You’ve seen them in Aliens (well, the Director’s Cut anyhow), in Half-Life 2, and in Team Fortress – but this guy built his own robotic sentry gun at home.
Using an airsoft P90 replica, a webcam & PC, and some servos, he built a very impressive, functional turret:
Most of the testing involved me directing my little brother in front of the turret, him getting shot, and then running away. Polo shirts, not surprisingly, offer very little protection from BB’s that are prone to leaving little welts. When I originally wrote the software, I added code so it would use the Microsoft speech API to say “Freeze” and offer various instructions to a target that it had acquired. At the end of 5 seconds, if the target moved 20 pixels in either direction, it would fire.
The test video is well worth watching. It gives you an external view, a cam view, and a software view of the targeting and firing in action.