Tech In Plain Sight: Field Guide To Power Plugs

April 12, 2023 by 72 Comments

It is the bane of worldwide travel: there isn’t just one way to get AC power from the wall. The exact connector — and what you can expect when you plug in — differs from country to country. Even if you stay home, you must account for this if your designs go places and expect to plug into the wall. If you’ve ever looked at a universal adapter, it is full of prongs and pins like a metallic porcupine. Where do all those pins go?

Of course, there are some easy ways to sidestep the whole issue if you don’t need AC power. Much low-power gear now just provides a USB or barrel connector. Then you can use an area-appropriate adapter or charger to power your device. Batteries work, too. But if you need to plug in, you will run into other kinds of plugs.

Switching power supplies have helped. In the old days, many things expected either 125V or 250V and didn’t work with the opposite voltage. Switching power supplies often allow a wide input range or have a switch to select one range or the other. These two voltages will cover almost any situation. If you have something that must have one voltage or the other, you’ll need a transformer — also called a converter — to step the voltage up or down. But most often, these days, you just need an adapter. There are slight variations. For example, some countries supply 100V or 110V, but that usually doesn’t make much difference. You also need to understand if your equipment cares if the AC is 50 Hz or 60 Hz.

Most of the power sockets you’ll find around the world will fall into one of several categories. The categories range from A to N. Even among these, however, there are variations.

Type A

For example, the common type A plug and socket are what Americans call “two prong.” If you live in the US, you’ve probably noticed that the plug is polarized. That is, one pin is slightly wider than the other so the plug can only go in one way. The wide pin is connected to the circuit neutral. The maximum load for this connector is 15A. It is difficult to find type A sockets anymore, other than on cheap extension cords or things like lamps that pass through their electrical connections to a second socket. Type B is far more common and type A plug will fit in a type B socket.

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Dual Extrusion Support Without PVA

April 12, 2023 by 5 Comments

If you have an FDM printer that features multiple hotends or can otherwise switch between different filaments, you’ve surely thought about using the capability to lay down dedicated support material. Historically the filament of choice for this is PVA, since it can be dissolved in water once the print has finished. But if you’ve ever used it, you’ll know it’s not without its own challenges. Luckily, there may be an alternative — [ModBot] had heard that it is possible to use PLA to support PETG and vice-versa so he decided to try it. You can see how it works in the video below.

Of course, you can simply use PLA to support PLA and PETG to support PETG. Depending on the supports and slicer settings, though, it can be hard to remove the support after printing cleanly. Slicers have made major improvements in this area, but it still isn’t ideal. Some use HIPS for support, but that requires a solvent to dissolve and is also a bit exotic compared to PLA and PETG.

To illustrate, [ModBot] printed some test articles with the alternate support and did more reference prints using the same material with different parameters. The typical gap slicers use is 0.2 mm, but when using the different materials you can set the gap to zero. For the reference parts he set the gap to zero and 0.1 mm, both closer than you would normally print.

The PLA-only prints were essentially impossible to separate. While the PETG prints separated with tools, the resulting surfaces were ugly, with support residue and scarring. But the prints with two materials and zero gap pulled apart readily with no tools and left a beautiful surface underneath.

If you have the ability to do dual extrusion, this could be a great trick to have in your toolbox. Granted, PVA will still be of interest if you have support buried deep inside some structure where it is physically difficult to get to. Water can go where tweezers can’t. But for supporting large accessible areas, this looks like a game-changer.

Sometimes automatic supports can use a little help. There are plenty of supports and best practices for supports if you want to fine-tune your process.

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Signed Distance Functions: Modeling In Math

April 12, 2023 by 13 Comments

What if instead of defining a mesh as a series of vertices and edges in a 3D space, you could describe it as a single function? The easiest function would return the signed distance to the closest point (negative meaning you were inside the object). That’s precisely what a signed distance function (SDF) is. A signed distance field (also SDF) is just a voxel grid where the SDF is sampled at each point on the grid. First, we’ll discuss SDFs in 2D and then jump to 3D.

SDFs in 2D

A signed distance function in 2D is more straightforward to reason about so we’ll cover it first. Additionally, it is helpful for font rendering in specific scenarios. [Vassilis] of [Render Diagrams] has a beautiful demo on two-dimensional SDFs that covers the basics. The naive technique for rendering is to create a grid and calculate the distance at each point in the grid. If the distance is greater than the size of the grid cell, the pixel is not colored in. Negative values mean the pixel is colored in as the center of the pixel is inside the shape. By increasing the size of the grid, you can get better approximations of the actual shape of the SDF. So, why use this over a more traditional vector approach? The advantage is that the shape is represented by a single formula calculated at many points. Most modern computers are extraordinarily good at calculating the same thing thousands of times with slightly different parameters, often using the GPU. GLyphy is an SDF-based text renderer that uses OpenGL ES2 as a shader, as discussed at Linux conf in 2014. Freetype even merged an SDF renderer written by [Anuj Verma] back in 2020. Continue reading “Signed Distance Functions: Modeling In Math” →

The Challenges Of Producing Graphene In Quantity

April 12, 2023 by 26 Comments

We’ve all heard the incredible claims made about graphene and its many promising applications, but so far the wonder-material has been held back by the difficulty of producing it in large quantities. Although small-scale production was demonstrated many years ago using basic Scotch tape, producing grams or even kilograms of it in a scalable industrial process seemed like a pipedream — until recently. As [Tech Ingredients] demonstrates in a new video, the technique of flash Joule heating of carbon may enable industrial graphene production.

The production of this flash graphene (FG) was first demonstrated by Duy X. Luong and colleagues in a 2020 paper in Nature, which describes a fairly straightforward process. In the [Tech Ingredients] demonstration it becomes obvious how easy graphene manufacturing is using this method, requiring nothing more than carbon black as ingredient, along with a capacitor bank, vacuum chamber and a number of reasonably affordable items.

Perhaps best of all is that no refinement or other complicated processes are required to separate the produced graphene from the left-over carbon black and other non-graphene products. Using multiple of these carbon black-filled tubes in parallel, producing graphene could conceivably be scaled up to industrial levels. This would make producing a few kilograms of graphene significantly easier than coating hard drive platters with the substance.

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A milled PCB next to a woman wearing a dress that includes it

Elegant Evening Dress Sports Servo-Actuated Flowers

April 12, 2023 by 13 Comments

There’s been plenty of research into “smart fabrics”, and we’ve seen several projects involving items of clothing with electronics integrated inside. These typically include sensors and simple actuators like LEDS, but there’s no reason you can’t integrate moving electromechanical systems as well. [Rehana Al-Soltane] did just that: she made an elegant evening dress with flowers that open and close on command.

It took [Rehana] a bit of experimentation to figure out a floral design that opens and closes smoothly without crumpling the fabric or requiring excessive force to actuate. She finally settled on a plastic sheet sandwiched between two layers of fabric, with pieces of fishing line attached that pull the edges inward. The lines are guided through a tube down the back of the dress, where a servo pulls or releases them.

The mechanical flower can be operated by touch — [Rehana] made one of the other flowers conductive by embedding copper tape between its petals and connected it to the capacitive touch sensor interface of an Atmel microcontroller. The micro is sitting on a custom PCB that’s worn on the hip, with wires going to the servo at the back. You can see how the system operates in the video embedded below.

The dress is [Rehana]’s final project for the famous “How To Make (almost) Anything” course at MIT, and required a wide variety of skills: the cable guide was 3D printed, the flower petals were laser cut, the PCB was milled, and the end product was sewn together. [Rehana] has a knack for making electronics-infused clothes and accessories, including the flexible PCB crown that she’s wearing in the image above. Continue reading “Elegant Evening Dress Sports Servo-Actuated Flowers” →

A "portable" computer in a grey enclosure. There is a small CRT on the left hand side of the face of the enclosure and a disk drive and a couple ports exposed on the right hand side. The keyboard is attached with a purple cable. A black cartridge with a grey and red label sticks out of the top of the enclosure.

Portable MSX2 Brings The Fun On The Go

April 11, 2023 by 6 Comments

Something of a rarity in the US, the MSX computer standard was rather popular in other parts of the world but mostly existed in the computer-in-a-keyboard format popular in the 80s. [Aron Hoekstra aka “nullvalue”] wanted to build an MSX2 of their own, but decided to build it in a period-appropriate luggable form factor.

This build really tries to make the computer as plausibly vintage as possible including an actual CRT for the display instead of using an easier to obtain and package LCD. Computing is accomplished with an Omega Home Computer MSX2 SBC by [Sergey Kiselev] which uses components that could have been found when the MSX computers were in production. While 3D printing wasn’t widespread in the 80s, we can assume any of the plastic parts like the internal mounts would have been injection molded instead.

An impressive number of different techniques were used to bring this computer to life including PCB design, 3D printing, CNC, and plenty of soldering. After some troubleshooting on the 50 pin cartridge connector and all the assembly, [Hoekstra]’s Mega Omega MSX2 Portable Computer makes for a very impressive reimagining of the MSX platform that feels like a product that might have actually existed at the time.

If you want more MSX hacks, checkout how to add a Wii Nunchuck or PS2 or USB keyboards to your MSX.

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Using Old Coal Mines As Cheap Sources Of Geothermal Heat

April 11, 2023 by 33 Comments

For as much old coal mines are a blight upon the face of the Earth, they may have at least one potential positive side-effect. Where the coal mine consists out of tunnels that were drilled deep into the soil, these tend to get flooded by groundwater after the pumps that keep them dry are turned off. Depending on the surrounding rock, this water tends to get not only contaminated, but also warmed up. As the BBC explains in a recent video as a follow-up to a 2021 article, when the water is pumped up for decontamination, it can be run through a heat exchanger in order to provide heat for homes and businesses. Continue reading “Using Old Coal Mines As Cheap Sources Of Geothermal Heat” →