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Motors and Sensors [was: Re: Webpages? #1: mech + elec pages...]

On Fri, Nov 19, 1999 at 07:13:03PM -0500, Joyce Poon wrote:
> http://www.cs.uiowa.edu:80/~jones/step/
> 	a tutorial on step motors! with links to other info on motors. 

This has some interesting information on how to use a stepper motor
from an old computer harddrive.  Did anyone pick-up some of Malone's
old hardware?

Although, even if so, I'm not sure the extra complexity of a stepper
motor is needed for our project (as discussed already, they're really
meant for precision work where it's important that the motor turns
exactly X degrees).

FWIW, a rough idea of motor sizes: The two fourth-years I talked to
said that their tag robot was vastly overpowered.  The motors they
used were maybe 10cm cubed.  They believe their robot would have
worked _better_ with smaller motors (the weight of their motors
apparently had an adverse effect on the robot's structure... :).  They
did need to gear-down the motor (no surprise).  They also believe that
their robot would have beaten, hands-down, any other tag robot in a

The servo-tachs in my room are 14cm long with a 5cm diameter.  :)

They were also convinced that infra-red beacons are the beacon of
choice.  Apparently the circuitry for eg. a radio or a ultrasonic
beacon is more complex.  I'm not entirely convinced, but it seems we
certainly want to start with IR.

They mentioned one robot that used (whether by accident or intention, I
don't know) an interesting strategy...  We are allowed a max speed of
3ft/s.  Apparently most robots will not attain this max speed.  One
group, however, built a robot that accelerated to this max speed very
quickly.  The (effective, if not intentional) strategy of the robot
was simply to bounce off of barriers in random directions and simply
_go_ at maximum speed.  Rather than trying to carefully sense the
enemy robot, it would achieve a tag simply by the fact that driving
around at 3ft/s in essentially random directions means that within the
space of 90seconds, you will probably tag every barrier and object
that can be found.  3ft/s is pretty fast.  :)

(90 seconds * 3ft / s * 45cm diameter = ~90 square metres of ground
 that can be covered within 90 seconds!!)


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