Making a Coil Gun Without Giant Caps

Whenever we see a coil gun project on the Internet, it seems to involve a bank of huge capacitors. [miroslavus] took a different approach with his gun–he wanted his project to be built without those monster caps.

It’s powered by quadcopter LiPo batteries, 2x 1400 MaH drone batteries wired up in series and triggering 21SWG copper coils that [miroslavus] created with the help of a custom 3D-printed winding rig he designed. The rigs have ridges to help you lay the coils down neatly, and they also have mounts for photodiodes, ensuring the gun knows when it’s loaded.

When triggered, the Arduino Nano activates a pair of IRF3205 MOSFETS with logic signals stepped up to 20V, shooting lengths of 7mm or 8mm steel rod. The gun isn’t exactly creating plasma discharges with its launches, but it’s a fascinating project nonetheless.

Check out the disposable camera coil gun project and the coil guns for newbies posts we previously ran.

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Hackaday Prize Entry: Smart Composting System

Composting serves an important purpose in our society, reusing our food scraps and yard waste to fertilize gardens rather than fill up landfills. Knowing that most people don’t compost, [Darian Johnson] set out to create a Arduino-controlled composting system to make it as simple as possible. It monitors your bin’s moisture, temperature, and gas emissions to ensure it’s properly watered and aerated.

[Darian]’s project combines a MQ4 gas sensor that detects combustible gas, a soil moisture sensor, and a temperature and humidity probe. The nearby water reservoir is monitored by an ultrasonic sensor that keeps track of the water level; a pump triggered by a TIP120 turns on the water. Meanwhile, a servo-controlled vent keeps the air flowing just right.

The Smart Composting System sounds like it would be useful to home gardeners; it’s a Best Product finalist in the 2017 Hackaday Prize.

Hackaday Prize Entry: Robo-Dog Learns to Heel

[Radu Motisan] is working on a small rover whose primary trick is being able to identify its owner. Robo-Dog is his proof of concept, a rover that uses five ultrasonic sensors to move toward the nearest obstruction. Obviously, this isn’t the same as being able to recognize one person from another, but it’s a start.

The sensors were home-built using ultrasonic capsules soldered into a custom board, with the tube-shaped enclosures made out of PVC pipe. He made an ultrasonic beacon that uses a 556 timer IC to emit 40 KHz pulses so he can get the hang of steering the robot purely with sound. If that fails, Robo-Dog also has an infrared proximity sensor in front. All of it is controlled by an ATmega128 board and a custom H-bridge motor controller.

[Radu] has been fine-tuning the algorithm, making Robo-Dog move faster to catch up with a target that’s far away, but slower to one that’s close by. It compares the readings from two sensors to compute the angle of approach.

Manually-Adjustable Three-Axis Gimbal

[Tim Good] built a 3-axis gimbal out of 3D-printed and machined pieces, and the resulting design is pretty sweet, with a nice black-on-black look. He machined the flat pieces because they were too long to be printed in his 3D-printer.

The various axes swivel on four bearings each, and each ring features a manual locking mechanism made out of steel stainless pins that immobilize each axis. The gimbal operation itself appears to be manual. That said, [Tim] used 12-wire slip rings to power whatever camera gets mounted on it–it looks like the central enclosure could hold a camera the size of a GoPro.

[Tim] has shared his design files on Thingiverse: it’s a complicated build with 23 different files. This complexity got us wondering: aren’t there two pitch axes?

We definitely love seeing gimbal projects here on Hackaday. A few cases in point, a gimbal-mounted quadcopter, another project with a LIDAR added to a camera gimbal, and this gimbal-mounted coffee cup.



3DP Enigma Keyboard Improves on the Original

[Asciimation], who previously created an Enigma Machine wristwatch, decided to go all-in and make a 3D-printed Enigma machine. Not a perfect replica, but rather an improved version that works the same but doesn’t concern itself with historical accuracy. For instance, the current step involves building the keyboard. Rather than trying to re-create the spring-and-pin method of the original, he simply swapped in readily available, double-throw micro switches.

This project has a tremendous amount of fascinating detail. [Asciimation] did his research and it shows; he downloaded blueprints of the original and used hacked digital calipers to precisely measure each rotor’s teeth, so that it could be re-created for printing. He even re-created the Enigma font to ensure that his printed rotor wheels would look right–though in doing so he discovered that the original machine used one typeface for the keyboard, one for the wheels, and one for the indicator lamps.

We previously published [Asciimation]’s Enigma machine wristwatch project, where he simulated the functionality of an Enigma with an Arduino.

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Mindstorms Soccer Robot Inspired by Real Soccer Robot

[Bram], a 17-year-old robot fan from the Nertherlands, had an opportunity to watch a RoboCup soccer match played by autonomous robots, and was inspired to create his own Mindstorms version of the robot for a school project.

The robot he created is around 80 cm in diameter and is controlled by four daisy-chained EV bricks. There are nine large motors for controlling the wheels, two more large motors for grabbing the ball, and two medium motors for the ball-shooting mechanism. It uses a Pixycam for ball detection, and it can identify and move toward the ball so long as it’s within 2.5 m. A gyro sensor determines the robot’s rotational direction.

Our favorite detail of the robot is its giant omni wheels, constructed out of LEGO elements. Each one consists of sixteen Mindstorms-standard wheels arranged in a circle, with an offset double row of rollers to give the same angled effect as a Mechanum wheel’s rollers.

This story has even geekier roots. [Bram]’s robot was based off of the Turtle, a soccer-playing robot used to teach programming to college students. Like [Bram]’s creation, they also have omni wheels, and see with a Kinect as well as a 360-degree camera up top that uses a parabolic mirror to keep an eye on its surroundings. The Turtle uses a compass sensor to distinguish its goal from the opposing team’s goal.

We’ve covered soccer bots in the past, watch a soccer-playing robot score on a human goalie.
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Testing Distance Sensors

I’m working on a project involving the need to precisely move a tool based on the measured distance to an object. Okay, yeah, it’s a CNC mill. Anyway, I’d heard of time of fight sensors and decided to get one to test out, but also to be thorough I wanted to include other distance sensors as well: a Sharp digital distance sensor as well as a more sophisticated proximity/light sensor. I plugged them all into a breadboard and ran them through their paces, using a frame built from aluminum beams as a way of holding the target materials at a specific height.

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