The Imperfect Bipolar Transistor

April 16, 2021 by Al Williams 15 Comments

We like to pretend that our circuit elements are perfect because, honestly, it makes life easier and it often doesn’t matter much in practice. For a normal design, the fact that a foot of wire has a tiny bit of resistance or that our capacitor value might be off by 10% doesn’t make much difference. One place that we really bury our heads in the sand, though, is when we use bipolar transistors as switches. A perfect switch would have 0 volts across it when it is actuated. A real switch won’t quite get there, but it will be doggone close. But a bipolar transistor in saturation won’t be really all the way on. [The Offset Volt] looks at how a bipolar transistor switches and why the voltage across it at saturation is a few tenths of a volt. You can see the video below.

To understand it, you’ll need a little bit of math and some understanding of the construction of transistors. The idea of using a transistor as a switch is that the transistor is saturated — that is, increasing base current doesn’t make much change in the collector current. While it isn’t perfect, it is good enough to switch a relay or do other common switching tasks.

Continue reading “The Imperfect Bipolar Transistor” →

Ambitious Spot Welder Really Pushes The Amps

April 16, 2021 by Dan Maloney 18 Comments

On the face of it, a spot welder is a simple device. If you dump enough current through two pieces of metal very quickly, they’ll heat up enough to melt and fuse together. But as with many things, the devil is in the details, and building a proper spot welder can be as much about addressing those details as seeing to the basics.

We haven’t featured anything from our friends over at [Make It Extreme], where they’re as much about building tools as they are about using them to build other things, if not more so. We expect, though, that this sturdy-looking spot welder will show up in a future video, because it really looks the business, and seems to work really well. The electronics are deceptively simple — just rewound microwave oven transformers and a simple timer switch to control the current pulse. What’s neat is that they used a pair of transformers to boost the current considerably — they reckon the current at 1,000 A, making the machine capable of welding stock up to 4 mm thick.

With the electrical end worked out, the rest of the build concentrated on the housing. A key to good-quality spot welds is solid physical pressure between the electrodes, which is provided by a leverage-compounding linkage as well as the long, solid-copper electrodes. We’ve got to say that the sweep of the locking handle looks very ergonomic, and we like the way closing down the handle activates the current pulse. Extra points for the carbon-fiber look on the finished version. The video below shows the build and a demo of what it can do.

Most of the spot welders we see are further down the food chain than this one, specialized as they are for welding battery packs and the like. We do recall one other very professional-looking spot welder, though.

Continue reading “Ambitious Spot Welder Really Pushes The Amps” →

The Beat Goes On With This ESP32 Page Turner

April 16, 2021 by Tom Nardi 3 Comments

Looking for a hands-free way to page through sheet music on an iPad, [The_Larch] came up with this simple Bluetooth input device based on the ESP32. The microcontroller just needed to have two switches wired into the GPIO pins, in this case the same heavy-duty plungers you’d find on a guitar pedal, and a USB bulkhead pass-through to provide power. Thanks to the excellent ESP32-BLE-Keyboard library, it only took a few lines of code to fire off the appropriate key strokes when the left or right button was pressed.

While undeniably a simple project from an electronics standpoint, the wooden enclosure [The_Larch] built is an interesting change of pace from the 3D printed fare we normally see around these parts. It started life as strips of oak reclaimed from an old kitchen table, which were laminated together to make a solid block. A large spade bit was then used to bore into the block to make a void for the electronics, and a second flat piece of oak was fashioned into a front panel.

Creating Bluetooth input devices with the ESP32 is so incredibly straightforward that we’re honestly a little surprised we don’t see the trick used more often. Especially when you consider all of the custom made keyboards that have graced these pages over the last couple of years. The tools are available for anyone who wants them, so you have to wonder if hackers just aren’t fond of using Bluetooth for something as important as a keyboard?

New Whitest Paint Might Help Fight Climate Change

April 16, 2021 by Lewin Day 69 Comments

It’s hot! Hotter than it used to be, and too hot for things to remain nice in the future. The sun keeps beating down, and as our greenhouse gas emissions continue to blanket the earth, more of that heat is trapped, leading to the steady uptick in global average temperatures. Reducing these emissions can help, but there’s other possibilities too. A team of researchers with a new very white paint think it might be of some use in solving the problem.

Thermal imaging shows the white paint’s ability to cool a surface below ambient temperature, by radiating away excess heat.

The new “whitest white” paint comes to us from Purdue University in the US. It’s capable of reflecting 98% of sunlight reaching its surface, a big step up over the typical 80-90% of conventional white paints. Additionally, it doesn’t absorb UV light, and can also radiate out heat in infrared wavelengths that pass out of the atmosphere. This allows the paint to cool surfaces below ambient temperature. The paint achieves these feats by using barium sulphate as a pigment, which doesn’t absorb UV like conventional titanium dioxide white pigments do. The paint also uses a lot of pigment – 60%, versus 20-40% in a more typical paint. This is similar to techniques used in producing Vantablack, the blackest black acrylic paints.

The hope is that by painting roofs and walls of buildings with white paint, more sunlight will be reflected back out into space, and buildings will be naturally cooler with less reliance on air conditioning, helping to reduce emissions. This could go a long way to solving the heat island effect in many major cities. Municipalities around the world have already begun adopting the technique, from California, to New York and Ahmedabad. It’s an easy thing to do, with few drawbacks, so we expect to see the practice grow more popular in coming years. While it won’t solve the climate crisis on its own, the world could surely use every bit of help it can get.

The False Alarm That Nearly Sparked Nuclear War

April 16, 2021 by Lewin Day 54 Comments

The date was September 26, 1983. A lieutenant colonel in the Soviet Air Defence Forces sat at his command station in Serpukhov-15 as sirens blared, indicating nuclear missiles had been launched from the United States. As you may have surmised by the fact you’re reading this in 2021, no missiles were fired by either side in the Cold War that day. Credit for this goes to Stanislav Petrov, who made the judgement call that the reports were a false alarm, preventing an all-out nuclear war between the two world powers. Today, we’ll look at what caused the false alarm, and why Petrov was able to correctly surmise that what he was seeing was an illusion.

Continue reading “The False Alarm That Nearly Sparked Nuclear War” →

Hackaday Podcast 114: Eye Is Watching You, Alien Art, CNC Chainsaw, And The Galvie Flu

April 16, 2021 by Mike Szczys No comments

Hackaday editors Elliot Williams and Mike Szczys marvel at the hacks that surfaced over the past week. An eye-popping webcam hack comes in the form of an animatronic that gives that camera above your screen an eyeball to look around, an eyelid to blink with, and the skin, eyelashes, and eyebrow to complete the illusion (and make us shudder at the same time).

Dan did a deep dive on Zinc Flu — something to avoid when welding parts that contain zinc, like galvanized metals. A robot arm was given a chainsaw, leading to many hijinks; among them the headache of path planning such a machine. And we got to hear a really awesome story about resurrecting a computer game lost to obscurity, by using one of the main tools of the copyright office.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (~60 MB)

Places to follow Hackaday podcasts:

Continue reading “Hackaday Podcast 114: Eye Is Watching You, Alien Art, CNC Chainsaw, And The Galvie Flu” →

Unmasking The Identity Of An Unusual Nintendo DS

April 16, 2021 by Tom Nardi 9 Comments

The Nintendo DS family encompasses a dizzying array of portable game systems released over a span of 17 years. The original DS received several refreshes and special editions, and when the next generation 3DS came along, it spawned a whole new collection of spin-offs. But even among all those machines there’s a name that even Mario himself would never have heard of: the Nintendo DS ML.

In a recent video, [The Retro Future] says he discovered this oddball system selling for around $25 USD on Chinese shopping site Taobao and bought one so he could get a closer look at it. Externally the system looks quite a bit like the refreshed DS Lite, but it’s notably larger and the screens look quite dated. That was already a strong hint to its true identity, as was the placement of its various buttons and controls.

Note the conspicuous absence of Nintendo’s name.

But it wasn’t until [The Retro Future] cracked the system open that he could truly confirm what he had on his hands. This was an original Nintendo DS, potentially a new old stock unit that had never been distributed, which was transplanted into a custom enclosure designed to look like one of the later upgraded models. As for what this seller meant by calling this chimera the DS ML is anyone’s guess, though one of the commenters on the video thought “Maybe Legal” had a nice ring to it.

Now assuming these really are brand new systems that were simply installed in fresh cases, $25 is arguably a good deal. So long as you aren’t concerned with playing the latest titles, anyway. But at the same time its a reminder that you get what you pay for when dealing with shady overseas sellers. It’s just as likely, perhaps even more so, that these were used systems that got spruced up to make a quick buck.

Fake components are everywhere. In fact there’s an excellent chance most of the people reading this site have received some fake parts over the years, even if they didn’t realize it at the time. When there’s fly by night companies willing to refurbish a nearly 20 year old Nintendo handheld for $25, what are the chances that Bosch actually made that $2 temperature sensor you just ordered on eBay?

Continue reading “Unmasking The Identity Of An Unusual Nintendo DS” →