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Friday
Oct152010

Compact Sumobot: Dozer

TRS is planning a sumo competition soon, and I've just realized I haven't been very active in my bot building at all.  The last meet-up included some basic H-bridge and sensor instruction, so I assume that everyone is expected to use small DC motors in the bots.  The only rules I've heard however, have been that the final entries must fit in a 6"x 6" square.  After scrounging around my parts bins, I can't find any handy DC motors that would work properly as a pair.  So I'm "cheating": servos it is!  I hope it isn't decided to be unfair, the torque in these things is killer.  We shall see.

 

In the interest of keeping the bot as compact as I can, I'm going for an all hot glue and Velcro method.  The control board is a simple piece of Radio Shak protoboard that Rob kindly provided a few weeks back, and I'll be driving the servos and running the microcontroller from separate power sources.  I'm trying out a Dorkboard for the brains, as the Arduino servo libraries are killer, and I've been meaning to work out the interrupt issues from ADAM anyway.  Speaking of ADAM, I've officially scrapped him for parts.  Again.  Poor lil' guy... never even had a chance.

 

Anyway, here's a few pics of the little bit of preliminary work I've done so far.

 

I'm spending most of the time so far laying out all of the little bends in the wiring.  It's amazingly helpful to spend the extra few minutes on the layout so far, since I won't get so lost in the tangle I usually find myself in trying for a more "universal" design.  You can see the headers in use for left and right servos, and the small header delivering power to them up front.  Not much to look at, but sumo-bots generally aren't.

 

The next steps are to work on the sensor deployment and write some code.  I'm not sure what we're laying out the arena edges with yet.   That would be helpful, as if it's something I can detect with an optical sensor looking at the ground, I can keep this guy in the ring.  It's really embarrassing to turn on your creation, step back, and have it happily escape the area.  No freedom for you little bot!

 

UPDATE:

Been working through the wee hours.  Go insomnia.  Attempted to rig up an LM7805 regulator circuit to run the Dorkboard off the same battery as the servos.  I figured it'd be isolated enough from the current draw, but I was totally wrong.  Poor little guy can't keep up with the surges the servos pull when you move them, and the Dorkboard resets.  Bah!  The wiring was suer tight too... Oh well.  I'll just adapt what I have in there for running off a 9V cell.

Bedtime!

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