What kind of encoder to use on a DC motor driven base?

[Littlejohn]

Hello everyone, my first post so I hope I do it right.

I am building a 2 wheeled, 1 caster, robot base. For the drive I am using the gears and motors out of a Mattel Jeep at 12V DC. These are controlled by a Solarbotics L298, which I am in turn controlling with an Arduino, that will one day be controlled by an Apple IIGS motherboard.

The question I have is what would be the best/cheapest way to measure the rotation of the 2 8" lawn mower wheels. I need to compare the rotation with the Arduino because the 2 DC motors do not run at exactly the same speed. The wheels have a little wobble in them that I can't seem to remedy, but still works great.

I am including a video to answer (hopefully) all questions.

[youtube]fwtlwTWdHBc[/youtube]

[chelmi]

The question I have is what would be the best/cheapest way to measure the rotation of the 2 8" lawn mower wheels. I need to compare the rotation with the Arduino because the 2 DC motors do not run at exactly the same speed. The wheels have a little wobble in them that I can't seem to remedy, but still works great.

Rotary encoders: http://www.societyofrobots.com/sensors_encoder.shtml

[waltr]

I have used printed encoder disks with radial 'pie' shaped black and white bars that are glued to the wheels. Then use a reflective photosensor to 'read' the encoder bars.

Like this one:
http://www.acroname.com/robotics/parts/R253-WW02.html

This is fairly easy to do your self for very little money. The disks can be created in various graphic programs and even in Excel then printed. reflective photo sensors can be bought at many electronic suppliers or build your own with an LED and a photo-transistor.

[Soeren]

Hi,

The easy way to create an encoder disc is by a postscript file Here's a bunch

An online encoder drawing page

There also exists a few programs to generate the discs.