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Aegis, side view PREAMBLE

Aegis uses the LEGO Mindstorms Vision Command system to track movement or color and fire Cyberslam missiles. I designed this as an anti-squirrel device to track and deter the little brutes who were digging up the roots of the plants in my wife's window boxes. However, after a discussion in the LEGO Mindstorms forums about pets chewing through computer cables [ 'ARCHIVE > MISCELLANEOUS > Beware the Killer Rabbit' ], it occurred to me that a squirrel might well chew through the USB cables and trash the LEGO Cam. In the end I have just had it kicking around the office to keep co-workers away from my office supplies

Aegis sits on two 6AA battery boxes. The battery boxes do not act as a power source -- they are just heavy (because of the batteries in them) and wide, and so make a stable base.


Firing works by rotating the missile magazine around the central axle, bringing each missile launcher's firing pin into contact with a spring-loaded beam (on top of the missile assembly, just below the camera). The beam tips the firing pin of the CyberSlam Missile launcher to release the missile; as the magazine continues to revolve the beam is pushed back out of the way and then springs back into place ready to fire the next shot.


There are three motors: two control the rotation and elevation of the missile launcher, linked via chain drives to worm screws which turn the large Technic turntables; the third motor spins the missile launcher to fire the missiles one after another.

Aegis, front view
Aegis, composite showing elevation OPERATION

The Aegis can operate on single shot (15 second pause between shots) or full auto (it will empty the magazine in less than a second). The launcher, with the VC camera mounted above it, can rotate from +90 to -80 vertically (taking 0 to be the horizon), and from +135 to -135 in the horizontal plane (click here for an animated GIF). A rotation sensor tracks the position of each of the motors, and the RCX has a custom NQC program loaded to interpret the commands from the Vision Command software.

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