Auto-Tracking Sentry Gun Gives Deer a Super Soaking

Things rarely go well when humans mix with wildlife. The problems are exacerbated in the suburbs, where bears dine on bird feeders and garbage cans, raccoons take up residence in attics, and coyotes make off with the family cat. And in the suburbs, nuisance wildlife can be an intractable problem because the options for dealing with it are so limited.

Not to be dissuaded in the battle to protect his roses, [dlf.myyta] built this motion-activated sentry gun to apply some watery aversion therapy to marauding deer. Shown in action below against a bipedal co-conspirator, the sentry gun has pretty much what you’d expect under the hood — Raspberry Pi, NoIR camera, a servo for aiming and a solenoid valve to control the water. OpenCV takes care of locating the intruders and swiveling the nozzle to center mass; since the deer are somewhat constrained by a fence, there’s no need to control the nozzle’s elevation. Everything is housed nicely in a plastic ammo can for portability and waterproofing. Any target that stands still for more than three seconds gets a hosing; we assume this is effective, but alas, no snuff films were provided.

We’re not sure if [dlf.myyta]’s code can discern friend from foe, and in this litigious world, hosing the neighbor’s kid could be a catastrophe. Perhaps version 2.0 can include image recognition for target verification.

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Solenoids and Servos for Self Actuated Switches

The new hotness in home automation is WiFi controlled light switches. Sure, we’ve had computer-controlled home lighting for literally forty years with X10 modules, but now we have VC money pouring into hardware, and someone needs to make a buck. A few years ago, [Alex] installed WiFi switches in a few devices in his house and discovered the one downside to the Internet of Light Switches — his light switches didn’t have a satisfying manual override. Instead of cursing the darkness for want of an Internet-connected candle, [Alex] did the only sensible thing. He installed electromagnets, solenoids, and servos behind the light switches in his house.

The exact problem [Alex] is trying to solve here is stateful wall switches. With an Internet-connected lamp socket, the wall switch no longer functions. Being able to turn on a light when your phone is out of charge is something we all take for granted, and the solution is, of course, to have Internet-connected switches.

Being able to read the state of a switch and send some data off to a server is easy. For this, [Alex] used a WeMos D1 mini, a simple ESP8266-based board. The trick here, though, is stateful switches that can toggle themselves on and off. This is a mechanical build, and although self-actuated switches that can flip up and down by computer command exist, they’re horrifically expensive. Instead, [Alex] went the DIY route, first installing electromagnets behind the switches, then moving to solenoids, and finally designing a solution around four cheap hobby servos. The entire confabulation stuffed into a 2-wide electrical box consists of two switches, four hobby servos, the D1 mini, and an Adafruit servo driver board.

The software stack for this entire setup includes a NodeJS server connected to Orvibo Smart Sockets over UDP. Also on this server is a WebSocket server for browser-based clients that want to turn the lights on and off, a FauXMo server to turn the lights on and off via an Amazon Echo via WeMo emulation, and an HTTP server for other clients like [Alex]’ Pebble Watch.

This is, without question, the most baroque method of turning a lamp on and off that we’ve ever seen. Despite this astonishing complexity, [Alex] has something that is also intuitive to use and, to borrow an applhorism, ‘Just Works’. With a setup like this, anyone can flick a switch and turn a lamp on or off over the Internet, or vice-versa. This is the best Home Automation build we’ve ever seen.

You can check out [Alex]’ video demo of his build below, or his GitHub for the entire project here.

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Warhammer 40K Model Rocket Launcher

[Daniel L]’s friend has a passion for Warhammer 40K. [Daniel] himself has a similar zeal for perfection in details. When he remembered a long-forgotten request to build a working rocket launcher for one of his friend’s Warhammer 40K models — well — the result was inevitably awesome.

The MicroMaxx motors — one of the smallest commercial rocket motors on the market — he had on hand seemed to fit the model of the Hyperios Whirlwind anti-air rocket tank. Modeling and 3D printing all the parts proved to be easier than assembling the incredibly detailed model — on top of sanding and filling gaps, a perfect paint job was no simple matter.

The launcher has two main circuit boards: a STM32F407 microcontroller brain, a low-power A20737A Bluetooth module, and a voltage regulator. The second has the constant current source and MOSFET output stages for the rocket igniters. Pitch and yaw handled by a pair of RC servo motors. [Daniel L] has also gone the extra mile by creating an accompanying iPhone app using the Anaren Atmosphere IDE — it’s simple but it works!

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Rolling Robot With Two Motors, But None Are On the Wheels

This unusual 3D printed Rolling Robot by [ebaera] uses two tiny hobby servos for locomotion in an unexpected way. The motors drive the front wheel only indirectly, by moving two articulated arms in a reach-and-retract motion similar to a breaststroke. The arms are joined together at the front, where a ratcheting wheel rests underneath. When the arms extend, the wheel rolls forward freely. When the arms retract, the wheel’s ratchet locks and the rest of the body is pulled forward. It looks as though extending one arm more than the other provides for rudimentary steering.

The parts are all 3D printed but some of them look as though they might be a challenge to print well due to the number of small pieces and overhangs. A short video (embedded below) demonstrates how it all works together; the action starts about 25 seconds in.

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Afroman Teaches Intro to Servos, Builds Laser Turret

After a longish hiatus, we were pleased to see a new video from [Afroman], one of the most accessible and well-spoken teachers the internet has to offer. If you’re new to electronics, see the previous sentence and resolve to check out his excellent videos. The new one is all about servos, and it culminates in a simple build that provides a foundation for exploring robotics.

[Afroman] leaves no gear unturned in his tour de servo, which is embedded after the break. He explains the differences between open vs. closed loop motor systems, discusses the different sizes and types of servos available, and walks through the horns and pigtails of using them in projects. Finally, he puts this knowledge to use by building a laser turret based on a pan-tilt platform.

The Arduino-driven turret uses two micro servos controlled with pots to move by degrees in X/Y space. Interestingly, [Afroman] doesn’t program the board in the Arduino IDE using wiring. Instead, he uses an open-source microcontroller language/IDE called XOD that lets you code by building a smart sort of schematic from drag-and-drop components and logic nodes. Draw the connections, assign your I/O pin numbers, and XOD will compile the code and upload it directly to the board.

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Eat Some Pringles, Feed the Cat

You know the saying: “Dogs have people, cats have servants.” This is especially true when your feline overlord loses track of time and insists on being fed at oh-dark-thirty. You’re tempted to stay in bed feigning death, but that’s a tall order with the cat sitting on your chest and staring into your soul.

An automatic cat feeder would be nice at moments like these, but off-the-shelf units are pricey. [Mom Will Be Proud] decided to roll his own cat feeder, and the results are pretty impressive for what amounts to a trash can build. Two old food cans form the body — a Pringles can on top to hold the food and a nut can below for the servo. The metal ends of the cans nest together nicely, and with a large section removed from each, an aperture opens every time the hopper rotates, dropping food down a chute. A BeagleBone Black controls the servo, but anything with PWM outputs should do the trick. We’d lean toward the ESP8266 ecosystem for WiFi support for remotely controlling feedings, and we’d probably beef up the structure with PVC tube to prevent unauthorized access. But it’s a simple concept, and simple is a good place to start.

You shall not want for pet feeder builds around these parts. Take your pick — snazzy Steampunk, super cheap, or with an Archimedean twist.

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Skelly The Skeleton Is A Scary Good Musician

There are a lot of things to like about [BoneConstructor]’s Skelly the skeleton robot project. Note that we said, “project”. That’s because not only does the robot work well and is built well, but the journey he took to make it contains steps we’ve all taken ourselves. We can say that with confidence since it’s his first, and we’ve all had those.

Skelly started life as a skeleton sitting in [BoneConstructor]’s antique race car at local car shows. Its eyes lit up and it made a moaning sound, which didn’t always work right.  From there came lessons learned with head and arm servos, followed by problems with a PS2 remote and a control board. When he realized he’d have to write his own code, he was stymied by his lack of programming skills. But then he found Visuino, which as you can guess from the name is a visual way to program Arduinos, mostly consisting of drag-and-drop. From there on, the path was smoother, if not completely linear.

Rather than rapidly burn through servos by mounting the bones directly to the servo arms, he fitted bearings into the bone sockets, put the limbs on shafts through those bearings, and used pusher rods connected to the servo arms to turn those shafts. It’s no wonder the arms work so well. He took that sturdy and resilient approach with the wrists and neck too. He even made its right foot able to tap in tune with the music.

And from there we begin to understand some of the method to his madness. Check out the videos below, and on his page and you’ll see how wonderfully Skelly moves to the music. It even took a moment for us to realize he wasn’t actually playing the piano. But best of all, we like how he rocks out to AC/DC’s Shoot To Thrill (Iron Man 2 Version). We’re really impressed by how well those robot arms hold up given that this is a first robot.

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