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.
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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.