fine.
http://www.bgmicro.com/lmad3.asp
8.95 plus shipping. There are also some goodies in the catalog. They have some tech docs online but they suck.

Re: Which shaft encoder to use?
 

I checked Grayhill, and it is a continuous-rotation encoder, but it's only rated for 16.6 RPM, and has detents on it. So, it looks like this one won't work, after all.

Re: Which shaft encoder to use?
 

The variation offered for sale by Digikey does not have detents, but it is a slow turning shaft.

Re: Which shaft encoder to use?
 

So I'll pose another question: does anyone know where I could get acceptable encoders for less than $45-50? I have a limited budget, so I'd rather not have to spend that much if I don't have to.

Re: Which shaft encoder to use?
 

This may be a really dumb suggestion, but.....

Would it make sense to try to salvage encoders out of something like an old copier or printer? You could use an oscilliscope to figure out the wiring of it. Would be cheap.

?

Re: Which shaft encoder to use?
 

Jeff, my limited experience with encoders is with the Grayhill 63R series, which would work great, but are a little above your price range.

HOWEVER, we did use the hall effect gear tooth counters that came in the 2005 kit with varying amounts of success. They are definitely affordable, however to determine direction, all we did was check what our PWM output was for the appropriate motor.

We actually didn't count gear teeth, but sprocket teeth. The sensors seem to be resilient enough to pick up just about any ferrous material that comes close enough to it.

It's not an encoder, but it might be an affordable option.