Digital Panel Meter Tear Down

November 22, 2017 by 18 Comments

[Big Clive] had some 22mm digital AC voltmeters, made to put in a panel. There was a time when this would have been a significant pain, since it required you to make a large square hole. Of course, in a world of CNC and 3D printers that isn’t as big a deal as it used to be, but the ones [Clive] has are nice because having a round footprint you can drill a hole for them with a hole saw or a stepped bit. Of course, he wasn’t satisfied to just use these inexpensive meters. He had to tear one apart to look inside. You can see his review and teardown in the video below. The meters are available in a range of AC voltages, although [Clive] didn’t think the ones he had would safely handle their rated maximum.

Inside, the modules reminded us of cordwood construction in a way. Most of the electronics are on a small round board. But several components connect to the board and the bottom cap in a vertical orientation. The meters are available in several colors, but [Clive] likes the red ones as they appear brighter than the others. The voltage reading compared favorably to a Fluke meter.

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Trinket Chills Your Drinks

November 22, 2017 by 7 Comments

Who wants warm drinks? Well, coffee drinkers, we guess. Other than them, who wants warm drinks? Tea drinkers, sure. How about room temperature drinks? No one, that’s who. It’s silly to buy a refrigerator to cool down a single drink, so what option are you left with? Ice cubes? They’ll dilute your drink. Ice packs and a cooler? Sure, they’ll keep your drinks cold, but they’re hardly cool are they? No, if you want a cold drink the cool way, you build a thermoelectric cooler. And if you want to build one, you’re in luck, because [John Park] has a tutorial to do just that up on AdaFruit.

The parts list includes an AdaFruit Trinket M0, a more powerful version of AdaFruit’s Trinket line. The Trinket is used to control the main part in this build, a Peltier thermoelectric cooler, as well as the temperature display and switches. The other part controlled by the microcontroller is a peristaltic pump, which is used to do the dispensing of the liquid. The code to control everything is written in Python as the Trinket M0 comes with AdaFruit’s CircuitPython by default. Also included in the tutorial are the files for the stand, should you want to 3D print it or cut it with a CNC or laser cutter.

After the break, you can watch as [John] goes over the project and builds it, or go to the AdaFruit website and follow the instructions to build your own. As [John] says, there might be better ways to chill your drinks, but this is “definitely one of the more science-y and interesting ones.” For more projects using the Peltier Effect, try this one that uses the effect in sous-vide cooking, or this one, a Peltier cooled micro-fridge!

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A Passion For The Best Is In Mechanical Keyboards

November 22, 2017 by 21 Comments

There is an entire subculture of people fascinated by computer keyboards. While the majority of the population is content with whatever keyboard came with their computer or is supplied by their employer — usually the bottom basement squishy membrane keyboards — there are a small group of keyboard enthusiasts diving into custom keycaps, switch mods, diode matrices, and full-blown ground-up creations.

Ariane Nazemi is one of these mechanical keyboard enthusiasts. At the 2017 Hackaday Superconference, he quite literally lugged out a Compaq with its beautiful brominated keycaps, and brought out the IBM Model M buckling spring keyboard.

Inspired by these beautiful tools of wordcraft, [Ariane] set out to build his own mechanical keyboard and came up with something amazing. It’s the Dark Matter keyboard, a custom, split, ergonomic, staggered-columnar, RGB backlit mechanical keyboard, and at the 2017 Hackaday Superconference, he told everyone how and why he made it.

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Radio Apocalypse: The GWEN System

November 22, 2017 by 42 Comments

Recent developments on the world political stage have brought the destructive potential of electromagnetic pulses (EMP) to the fore, and people seem to have internalized the threat posed by a single thermonuclear weapon. It’s common knowledge that one bomb deployed at a high enough altitude can cause a rapid and powerful pulse of electrical and magnetic fields capable of destroying everything electrical on the ground below, sending civilization back to the 1800s in the blink of an eye.

Things are rarely as simple as the media portray, of course, and this is especially true when a phenomenon with complex physics is involved. But even in the early days of the Atomic Age, the destructive potential of EMP was understood, and allowances for it were made in designing strategic systems. Nowhere else was EMP more of a threat than to the complex web of communication systems linking far-flung strategic assets with central command and control apparatus. In the United States, one of the many hardened communications networks was dubbed the Groundwave Emergency Network, or GWEN, and the story of its fairly rapid rise and fall is an interesting case study in how nations mount technical responses to threats, both real and perceived. Continue reading “Radio Apocalypse: The GWEN System” →

Fail Of The Week: Cheap Chips Cause Chaos

November 22, 2017 by 87 Comments

We all know the old saw: if it’s too good to be true, it probably is. But nowhere does this rule seem to break down as regularly as when we order parts. Banggood, AliExpress, and eBay are flooded with parts ready to be magically transported across the globe to our doorsteps, all at prices that seem to defy the laws of economics.

Most of these transactions go off without a hitch and we get exactly what we need to complete our Next Cool Thing. But it’s not always so smooth, as [Kerry Wong] recently discovered with an eBay order that resulted in some suspicious chips. [Kerry] ordered the AD633 analog multiplier chips as a follow-up to his recent Lorenz Attractor X-Y recorder project, where he used an Arduino to generate the chaotic butterfly’s data set as a demo for the vintage instrument. Challenged in the comments to do it again in analog, [Kerry] did his homework and found a circuit to make it happen. The needed multipliers were $10 a pop on DigiKey, so he sourced cheaper chips from eBay. The $2 chips seemed legit, with the Analog Devices logo and everything, but the circuit didn’t work. [Kerry]’s diagnosis in the video below is interesting, and it’s clear that the chips are fakes. Caveat emptor.

Here’s hoping that [Kerry] sources good chips soon and regales us with a successful build. Until then, what are your experiences with cheap chips? Have you been burned by overseas or domestic suppliers before? Does any single supplier seem like a better bet to you, or is it all hit or miss? Sound off in the comments below.

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Skin (Effect) In The Game

November 22, 2017 by 70 Comments

We love to pretend like our components are perfect. Resistors don’t have capacitance or inductance. Wires conduct electricity perfectly. The reality, though, is far from this. It is easy to realize that wire will have some small resistance. For the kind of wire lengths you usually encounter, ignoring it is acceptable. If you start running lots of wire or you are carrying a lot of current, you might need to worry about it. Really long wires also take some time to get a signal from one end to the other, but you have to have a very long wire to really worry about that. However, all wires behave strangely as frequency goes up.

Of course there’s the issue of the wire becoming a significant part of the signal’s wavelength and there’s always parasitic capacitance and inductance. But the odd effect I’m thinking of is the so-called skin effect, first described by [Horace Lamb] in 1883. [Lamb] was working with spherical conductors, but [Oliver Heaviside] generalized it in 1885.

Put simply, when a wire is carrying AC, the current will tend to avoid traveling in the center of the wire. At low frequencies, the effect is minimal, but as the frequency rises, the area in the center that isn’t carrying current gets larger. At 60 Hz, for example, the skin depth for copper wire — the depth where the current falls below 1/e of the value near the surface — is about 0.33 inches. Wire you are likely to use at that frequency has a diameter less than that, so the effect is minimal.

However, consider a 20 kHz signal — a little high for audio unless you are a kid with good ears. The depth becomes about 0.018 inches. So wire bigger than 0.036 inches in diameter will start losing effective wire size. For a 12-gauge wire with a diameter of 0.093 inches, that means about 25% of the current-handling capacity is lost. When you get to RF and microwave frequencies, only the thinnest skin is carrying significant current. At 6 MHz, for example, copper wire has a skin depth of about 0.001 inches. At 1 GHz, you are down to about 0.000081 inches. You can see this (not to scale) in the accompanying image. At DC, all three zones of the wire carry current. At a higher frequency, only the outer two zones carry significant current. At higher frequencies, only the outer zone is really carrying electrons.

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Hacking A K40 Laser Cutter

November 22, 2017 by 26 Comments

The distinctive blue-and-white enclosure of the Chinese-made K40 laser cutter has become a common sight in workshops and hackerspaces, as they represent the cheapest route to a working cutter that can be found. It’s fair to say though that they are not a particularly good or safe machine when shipped, and [Archie Roques] has put together a blog post detailing the modifications to make something better of a stock K40 performed at Norwich Hackspace.

After checking that their K40 worked, and hooking up suitable cooling and ventilation for it, the first task facing the Norwich crew was to install a set of interlocks. (A stock K40 doesn’t shut off the laser when you open the lid!) A switch under the lid saw to that, along with an Arduino Nano clone to aggregate this, a key switch, and an emergency stop button. A new front panel was created to hold this, complete a temperature display and retro ammeter to replace the modern original.

Norwich’s laser cutter has further to go. For example, while we secretly approve of their adjustable bed formed from a pile of beer mats, we concede that their plans to make something more practical have merit. The K40 may not be the best in the world, indeed it’s probable we should be calling it an engraver rather than a cutter, but if that means that a small hackerspace can have a cutter and then make it useful without breaking the bank, it’s good to see how it’s done.

This isn’t the first K40 enhancement we’ve featured. Norwich might like to look at this improved controller, or even extend their cutter’s bed. Meanwhile if [Archie]’s name rings a bell, it might be because of his Raspberry Pi laptop.