Looking for smallest lowest cost motor with encoder.

[CJAlbertson]

I'm looking for the smallest, lowest cost gear motor that comes with or can be fitted with encoders.  The task is simply to move over a solid indoor floor the biggest payload will be the battery.    It's really just a software development platform.   I must be looking in the wrong places, some one must sell low power motors with encodes

Those plastic $6 gear motors might be enough but I don't see a way to do odometery with them

[waltr]

Sounds like you just need encoders on the wheels. Check these (about half way down the page):
http://www.pololu.com/category/7/sensors
you can also build encoders yourself with LED and phototransistor.

If you need a decent quality gear motor check Pololu's selection. If used their micro and mini gear motors and they work well.
http://www.pololu.com/category/22/motors-and-gearboxes

[jwatte]

What's wrong with these motors with built-in encoders?
http://www.pololu.com/product/2286
http://www.pololu.com/product/1445

Or these, smaller, motors, which you can add encoders to?
http://www.pololu.com/product/2215
http://www.pololu.com/product/2590

[CJAlbertson]

I'm looking for the smallest, lowest cost gear motor that comes with or can be fitted with encoders.  The task is simply to move over a solid indoor floor the biggest payload will be the battery.    It's really just a software development platform.   I must be looking in the wrong places, some one must sell low power motors with encodes

Those plastic $6 gear motors might be enough but I don't see a way to do odometery with them

Yes it turns out you can, at least on the slower ones that have two output shafts.  To answer my own question,

Look here http://www.ebay.com/itm/Smart-Robot-Car-with-Plastic-Tire-Wheel-1-48-1-120-DC-Gear-Motor-Encoder-Disc-/231130151482?pt=Apparel_Merchandise&var=&hash=item35d06e3a3a&vxp=mtr
Added to the above you'd need one of those U shape IR switches too.  Add another $2.
 
I was looking for cheap just to test some software, so I don't care about performance.