How well do the optical shaft encoders work? The description says it has a resolution of 90 pulses per second, so it’s pretty precise, but is it accurate? As in, does the internal assembly wobble or does it fit very tightly on the shaft?
I need an encoder that’s precise and accurate for a hobby application. I can’t use the Vex ones if they don’t work extremely well.
I’d appreciate any advice or reviews on the Vex optical shaft encoders 
Thanks!
They have play, in their un-hooked up form. There is a few mm of travel in their mounting. But once you get them on an axel and bolted down, the only play would be from your own setup.
For hobby usage, why not steal the guts of an old optical encoded mouse?
Well, for one thing, I don’t have any old mice laying around 
I’m trying to build a little CNC machine and have to make the decision of whether to use stepper motors, or motors with encoders. I thought since I already had the Vex motors working with my PIC microcontroller that I’d just throw encoders on them and see how it worked, but they may not be accurate enough (I’m building the little machine to drill tiny PCBs).
You probably would want to use stepper motors if they can make small enough steps for your use. Otherwise you would have to use encoders. You could potentially minimize the play if you constantly kept tension on the axle. Good luck.
The potentiometer is more precise and might be better suited to your application.
Many of the hobby CNC mill platforms use stepper motors with encoders.
How much linear distance will you travel ?
How much load do you expect to carry on your milling table?
Search the web for tutorials on building a CNC,
http://buildyourcnc.com/default.aspx ( A friend of mine was able to build a hobby CNC using this site)
Thanks for the link, I’ll check it out.
The main reason I was thinking about using Vex motors is because I have a few on-hand. But really, using stepper motors does seem more practical. I can drive them open-loop since I don’t think they’ll lose steps with such a small load, and they will be FAR more powerful then hobby motors. I’m looking at some cheap NEMA 23’s right now.
The PCBs I’ll be making will be about 4"x3" and the weight of the copper clad board is negligible. The only real weight will be the second axis on top of the first axis.
I get most all my mice at Goodwill, $3.00 to $4.00 (USD) each.
That sounds like a good project…
Also the Vex Optical Encoders are 90 pulses per revolution, the amount of Pulses per Second is directly related to the RPM. The Inventors Guide for the Optical Encoders states on page 3:
The Optical Shaft Encoder can detect up to 1700 pulses per
second, which corresponds to 18.9 revolutions per second and
1133 rpm (revolutions per minute). Faster revolutions will not
be interpreted correctly, resulting in erroneous positional data
being passed to the microcontroller.
I have adapted stepper motors to some of my Vex projects and they work very well indeed!