Handling Bulk Material: Why Does My Cat Food Get Stuck?

May 24, 2022 by 44 Comments

Bulk material is stuff handled ‘in bulk’. One LEGO piece is a brick but 1,000 poured into a bag is bulk material. Corn starch, sand, flour, powder-coat powder, gravel, cat food, Cap’n Crunch, coins, screws, Styrofoam beads, lead shot, and gummy worms are bulk materials.

Applications abound where you need to move stuff in bulk. Selective sintering 3D printers, animal feeders, DIY injection molders, toner based PCB makers, home powder coating, automatic LEGO/domino/whatever sorters or assemblers, automated gardeners, airsoft accessories – handling bulk material is part of hacking. College science classes cover solids and liquids, but rarely bulk materials.

Most hackers just pray it works and tap the bin when it doesn’t. Industry does better, but the slang term “bin rash”, the long term result of tapping a 300 ton bin with sledgehammers (video),  shows they don’t get it right all the time either. At the same time, it’s a fun area you can experiment with using kitchen items. So come along with us for a short series on the basics of bulk material handling. Continue reading “Handling Bulk Material: Why Does My Cat Food Get Stuck?” →

many revisions of the ball and socket robot

Practice Makes Perfect For This Ball And Socket Robot

May 20, 2022 by 3 Comments

Ball and socket joints are useful, but making a part slide over the surface of a sphere, held by magnets, requires a lot of fiddling to get right. We admire persistence and nailing all the details. [Matthew Finlay] has been doing just that with his ball and socket robot. He’s on version six, a testament to his desire to do the idea justice. Luckily for us, he’s documented each version as he went.

Version one, made from a DIY Christmas ornament ball, had no stability around the radial axis, and oscillated badly. Version two demonstrated the problem of centering the mechanism in the ball. Version 3 fixed this problem (it’s covered in the same video). Then version four fixed many of the assembly issues and replaced the servo controllers with an Arduino, but the ‘arm’ piece was too small and mechanically iffy.

Version five used a fabricated bearing. Matthew used airsoft rounds as the balls. Not a good idea. And assembly was a nightmare. So all this progress up to version six shows his improving technique.  Artists say ‘work on your process, not on your pieces’. He’s become much more analytic about what’s needed. He’s started measuring the strength of the robot, and handled issues like adding limit switches so it doesn’t crash at the limits of travel.

Fun build, reminds us of [Stephen Dufresne]’s BB-8.

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As Fast As A Speeding Bullet

February 14, 2022 by 41 Comments

[Electronoobs] built a coil gun and the obvious question is: how fast is the projectile? To answer it, he built a chronograph suitable for timing a bullet. The principle is straightforward. A laser and a light sensor would mark the entry and exit of the projectile over a known distance. As it turns out, there are some issues to resolve.

For one thing, a laser is too narrow and might miss the projectile. The first attempt to rectify this used mirrors, but the loss was too great — we suspect he was using a second surface mirror. The final answer was to use an array of detectors and removed the laser’s collimation lens to cover a wider area.

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Haptic Feedback “Rifle” Lets You Take Aim In VR

January 5, 2022 by 25 Comments

There was a time when virtual reality seemed like it would remain in the realm of science fiction at least for the foreseeable future. Then we were blessed with products like the Power Glove and Virtual Boy which seemed to make it more of a reality, if not a clunky and limited one. Now, though, virtual reality is taking more of a center stage as the technology for it improves and more and more games are released. We can see no greater proof of this than the fact that some gamers are building their own custom controllers to interact with the virtual world in more meaningful ways, like this game controller specifically built for first-person shooter games.

The controller is based on an airsoft gun but completely lacks the ability to fire a projectile, instead using the gun as a base for building the controller. In fact, the gun’s operation is effectively reversed in order to immerse the player into the game by using haptic feedback provided by pressurized air. The air is pumped in to what would be the front of the barrel and is discharged through the receiver when a trigger pull is detected in order to generate a recoil effect. The controller includes plenty of other features as well, including the ability to reload ammunition, change the firing mode, and track motion thanks to its pair of integrated Oculus controllers.

All of the parts for this controller are either 3D printed or readily available off-the-shelf, making this an ideal platform for customization and improvement. There’s also a demo game available from Unity which allows for a pretty easy setup for testing. While the controller looks like an excellent way to enjoy an FPS virtual reality experience, if you’re looking for a more general-purpose controller we are also starting to see a lot of development on that end as well.

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Marble-elevator dot-matric display

Simple Design Elevates This Mechanical Dot Matrix Display

December 7, 2021 by 11 Comments

Don’t get us wrong — we love unique displays as much as anyone. But sometimes we stumble across one that’s so unique that we lack the basic vocabulary to describe it. Such is the case with this marble-raising dot-matrix alphanumeric display. But it’s pretty cool, so we’ll give it a shot.

The core — literally — of [Shinsaku Hiura]’s design is a 3D-printed cylinder with a spiral groove in its outside circumference. The cylinder rotates inside a cage with vertical bars; the bars and the grooves are sized to trap 6-mm AirSoft BBs, which are fed into the groove by a port in the stationary base of the display. BBs are fed into the groove at the right position to form characters, which move upwards as the cylinder rotates. Just watch the video below — it explains it far better than words can.

The clever bit is how the BBs are fed into the groove. Rather than have a separate mechanism to gate the feed port, there’s a backlash mechanism that opens the port when the motor powering the drum runs in reverse for a bit. It’s a clever use of cams to get the job done without adding an extra servo, which sort of reminds us of the design parsimony exhibited in his one-servo seven-segment display.

It’s not clear that this would be a very practical display, but that doesn’t stop it from being cool. Although, [Shinsaku Hiura] just released a follow-up video showing a bigger version of this used to display upcoming events from Google Calendar, so perhaps we’re wrong. Continue reading “Simple Design Elevates This Mechanical Dot Matrix Display” →

This Eyeball Watches You Thanks To Kinect Tracking

October 29, 2021 by 4 Comments

Eyeballs are often watching us, but they’re usually embedded in the skull of another human or animal. When they’re staring at you by themselves, they can be altogether more creepy. This Halloween project from [allpartscombined] aims to elicit that exact spooky vibe.

The project relies on a Kinect V2 to do body tracking. It feeds data to a Unity app that figures out how to aim the eyeball at any humans detected in the scene. The app sends angle data to an Arduino over serial, with the microcontroller generating the necessary signals to command servos which move the eyeball.

With tilt and pan servos fitted and the precision tracking from the Kinect data, the eye can be aimed at people  in two dimensions. It’s significantly spookier than simply panning the eye back and forth.

The build was actually created by modifying an earlier project to create an airsoft turret, something we’ve seen a few times around these parts. Fundamentally, the tracking part is the same, just in this case, the eye doesn’t shoot at people… yet! Video after the break.

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Automated Sentry Turret For Your Secret Lab

June 6, 2021 by 1 Comment

There are few things as frustrating when you’re trying to get some serious hacking done than intruders repeatedly showing up without permission. [All Parts Combined] has the solution for you, with a Kinect-based robotic sentry turret to keep them at bay.

The system consists of a Microsoft Kinect V2 connected to a PC, which runs an app to do all the processing, and outputs the targeting information to an Arduino over serial. The Arduino controls a simple 2-axis servo mount with an electric airsoft gun zip-tied to it. The trigger switch is replaced with a relay, also connected to the Arduino.

The Kinect V2 comes with SDKs that really simplify tracking human movement, and outputs the data in an easy-to-use format. [All Parts Combined] used the SDK in Unity, which allows him to choose which body parts to track. He added scripts that detect a few basic gestures, issues voice commands, and generates the serial commands for the Arduino. The servo angles are calculated with simple geometry, using XY coordinates of the target received from the SDK, and the known distance between the Kinect and turret. When an intruder enters the Kinect’s field of view it immediately starts aiming at the intruder’s heart, issues a “Hands Up!” command, and tells the intruder to leave. If the intruder doesn’t comply, it starts an audible countdown before firing. [All Parts Combined] also added a secret disarming gesture (double hand pistols), which turns the turret into an apologetic comrade. All it needs is a Portal-inspired enclosure.

It’s a fun project that illustrates how the Kinect can make complex computer vision tasks relatively simple. Unfortunately the V2 is no longer in production, having been replaced by the more expensive, developer focused Azure Kinect. We’ve covered several Kinect-based projects, including a 3D room scanner and a robotic basketball hoop.

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