Author: Jenny List

3286 Articles

A Trio Of Photodiodes Make A Radiation Detector

August 6, 2021 by 44 Comments

The instinctive reaction when measuring nuclear radiation is to think of a Geiger counter, as the low-pressure gas tube detectors have entered our popular culture through the Cold War. A G-M tube is not the only game in town though, and even the humble photodiode can be pressed into service. [Robert] gives us a good example, with a self-contained radiation detector head that uses a trio of BPW34s to do the job.

At its heart is a transimpedance amplifier, a not-often-seen op-amp configuration that serves as a very high gain current-to-voltage converter. This produces a spike for every radiation event detected by the diodes, which is fed to a comparator to produce a logic pulse. The diodes require a significant bias voltage, for which he’s used 48 V from a stack of 12 V photographic dry cells rather than a boost converter or other potentially noisy power supply. Such a sensitive high-gain device needs to be appropriately shielded, so the whole circuit is contained in a diecast box with a foil window to allow radiation to reach the diodes.

This isn’t the first BPW34-based radiation detector we’ve seen, so perhaps before looking for a Cold War era relic for our radiation experiments we should be looking in a semiconductor catalogue instead.

New Part Day: An ESP With ZigBee

August 4, 2021 by 26 Comments

It seems that the folks at Espressif are doing their best to produce chips to fit every possible niche in the microcontroller-with-radio market, because here comes news of their latest chip bearing the ESP32 name: a single-core 96MHz RISC-V part with built-in IEEE 802.15.4 to support ZigBee 3.x and Thread 1.x. The ESP32-H2 is not the most powerful of the Espressif line-up, but it will find its place in home automation products and projects.

The ESP32-H2 joins a multitude of other IEEE 802.15.4 devices from manufacturers such as Microchip, ST, NXP, and Nordic in an increasingly crowded marketplace, so what can if offer that the others can’t? If previous ESP chips are anything to go by we’d expect it to compete on price as well as the obvious attraction for developers used to working with other Espressif products. We look forward as always to seeing what you do with it.

Semiconductor Shortage? Never Mind That, There’s A Vacuum Shortage!

August 4, 2021 by 28 Comments

As those of us who work in electronics are grappling with a semiconductor shortage making common devices unobtainable and less common ones very expensive, it’s worth noting that there’s another supply crunch playing out elsewhere in the electronics industry. It’s not one that should trouble most readers but it’s a vexing problem in the guitar amp business, as guitar.com reports. At its root is the Chinese Shuguang factory, which it is reported has been forced to close down and move its operations. There’s nothing about this on the Shuguang website, so we hope that the plant has been relocated successfully and production will resume.

The specialist audio market that forms the lion’s share of tube customers in 2021 is a relatively tiny corner of the electronics business, but it’s interesting to note that the three major plants which supply it, in Slovakia, Russia, and China, are still not enough to prevent it being vulnerable when one of them fails. The likelihood of a fourth tube plant emerging somewhere else in the 2020s to take up the slack is not high, but it’s evident that the demand remains healthy enough.

If you’d like to know more about the supply of new vacuum tubes, we went into the subject in greater detail last year.

Ostrich Robot Machine-Learns Itself To 5K

August 1, 2021 by 43 Comments

Ever since humanity has grasped the idea of a robot, we’ve wanted to imagine them into walking humanoid form. But making a robot walk like a human is not an easy task, and even the best of them end up with the somewhat shuffling gait of a Honda Asimo rather than the graceful poise of a balerina. Only in recent years have walking robots appeared to come of age, and then not by mimicking the human gait but something more akin to a bird.

We’ve seen it in the Boston Dynamics models, and also now in a self-balancing two-legged robot developed at Oregon State University that has demonstrated its abilities by completing an unaided 5 km run having used its machine learning skills to teach itself to run from scratch. It’s believed to be the first time a robot has achieved such a feat without first being programmed for the specific task.

The university’s PR piece envisages a time in which walking robots of this type have become commonplace, and when humans interact with them on a daily basis. We can certainly see that they could perform a huge number of autonomous outdoor tasks that perhaps a wheeled robot might find to be difficult, so maybe they have a bright future. Decide for yourself, after watching the video below the break.

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Stereo Recording Made Easy With A 3D-Printed Mount

August 1, 2021 by 15 Comments

When making a recording it can be surprisingly difficult to capture a good stereo image. A well-known technique is the ORTF microphone arrangement in which two cardoid microphones sit at 110 degrees to each other and 17cm apart, and thus pick up a readily reproducible stereo separation. It’s something that we’ve been known to do in our student days with a pair of Shure SM58s and a stack of Post Office elastic bands, but [marsairforce] has done a much nicer job with a very neat 3D-printed microphone clip.

Designed in OpenSCAD, the first iteration printed on a resin printer proved to be too brittle for the task, so a second version was printed on an FDM machine. This incorporated significant strengthening, as well as a screw mount for a microphone stand. The result is an extremely useful and cheap addition to any recording set-up, and anyone who has wrestled with achieving a good stereo image will appreciate it. You can see some of what went into it in the video below the break.

If this is your field of interest, you might also wish to look at a binaural microphone.

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An Epic Tale Of Reset Line Detective Work

July 31, 2021 by 10 Comments

The Pine64 folks have given us so many tasty pieces of hardware over the last few years, but it’s fair to say that their products are for experimenters rather than consumers and can thus be a little rough around the edges at times. Their Clusterboard for example is a Mini-ITX PCB which takes up to seven of their SOPINE A64 compute modules, and networks them for use as a cluster by means of an onboard Gigabit Ethernet switch. It’s a veritable powerhouse, but it has an annoying bug in that it appears reluctant to restart when told. [Eric Draken] embarked upon a quest to fix this problem, and while he got there in the end his progress makes for a long and engrossing read.

We journey through the guts of the board and along the way discover a lot about how reset signals are generated. The eventual culprit is a back-EMF generated through the reset distribution logic itself causing the low-pulled line to never quite descend into logic 0 territory once it has been pulled high, and the solution an extremely simple application of a diode. For anyone who wishes to learn about logic level detective work it’s well worth a look. Meanwhile the board itself with its 28 ARM cores appears to have plenty of potential. It’s even a board we’ve mentioned before, in a personal supercomputer project.

A Satellite Upconverter Need Not Be Impossible To Make

July 31, 2021 by 8 Comments

Those readers whose interests don’t lie in the world of amateur radio might have missed one of its firsts, for the last year or two amateurs have had their own geostationary satellite transponder. Called Es’hail-2 / AMSAT Phase 4-A / Qatar-OSCAR 100, it lies in the geostationary orbit at 25.9° East and has a transponder with a 2.4 GHz uplink and a 10.489 GHz downlink. Receiving the downlink is possible with an LNB designed for satellite TV, but for many hams the uplink presents a problem. Along comes [PY1SAN] from Brazil with a practical and surprisingly simple solution using a mixture of odd the shelf modules and a few hand-soldered parts.

An upconverter follows a simple enough principle, the radio signal is created at a lower frequency (in this case by a 435 MHz transmitter) and mixed with a signal from a local oscillator. A filter then picks out the mixer product — the sum of the two — and amplifies it for transmission. [PY1SAN]’s upconverter takes the output from the transmitter and feeds it through an attenuator to a MiniCircuits mixer module which takes its local oscillator via an amplifier from a signal generator module. The mixer output goes through a PCB stripline filter through another amplifier module to a power amplifier brick, and thence via a co-ax feeder to a dish-mounted helical antenna.

The whole thing is a series of modules joined by short SMA cables, and could probably be largely sourced from a single AliExpress order without too much in the way of expenditure. It’s by no means easy to get on air via Es’hail-2, but at least now it need not be impossibly expensive. Even the antenna can be made without breaking the bank.

We covered Es’hail-2 when it first appeared. May it long provide radio amateurs with the chance to operate worldwide with homebrew microwave equipment!

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