Autonomous Sentry Gun Packs A Punch And A Ton Of Build Tips

What has dual compressed-air cannons, 500 roll-on deodorant balls, and a machine-learning brain with a bad attitude? We didn’t know either, until [Leo Fernekes] dropped this video on his autonomous robot sentry gun and saw it in action for ourselves.

Now, we’ve seen tons of sentry guns on these pages before, shooting everything from water to various forms of Nerf. And plenty of those builds have used some form of machine vision to aim the gun onto the target. So while it might appear that [Leo]’s plowing old ground here, this build is chock full of interesting tips and tricks.

It started when [Leo] saw a video on TensorFlow basics from our friend [Edje Electronics], which gave him the boost needed to jump into an AI project. The controller he ended up with looks for humans in the scene and slews the turret onto target, where the air cannons can do their thing. The hefty ammo is propelled by compressed air, which is dumped into the chamber using a solenoid valve with an interesting driver that maximizes the speed at which it opens. Style points go to the bacteriophage T4-inspired design, and to the sequence starting at 1:34 which reminded us of the factory scene from RoboCop.

[Leo] really put a ton of work into this project, and the results show. He is hoping to get an art gallery or museum to show it as an interactive piece to comment on one possible robot-human future, presumably after getting guests to sign a release. Whatever happens to it, the robot looks great and [Leo] learned a lot from it, as did we.

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Locating Targets With Charm Courtesy Of A Life Size Portal Turret

What better way to count down the last 7 weeks to a big hacker camp like SHA2017 than by embarking on a last-minute, frantic build? That was [Yvo]’s thought when he decided to make a life-sized version of the adorably lethal turrets from the Valve’s Portal video games. Since that build made it to the finish line back then with not all features added, he finished it up for the CCC camp 2019 event, including the ability to close, open, target and shoot Nerf darts.

Originally based on the miniature 2014 turret (covered on Hackaday as well), [Yvo] details this new project in a first and second work log, along with a detailed explanation of how it all goes together and works. While the 2017 version took a mere 50 days to put together, the whole project took about 300 hours of 3D printing. It also comes with four Nerf guns which use flywheels to launch the darts.  The wheels are powered using quadcopter outrunner motors that spin at 25,000 RPM. The theoretical speed of a launched dart is over 100km/h, with 18 darts per gun and a fire rate of 2 darts per second.

The basic movement control for the system is handled by an Arduino Mega, while the talking and vision aspects are taken care of by a Raspberry Pi 3+, which ultimately also makes the decisions about how to move the system. As one can see in the video after the link, the system seems to work pretty well, with a negligible number of fatalities among company employees.

Though decidedly not a project for the inexperienced tinkerer, [Yvo] has made all of the design files available along with the software. We’re still dubious about the claims about the promised cake for completing one of these turrets, however.

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Well-Built Sentry Gun Addresses The Menace Of Indoor Micro-UAVs

What is this world coming to when you can’t even enjoy sitting in your living room without some jamoke flying a drone in through the window? Is nothing sacred? Won’t someone think of the children?

Apparently [Drew Pilcher] did, and the result is this anti-drone sentry gun.  It’s a sturdily built machine – one might even say it’s overbuilt. The gimbal is made from machined steel pieces, and the swivels are a pair of Sherline stepper-controlled rotary tables with 1/40 of a degree accuracy selling for $400 each. Riding atop that is a Nerf rifle, which is cocked by a stepper-actuated linear slide, as well as a Kinect for object tracking. The tracking app is a little rough – just OpenCV hacked onto the Kinect SDK – but good enough for testing. The gun tracks as smoothly as one would expect given the expensive hardware, and the auto-cocking feature works well if a bit slowly. Based as it is on Nerf technology, this sentry is only indicated for the control of the micro-drones seen in the snuff video below, but really, anyone afflicted by indoor infestations of Phantoms or Mavics has bigger problems to worry about.

Over-engineered? Perhaps, but it’s better than letting the menace of indoor drones go unanswered. And it’s far from the first sentry gun we’ve seen, targeting everything from cats to squirrels using lasers, paintballs, and even plain water.

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The Empire Strikes Back With The ESP8266

Like many of us, [Matthew Wentworth] is always looking for a reason to build something. So when he found a 3D model of the “DF.9” laser turret from The Empire Strikes Back intended for Star Wars board games on Thingiverse, he decided it was a perfect excuse opportunity to not only try his hand at remixing an existing 3D design, but adding electronics to it to create something interactive.

As the model was originally intended for a board game, it was obviously quite small. So the first order of business was scaling everything up to twice the original dimensions. As [Matthew] notes, the fact that it still looks so good when expanded by such a large degree is a credit to how detailed the original model is. Once blown up to more useful proportions, he modified the head of the turret as well as the barrel to accept the electronics he planned on grafting into the model.

He created a mount for a standard nine gram servo inside the head of the turret which allows it to rotate, and the barrel got an LED stuck in the end. Both of which are controlled with a NodeMCU ESP8266 development board, allowing [Matthew] to control the direction and intensity of the pew-pew over WiFi. He mentions that in the future he would like to add sound effects that are synchronized to the turret rotation and LED blinking.

For the software side of the project, he used Blynk to quickly build a smartphone interface for the turret. This is the first time he had used Blynk, and reports that outside of a little trial and error, it was some of the easiest code he’s ever written for the Arduino. This is a sentiment we’ve been seeing a lot of recently towards Blynk, and it’s interesting to see how often it shows up in ESP8266 projects now.

Looking ahead [Matthew] says he wants to paint and detail the turret, as the bright orange color scheme probably wouldn’t do terribly well on Hoth. If he can manage the time, he’d also like to add it to the long list of OpenCV-powered turrets that hackers love harassing their friends and family with.

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Arduino One Pixel Camera Sees All (Eventually)

Taking pictures in the 21st century is incredibly easy. So easy in fact that most people don’t even own a dedicated camera; from smartphones to door bells there are cameras built into nearly electronic device we own. So in this era of ubiquitous photography, you might think that a very slow and extremely low resolution camera wouldn’t be of interest. Under normal circumstances that’s probably true, but this single pixel camera built by [Tucker Shannon] is anything but normal.

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Alexa, Attack Intruders

If our doom at the hands of our robot overlords is coming, I for one welcome the chance to get a preview of how they might go about it. That’s the idea behind Project Icarus, an Alexa-enabled face-tracking Nerf turret. Designed by [Nick Engmann],  this impressive (or terrifying) project is built around a Nerf Vulcan, a foam dart firing machine gun mounted on a panning turret that is hidden behind a drop-down cabinet door. This is connected to a Pi Zero equipped with a Pi camera. The Zero is running OpenCV and Google Firebase, which connects it with Amazon’s Alexa service.

It works like this: you say “Alexa, open Project Icarus”. Through the Alexa skill that [Nick] created, this connects to the Pi and starts the system. If you then say “Alexa, activate alpha”, it triggers a relay to open the cabinet and the Nerf gun starts panning around, while the camera mounted on the top of it searches for faces. The command “Alexa, activate beta” triggers the Nerf to open fire.

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Super squirter automatic water gun

Motion Activated Super-Squirter Stands Guard

Thieves beware. If you prowl around [Matthew Gaber]’s place, you get soaked by his motion activated super-squirter. Even if he’s not at home, he can aim and fire it remotely using an iPhone app. And for the record, a camera saves photos of your wetted-self to an SD card.

ESPino, ArduCAM UNO and voltage converter boards
ESPino, ArduCAM UNO and voltage converter boards

The whole security system is handled by three subsystems for target acquisition, photo documentation, and communications. The first subsystem is centered around an ESPino which utilizes a PIR sensor to detect motion. It then turns on a windscreen washer pump and uses pan and tilt servos to squirt water in a pattern toward the victim.

The target acquisition hardware also sends a message to the second subsystem, an ArduCAM ESP8266 UNO board. It takes a burst of photos using an ArduCAM Mini Camera mounted beside the squirter outlet. The UNO can also serve up a webpage with a collection of the photos.

The final subsystem is an iPhone app which talks to both the ESPino and the UNO board. It can remotely control the squirter and provide a video feed of what the camera sees.

One detail of the build we really enjoyed is the vacuum relief valve he fabricated himself. It prevents siphoning through the pump when it’s not on. Don’t miss a demo of the squirter in action after the break.

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