Know Audio: Amplifier Nuts And Bolts

August 24, 2021 by Jenny List 31 Comments

As we’ve followed a trail through Hi-Fi and audio systems from the listener’s ear towards the music source, we’ve reached the amplifier. In our previous article we gave a first introduction to distortion and how some amplifier characteristics can influence it, and here we’ll continue along that path and look at the amplifier itself. What types of audio amplifier circuits will you encounter, and what are their relative merits and disadvantages?

A Few Amplifier Basics

Horowitz and Hill's Transistor Man — Horowitz and Hill’s Transistor Man

If you know anything about a transistor, it’s probably that it’s a three terminal device whose output pin forms part of a potential divider whose state is dependent on what is presented to its input pin. The Art of Electronics had it as a cartoon of a man standing inside a bipolar transistor and adjusting a variable resistor between collector and emitter while watching an ammeter on the base.

Properly biased in its conducting range, a transistor can behave as a linear device, in which the potential divider voltage moves in response to the input in a linear relationship, and thus the voltage on the output is an amplified version of the voltage on the output. This is the simplest of transistor amplifiers, and because different types of amplifier are referred to by lettered classes, it’s known as a class A amplifier. Continue reading “Know Audio: Amplifier Nuts And Bolts” →

Drone Hits Plane — And This Time It’s A Real (Police) One!

August 23, 2021 by Jenny List 70 Comments

Over the years we’ve brought you many stories that follow the world of aviation as it struggles with the arrival of multirotors. We’ve seen phantom drone encounters cause panics and even shut airports, but it’s been vanishingly rare for such a story to have a basis in evidence. But here we are at last with a drone-aircraft collision story that involves a real drone. This time there’s a twist though, instead of one piloted by a multirotor enthusiast that would prompt a full-on media panic, it’s a police drone that collided with a Cesna landing at Toronto’s Buttonville airport. The York Regional Police craft was part of an operation unrelated to the airport, and its collision with the aircraft on August 10th was enough to make a significant dent in its engine cowling. The police are reported to be awaiting the result of an official investigation in the incident.

This is newsworthy in itself because despite several years and significant resources being devoted to the problem of drones hitting planes, demonstrable cases remain vanishingly rare. The machine in this case being a police one will we expect result in many fewer column inches for the event than had it been flown at the hands of a private multirotor pilot, serving only to heighten the contrast with coverage of previous events such as the Gatwick closure lacking any drone evidence.

It’s picking an easy target to lay into the Your Regional Police over this incident, but it is worth making the point that their reaction would have been disproportionately larger had the drone not been theirs. The CTV news report mentions that air traffic regulators were unaware of the drone’s presence:

NAV Canada, the country’s air navigation service provider, had not been notified about the YRP drone, Transport Canada said.

Given the evident danger to aviation caused by their actions it’s not unreasonable to demand that the officers concerned face the same penalties as would any other multirotor pilot who caused such an incident. We aren’t holding our breath though.

Header image: Raysonho @ Open Grid Scheduler / Grid Engine, CC0.

Electromagnetic Interference For Fun And Profit

August 22, 2021 by Jenny List 24 Comments

There was an urban legend back in the days of mechanical electricity meters, that there were “lucky” appliances that once plugged in would make the meter go backwards. It probably has its origin in the interaction between a strongly capacitive load and the inductance of the coils in the meter but remains largely apocryphal for the average home user. That’s not to say that a meter can’t be fooled into doing strange things though, as a team at the University of Twente have demonstrated by sending some more modern meters running backwards. How have they performed this miracle? Electromagnetic interference from a dimmer switch.

Reading the paper (PDF link) it becomes apparent that this behavior is the result of the dimmer switch having the ability to move the phase of the current pulse with respect to the voltage cycle. AC dimmers are old hat in 2021, but for those unfamiliar with their operation they work by switching themselves on only for a portion of the mains cycle. The cycle time is varied by the dimming control. Thus the time between the mains zero-crossing point and their turn-on point is equivalent to a phase shift of the current waveform. Since electricity meters depend heavily upon this phase relationship, their performance can be tuned. Perhaps European stores will now brace themselves for a run on dimmer switches.

If you’re curious about these old-style dimmers, take a look at some of their basic functionality.

Thanks [Dorus] for the tip.

Traditional Analogue And An FPGA Make This Junkbox HF Receiver A Bit Special

August 20, 2021 by Jenny List 2 Comments

We will have all at some point seen a fascinating project online, only to find not enough information to really appreciate and understand it. Such a project came [Bill Meara]’s way over at the SolderSmoke podcast, and he was fortunately able to glean more from its creator. What [Tom] had made from junkbox parts was a fairly traditional analogue receiver for the 20m amateur band which would be quite an achievement in itself, but what makes it special is its use of an FPGA to augment the analogue tuning.

A traditional analogue radio has a local oscillator which is mixed with the signal from the antenna, and an intermediate frequency of the difference between oscillator and desired signal is filtered from the result and amplified. The oscillator on older receivers would have used a free running tuned circuit, while a newer device might use a phase-locked loop to derive a stable frequency from a crystal.

What [Tom]’s receiver does is take a free-running traditional receiver and use the FPGA as a helper. It has a frequency meter that drives the display, but it also uses the measured figure to adjust the oscillator and keep it on frequency. It has two modes; while tuning it’s a traditional analogue receiver, but when left alone the FPGA stops it drifting. We like it, it’s definitely a special project.

We’ve featured a lot of radio receivers over the years, and this certainly isn’t the only one that’s a bit unconventional.

A 3D-Printed Block And Tackle For Those Annoying Lifts

August 19, 2021 by Jenny List 11 Comments

Perhaps the humble block and tackle — multiple parallel pulleys to reduce the effort of lifting — is not such a common sight as it once was in this age of hydraulic loaders, but it remains a useful mechanism for whenever there is a lifting task. To that end [semi] has produced a 3D-printed block and tackle system, which as can be seen in the video below the break, makes lifting moderately heavy loads a breeze.

It’s a simple enough mechanism, with the 3D printer supplying pulleys, chocks, and attachment points, and steel bolts holding everything together. It’s demonstrated with a maximum weight of 20 kilograms (44 pounds), and though perhaps some hesitation might be in order before trusting it with 200 Kg of engine, we’re guessing it would be capable of much more that what we’re shown. Should you wish to give it a try, the files can be found on Thingiverse.

The block and tackle should hold a special place in the hearts of engineers everywhere, as the first product manufactured using mass-production techniques. It shouldn’t be a surprise that this early-19th century factory came from the work of Marc Brunel, father of Isambard Kingdom Brunel who we’ve made the subject of a previous Hackaday piece.

Continue reading “A 3D-Printed Block And Tackle For Those Annoying Lifts” →

Take Note: An E-Paper Tablet From Pine64

August 17, 2021 by Jenny List 20 Comments

Over the years we’ve seen a variety of interesting pieces of hardware emerging from the folks at Pine64, so it’s always worth a second look when they announce a new product. This time it’s the PineNote, a tablet that packs the same Rockchip RK3566 as used in the company’s Quartz64 single board computers behind a 10.1″ 1404 x 1872 16-tone greyscale e-paper screen.

Fitted with 4 GB of LPDDR4 RAM and 128 GB eMMC flash storage, it will feature the same Linux support as previous Pine64 products, with the slight snag of the display driver not yet being complete for 5.xx kernels. They are thus at pains to point out that this is not a ready-to-go consumer device and that early adopters will be expected to write code rather than notes on it.

That last sentence sums up Pine64’s offering perfectly, they produce interesting hardware with open-source support, but sometimes the path from hardware release to stable and usable product can be a rocky one. If you’re interested in hardcore hacking of an e-paper tablet, then you may want to be an early adopter. Otherwise, hang back for a while and buy one once some of the bugs have been ironed out. Meanwhile you can see the whole update in the video below; it has a few other things including a nifty keyboard for the PinePhone.

We’ve mentioned Pine64 a few times over the years, it’s worth noting that their products also lie outside the realm of Linux boxen.

Continue reading “Take Note: An E-Paper Tablet From Pine64” →

The Zeloof Z2 Intergrated Circuit Has 100 Transistors

August 14, 2021 by Jenny List 31 Comments

Back in 2018 we reported on the first silicon integrated circuit to be produced in a homemade chip fab. It was the work of [Sam Zeloof], and his Z1 chip was a modest six-transistor amplifier. Not one to rest on his laurels, he’s back with another chip, this time the Z2 is a hundred-transistor array. The Z2 occupies about a quarter of the area of the previous chip and uses a 10µm polysilicon gate process as opposed to the Z1’s metal gates. It won’t solve the global chip shortage, but this is a major step forward for anyone interested in building their own semiconductors.

The transistors themselves are FETs, and [Sam] is pleased with their consistency and characteristics. He’s not measured his yield on all samples, but of the twelve chips made he says he has one fully functional chip and a few others with at least 80% functionality. The surprise is that his process is less complex than one might expect, which he attributes to careful selection of a wafer pre-treated with the appropriate oxide layer.

You can see more about the Z2 in the video below the break. Meanwhile, should you wish to learn more about the Z1 you can see [Sam’s] Hackaday Superconference talk on the subject. We’re looking forward to the Z3 when it eventually arrives, with bated breath!

Continue reading “The Zeloof Z2 Intergrated Circuit Has 100 Transistors” →