Anyone who plays video games will know that few things protect an area like a well-placed sentry gun. In the real world, though, even a person's bedroom or office could use a little protection sometimes, which is why one designer has built the Nerf Vulcan Sentry Gun. Using a custom program and some servos, the sentry can automatically locate targets and unleash a stream of foam darts at over seven times the usual speed, while keeping its owner out of the crosshairs.
Britt Liv Ulrike Michelsen, a chemical and biological engineering student from Germany, designed and constructed the sentry using mostly basic electronics and some plywood. This isn't the first time she's modified a Nerf gun, but building this robotic turret is arguably her most ambitious project to date.
Luckily, the Nerf Vulcan already operates using an electric motor, so controlling the actual firing mechanism through a computer was just a matter of connecting it directly to an Arduino Uno and a laptop. From there, Michelsen crafted a stand from plywood and mounted the gun onto a couple of servos, which also control its turning and tilting through the Arduino.
While she was at it, she swapped out the Vulcan's usual 2 kg (4.4 lb) firing spring for a 5 kg (11 lb) one, upping the dart's velocity from 12 m/s (39 ft/s) to 90 m/s (295 ft/s). Aside from giving the darts some extra punch, the increased speed also improved the gun's accuracy. She also added a higher-voltage battery pack to raise the firing rate.
Then it was just a matter of downloading and running an open-source program created by Bob Rudolph of Project Sentry Gun and affixing a webcam to the front of the stand. The webcam scans the area, while the program automatically locks onto movement, aims the gun, and begins firing.
As a added feature though, the gun can be programmed to cease fire when it registers a particular symbol. So if a person is wearing that symbol on their shirt, for example, then they can safely walk in front of the sentry, while everyone around them attempts to dodge a hail of darts.
As it stands, the gun can be loaded with a 100-round ammo belt, which runs out quickly but could likely be expanded with a little extra modification. According to the designer, the sentry is extremely accurate and will even anticipate where a target is moving to so as to catch up with them. If needed, the gun can also be controlled using a regular gamepad or joystick connected to the laptop.
It sounds like a lot of work to put this together, but it's probably all worth it to have an automated guard posted anywhere you want. If you'd like to take a crack at building your own Nerf Vulcan Sentry Gun, Michelsen has posted detailed step-by-step instructions on Instructables.
Check out the video below to see Michelsen demonstrate how the sentry locates and follows targets.