Sunday, August 19, 2012

Mindstorms Rocket Turret (v2) (2001)

In 2000-2001 I did a pair of internships at alt.software (as they styled it back then), which was great fun.  On one Friday afternoon, our boss came in with a bundle of Nerf toys and distributed them around for people to have fun with.  I was assigned a toy which shot micro darts, could be mounted to a wall with a suction cup, and was meant to have its trigger tied down to a door handle or some such in order to fire upon unsuspecting victims when they entered a room.

I brought it home, and over the weekend, I used some Mindstorms to build a motorized base for it.  Yaw and pitch could be controlled by keyboard over infrared, and the rocket could be fired remotely by mashing the spacebar.  It was great fun.  Unfortunately, I do not have pictures of this.

However, a few weeks later I built a second, better version of the rocket turret.  The turret could still be controlled over infrated, but this time I also built a Lego "glove" somebody could wear to control the turret with their wrist.


Here is another shot of the turret:


And a close-up of the "glove":


By flexing your wrist up and down, the turret would pitch up and down; by flexing your wrist left and right, the turret would yaw.  You could fire the turret by squeezing the index finger.  To regain the use of both hands (useful to rearm the turret), you could pause the wrist tracking by holding down the trigger for a few seconds.

You can sort of make out the constituents of the wrist-mounted device in the pictures above.  The "glove" was in two segments, one around the hand and one around the wrist.  These segments held in place with the use of flexible tubing and a simple ratchet system, visible in the first picture.  To track wrist flexion, two light sensors were used, one on each axis of deflection.  The hand was connected by flexible tubing (visible in the last picture) to colored brick strips which slid in a linear fashion through a small casing, one side of which was fitted with the light sensor.  The light sensors detected the luminance of the bricks presently inside the casing, which told the Mindstorms RCX unit which part of the brick strip was visible to the light sensor; I arranged the brick coloring so the light levels varied in approximate proportion to the amount of wrist deflection.

I wish I had more pictures and/or movies, but I did not own a camera at the time!

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