Day: December 16, 2020

Skittle Sorter Makes Long Task Shorter

December 16, 2020 by 11 Comments

One of the most common complaints fielded by the agents of Big Candy regards the non-homogenous nature of their products. Skittles and M&Ms are two egregious offenders in this area, and it’s left up to the determined consumer to handle sorting these candies themselves. Of course, you can always do it by hand, but as we all know – machines will do the work.

This Skittle sorter is the creation of [Lewis] of [DIY Machines], and it’s a build targeted at the beginner level. Constructed out of cardboard, it uses a pair of servos to handle the transport of the candies into their requisite colored bins, via a rotating disc and chute. Skittles are scanned with a TCS34725 color scanner hooked up to an Arduino Nano, which changes the angle of the output chute to dump the candy in the proper location. The hopper is able to handle a standard 180 gram bag of Skittles without problems.

[Lewis] does a great job explaining each stage of the build, from the mechanical and electronic side of things, to the required calibrations to make everything play together nicely. The project teaches builders a multiude of useful lessons, like how to use limit switches and other concepts of automation.  We’ve featured [Lewis] on these pages before, too; his stylish shelf clock is a particular delight. Video after the break.

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Learn Compilers Online From Cornell

December 16, 2020 by 29 Comments

It sounds like the start of a joke, but what’s the difference between taking Cornell’s CS6120 online and in-person? The instructor, [Adrian Samspon] notes that the real class has deadlines, an end-of-semester project, and a discussion board that is only open to real-life students. He also notes that you only earn “imagination credits.”

Still, this is a great opportunity to essentially audit a PhD-level computer science class on a fascinating topic. The course consists of videos, papers, and open source projects using LLVM and a custom internal representation based on JSON that is made for the class. It is all open source, too. You do however need access to the papers, some of which are behind paywalls. Your local library can help if you can’t otherwise find copies of the papers.

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Automatic Sanitizer For Your Cupholder

December 16, 2020 by 6 Comments

Why is it so hard to remember to use hand sanitizer between going into the store and driving back home? We tried hanging a bottle off the windshield wiper stalk, but it gets in the way and is hard to use and share with passengers. The ideal thing would be to have a hands-free pump in the car that reminds you to use it.

You don’t have to wire this to the ignition or anything — all you have to do is power it with the cigarette lighter (or straight-up outlet, if you’re lucky). Every time you turn the key, this pump powers up and performs a little song to remind you to use it. Electronically speaking, it couldn’t be simpler — an Arduino UNO reads your hand from the distance sensor and activates a servo that dispenses three short pumps of isopropyl alcohol. Check it out in action after the break.

Want a hands-free solution for the house? Just build something you can step on.

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Building Distributed Mode Loudspeakers With Plywood

December 16, 2020 by 18 Comments

Distributed-mode loudspeakers work rather differently from the typical drivers used in 99% of applications. Instead of using piston-like motion to create sound waves, they instead rely on exciting an entire panel to vibrate and thus produce sound. [JGJMatt] decided to build a pair of bookshelf-sized units, with great results.

The build begins with a pair of 44mm DML exciters, readily available online. These had to be modified to remove their stock metal mounting plates that degraded the sound output in early tests. Instead, 3D printed pieces were used to mount the exciters to the 3mm plywood boards, which were lasercut to act as the main DML panels. Additionally, whizzer cones were fitted to the panels in an effort to further boost the high frequency response of the speakers. The speaker stands are assembled out of more 3D printed pieces and aluminium rods, giving a clean, modern look to the final product.

The performance of the speakers is admirable based on the test video, though [JGJMatt] notes that they should be paired with a subwoofer in use as the DML units do not readily produce frequencies below 100Hz. We’ve seen similar builds before on a larger scale, too. Video after the break.

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Enormous CNC Router Uses Clever Tricks To Improve Performance

December 16, 2020 by 32 Comments

CNC machines made from wood and 3D-printed parts may be popular, but they aren’t always practical from a precision and repeatability standpoint. This is especially true as the machines are scaled up in size, where the compliance of their components starts to really add up. But can those issues be resolved? [jamie clarke] thinks so, and he’s in the process of building a CNC router that can handle a full sheet of plywood. (Video, embedded below.)

This is very much a work in progress, and the videos below are only the very beginning of the process. But we found [jamie]’s build interesting even at this early point because he has included a few clever tricks to control the normal sources of slop that plague larger CNC machines. To provide stiffness on a budget, [jamie] went with a wooden torsion-box design for the bed of his machine. It’s the approach taken by the Root CNC project, which is the inspiration for this build. The bed is formed from shallow boxes that achieve their stiffness through stressed skins applied to rigid, lightweight frames.

Upon the torsion-box bed are guide rails made from commodity lengths of square steel tubing. Stiff these may be over short lengths, but over the three meters needed to access a full sheet of plywood, even steel will bend. [jamie]’s solution is a support that moves along with the carriage, which halves the unsupported length of the beam at all points of travel. He’s using a similar approach to fight whip in the ball screw, with a clever flip-down cradle at the midpoint of the screw.

So far, we’re impressed by the quality of this build. We’re looking forward to seeing where this goes and how well the machine performs, so we’re paying close attention to the playlist for updates. At an estimated build cost of £1,500, this might be just the CNC build you’ve been looking for.

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Tracking Satellites: The Nitty Gritty Details

December 16, 2020 by 18 Comments

If you want to listen to satellites, you have to be able to track them as they pass over the sky. When I first started tracking amateur satellites, computing the satellite’s location in the sky was a part of the challenge. Nowadays, that’s trivial. What’s left over are all the extremely important real-world details.  Let’s take a look at a typical ham satellite tracking setup and see how it all ties together.

Rotators for Steering

The popularity of robotics, 3D printing, and CNC machines has resulted in a deluge of affordable electric motors and drivers. It’s hard to imagine that an electric motor for rotating an antenna would be anything special, but in fact, antenna rotators are non-trivial engineering designs. Most of the challenges are mechanical, not electrical — the antennas that they drive can be huge, have significant wind loading and rotational inertial, and just downright weigh a lot. A rotator design has to consider bearings, weather exposure, all kinds of loads, not just rotational. And usually a brake is required to keep the antenna pointed in windy conditions.

There’s been a 70-some year history of these mechanisms from back in the 1950s when Cornell Dubilier Electronics, the company you know as a capcacitor manufacturer, began making these rotators for television antennas in the 1950s. I was a little surprised to see that the rotator systems you can buy today are not very different from the ones we used in the 1980s, other than improved electronic controls. Continue reading “Tracking Satellites: The Nitty Gritty Details” →

Sit Up Straight!: Open Source Bluetooth Posture Sensing

December 16, 2020 by 4 Comments

As more and more people spend their working hours behind a computer, bad posture and the accompanying back pain and back problems become a growing epidemic. To combat this in his own daily life, [ImageryEel] made PosturePack, a wearable Bluetooth-enabled posture sensor.

The PosturePack is designed to fit into a small pocket sewn into the pack of an undershirt, between the shoulder blades. It consists of a custom PCB with an ATmega32U4, BNO055 IMU, Bluetooth module,  small LiPo and power circuitry. Based on the orientation data from the IMU, a notification is sent over Bluetooth to a smartphone whenever the user hunches forward.

[ImageryEel] says although the mobile notifications worked, haptic feedback integrated into the unit would be a better option. This could also be used to remind the user to stand up and take a break now and then, and provide an alternative to a smartwatch for activity monitoring without sending every movement to someone else’s servers. Software will always be the hardest part for projects like these, especially as the device become “smarter”. Learning to recognize activity and postures is actually a good place for tiny machine learning models.

Compared The posture sensors we covered before had to be installed and set up at a specific workstation, like an ultrasound-based version attached to a chair, and a webcam-based version.