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Originally Posted by BurningQuestion
My friend Dillon (aka Cmptrgk on these forums) and I are trying to find ways other than time to program next years robot's autonomous mode. One of the ways we thought we might do this is by using wheel encoders.
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Kini,
What you are proposing is perfectly OK but the optical sensor with an alternating wheel is the same thing but with less wear and tear on the components. The switch is not likely able to respond above a certain speed as the contacts just can't go up and down that fast. Lubrication and a special tooth follower is needed as well. There are some encoders that magnetize the gear assy, then use a coil to count the teeth going by. That works just as well as the optical and is not affected by ambient light. Those encoders are not available from normal sources, though and would require you to make the interface. If you use the pattern that Tom suggested with an optical sensor, you can actually sense the change from light to dark (an edge detector) and get twice the resolution. Tom's diagram shows 16 light and 16 dark segments which properly implemented would produce 32 counts per rev. On a wheel of a circumference of 16 inches (about 5" diameter) you would get resolution of 1/2" robot travel per tick. This is the system we use with a little less resolution, i.e. about 1" per tick.