Why Not Try A DIAC?

There are plenty of electronic components which were once ubiquitous but once the niche which led to their existence has passed, they fade away to remain a junkbox curio. The DIAC is the subject of a recent ElectronicsNotes video, and while it might not quite yet have slid into total obscurity yet it’s definitely not the most common of parts in 2023.

If you’ve encountered one it will almost certainly be in the trigger circuit of a lighting dimmer or motor controller, where its bidirectional breakover makes for symmetrical control of a triac gate. This extremely simple circuit allows for perfect control of AC-powered devices, and could once be found everywhere. Its demise over recent years tells an interesting story of our changing use of electricity, as not only have other devices such as smart lights and brushless motors appeared which preclude traditional dimmers, but also we now demand better RF performance from our lighting controls.

The DIAC is still a handy part to know about, and you can take a look at the video below the break. We would normally try to link to another Hackaday story using a DIAC, but is it telling that we couldn’t find one? If you can, link it in the comments!

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How To Survive A Wet Bulb Event

Territories across the northern hemisphere are suffering through record-breaking heatwaves this summer. Climate scientists are publishing graphs with red lines jagging dangerously upwards as unprecedented numbers pour in. Residents of the southern hemisphere watch on, wondering what the coming hot season will bring.

2023 is hinting at a very real climate change that we can’t ignore. As the mercury rises to new heights, it’s time to educate yourself on the very real dangers of a wet bulb event. Scientists predict that these deadly weather conditions could soon strike in the hottest parts of the world. What you learn here could end up saving your life one day.

Hot Bodies

The body has methods of maintaining a set temperature. Credit: Wikimedia Commons, CNX OpenStax, CC BY-SA 4.0

To understand the danger of a wet bulb event, we must first understand how our bodies work. The human body likes to maintain its  temperature at approximately 37 °C (98.6 °F). That temperature can drift slightly, and the body itself will sometimes move its temperature setpoint higher to tackle infection, for example. The body is a delicate thing, however, and a body temperature above 40 °C (104 °F) can become life threatening. Seizures, organ failures, and unconsciousness are common symptoms of an overheating human. Death is a near-certainty if the body’s temperature reaches 44 °C (112 °F), though in one rare case, a patient in a coma survived a body temperature of 46.5 °C (115.7 °F).

Thankfully, the body has a host of automated systems for maintaining its temperature at its chosen set point. Blood flow can be controlled across the body, and we instinctively seek to shed clothes in the heat and cover ourselves in the cold. However, the bare naked fact is that one system is most crucial to our body’s ability to cool itself. The perspiration system is vital, as it uses sweat to cool our body via evaporation. Water is a hugely effective coolant in this way, with beads of sweat soaking up huge amounts of heat from our skin as they make the phase change from liquid to vapor.

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Tech In Plain Sight: Field Guide To Power Plugs

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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The Benefits Of Displacement Ventilation

The world has been shaken to its core by a respiratory virus pandemic. Humanity has been raiding the toolbox for every possible weapon in the fight, whether that be masks, vaccinations, or advanced antiviral treatments.

As far as medicine has come in tackling COVID-19 in the past two years, the ultimate solution would be to cut the number of people exposed to the pathogen in the first place. Improving our ventilation methods may just be a great way to cut down on the spread. After all, it’s what they did in the wake of the Spanish Flu.

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Tricking A Smart Meter Into Working On The Bench

When the widget you’re working on is powered by a battery or a USB charger, running it on the bench is probably pretty safe. But when the object of your reverse-engineering desire is a residential electrical meter, things can get a little dicey.

Not that this elevated danger level has kept [Hash] from exploring the mysteries presented by smart meters. Still, with a desire to make things a little safer, he came up with a neat trick for safely powering electrical meters on the bench. [Hash] found that the internal switch-mode power supply on the meter backplane was easy enough to back-feed with a 12-volt bench supply, rather than supplying the meter with the full 240-volt AC supply it normally gets when plugged into a meter base (these are meters for the North American market, where split-phase 240-volt is the norm for residential connections.) But that wasn’t enough for the meter — it powered up, but stayed in a reset state without fully booting. Something more was needed to bring the meter fully to life.

That something proved to be a small AC signal. Normally, a resistor network divides the 240-volt supply down to about 3 volts, which is used by the sensing circuit in the meter. [Hash] found that injecting a 60-Hz, 600-mV sine wave signal with about a 3-volt DC bias into the sensing circuit was enough to spoof the meter into thinking it’s plugged into the meter base. The video below has a walkthrough of the hack, and some nice shots of the insides of the meters he’s been working with.

[Hash] has been working with these meters for a while now, and some of the stuff he’s learned is pure gold. Be sure to check out his 2021 Remoticon talk on meter hacking for all the fascinating details.

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Building A Mechanical Oscillator, Tesla Style

Before Tesla devised beautifully simple rotary machinery, he explored other methods of generating alternating current. One of those was the mechanical oscillator, and [Integza] had a go at replicating the device himself. (Video, embedded below the break.)

Initial attempts to reproduce the technology using 3D-printed parts were a failure. The round cylinder had issues sealing, and using O-ring seals introduced too much friction to allow the device to oscillate properly. A redesign that used external valving and a square cylinder proved more successful.

Once the oscillator was complete, the output shaft was fitted with magnets and a coil to generate electricity. After generating a disappointing 0.14 volts, [Integza] went back and had a look at the Maxwell-Faraday equations. Using this to guide the design, a new coil was produced with more turns, and the magnetic flux was maximised. With this done, the setup could generate seven volts, enough to light several LEDs.

While it’s not a particularly efficient generator, it’s a great proof-of-concept. Yes, Tesla’s invention worked, but it’s easy to see why he moved on to rotary designs when it came to real-world applications. We’ve seen [Integza] take on other builds too, like the ever-popular Tesla turbine.

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Hackaday Links: July 28, 2019

It looks like Apple is interested in buying Intel’s modem chip business. Seriously interested; a deal worth $1 billion could be announced as early as this week. That might look like a small potato purchase to the world’s biggest company – at least by market capitalization – but since the technology it will be buying includes smartphone modems, it provides a look into Apple’s thinking about the near future with regard to 5G.

It turns out that Make Magazine isn’t quite dead yet. [Dale Dougherty], former CEO of Maker Media, which went under in June, has just announced that he and others have acquired the company’s assets and reformed under the name “Maker Community LLC.” Make: Magazine is set to resume publication, going back to its roots as a quarterly publication in the smaller journal format; sadly there’s no specific word about the fate of Maker Faire yet.

The hoopla over the 50th anniversary of Apollo 11 may be over, but we’d be remiss not to call out one truly epic hack related to the celebration: the full restoration of an actual Apollo Guidance Computer. The AGC was from a test model of the Lunar Module, and it ended up in the hands of a private collector. Since November of 2018 the AGC has been undergoing restoration and tests by [Ken Shirriff], [Mike Stewart], and [Carl Claunch]. The whole effort is documented in a playlist by [Marc “CuriousMarc” Verdiell] that’s worth watching to see what was needed to restore the AGC to working condition.

With the summer sun beating down on the northern hemisphere, and air conditioners at working extra hard to keep things comfortable. [How To Lou] has a quick tip to improve AC efficiency. Turns out that just spraying a fine mist of water on the condenser coils works wonders; [Lou] measured a 12% improvement in cooling. It may not be the best use of water, and it may not work as well in very humid climates, but it’s a good tip to keep in mind.

Be careful with this one; between the bent spoon, the syringe full of amber liquid, and the little candle to heat things up, this field-expedient reflow soldering setup might just get you in trouble with the local narcotics enforcement authorities. Even so, knowing that you can assemble a small SMD board without a reflow oven might prove useful someday, under admittedly bizarre circumstances.

From the “Considerably more than 8-bits music” file, check out the Hull Philharmonic Orchestra’s “8-Bit Symphony.” If your personal PC gaming history included a Commodore 64, chances are you’ll recognize songs from titles like “Monty on the Run”, “Firelord”, “Green Beret”, and “Forbidden Forest.” Sure, composers like [Ben Daglish] and [Paul Norman] worked wonders with the three-channel SID chip, but hearing those tunes rendered by a full orchestra is something else entirely. We found it to be particularly good background music to write by.