Optical Encoder?

The cheapest choice is to cannibalize a mouse.

I've dissected a few mice before, and their encoders aren't especially easy to interface. I'm looking for something with absolute position readout, and something more unified than just a baffled emitter/receiver pair on a breadboard.

Not all optical (i.e. some Hall-effect, etc.) but maybe worth a look:

I>>>s anyone aware of a small, cheap optical encoder for use in measuring

I vote for US Digital, though, nothing that has absolute positioning capabilities is going to be THAT cheap. If you're willing to dial in the home position on startup, then a regular quadrature encoder is fine. They even sell counters that hook up to their products, thereby giving you the readout.

Andy

OIC. Well, the "cheap" part of the equation is why I suggested a mouse. The absolute-position optical encoders tend to be expensive. It's much cheaper to use a simple quadrature encoder with a micro attached (doesn't have to be anything major; an 8-pin PIC is perfect for the job). And the cheapest optical quadrature encoders are in mice.

There is no such thing as a cheap optical encoder, unless you build it yourself. Although, they typically have optical encoders on ebay from time to time at cheaper prices. Some of the other guys posted links to where most of the encoders are found already, so i won't burden you with any more. :)

Wow, thanks for the references. I noticed some offer linear as well as rotary position transducers. My end goal is to measure the position on armatures, ones too small for practical use of servos. Could anyone recommend the best method of motion feedback in this case?

The huge majority of nowadays optical mouses don't use optical "encoders" anymore. They use optical chips that have a built-in CMOS sensor and DSP which processes the successive images to detect the motion. Absolutely useless to mesasure rotation, although they can be used to measure translation - as long as you only need a relative, and not absolute, position. You may need to use a specific lens instead of the plastic lens used in mouses, according to the distance between the chip and the moving area.

These chips aren't so hard to interface. Most of them are made by Agilent: just take a look at their web site to find the data sheets.

The armatures of a 30 HP motor or a slot car motor ???

I was referring to traditional ball-and-roller mice, which are still sold.