A Trio Of Photodiodes Make A Radiation Detector

August 6, 2021 by Jenny List 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.

SMART Response XE Turned Pocket BASIC Playground

June 29, 2021 by Tom Nardi 13 Comments

Ever since the SMART Response XE was brought to our attention back in 2018, we’ve been keeping a close lookout for projects that make use of the Arduino-compatible educational gadget. Admittedly it’s taken a bit longer than we’d expected for the community to really start digging into the capabilities of the QWERTY handheld, but occasionally we see an effort like this port of BASIC to the SMART Response XE by [Dan Geiger] that reminds us of why we were so excited by this device to begin with.

This project combines the SMART Response XE support library by [Larry Bank] with Tiny BASIC Plus, which itself is an update of the Arduino BASIC port by [Michael Field]. The end result is a fun little BASIC handheld that has all the features and capabilities you’d expect, plus several device-specific commands that [Dan] has added such as BATT to check the battery voltage and MSAVE/MLOAD which will save and load BASIC programs to EEPROM.

To install the BASIC interpreter to your own SMART Response XE, [Dan] goes over the process of flashing it to the hardware using an AVR ISP MkII and a few pogo pins soldered to a bit of perboard. There are holes under the battery door of the device that exposes the programming pads on the PCB, so you don’t even need to crack open the case. Although if you are willing to crack open the case, you might as well add in a CC1101 transceiver so the handy little device can double as a spectrum analyzer.

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Plasma Discharges Show You Where The Radiation Is

February 23, 2021 by Dan Maloney 11 Comments

Depending on the context of the situation, the staccato clicks or chirps of a Geiger counter can be either comforting or alarming. But each pip is only an abstraction, an aural indication of when a particle or ray of ionizing radiation passed through a detector. Knowing where that happened might be important, too, under the right circumstances.

While this plasma radiation detector is designed more as a demonstration, it does a pretty good job at localizing where ionization events are happening. Designed and built by [Jay Bowles], the detector is actually pretty simple. Since [Jay] is the type of fellow with plenty of spare high-voltage power supplies lying around, he took a 6 kV flyback supply from an old build and used it here. The detector consists of a steel disk underneath a network of fine wires. Perched atop a frame of acrylic and powered by a 9 V battery, the circuit puts high-voltage across the plate and the wires. After a substantial amount of tweaking, [Jay] got it adjusted so that passing alpha particles from a sample of americium-241 left an ionization trail between the conductors, leading to a miniature lightning bolt.

In the video below, the detector sounds very similar to a Geiger counter, but with the added benefit of a built-in light show. We like the way it looks and works, although we’d perhaps advise a little more caution to anyone disassembling a smoke detector. Especially if you’re taking apart Soviet-era smoke alarms — you might get more than you bargained for.

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Civil Defense Disco Ball Rocks Ground Zero

January 15, 2021 by Tom Nardi 9 Comments

Old Civil Defense survey meters like the V-715 are interesting conversation starters, but of very little practical use today. These devices were intended to be a sort of litmus test that survivors of a nuclear blast could use to determine when it was safe to venture out of their radiation shelter: if the needle on the meter moves, even when it’s on the most sensitive setting, you should probably go back inside. Since [Hamilton Karl] would (hopefully) never need such an indicator, he decided to have a little fun with this Cold War holdover and turn it into a Disco Containment Unit.

Technical details are a little sparse on this one, but we can infer most of it just from the pictures. In place of the original meter [Hamilton] has mounted a tiny mirrored ball inside of a protective cage, which is spun by a geared motor that’s occupying the space that used to be taken up by the ion chamber.

A handful of Adafruit NeoPixel RGB LEDs, an Arduino Nano, and a few switches to control it all round out the functional aspects of the build, and a new disco-themed trefoil replaces the original Civil Defense logo on the side. The project page mentions there’s a piezo buzzer onboard that performs a stirring rendition of “Stayin’ Alive” by the Bee Gees, but alas there’s no video that shows it in action.

Thanks to the rugged construction and built-in handle of these old survey meters, [Hamilton] can now take the party with him wherever he goes. Not that he can really go anywhere with this whole global pandemic hanging over our heads, but at least he’ll be ready when things start trending towards normal. In a way the device’s functionality has now been reversed from how it originally worked, since the meter going wild will now be an indicator that its safe to come out.

While the V-715 isn’t of much use outside of a post-apocalyptic hellscape, the V-700 is actually a proper Geiger counter that’s still useful for surveying or research. An important distinction to remember if you ever get a chance to snap one of them up at a swap meet or flea market. Whenever we can start having those again, anyway.

Still Working After All These Years: The Voyager Plasma Wave Subsystem

December 31, 2020 by Dan Maloney 49 Comments

NASA is always keen to highlight the space agency’s many successes, and rightly so — those who pay for these expensive projects have a right to know what they’re getting for their money. And so the news was recently sprinkled with stories of the discovery of electron bursts beyond the edge of our solar system, caused by shock waves from coronal mass ejection (CME) from our Sun reflecting and accelerating electrons in interstellar plasmas. It’s a novel mechanism and an exciting discovery that changes a lot of assumptions about what happens out in the lonely space outside of the Sun’s influence.

The recent discovery is impressive in its own right, but it’s even more stunning when you dig into the details of how it was made: by the 43-year-old Voyager spacecraft, each now about 17 light-hours away from Earth, and each carrying an instrument so simple and efficient that they’re still working all after this time — and which very nearly were left out of the mission’s science payload.

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A Tentacle That’s A Work Of Art

September 15, 2020 by Jenny List 8 Comments

We all bring our own areas of expertise to our work when we build the projects that find their way in front of Hackaday writers, for instance a software developer brings clever brains to their microcontroller, or an electronic engineer might bring a well-designed piece of circuitry. [Yvo de Haas] is a mechanical engineer, and it’s pretty clear from his animatronic tentacle that he has used his expertise in that field to great effect.

If you think it looks familiar then some readers may recall that we saw a prototype model back in February at Hacker Hotel 2020. In those last weeks before the pandemic hit us with lockdowns and cancellations he’d assembled a very worthy proof of concept, and from what we can see from his write-up and the video below he’s used all the COVID time to great effect in the finished product. Back in February the control came via a pair of joysticks, we’re particularly interested to see his current use of a mini tentacle as a controller.

At its heart is a linkage of 3D-printed anti-parallelograms linked by gears, with cables holding the tension and controlling the movement of the tentacle from a set of winches. The design process is detailed from the start and makes a fascinating read, and with its gripper on the end we can’t wait for an event that goes ahead without cancellation at which we can see the tentacle for real.

If you’d like to see more of [Yvo]’s work, maybe you remember his wearable and functioning Pip-Boy, and his working Portal turret.

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Hackaday Links: August 23, 2020

August 23, 2020 by Dan Maloney 14 Comments

Apple, the world’s first trillion-dollar company — give or take a trillion — has built a bit of libertarian cachet by famously refusing to build backdoors into their phones, despite the entreaties of the federal government. So it came as a bit of a surprise when we read that the company may have worked with federal agents to build an “enhanced” iPod. David Shayer says that he was one of three people in Apple who knew about the 2005 program, which was at the behest of the US Department of Energy. Shayer says that engineers from defense contractor Bechtel, seemed to want to add sensors to the first-generation iPod; he was never clued in fully but suspects they were adding radiation sensors. It would make sense, given the climate in the early 2000s, walking down the street with a traditional Geiger counter would have been a bit obvious. And mind you, we’re not knocking Apple for allegedly working with the government on this — building a few modified iPods is a whole lot different than turning masses of phones into data gathering terminals. Umm, wait…

A couple of weeks back, we included a story about a gearhead who mounted a GoPro camera inside of a car tire. The result was some interesting footage as he drove around; it’s not a common sight to watch a tire deform and move around from the inside like that. As an encore, the gearhead in question, Warped Perception, did the same trick bit with a more destructive bent: he captured a full burnout from the inside. The footage is pretty sick, with the telltale bubbles appearing on the inside before the inevitable blowout and seeing daylight through the shredded remains of the tire. But for our money, the best part is the slo-mo footage from the outside, with the billowing smoke and shredded steel belts a-flinging. We appreciate the effort, but we’re sure glad this guy isn’t our neighbor.

Speaking of graphic footage, things are not going well for some remote radio sites in California. Some towers that host the repeaters used by public service agencies and ham radio operators alike have managed to record their last few minutes of life as wildfires sweep across the mountains they’re perched upon. The scenes are horrific, like something from Dante’s Inferno, and the burnover shown in the video below is terrifying; watch it and you’ll see a full-grown tree consumed in less than 30 seconds. As bad as the loss of equipment is, it pales in comparison to what the firefighters face as they battle these blazes, but keep in mind that losing these repeaters can place them in terrible jeopardy too.

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