The last time we used a scanning electron microscope (a SEM), it looked like something from a bad 1950s science fiction movie. These days SEMs, like the one at the IBM research center, look like computers with a big tank poised nearby. Interestingly, the SEM is so sensitive that it has to be in a quiet room to prevent sound from interfering with images.

As a demo of the machine’s impressive capability, [John Ott] loads two US pennies, one facing up and one face down. [John] notes that Lincoln appears on both sides of the penny and then proves the assertion correct using moderate magnification under the electron beam.

Some electron microscopes pass electrons through thin samples much as light passes through a sample on a microscope slide. However, SEMs and REMs (reflection electron microscopes) use either secondary electron emission or reflected electrons from the surface of items like the penny.

You often see SEMs also fitted with EDS — energy dispersive X-ray spectrometers, sometimes called EDX — that can reveal the composition of a sample’s surface. There are other ways to examine surfaces, like auger spectrometers (pronounced like OJ), which can isolate thin films on surfaces. There’s also SIMS (secondary ion mass spectrometry) which mills bits of material away using an ion beam. and Rutherford backscattering spectrometry, which also uses an ion beam.

We keep waiting for someone to share plans to make a cheap, repeatable SEM. There are a few attempts out there, but we don’t see many in the wild. While the device is conceptually simple, you do need precise high voltages and high vacuums,. Also, you frequently need ancillary devices to do things like sputter gold in argon gas to coat nonconductive samples, so the barrier to entry is high.

It didn’t take long for us to get an answer to the question nobody was asking: Can you use toilet paper as solder wick? And unsurprisingly, the answer is a resounding “No.”

Confused? If so, you probably missed our article a few days ago describing the repair of corroded card edge connectors with a bit of homebrew HASL. Granted, the process wasn’t exactly hot air solder leveling, at least not the way PCB fabs do it to protect exposed copper traces. It was more of an en masse tinning process, for which [Adrian] used a fair amount of desoldering wick to pull excess solder off the pins.

During that restoration, [Adrian] mentioned hearing that common toilet paper could be used as a cheap substitute for desoldering wick. We were skeptical but passed along the tip hoping someone would comment on it. Enter [KDawg], who took up the challenge and gave it a whirl. The video below shows attempts to tin a few pins on a similar card-edge connector and remove the excess with toilet paper. The tests are done using 63:37 lead-tin solder, plus and minus flux, and using Great Value TP in more or less the same manner you’d use desoldering braid. The results are pretty much what you’d expect, with charred toilet paper and no appreciable solder removal. The closest it comes to working is when the TP sucks up the melted flux. Stay tuned for the bonus positive control footage at the end, though; watching that legit Chemtronics braid do its thing is oddly satisfying.

So, unless there’s some trick to it, [KDawg] seems to have busted this myth. If anyone else wants to give it a try, we’ll be happy to cover it.

When you need to make very tiny measurements, even noise in closed relays can throw you off. [Marco] was able to observe this effect and wanted to build a switch that didn’t have this problem. He found a technical paper that used rotary switches operated by stepper motors instead of relays. So he decided to try making his own version. The video below shows how it turned out.

The first part of the video talks about why relays sometimes inject a tiny voltage into a closed circuit. He then looks at costly switches that would work. However, since he needed many switches, he decided to roll his own.

While this is painful, it does let you optimize for your particular application. That’s why it was important to understand why relays don’t work well in this application. Copying part of a design from a very interesting-looking switch, custom PCB switch decks arrived in the mail.

Did it work? Watch the video to find out. There was something very comforting about watching the switch rotors turn under automatic control. [Marco] reminded us that the switches look somewhat like an old auto distributor.

Measuring nanovolts isn’t for the faint of heart. With a little help, your existing gear might be able to read nanoamps, however.

Now that we have decent VR goggles, the world is more desperate than ever for a decent haptic interface for interacting with computers. We might be seeing a new leap forward in this wild new haptic glove design from the Future Interfaces Group at Carnegie Mellon University.

The glove gives each fingertip and thumb a small haptic pad. The pads are driven by electro-osmotic pumps, which are effectively solid-state. They use electricity to move fluid to create small dimples on the pad to provide haptic feedback to the user. The pads have 20 pixels per square centimeter, are quick and responsive, and can deform up to 0.5 mm in less than half a second.

The lightweight and self-contained electro-osmotic pads mean the haptic system can be far lighter and more practical than designs that use solenoids or other traditional technologies. The device is also high resolution enough that a user can feel pressure from a surface or the edges of an object in VR. If you watch the video, some of the demonstrations are quite revolutionary.

We’ve seen some other great haptics projects before too, like these low-cost force feedback gloves. Video after the break.

[Thanks to Keith Olson for the tip!]

Most of the Hackaday community would never wire a power supply to a circuit without knowing the expected voltage and the required current. But our mechanical design is often more bodged. We meet folks who carefully budget power to their microcontroller, sensors, and so on, but never measure the forces involved in their mechanical designs. Then they’re surprised when the motor they chose isn’t big enough for the weight of their robot.

An obstacle to being more numbers oriented is lack of basic data about the system. So, here are some simple tools for measuring dynamic properties of small mechanisms; distances, forces, velocities, accelerations, torques, and other things you haven’t thought about since college physics. If you don’t have these in your toolkit, how do you measure?

Distance

For longer distances the usual homeowner’s tools work fine. The mechatronics tinkerer benefits from two tools on the small end. A dial or electronic caliper for measuring small things, and a thickness gauge (or leaf gauge) for measuring small slots.

A thickness gauge is just metal leaves in different thicknesses, bolted together at one end. Find a combination of leaves that just fits in the space.

Force

Here’s four force measuring tools we use to cover different magnitudes of force: a postage scale, a push stick, a spring scale, and a letter scale. The postage scale is best purchased. For big things, the bathroom scale works.

A push stick is a force measurement device that you can make yourself. We first saw one of these used to tune slot cars, but they’re universally useful. It’s a simple pen shaped device made with a barrel from any small transparent parts tube, a spring, and a plunger with a protruding pin. Grasp the barrel and push the gizmo with the pin, and you can read the force off the tube.

If you need it to be calibrated, remember that you just bought a postage scale. Push it into the scale and mark off reasonable increments. Make several, in different sizes. A Z or L shaped plunger is useful for hard to reach places.

The conventional spring tension scale is useful, but most commercial ones are terribly made and inaccurate. You can make yourself a better one. They are useful for measuring the spring constant of springs, for learning the tractive effort needed to move a robot, finding the center of gravity of a robot arm, and a hundred other ‘how much oomph’ things. Again, it’s just a matter of connecting a hook to a spring, and measuring its deflection.

For yet lighter weights, you could buy a letter scale, at least in the old days. Today you might have to make your own.  It can be as simple as a piece of spring steel fixed to a sheet of calibrated cardboard.

Torque

Torque measurements are good not only for sizing actuators, but for measuring efficiency.

How you do torque measurements depend on the speed you want to make them at. For static loads, just put a lever of known length on the shaft and measure the force. Torque = distance * force. For fast rotating systems, you can run the system at a known speed and measure the electrical energy used.

If you just want to apply a varying known torque to measure efficiency, your life is much easier. Mount a broad wheel of some sort on the shaft — RC airplane tires work well. Drape a piece of ribbon over the tire. Anchor it at the “out” end and hang a small weight at the “in” end. This is a Prony Brake, and it’s a useful device to know about. The force on the outside of the wheel is just enough to lift the weight – after that the ribbon slips. The measured torque is then the weight times the wheel radius.

You may also want to measure speeds and accelerations. Here, the ubiquity of cell phone cameras is your friend. Suppose you’re animating a crane on your model railroad. Record yourself on video moving the crane with your hands against a protractor to get a feel for speed and acceleration. In video editing software check the positions for various frames, and you now have position changes. The number of frames and distance can help you calculate the speed, and the change in speed vs time is acceleration.

If your mechanism is moving too fast for video, use a fast phototransistor or hall effect device and an oscilloscope, or gear down by holding a toy wheel against the shaft and measure the more slowly rotating wheel.

In the crane example, the torque you need to supply is the frictional torque plus the acceleration torque, and to calculate the acceleration torque you need the moment of inertia. For refresher: angular acceleration = torque / moment of inertia (ω = τ / I) and moment of inertia = mass * radius² (I = m * r² ) for point mass.

You can drive the crane with a repeatable torque, say using a pulley and weight or a motor, and get the acceleration ω₁ from the still frames on your video. If you repeat this with a known mass m a known distance r from the shaft axis, like a lump of putty on the end of the crane arm, you can get a second value: ω_2. 

Write the ω = τ / I equations, ω₁ = τ / I_crane and ω₂ = τ / (I_crane + r ² * m). Combining and isolating I_crane and holding our tongues just right, I_crane = r² * m / (ω₁ / ω₂ – 1).

Be careful to subtract the moment of inertia of your measuring apparatus, and add in the moment of inertia of the final drive if needed. Now you can size your servo with some confidence. Believe me, once you’ve done this a couple times, you’ll never go back to winging it.

Power

The easiest way to get a ballpark feel for power is to simply measure the system’s consumed power by measuring the electrical power at the motor, but this ignores losses in the drive train. And losses are one of the really interesting things to measure. Bad performance is usually friction, and efficiency is a goal for other reasons than just motor sizing or battery life. It’s a measure of how janky your setup is.

Does your model train or robot run poorly? Set it to climb a steep grade on a test track. Calculate the work it does: mass * height change. Measure the input electrical power and the time, Energy = V*I*T. You now have an idea of how much the actual power consumption differs from the maximally efficient system. Any power that went in but didn’t appear as potential energy in the choo-choo’s new position is frictional loss. Now you can experiment with loosening and tightening screws, changing gear mesh, and such, and have some idea if you’re making things better or worse.

Conclusion

None of the above was rocket science, and you don’t need to do some complex FEM analysis to make the average hacker project. But a bit of real engineering can go a long way towards more reliable mechanisms, and that starts with knowing the numbers you’re dealing with. Taking the required measurements can be simple if you know how to build the tools you need,  and your life will be easier with some numbers to guide you.

Smartphones are an integral part of life, but what if you can’t see the screen? There is text-to-speech available, but that’s not always handy and can be slow. It also doesn’t help users who can’t hear or see. Refreshable braille devices are also available, but they are expensive and not very convenient to use. [Bmajorspin] proposed a different method and built a prototype braille device that worked directly with a cell phone. The post admits that as the device stands today, it isn’t a practical alternative, but it does work and is ripe for future development to make it more practical.

The device saves costs and increases reliability by using six vibration motors to represent the six dots of a braille cell. However, this leads to an important issue. The motor can’t directly mount to the case because you have to feel each one vibrating individually. A spring mounting system ensures that each motor only vibrates the tactile actuator it is supposed to. However, the system isn’t perfect, and fast output is difficult to read due to the spread of vibrations.

The whole thing sits in a magnetic case and connects to the phone for power. The data is sent via Bluetooth (BLE, actually, in this version).  The electronics are simple: just some basic motor drivers and an Arduino. Slowing them down might make the vibrations easier to manage, and that might be an idea for the next version.

Overall, this seems like a good idea that maybe needs a bit of refinement. The post ends with several ideas for future development.

This made us think of a system we saw that requires no contact at all. Even machines can learn to read braille.

There have been all kinds of wild ideas to get spacecraft into orbit. Everything from firing huge cannons to spinning craft at rapid speed has been posited, explored, or in some cases, even tested to some degree. And yet, good ol’ flaming rockets continue to dominate all, because they actually get the job done.

Rockets, fuel, and all their supporting infrastructure remain expensive, so the search for an alternative goes on. One daring idea involves using airships to loft payloads into orbit. What if you could simply float up into space?

Lighter Than Air

The concept sounds compelling from the outset. Through the use of hydrogen or helium as a lifting gas, airships and balloons manage to reach great altitudes while burning zero propellant. What if you could just keep floating higher and higher until you reached orbital space?

This is a huge deal when it comes to reaching orbit. One of the biggest problems of our current space efforts is referred to as the tyranny of the rocket equation. The more cargo you want to launch into space, the more fuel you need. But then that fuel adds more weight, which needs yet more fuel to carry its weight into orbit. To say nothing of the greater structure and supporting material to contain it all.

Carrying even a few extra kilograms of weight to space can require huge amounts of additional fuel. This is why we use staged rockets to reach orbit at present. By shedding large amounts of structural weight at the end of each rocket stage, it’s possible to move the remaining rocket farther with less fuel.

If you could get to orbit while using zero fuel, it would be a total gamechanger. It wouldn’t just be cheaper to launch satellites or other cargoes. It would also make missions to the Moon or Mars far easier. Those rockets would no longer have to carry the huge amount of fuel required to escape Earth’s surface and get to orbit. Instead, they could just carry the lower amount of fuel required to go from Earth orbit to their final destination.

Of course, it’s not that simple. Reaching orbit isn’t just about going high above the Earth. If you just go straight up above the Earth’s surface, and then stop, you’ll just fall back down. If you want to orbit, you have to go sideways really, really fast.

Thus, an airship-to-orbit launch system would have to do two things. It would have to haul a payload up high, and then get it up to the speed required for its desired orbit. That’s where it gets hard. The minimum speed to reach a stable orbit around Earth is 7.8 kilometers per second (28,000 km/h or 17,500 mph). Thus, even if you’ve floated up very, very high, you still need a huge rocket or some kind of very efficient ion thruster to push your payload up to that speed. And you still need fuel to generate that massive delta-V (change in velocity).

For this reason, airships aren’t the perfect hack to reaching orbit that you might think. They’re good for floating about, and you can even go very, very high. But if you want to circle the Earth again and again and again, you better bring a bucketload of fuel with you.

Someone’s Working On It

Nevertheless, this concept is being actively worked on, but not by the usual suspects. Don’t look at NASA, JAXA, SpaceX, ESA, or even Roscosmos. Instead, it’s the work of the DIY volunteer space program known as JP Aerospace.

The organization has grand dreams of launching airships into space. Its concept isn’t as simple as just getting into a big balloon and floating up into orbit, though. Instead, it envisions a three-stage system.

The first stage would involve an airship designed to travel from ground level up to 140,000 feet. The company proposes a V-shaped design with an airfoil profile to generate additional lift as it moves through the atmosphere. Propulsion would be via propellers that are specifically designed to operate in the near-vacuum at those altitudes.

Once at that height, the first stage craft would dock with a permanently floating structure called Dark Sky Station. It would serve as a docking station where cargo could be transferred from the first stage craft to the Orbital Ascender, which is the craft designed to carry the payload into orbit.

The Orbital Ascender itself sounds like a fantastical thing on paper. The team’s current concept is for a V-shaped craft with a fabric outer shell which contains many individual plastic cells full of lifting gas. That in itself isn’t so wild, but the proposed size is. It’s slated to measure 1,828 meters on each side of the V — well over a mile long — with an internal volume of over 11 million cubic meters. Thin film solar panels on the craft’s surface are intended to generate 90 MW of power, while a plasma generator on the leading edge is intended to help cut drag. The latter is critical, as the craft will need to reach hypersonic speeds in the ultra-thin atmosphere to get its payload up to orbital speeds. To propel the craft up to orbital velocity, the team has been running test firings on its own designs for plasma thrusters.

The team at JP Aerospace is passionate, but currently lacks the means to execute their plans at full scale. Right now, the team has some experimental low-altitude research craft that are a few hundred feet long. Presently, Dark Sky Station and the Orbital Ascender remain far off dreams.

Realistically, the team hasn’t found a shortcut to orbit just yet. Building a working version of the Orbital Ascender would require lofting huge amounts of material to high altitude where it would have to be constructed. Such a craft would be torn to shreds by a simple breeze in the lower atmosphere. A lighter-than-air craft that could operate at such high altitudes and speeds might not even be practical with modern materials, even if the atmosphere is vanishingly thin above 140,000 feet.  There are huge questions around what materials the team would use, and whether the theoretical concepts for plasma drag reduction could be made to work on the monumentally huge craft.

Even if the craft’s basic design could work, there are questions around the practicalities of crewing and maintaining a permanent floating airship station at high altitude. Let alone how payloads would be transferred from one giant balloon craft to another. These issues might be solvable with billions of dollars. Maybe. JP Aerospace is having a go on a budget several orders of magnitude more shoestring than that.

One might imagine a simpler idea could be worth trying first. Lofting conventional rockets to 100,000 feet with balloons would be easier and still cut fuel requirements to some degree. But ultimately, the key challenge of orbit remains. You still need to find a way to get your payload up to a speed of at least 8 kilometers per second, regardless of how high you can get it in the air. That would still require a huge rocket, and a suitably huge balloon to lift it!

For now, orbit remains devastatingly hard to reach, whether you want to go by rocket, airship, or nuclear-powered paddle steamer. Don’t expect to float to the Moon by airship anytime soon, even if it sounds like a good idea.

According to [Asianometry], no one believed in the scanning electron microscope. No one, that is, except [Charles Oatley].The video below tells the whole story.

The Cambridge graduate built radios during World War II and then joined Cambridge as a lecturer once the conflict was over. [Hans Busch] demonstrated using magnets to move electron beams, which suggested the possibility of creating a lens, and it was an obvious thought to make a microscope that uses electrons.

After all, electrons can have smaller wavelength than light, so a microscope using electrons could — in theory — image at a higher resolution. [Max Knoll] and [Ernst Ruska], in fact, developed the transmission electron microscope or TEM.

The TEM works by passing an electron beam through a very thin sample and detecting it on the other side. However, the goal was to build an electron device that bounced electrons off an object — a SEM or scanning electron microscope. [Knoll] did build a device using this principle. However, it had a broad beam and could only magnify 10X or so, and it did not scan like a modern scope.

A practical SEM would wait for [Manfred Baron von Ardenne] in 1937. Working with Siemens (who, yes, owns Hackaday), he created a crude SEM. It took 20 minutes to create an image on a piece of film, so it wasn’t very practical. After two years, World War II broke out, and the work was lost.

At RCA, [Vladimir Zworykin] did some work on SEM, but abandoned the poorly-working device as TEM devices were more attractive. Then, in the 1950s, [Charles Oatley] decided he wanted to build an electron microscope for Cambridge.

Cambridge produced a very successful instrument that exploited secondary electrons and backscatter. They sold over 500 units. The video mentions that SEMs don’t require sample preparation, but they really don’t—they just don’t require thin slicing with a microtome. Semiconductor devices are often gold-coated to make the insulating surface conductive, for example, but that’s much easier to do than slicing very thin layers.

This is a great story of someone with a dream to create and took a shot. Granted, the time was right and the University was a bit easier to please than a conventional corporate overlord.

We are anxious for someone to create a DIY SEM that is buildable. For now, your best bet is to find a junker on the surplus market and fix it up.

Image credit: [Hannes Grobe] CC-BY-SA 2.5

It never fails. Lay down some kind of superlative — fastest, cheapest, smallest — around this place and someone out there says, “Hold my beer” and gets to work. In this case, it’s another, even simpler audio oscillator, this time with just a loudspeaker and a battery.

Attentive readers will recall the previous title holder was indeed pretty simple, consisting only of the mic and speaker from an old landline telephone handset wired in series with a battery. Seeing this reminded [Hydrogen Time] of a lucky childhood accident while experimenting with a loudspeaker, which he recreates in the video below. The BOM for this one is even smaller than the previous one — just a small speaker and a battery, plus a small scrap of solid hookup wire. The wire is the key; rather than connecting directly to the speaker terminal, it connects to the speaker frame on one end while the other is carefully adjusted to just barely touch the flexible wire penetrating the speaker cone on its way to the voice coil.

When power is applied with the correct polarity, current flows through the wire into the voice coil, which moves the cone and breaks the circuit. The speaker’s diaphragm resets the cone, completing the circuit and repeating the whole process. The loudspeaker makes a little click with each cycle, leading to a very rough-sounding oscillator. [Hydrogen Time] doesn’t put a scope on it, but we suspect the waveform would be a ragged square wave whose frequency depends on the voltage, the spring constant of the diaphragm, and the spacing between the fixed wire and the voice coil lead.

Yes, we realize this is stretching the definition of an audio oscillator somewhat, but you’ve got to admit it’s simple. Can you get it even simpler?

Another week in football, another VAR controversy to fill the column inches and rile up the fans. If you missed it, Coventry scored a last-minute winner in extra time in a crucial match—an FA Cup semi-final. Only, oh wait—computer says no. VAR ruled Haji Wright was offside, and the goal was disallowed. Coventry fans screamed that the system got it wrong, but no matter. Man United went on to win and dreams were forever dashed.

Systems like the Video Assistant Referee were brought in to make sport fairer, with the aim that they would improve the product and leave fans and competitors better off. And yet, years later, with all this technology, we find ourselves up in arms more than ever.

It’s my sincere belief that technology is killing sport, and the old ways were better. Here’s why.

The Old Days

For hundreds of years, we adjudicated sports the same way. The relevant authority nominated some number of umpires or referees to control the game. The head referee was the judge, jury, and executioner as far as rules were concerned. Players played to the whistle, and a referee’s decision was final. Whatever happened, happened, and the game went on.

It was not a perfect system. Humans make mistakes. Referees would make bad calls. But at the end of the day, when the whistle blew, the referee’s decision carried the day. There was no protesting it—you had to suck it up and move on.

This worked fine until the advent of a modern evil—the instant replay. Suddenly, stadiums were full of TV cameras that captured the play from all angles. Now and then, it would become obvious that a referee had made a mistake, with television stations broadcasting incontrovertible evidence to thousands of viewers across the land. A ball at Wimbledon was in, not out. A striker was on side prior to scoring. Fans started to groan and grumble. This wasn’t good enough!

And yet, the system hung strong. As much as it pained the fans to see a referee screw over their favored team, there was nothing to be done. The referee’s call was still final. Nobody could protest or overrule the call. The decision was made, the whistle was blown. The game rolled on.

Then somebody had a bright idea. Why don’t we use these cameras and all this video footage, and use it to double check the referee’s work? Then, there’ll never be a problem—any questionable decision can be reviewed outside of the heat of the moment. There’ll never be a bad call again!

Oh, what a beautiful solution it seemed. And it ruined everything.

The Villain, VAR

Enter the Video Assistant Referee (VAR). The system was supposed to bring fairness and accuracy to a game fraught with human error. The Video Assistant Referee was an official that would help guide the primary referee’s judgement based on available video evidence. They would be fed information from a cadre of Assistant Video Assistant Referees (AVARs) who sat in the stadium behind screens, reviewing the game from all angles. No, I didn’t make that second acronym up.

It was considered a technological marvel. So many cameras, so many views, so much slow-mo to pour over. The assembed VAR team would look into everything from fouls to offside calls. The information would be fed to the main referee on the pitch, and they could refer to a pitchside video replay screen if they needed to see things with their own eyes.

The key was that VAR was to be an assistive tool. It was to guide the primary referee, who still had the final call at the end of the day.

You’d be forgiven for thinking that giving a referee more information to do their job would be a good thing.  Instead, the system has become a curse word in the mouths of fans, and a scourge on football’s good name.

From its introduction, VAR began to pervert the game of football. Fans were soon decrying the system’s failures, as entire championships fell the wrong way due to unreliability in VAR systems. Assistant referees were told to hold their offside calls to let the video regime take over. Players were quickly chided for demanding video reviews time and again. New rules would see yellow cards issued for players desperately making “TV screen” gestures in an attempt to see a rivals goal overturned. Their focus wasn’t on the game, but on gaming the system in charge of it.

VAR achieves one thing with brutal technological efficiency: it sucks the life out of the game. The spontaneity of celebrating a goal is gone. Forget running to the stands, embracing team mates, and punching the air in sweet elation. Instead, so many goals now lead to minute-long reviews while the referee consults with those behind the video screens and reviews the footage. Fans sit in a stunted silence, sitting in the dreaded drawn-out suspense of “goal” or “no goal.”

The immediacy and raw emotion of the game has been shredded to pieces. Instead of jumping in joy, fans and players sit waiting for a verdict from an unseen, remote official. The communal experience of instant joy or despair is muted by the system’s mere presence. What was once a straightforward game now feels like a courtroom drama where every play can be contested and overanalyzed.

It’s not just football where this is a problem, either. Professional cricket is now weighed down with microphone systems to listen out for the slightest snick of bat on ball. Tennis, weighed down by radar reviews of line calls. The interruptions never cease—because it’s in every player’s interest to whip out the measuring tape whenever it would screw over their rival. The more technology, the more reviews are made, and the further we get from playing out the game we all came to see.

Making Things Right

With so much footage to review, and so many layers of referees involved, VAR can only slow football down. There’s no point trying to make it faster or trying to make it better. The correct call is to scrap it entirely.

As it stands, good games of football are being regularly interrupted by frustrating video checks. Even better games are being ruined when the VAR system fails or a bad call still slips through. Moments of jubilant celebration are all too often brought to naught when someone’s shoelace was thought to be a whisker’s hair ahead of someone’s pinky toe in a crucial moment of the game.

Yes, bad calls will happen. Yes, these will frustrate the fans. But they will frustrate them far less than the current way of doing things. It’s my experience that fans get over a bad call far faster when it’s one ref and and a whistle. When it’s four referees, sixteen camera angles, and a bunch of lines on the video screen? They’ll rage for days that this mountain of evidence suggests their team was ripped off. They won’t get over it. They’ll moan about it for years.

Let the referees make the calls. Refereeing is an art form. A good referee understands the flow of the game, and knows when to let the game breathe versus when to assert control. This subtle art is being lost to the halting interruptions of the video inspection brigade.

Football was better before. They were fools to think they could improve it by measuring it to the nth degree. Scrap VAR, scrap the interruptions. Put it back on the referees on the pitch, and let the game flow.

What’s the simplest audio frequency oscillator you can imagine? There’s the 555, of course, and we can think of a few designs using just two transistors or even a few with just one. But how about an oscillator with no active components? Now there’s a neat trick.

Replicating [Stelian]’s “simplest audio oscillator on the Internet” might take some doing on your part, since it relies on finding an old telephone. Like, really old — you’ll need one with the carbon granule cartridge in the handset, along with the speaker. Other than that, all you’ll need is a couple of 1.5-volt batteries, wiring everything in one big series loop, and placing the microphone and speaker right on top of each other. Apply power and you’re off to the races. [Stelian]’s specific setup yielded a 2.4-kHz tone that could be altered a bit by repositioning the speaker relative to the mic. On the oscilloscope, the waveform is a pretty heavily distorted sine wave.

It’s a bit of a mystery to [Stelian] as to how this works without something to provide at least a little gain. Perhaps the enclosure of the speaker or the mic has a paraboloid shape that amplifies the sound just enough to kick things off? Bah, who knows? Let the hand-waving begin!