Friday, March 21, 2008

Making a Robot : Building the Body (Mousey bot)

For our mousebot, we used an old Kensington Mouse-in-a-Box Scroll model. It's big enough to fit all of our robot components inside of it.Making sure there's enough room in the case is something you're going to have to be certain of before you unholster your Dremel tool & start unhooking your mouse. Unscrew the mouse case & eyeball the placement of all of the robot parts. The main thing you need to be certain of is that the 9V battery & the two DC motors fit inside the case for our robot.

You should be able to unhook the mouse cable (from its plug-type connector), pop out the scroll wheel (if it has one), & then pry out the PCB. Set all of these parts aside while you work on the mouse case itself.

After all above parts removed, what you should have left is the plastic mounts for the two encoder wheels (which are used to translate movement of the mouse ball to cursor movement on your screen), mounts for the scroll wheel , & the screw post(s) (which attaches the case top to the bottom). Using your Dremel tool (& a cut-off wheel), remove every thing but not the screw post

After you have the bottom part of the mouse body cleared out, flip over the top of the mouse case & have a look. It too is likely to have a lot of plastic structure you don't need. Zip all of it off with the Dremel

Robot Motor & Switch Placement

Then we have to make sure that you install your motors perpendicular to the centerline of the body so that the bot can move in a straight line.

  • After we figured out where the battery will sit, & where the motors for robot should be installed, you're ready to cut the openings for the motors.

  • You then keep cutting & test fitting your motors until they can rest comfortably in the case with the lid closed. We will use the drive shafts/gears of the motor themselves as our wheels. To do this, we need to angle the motors coming out of the mouse body so that they're at about a 60-degree angle.

  • After you're confident you have the right motor placement, you can use superglue (or epoxy, if you prefer) to glue your motors in place

  • The next thing we need to do is to make an opening in the case bottom for our bump switch. Our mousebot is going to have one giant "whisker" across its front that, when bumped, triggers its mousey, scuttle-away behavior. We'll actually use one of the tiny switches found in our computer mouse for this bump switch. All you need to do is find one of the button switches on the mouse's PCB & desolder it

  • The last mechanical item we need to attend to in the bottom half of the body is putting tires on the motors. This simply involves getting a rubber band the same width as the sprockets on the drive shafts, measuring out the necessary lengths (by wrapping a piece of the band around the sprocket, marking it, & cutting it), & then gluing the tires in place.

Installing our Robot`s Control Switch

Most switches come with two nuts on the bushing. You simply take one nut off, stick the bushing through the hole you've made in the top, & then tighten down the second nut on the outside of the case to attach your switch



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