You have a closed box. There may be a live cat inside, but you won’t know until you open the box. For most people, this situation is a theoretical conundrum that probes the foundations of quantum mechanics. For me, however, it’s a pressing practical problem, not least because physics completely skates over the vital issue of how annoyed the cat will be when the box is opened. But fortunately, engineering comes to the rescue, in the form of a new US $50 maker-friendly pulsed coherent radar sensor from SparkFun.

Perhaps I should back up a little bit. Working from home during the pandemic, my wife and I discovered a colony of feral cats living in the backyards of our block in New York City. We reversed the colony’s growth by doing trap-neuter-return (TNR) on as many of its members as we could, and we purchased three Feralvilla outdoor shelters to see our furry neighbors through the harsh New York winters. These roughly cube-shaped insulated shelters allow the cats to enter via an opening in a raised floor. A removable lid on top allows us to replace straw bedding every few months. It’s impossible to see inside the shelter without removing the lid, meaning you run the risk of surprising a clawed predator that, just moments before, had been enjoying a quiet snooze.

The enclosure for the radar [left column] is made of basswood (adding cat ears on top is optional). A microcontroller [top row, middle column] processes the results from the radar module [top row, right column] and illuminates the LEDs [right column, second from top] accordingly. A battery and on/off switch [bottom row, left to right] make up the power supply.James Provost

Feral cats respond to humans differently than socialized pet cats do. They see us as threats rather than bumbling servants. Even after years of daily feeding, most of the cats in our block’s colony will not let us approach closer than a meter or two, let alone suffer being touched. They have claws that have never seen a clipper. And they don’t like being surprised or feeling hemmed in. So I wanted a way to find out if a shelter was occupied before I popped open its lid for maintenance. And that’s where radar comes in.

SparkFun’s pulsed coherent radar module is based on Acconeer’s low-cost A121 sensor. Smaller than a fingernail, the sensor operates at 60 gigahertz, which means its signal can penetrate many common materials. As the signal passes through a material, some of it is reflected back to the sensor, allowing you to determine distances to multiple surfaces with millimeter-level precision. The radar can be put into a “presence detector” mode—intended to flag whether or not a human is present—in which it looks for changes in the distance of reflections to identify motion.

As soon as I saw the announcement for SparkFun’s module, the wheels began turning. If the radar could detect a human, why not a feline? Sure, I could have solved my is-there-a-cat-in-the-box problem with less sophisticated technology, by, say, putting a pressure sensor inside the shelter. But that would have required a permanent setup complete with weatherproofing, power, and some way of getting data out. Plus I’d have to perform three installations, one for each shelter. For information I needed only once every few months, that seemed a bit much. So I ordered the radar module, along with a $30 IoT RedBoard microcontroller. The RedBoard operates at the same 3.3 volts as the radar and can configure the module and parse its output.

If the radar could detect a human, why not a feline?

Connecting the radar to the RedBoard was a breeze, as they both have Qwiic 4-wire interfaces, which provides power along with an I2C serial connection to peripherals. SparkFun’s Arduino libraries and example code let me quickly test the idea’s feasibility by connecting the microcontroller to a host computer via USB, and I could view the results from the radar via a serial monitor. Experiments with our indoor cats (two defections from the colony) showed that the motion of their breathing was enough to trigger the presence detector, even when they were sound asleep. Further testing showed the radar could penetrate the wooden walls of the shelters and the insulated lining.

The next step was to make the thing portable. I added a small $11 lithium battery and spliced an on/off switch into its power lead. I hooked up two gumdrop LEDs to the RedBoard’s input/output pins and modified SparkFun’s sample scripts to illuminate the LEDs based on the output of the presence detector: a green LED for “no cat” and red for “cat.” I built an enclosure out of basswood, mounted the circuit boards and battery, and cut a hole in the back as a window for the radar module. (Side note: Along with tending feral cats, another thing I tried during the pandemic was 3D-printing plastic enclosures for projects. But I discovered that cutting, drilling, and gluing wood was faster, sturdier, and much more forgiving when making one-offs or prototypes.)

The radar sensor sends out 60-gigahertz pulses through the walls and lining of the shelter. As the radar penetrates the layers, some radiation is reflected back to the sensor, which it detects to determine distances. Some materials will reflect the pulse more strongly than others, depending on their electrical permittivity. James Provost

I also modified the scripts to adjust the range over which the presence detector scans. When I hold the detector against the wall of a shelter, it looks only at reflections coming from the space inside that wall and the opposite side, a distance of about 50 centimeters. As all the cats in the colony are adults, they take up enough of a shelter’s volume to intersect any such radar beam, as long as I don’t place the detector near a corner.

I performed in-shelter tests of the portable detector with one of our indoor cats, bribed with treats to sit in the open box for several seconds at a time. The detector did successfully spot him whenever he was inside, although it is prone to false positives. I will be trying to reduce these errors by adjusting the plethora of available configuration settings for the radar. But in the meantime, false positives are much more desirable than false negatives: A “no cat” light means it’s definitely safe to open the shelter lid, and my nerves (and the cats’) are the better for it.

Oh me, oh mesh! Many journalists in this business have at least one pet technology that’s never taken off in the way they think it should. Hypersonic passenger planes, deep-sea thermal-energy power plants, chording keyboards—all have their adherents, eager to jump at the chance of covering their infatuation. For me, it’s mesh radio systems, which first captivated me while I was zipping around downtown Las Vegas back in 2004. In that pre-smartphone, practically pre-3G era, I was testing a mesh network deployed by a local startup, downloading files at what was then a mind-boggling rate of 1.5 megabits per second in a moving car. Clearly, mesh and its ad hoc decentralized digital architecture were the future of wireless comms!

Alas, in the two decades since, mesh networking has been slow to displace conventional radio systems. It’s popped up on a small scale in things like the Zigbee wireless protocol for the Internet of Things, and in recent years it’s become common to see Wi-Fi networks extended using mesh-based products such as the Eero. But it’s still a technology that I think has yet to fulfill its potential. So I’ve been excited to see the emergence of the open-source Meshtastic protocol, and the proliferation of maker-friendly hardware around it. I had to try it out myself.

Meshtastic is built on top of the increasingly popular LoRa (long-range) technology, which relies on spread-spectrum methods to send low-power, low-bandwidth signals over distances up to about 16 kilometers (in perfect conditions) using unlicensed radio bands. Precise frequencies vary by region, but they’re in the 863- to 928-megahertz range. You’re not going to use a Meshtastic network for 1.5-Mb/s downloads, or even voice communications. But you can use it to exchange text messages, location data, and the like in the absence of any other communications infrastructure.

The stand-alone communicator [bottom of illustration] can be ordered assembled, or you can build your own from open-source design files. The RAKwireless Meshtastic development board is based around plug-in modules, including the carrier board, an environmental sensor, I/O expander board, radio module, OLED screen, and LoRa and Bluetooth modules.James Provost

To test out text messaging, I bought three HelTXT handheld communicators for US $85 each on Tindie. These are essentially just a battery, keyboard, small screen, ESP32-based microcontroller, and a LoRa radio in a 3D-printed enclosure. My original plan was to coerce a couple of my fellow IEEE Spectrum editors to spread out around Manhattan to get a sense of the range of the handhelds in a dense urban environment. By turning an intermediate device on and off, we would demonstrate the relaying of signals between handhelds that would otherwise be out of range of each other.

This plan was rendered moot within a few minutes of turning the handhelds on. A test “hello” transmission was greeted by an unexpected “hey.” The handhelds’ default setting is to operate on a public channel, and my test message had been received by somebody with a Meshtastic setup about 4 kilometers away, across the East River. Then I noticed my handheld had detected a bunch of other Meshtastic nodes, including one 5 km away at the southern tip of Manhattan. Clearly, range was not going to be an issue, even with a forest of skyscrapers blocking the horizon. Indeed, given the evident popularity of Meshtastic, it was going to be impossible to test the communicators in isolation! (Two Spectrum editors live in Minnesota, so I hope to persuade them to try the range tests with fewer Meshtastic users per square kilometer.)

I turned to my next test idea—exchanging real-time data and commands via the network. I bought a $25 WisBlock meshtastic starter kit from RAKwireless, which marries a LoRA radio/microcontroller and an expansion board. This board can accommodate a selection of cleverly designed and inexpensive plug-in hardware modules, including sensors and displays. The radio has both LoRa and Bluetooth antennas, and there’s a nice smartphone app that uses the Bluetooth connection to relay text messages through the radio and configure many settings. You can also configure the radios via a USB cable and a Python command-line-interface program.

In addition to basic things like establishing private encrypted channels, you can enable a number of software modules in the firmware. These modules are designed to accomplish common tasks, such as periodically reading and transmitting data from an attached environmental sensor plug-in. Probably the most useful software module is the serial module, which lets the Meshtastic hardware act as a gateway between the radio network and a second microcontroller running your own custom IoT application, communicating via a two- or three-wire connection.

The Meshtastic protocol has seen significant evolution. In the initial system, any node that heard a broadcast would rebroadcast it, leading to local congestion [top row]. But now, signal strength is used as a proxy for distance, with more-distant nodes broadcasting first. Nodes that hear a broadcast twice will not rebroadcast it, reducing congestion [bottom row].James Provost

For my demo, I wired up a button and an LED to an Adafruit Grand Central board running CircuitPython. (I chose this board because its 3.3-volt levels are compatible with the RAKwireless hardware.) I programmed the Grand Central to send an ASCII-encoded message to the RAKwireless radio over a serial connection when I pressed the button, and to illuminate the LED if it received an ASCII string containing the word “btn.”

On the radio side, I used a plug-in I/O expander to connect the serial transmit and receive wires. The tricky part was mapping the pin names as labeled on the adapter with the corresponding microcontroller pins. You need to know the microcontroller pins when setting up the receive and transmit pins with the serial module, as it doesn’t know how the adapter is set up. But after some paging through the documentation, I eventually found the mapping.

I pressed the button connected to my Grand Central microcontroller, and “button down” instantly popped up on my handheld communicators. Then I sent “btn,” and the LED lit up. Success! With that proof of concept done, pretty much anything else is doable as well.

Will makers building applications on top of Meshtastic lead to the mesh renaissance I’ve been waiting for? With more hands on deck, I hope to see some surprising uses emerge that will make the case for mesh better than any starry-eyed argument from me.

Stephen Cass: Hello and welcome to Fixing the Future, an IEEE Spectrum podcast where we look at concrete solutions to tough problems. I’m your host Stephen Cass, a senior editor at IEEE Spectrum. And before I start, I just wanted to tell you that you can get the latest coverage of Spectrum‘s most important beats, including AI, climate change, and robotics, by signing up for one of our free newsletters. Just go to spectrum.ieee.org/newsletters to subscribe.

We all love our mobile devices where the progress of Moore’s Law has meant we’re able to pack an enormous amount of computing power in something that’s small enough that we can wear it as jewelery. But their Achilles heel is power. They eat up battery life requiring frequent battery changes or charging. One company that’s hoping to reduce our battery anxiety is Exeger, which wants to enable self-charging devices that convert ambient light into energy on the go. Here to talk about its so-called Powerfoyle solar cell technology is Exeger’s founder and CEO, Giovanni Fili. Giovanni, welcome to the show.

Giovanni Fili: Thank you.

Cass: So before we get into the details of the Powerfoyle technology, was I right in saying that the Achilles heel of our mobile devices is battery life? And if we could reduce or eliminate that problem, how would that actually influence the development of mobile and wearable tech beyond just not having to recharge as often?

Fili: Yeah. I mean, for sure, I think the global common problem or pain point is for sure battery anxiety in different ways, ranging from your mobile phone to your other portable devices, and of course, even EV like cars and all that. So what we’re doing is we’re trying to eliminate this or reduce or eliminate this battery anxiety by integrating— seamlessly integrating, I should say, a solar cell. So our solar cell can convert any light energy to electrical energy. So indoor, outdoor from any angle. We’re not angle dependent. And the solar cell can take the shape. It can look like leather, textile, brushed steel, wood, carbon fiber, almost anything, and can take light from all angles as well, and can be in different colors. It’s also very durable. So our idea is to integrate this flexible, thin film into any device and allow it to be self-powered, allowing for increased functionality in the device. Just look at the smartwatches. I mean, the first one that came, you could wear them for a few hours, and you had to charge them. And they packed them with more functionality. You still have to charge them every day. And you still have to charge them every day, regardless. But now, they’re packed with even more stuff. So as soon as you get more energy efficiency, you pack them with more functionality. So we’re enabling this sort of jump in functionality without compromising design, battery, sustainability, all of that. So yeah, so it’s been a long journey since I started working with this 17 years ago.

Cass: I actually wanted to ask about that. So how is Exeger positioned to attack this problem? Because it’s not like you’re the first company to try and do nice mobile charging solutions for mobile devices.

Fili: I can mention there, I think that the main thing that differentiates us from all other previous solutions is that we have invented a new electrode material, the anode and the cathode with a similar almost like battery. So we have anode, cathode. We have electrolytes inside. So this is a—

Cass: So just for readers who might not be familiar, a battery is basically you have an anode, which is the positive terminal—I hope I didn’t forgot that—cathode, which is a negative terminal, and then you have an electrolyte between them in the battery, and then chemical reactions between these three components, and it can get kind of complicated, produce an electric potential between one side and the other. And in a solar cell, also there’s an anode and a cathode and so on. Have I got that right, my little, brief sketch?

Fili: Yeah. Yeah. Yeah. And so what we add to that architecture is we add one layer of titanium dioxide nanoparticles. Titanium dioxide is the white in white wall paint, toothpaste, sunscreen, all that. And it’s a very safe and abundant material. And we use that porous layer of titanium nanoparticles. And then we deposit a dye, a color, a pigment on this layer. And this dye can be red, black, blue, green, any kind of color. And the dye will then absorb the photons, excite electrons that are injected into the titanium dioxide layer and then collected by the anode and then conducted out to the cable. And now, we use the electrons to light the lamp or a motor or whatever we do with it. And then they turn back to the cathode on the other side and inside the cell. So the electrons goes the other way and the inner way. So the plus, you can say, go inside ions in the electrolytes. So it’s a regenerative system.

So our innovation is a new— I mean, all solar cells, they have electrodes to collect the electrons. If you have silicon wafers or whatever you have, right? And you know that all these solar cells that you’ve seen, they have silver lines crossing the surface. The silver lines are there because the conductivity is quite poor, funny enough, in these materials. So high resistance. So then you need to deposit the silver lines there, and they’re called current collectors. So you need to collect the current. Our innovation is a new electrode material that has 1,000 times better conductivity than other flexible electrode materials. That allows us as the only company in the world to eliminate the silver lines. And we print all our layers as well. And as you print in your house, you can print a photo, an apple with a bite in it, you can print the name, you can print anything you want. We can print anything we want, and it will also be converting light energy to electric energy. So a solar cell.

Cass: So the key part is that the color dye is doing that initial work of converting the light. Do different colors affect the efficiency? I did see on your site that it comes in all these kind of different colors, but. And I was thinking to myself, well, is the black one the best? Is the red one the best? Or is it relatively insensitive to the visible color that I see when I look at these dyes?

Fili: So you’re completely right there. So black would give you the most. And if you go to different colors, typically you lose like 20, 30 percent. But fortunately enough for us, over 50 percent of the consumer electronic market is black products. So that’s good. So I think that you asked me how we’re positioned. I mean, with our totally unique integration possibilities, imagine this super thin, flexible film that works all day, every day from morning to sunset, indoor, outdoor, can look like leather. So we’ve made like a leather bag, right? The leather bag is the solar cell. The entire bag is the solar cell. You wouldn’t see it. It just looks like a normal leather bag.

Cass: So when you talk about flexible, you actually mean this— so sometimes when people talk about flexible electronics, they mean it can be put into a shape, but then you’re not supposed to bend it afterwards. When you’re talking about flexible electronics, you’re talking about the entire thing remains flexible and you can use it flexibly instead of just you can conform it once to a shape and then you kind of leave it alone.

Fili: Correct. So we just recently released a hearing protector with 3M. This great American company with more than 60,000 products across the world. So we have a global exclusivity contract with them where they have integrated our bendable, flexible solar film in the headband. So the headband is the solar cell, right? And where you previously had to change disposable battery every second week, two batteries every second week, now you never need to change the battery again. We just recharge this small rechargeable battery indoor and outdoor, just continues to charge all the time. And they have added a lot of extra really cool new functionality as well. So we’re eliminating the need for disposable batteries. We’re saving millions and millions of batteries. We’re saving the end user, the contractor, the guy who uses them a lot of hassle to buy this battery, store them. And we increase reliability and functionality because they will always be charged. You can trust them that they always work. So that’s where we are totally unique. The solar cell is super durable. If we can be in a professional hearing protector to use on airports, construction sites, mines, whatever you use, factories, oil rig platforms, you can do almost anything. So I don’t think any other solar cell would be able to pass those durability tests that we did. It’s crazy.

Cass: So I have a question. It kind of it’s more appropriate from my experience with utility solar cells and things you put on roofs. But how many watts per square meter can you deliver, we’ll say, in direct sunlight?

Fili: So our focus is on indirect sunlight, like shade, suboptimal light conditions, because that’s where you would typically be with these products. But if you compare to more of a silicon, which is what you typically use for calculators and all that stuff. So we are probably around twice as what they deliver in this dark conditions, two to three times, depending. If you use glass, if you use flexible, we’re probably three times even more, but. So we don’t do full sunshine utility scale solar. But if you look at these products like the hearing protector, we have done a lot of headphones with Adidas and other huge brands, we typically recharge like four times what they use. So if you look at— if you go outside, not in full sunshine, but half sunshine, let’s say 50,000 lux, you’re probably talking at about 13, 14 minutes to charge one hour of listening. So yeah, so we have sold a few hundred thousand products over the last three years when we started selling commercially. And - I don’t know - I haven’t heard anyone who has charged since. I mean, surely someone has, but typically the user never need to charge them again, just charge themself.

Cass: Well, that’s right, because for many years, I went to CES, and I often would buy these, or acquire these, little solar cell chargers. And it was such a disappointing experience because they really would only work in direct sunlight. And even then, it would take a very long time. So I want to talk a little bit about, then, to get to that, what were some of the biggest challenges you had to overcome on the way to developing this tech?

Fili: I mean, this is the fourth commercial solar cell technology in the world after 110 or something years of research. I mean, the Americans, the Bell Laboratory sent the first silicon cell, I think it’s in like 1955 or something, to space. And then there’s been this constant development and trying to find, but to develop a new energy source is as close to impossible as you get, more or less. Everybody tried and everybody failed. We didn’t know that, luckily enough. So just the whole-- so when I try to explain this, I get this question quite a lot. Imagine you found out something really cool, but there’s no one to ask. There’s no book to read. You just realize, “Okay, I have to make like hundreds of thousands, maybe millions of experiments to learn. And all of them, except finally one, they will all fail. But that’s okay.” You will fail, fail, fail. And then, “Oh, here’s the solution. Something that works. Okay. Good.” So we had to build on just constant failing, but it’s okay because you’re in a research phase. So we had to. I mean, we started off with this new nanomaterials, and then we had to make components of these materials. And then we had to make solar cells of the components, but there were no machines either. We have had to invent all the machines from scratch as well to make these components and the solar cells and some of the non-materials. That was also tough. How do you design a machine for something that doesn’t exist? It’s pretty difficult specification to give to a machine builder. So in the end, we had to build our own machine building capacity here. We’re like 50 guys building machines, so.

But now, I mean, today we have over 300 granted patents, another 90 that will be approved soon. We have a complete machine park that’s proprietary. We are now building the largest solar cell factory— one of the largest solar cell factories in Europe. It’s already operational, phase one. Now we’re expanding into phase two. And we’re completely vertically integrated. We don’t source anything from Russia, China; never did. Only US, Japan, and Europe. We run the factories on 100 percent renewable energy. We have zero emissions to air and water. And we don’t have any rare earth metals, no strange stuff in it. It’s like it all worked out. And now we have signed, like I said, global exclusivity deal with 3M. We have a global exclusivity deal with the largest company in the world on computer peripherals, like mouse, keyboard, that stuff. They can only work with us for years. We have signed one of the large, the big fives, the Americans, the huge CE company. Can’t tell you yet the name. We have a globally exclusive deal for electronic shelf labels, the small price tags in the stores. So we have a global solution with Vision Group, that’s the largest. They have 50 percent of the world market as well. And they have Walmart, IKEA, Target, all these huge companies. So now it’s happening. So we’re rolling out, starting to deploy massive volumes later this year.

Cass:So I’ll talk a little bit about that commercial experience because you talked about you had to create verticals. I mean, in Spectrum, we do cover other startups which have had these— they’re kind of starting from scratch. And they develop a technology, and it’s a great demo technology. But then it comes that point where you’re trying to integrate in as a supplier or as a technology partner with a large commercial entity, which has very specific ideas and how things are to be manufactured and delivered and so on. So can you talk a little bit about what it was like adapting to these partners like 3M and what changes you had to make and what things you learned in that process where you go from, “Okay, we have a great product and we could make our own small products, but we want to now connect in as part of this larger supply chain.”

Fili: It’s a very good question and it’s extremely tough. It’s a tough journey, right? Like to your point, these are the largest companies in the world. They have their way. And one of the first really tough lessons that we learned was that one factory wasn’t enough. We had to build two factories to have redundancy in manufacturing. Because single source is bad. Single source, single factory, that’s really bad. So we had to build two factories and we had to show them we were ready, willing and able to be a supplier to them. Because one thing is the product, right? But the second thing is, are you worthy supplier? And that means how much money you have in the bank. Are you going to be here in two, three, four years? What’s your ISO certifications like? REACH, RoHS, Prop 65. What’s your LCA? What’s your view on this? Blah, blah, blah. Do you have professional supply chain? Did you do audits on your suppliers? But now, I mean, we’ve had audits here by five of the largest companies in the world. We’ve all passed them. And so then you qualify as a worthy supplier. Then comes your product integration work, like you mentioned. And I think it’s a lot about— I mean, that’s our main feature. The main unique selling point with Exeger is that we can integrate into other people’s products. Because when you develop this kind of crazy technology-- “Okay, so this is solar cell. Wow. Okay.” And it can look like anything. And it works all the time. And all the other stuff is sustainable and all that. Which product do you go for? So I asked myself—I’m an entrepreneur since the age of 15. I’ve started a number of companies. I lost so much money. I can’t believe it. And managed to earn a little bit more. But I realized, “Okay, how do you select? Where do you start? Which product?”

Okay, so I sat down. I was like, “When does it sell well? When do you see market success?” When something is important. When something is important, it’s going to work. It’s not the best tech. It has to be important enough. And then, you need distribution and scale and all that. Okay, how do you know if something is important? You can’t. Okay. What if you take something that’s already is— I mean, something new, you can’t know if it’s going to work. But if we can integrate into something that’s already selling in the billions of units per year, like headphones— I think this year, one billion headphones are going to be sold or something. Okay, apparently, obviously that’s important for people. Okay, let’s develop technology that can be integrated into something that’s already important and allow it to stay, keep all the good stuff, the design, the weight, the thickness, all of that, even improve the LCA better for the environment. And it’s self-powered. And it will allow the user to participate and help a little bit to a better world, right? With no charge cable, no charging in the wall, less batteries and all that. So our strategy was to develop such a strong technology so that we could integrate into these companies/partners products.

Cass: So I guess the question there is— so you come to a company, the company has its own internal development engineers. It’s got its own people coming up with product ideas and so on. How do you evangelize within a company to say, “Look, you get in the door, you show your demo,” to say, product manager who’s thinking of new product lines, “You guys should think about making products with our technology.” How do you evangelize that they think, “Okay, yeah, I’m going to spend the next six months of my life betting on these headphones, on this technology that I didn’t invent that I’m kind of trusting.” How do you get that internal buy-in with the internal engineers and the internal product developers and product managers?

Fili: That’s the Holy Grail, right? It’s very, very, very difficult. Takes a lot of time. It’s very expensive. And the point, I think you’re touching a little bit when you’re asking me now, because they don’t have a guy waiting to buy or a division or department waiting to buy this flexible indoor solar cell that can look like leather. They don’t have anyone. Who’s going to buy? Who’s the decision maker? There is not one. There’s a bunch, right? Because this will affect the battery people. This will affect the antenna people. This will affect the branding people. It will affect the mechanic people, etc., etc., etc. So there’s so many people that can say no. No one can say yes alone. All of them can say no alone. Any one of them can block the project, but to proceed, all of them have to say yes. So it’s a very, very tough equation. So that’s why when we realized this— this was another big learning that we had that we couldn’t go with the sales guy. We couldn’t go with two sales guys. We had to go with an entire team. So we needed to bring our design guy, our branding person, our mechanics person, our software engineer. We had to go like huge teams to be able to answer all the questions and mitigate and explain.

So we had to go both top down and explain to the head of product or head of sustainability, “Okay, if you have 100 million products out in five years and they’re going to be using 50 batteries per year, that’s 5 billion batteries per year. That’s not good, right? What if we can eliminate all these batteries? That’s good for sustainability.” “Okay. Good.” “That’s also good for total cost. We can lower total cost of ownership.” “Okay, that’s also good.” “And you can sell this and this and this way. And by the way, here’s a narrative we offer you. We have also made some assets, movies, pictures, texts. This is how other people talk about this.” But it’s a very, very tough start. How do you get the first big name in? And big companies, they have a lot to risk, a lot to lose as well. So my advice would be to start smaller. I mean, we started mainly due to COVID, to be honest. Because Sweden stayed open during COVID, which was great. We lived our lives almost like normal. But we couldn’t work with any international companies because they were all closed or no one went to the office. So we had to turn to Swedish companies, and we developed a few products during COVID. We launched like four or five products on the market with smaller Swedish companies, and we launched so much. And then we could just send these headphones to the large companies and tell them, “You know what? Here’s a headphone. Use it for a few months. We’ll call you later.” And then they call us that, “You know what? We have used them for three months. No one has charged. This is sick. It actually works.” We’re like, “Yeah, we know.” And then that just made it so much easier. And now anyone who wants to make a deal with us, they can just buy these products anywhere online or in-store across the whole world and try them for themselves.

And we send them also samples. They can buy, they can order from our website, like development kits. We have software, we have partnered up with Qualcomm, early semiconductor. All the big electronics companies, we’re now qualified partners with them. So all the electronics is powerful already. So now it’s very easy now to build prototypes if you want to test something. We have offices across the world. So now it’s much easier. But my advice to anyone who would want to start with this is try and get a few customers in. The important thing is that they also care about the project. If we go to one of these large companies, 3M, they have 60,000 products. If they have 60,001, yeah. But for us, it’s like the project. And we have managed to land it in a way. So it’s also important for them now because it just touches so many of their important areas that they work with, so.

Cass: So in terms of future directions for the technology, do you have a development pathway? What kind of future milestones are you hoping to hit?

Fili: For sure. So at the moment, we’re focusing on consumer electronics market, IoT, smart home. So I think the next big thing will be the smart workplace where you see huge construction sites and other areas where we connect the workers, anything from the smart helmet. You get hit in your head, how hard was it? I mean, why can’t we tell you that? That’s just ridiculous. There’s all these sensors already available. Someone just needs to power the helmet. Location services. Is the right person in the right place with the proper training or not? On the construction side, do you have the training to work with dynamite, for example, or heavy lifts or different stuff? So you can add the geofencing in different sites. You can add health data, digital health tracking, pulse, breathing, temperature, different stuff. Compliance, of course. Are you following all the rules? Are you wearing your helmet? Is the helmet buttoned? Are you wearing the proper other gear, whatever it is? Otherwise, you can’t start your engine, or you can’t go into this site, or you can’t whatever. I think that’s going to greatly improve the proactive safety and health a lot and increase profits for employers a lot too at the same time. In a few years, I think we’re going to see the American unions are going to be our best sales force. Because when they see the greatness of this whole system, they’re going to demand it in all tenders, all biggest projects. They’re going to say, “Hey, we want to have the connected worker safety stuff here.” Because you can just stream-- if you’re working, you can stream music, talk to your colleagues, enjoy connected safety without invading the privacy, knowing that you’re good. If you fall over, if you faint, if you get a heart attack, whatever, in a few seconds, the right people will know and they will take their appropriate actions. It’s just really, really cool, this stuff.

Cass: Well, it’ll be interesting to see how that turns out. But I’m afraid that’s all we have time for today, although this is fascinating. But today, so Giovanni, I want to thank you very much for coming on the show.

Fili: Thank you so much for having me.

Cass: So today we were talking with Giovanni Fili, who is Exeger’s founder and CEO, about their new flexible powerfoyle solar cell technology. For IEEE Spectrum‘s Fixing the Future, I’m Stephen Cass, and I hope you’ll join me next time.

Stephen Cass: Hello and welcome to Fixing the Future, an IEEE Spectrum podcast where we look at concrete solutions to tough problems. I’m your host, Stephen Cass, a senior editor at IEEE Spectrum. And before I start, I just want to tell you that you can get the latest coverage of some of Spectrum’s most important beats, including AI, climate change, and robotics, by signing up for one of our free newsletters. Just go to spectrum.ieee.org/newsletters to subscribe. We’ve been covering the drone delivery company Zipline in Spectrum for several years, and I do encourage listeners to check out our great onsite reporting from Rwanda in 2019 when we visited one of Zipline’s dispatch centers for delivering vital medical supplies into rural areas. But now it’s 2024, and Zipline is expanding into commercial drone delivery in the United States, including into urban areas, and hitting some recent milestones. Here to talk about some of those milestones today, we have Keenan Wyrobek, Zipline’s co-founder and CTO. Keenan, welcome to the show.

Keenan Wyrobek: Great to be here. Thanks for having me.

Cass: So before we get into what’s going on with the United States, can you first catch us up on how things have been going on with Rwanda and the other African countries you’ve been operating in?

Wyrobek: Yeah, absolutely. So we’re now operating in eight countries, including here in the US. That includes a handful of countries in Africa, as well as Japan and Europe. So in Africa, it’s really exciting. So the scale is really impressive, basically. As we’ve been operating, started eight years ago with blood, then moved into vaccine delivery and delivering many other things in the healthcare space, as well as outside the healthcare space. We can talk a little bit about in things like animal husbandry and other things. The scale is really what’s exciting. We have a single distribution center there that now regularly flies more than the equivalent of once the equator of the Earth every day. And that’s just from one of a whole bunch of distribution centers. That’s where we are really with that operation today.

Cass: So could you talk a little bit about those non-medical systems? Because this was very much how we’d seen blood being parachuted down from these drones and reaching those distant centers. What other things are you delivering there?

Wyrobek: Yeah, absolutely. So start with blood, like you said, then vaccines. We’ve now done delivered well over 15 million vaccine doses, lots of other pharmaceutical use cases to hospitals and clinics, and more recently, patient home delivery for chronic care of things like hypertension, HIV-positive patients, and things like that. And then, yeah, moved into some really exciting use cases and things like animal husbandry. One that I’m personally really excited about is supporting these genetic diversity campaigns. It’s one of those things very unglamorous, but really impactful. One of the main sources of protein around the world is cow’s milk. And it turns out the difference between a non-genetically diverse cow and a genetically diverse cow can be 10x difference in milk production. And so one of the things we deliver is bull semen. We’re very good at the cold chain involved in that as we’ve mastered in vaccines and blood. And that’s just one of many things we’re doing in other spaces outside of healthcare directly.

Cass: Oh, fascinating. So turning now to the US, it seems like there’s been two big developments recently. One is you’re getting close to deploying Platform 2, which has some really fascinating tech that allows packages to be delivered very precisely by tether. And I do want to talk about that later. But first, I want to talk about a big milestone you had late last year. And this was something that goes by the very unlovely acronym of a BVLOS flight. Can you tell us what a BVLOS stands for and why that flight was such a big deal?

Wryobek: Yeah, “beyond visual line of sight.” And so that is basically, before this milestone last year, all drone deliveries, all drone operations in the US were done by people standing on the ground, looking at the sky, that line of sight. And that’s how basically we made sure that the drones were staying clear of aircraft. This is true of everybody. Now, this is important because in places like the United States, many aircraft don’t and aren’t required to carry a transponder, right? So transponders where they have a radio signal that they’re transmitting their location that our drones can listen to and use to maintain separation. And so the holy grail of basically scalable drone operations, of course, it’s physically impossible to have people standing around all the world staring at the sky, and is a sensing solution where you can sense those aircraft and avoid those aircraft. And this is something we’ve been working on for a long time and got the approval for late last year with the FAA, the first-ever use of sensors to detect and avoid for maintaining safety in the US airspace, which is just really, really exciting. That’s now been in operations in two distribution centers here, one in Utah and one in Arkansas ever since.

Cass: So could you just tell us a little bit about how that tech works? It just seems to be quite advanced to trust a drone to recognize, “Oh, that is an actual airplane that’s a Cessna that’s going to be here in about two minutes and is a real problem,” or, “No, it’s a hawk, which is just going about his business and I’m not going to ever come close to it at all because it’s so far away.

Wryobek: Yeah, this is really fun to talk about. So just to start with what we’re not doing, because most people expect us to use either a radar for this or cameras for this. And basically, those don’t work. And the radar, you would need such a heavy radar system to see 360 degrees all the way around your drone. And this is really important because two things to kind of plan in your mind. One is we’re not talking about autonomous driving where cars are close together. Aircraft never want to be as close together as cars are on a road, right? We’re talking about maintaining hundreds of meters of separation, and so you sense it a long distance. And drones don’t have right of way. So what that means is even if a plane’s coming up behind the drone, you got to sense that plane and get out of the way. And so to have enough radar on your drone that you can actually see far enough to maintain that separation in every direction, you’re talking about something that weighs many times the weight of a drone and it just doesn’t physically close. And so we started there because that’s sort of where we assumed and many people assume that’s the place to start. Then looked at cameras. Cameras have lots of drawbacks. And fundamentally, you can sort of-- we’ve all had this, you taken your phone and tried to take a picture of an airplane and you look at the picture, you can’t see the airplane. Yeah. It takes so many pixels of perfectly clean lenses to see an aircraft at a kilometer or two away that it really just is not practical or robust enough. And that’s when we went back to the drawing board and it ended up where we ended up, which is using an array of microphones to listen for aircraft, which works very well at very long distances to then maintain separation from those other aircraft.

Cass: So yeah, let’s talk about Platform 2 a little bit more because I should first explain for listeners who maybe aren’t familiar with Zipline that these are not the kind of the little purely sort of helicopter-like drones. These are these fixed wing with sort of loiter capability and hovering capabilities. So they’re not like your Mavic drones and so on. These have a capacity then for long-distance flight, which is what it gives them.

Wyrobek: Yeah. And maybe to jump into Platform 2— maybe starting with Platform 1, what does it look like? So Platform 1 is what we’ve been operating around the world for years now. And this basically looks like a small airplane, right? In the industry referred to as a fixed-wing aircraft. And it’s fixed wing because to solve the problem of going from a metro area to surrounding countryside, really two things matter. Your range and long range and low cost. And a fixed-wing aircraft over something that can hover has something like an 800% advantage in range and cost. And that’s why we did fix wing because it actually works for our customers for their needs for that use case. Platform 2 is all about, how do you deliver to homes and in metro areas where you need an incredible amount of precision to deliver to nearly every home. And so Platform 2—we call our drone zips—our drone, it flies out to the delivery site. Instead of floating a package down to a customer like Platform 1 does, it hovers. Platform 2 hovers and lowers down what we call a droid. And so the droids on tether. The drone stays way up high, about 100 meters up high, and the drone lowers down. And the drone itself-- sorry, the droid itself, it lowers down, it can fly. Right? So you think of it as like the tether does the heavy lifting, but the droid has fans. So if it gets hit by a gust of wind or whatnot, it can still stay very precisely on track and come in and deliver it to a very small area, put the package down, and then be out of there seconds later.

Cass: So let me get this right. Platform 2 is kind of as a combo, fixed wing and rotor wing. It’s like a VTOL like that. I’m cheating here a little bit because my colleague Evan Ackerman has a great Q&A on the Spectrum website with you, some of your team members about the nitty-gritty of how that design was evolved. But first off, it’s like a little droid thing at the end of the tether. How much extra precision do all those fans and stuff give you?

Wyrobek: Oh, massive, right? We can come down and hit a target within a few centimeters of where we want to deliver, which means we can deliver. Like if you have a small back porch, which is really common, right, in a lot of urban areas to have a small back porch or a small place on your roof or something like that, we can still just deliver as long as we have a few feet of open space. And that’s really powerful for being able to serve our customers. And a lot of people think of Platform 2 as like, “Hey, it’s a slightly better way of doing maybe a DoorDash-style operation, people in cars driving around.” And to be clear, it’s not slightly better. It’s massively better, much faster, more environmentally friendly. But we have many contracts for Platform 2 in the health space with US Health System Partners and Health Systems around the world. And what’s powerful about these customers in terms of their needs is they really need to serve all of their customers. And this is where a lot of our sort of-- this is where our engineering effort goes is how do you make a system that doesn’t just kind of work for some folks, and they can use it if they want to, but a health system is like, “No, I want this to work for everybody in my health network.” And so how do we get to that near 100 percent serviceability? And that’s what this droid really enables us to do. And of course, it has all these other magic benefits too. It makes some of the hardest design problems in this space much, much easier. The safety problem gets much easier by keeping the drone way up high.

Cass: Yeah, how high is Platform 2 hovering when it’s doing its deliveries?

Wyrobek: About 100 meters, so 300 plus feet, right? We’re talking about high up as a football field is long. And so it’s way up there. And it also helps with things like noise, right? We don’t want to live in a future where drones are all around us sounding like swarms of insects. We want drones to make no noise. We want them to just melt into the background. And so it makes that kind of problem much easier as well. And then, of course, the droid gets other benefits where for many products, we don’t need any packaging at all. We can just deliver the product right onto a table in your porch. And not just from a cost perspective, but again, from— we’re all familiar with the nightmare of packaging from deliveries we get. Eliminating packaging just has to be our future. And we’re really excited to advance that future.

Cass: From Evan’s Q&A, I know that a lot of effort went into making the droid element look rather adorable. Why was that so important?

Wryobek: Yeah, I like to describe it as sort of a cross between three things, if you kind of picture this, like a miniature little fan boat, right, because it has some fan, a big fan on the back, looks like a little fan boat, combined with sort of a baby seal, combined with a toaster. It sort of has that look to it. And making it adorable, there’s a bunch of sort of human things that matter, right? I want this to be something that when my grandmother, who’s not a tech-savvy, gets these deliveries, it’s approachable. It doesn’t come off as sort of scary. And when you make something cute, not only does it feel approachable, but it also forces you to get the details right so it is approachable, right? The rounded corners, right? This sounds really benign, but a lot of robots, it turns out if you bump into them, they scratch you. And we want you to be able to bump into this droid, and this is no big deal. And so getting the surfaces right, getting them— the surface is made sort of like a helmet foam. If you can picture that, right? The kind of thing you wouldn’t be afraid to touch if it touched you. And so getting it both to be something that feels safe, but is something that actually is safe to be around, those two things just matter a lot. Because again, we’re not designing this for some piloty kind of low-volume thing. Our customers want this in phenomenal volume. And so we really want this to be something that we’re all comfortable around.

Cass: Yeah, and one thing I want to pull out from that Q&A as well is it was an interesting note, because you mentioned it has three fans, but they’re rather unobtrusive. And the original design, you had two big fans on the sides, which was very great for maneuverability. But you had to get rid of those and come up with a three-fan design. And maybe you can explain why that was so.

Wryobek: Yeah, that’s a great detail. So the original design, the picture, it was like, imagine the package in the middle, and then kind of on either side of the package, two fans. So when you looked at it, it kind of looked like— I don’t know. It kind of looked like the package had big mouse ears or something. And when you looked at it, everybody had the same reaction. You kind of took this big step back. It was like, “Whoa, there’s this big thing coming down into my yard.” And when you’re doing this kind of user testing, we always joke, you don’t need to bring users in if it already makes you take a step back. And this is one of those things where like, “That’s just not good enough, right, to even start with that kind of refined design.” But when we got the sort of profile of it smaller, the way we think about it from a design experiment perspective is we want to deliver a large package. So basically, the droid needs to be as sucked down as small additional volume around that package as possible. So we spent a lot of time figuring out, “Okay, how do you do that sort of physically and aesthetically in a way that also gets that amazing performance, right? Because when I say performance, what I’m talking about is we still need it to work when the winds are blowing really hard outside and still can deliver precisely. And so it has to have a lot of aero performance to do that and still deliver precisely in essentially all weather conditions.

Cass: So I guess I just want to ask you then is, what kind of weight and volume are you able to deliver with this level of precision?

Wryobek: Yeah, yeah. So we’ll be working our way up to eight pounds. I say working our way up because that’s part of, once you launch a product like this, there’s refinement you can do overtime on many layers, but eight pounds, which was driven off, again, these health use cases. So it does basically 100 percent of what our health partners need to do. And it turns out it’s, nearly 100 percent of what we want to do in meal delivery. And even in the goods sector, I’m impressed by the percentage of goods we can deliver. One of our partners we work with, we can deliver over 80 percent of what they have in their big box store. And yeah, it’s wildly exceeding expectations on nearly every axis there. And volume, it’s big. It’s bigger than a shoebox. I don’t have a great-- I’m trying to think of a good reference to kind of bring it to life. But it looks like a small cooler basically inside. And it can comfortably fit a meal for four to give you a sense of the amount of food you can fit in there. Yeah.

Cass: So we’ve seen this history of Zipline in rural areas, and now we’re talking about expanding operations in more urban areas, but just how urban? I don’t imagine that we’ll see the zip lines of zooming around, say, the very hemmed-in streets, say, here in Midtown Manhattan. So what level of urban are we talking about?

Wryobek: Yeah, so the way we talk about it internally in our design process is basically we call three-story sprawl. Manhattan is the place where when we think of New York, we’re not talking about Manhattan, but most of the rest of New York, we are talking about it, right? Like the Bronx, things like that. We just have this sort of three stories forever. And that’s a lot of the world out here in California, that’s most of San Francisco. I think it’s something like 98 percent of San Francisco is that. If you’ve ever been to places like India and stuff like that, the cities, it’s just sort of this three stories going for a really long way. And that’s what we’re really focused on. And that’s also where we provide that incredible value because that’s also matches where the hardest traffic situations and things like that can make any other sort of terrestrial on-demand delivery be phenomenally late.

Cass: Well, no, I live out in Queens, so I agree there’s not much skyscrapers out there. Although there are quite a few trees and so on, but at the same time, there’s usually some sort of sidewalk availability. So is that kind of what you’re hoping to get into?

Wyrobek: Exactly. So as long as you’ve got a porch with a view of the sky or an alley with a view of the sky, it can be literally just a few feet, we can get in there, make a delivery, and be on our way.

Cass: And so you’ve done this preliminary test with the FAA, the BVLOS test, and so on. How close do you think you are to, and you’re working with a lot of partners, to really seeing this become routine commercial operations?

Wyrobek: Yeah, yeah. So at relatively limited scale, our operations here in Utah and in Arkansas that are leveraging that FAA approval for beyond visual line-of-sight flight operations, that’s been all day, every day now since our approval last year. With Platform 2, we’re really excited. That’s coming later this year. We’re currently in the phase of basically massive-scale testing. So we now have our production hardware and we’re taking it through a massive ground testing campaign. So this picture dozens of thermal chambers and five chambers and things like that just running to really both validate that we have the reliability we need and flush out any issues that we might have missed so we can address that difference between what we call the theoretical reliability and the actual reliability. And that’s running in parallel to a massive flight test campaign. Same idea, right? We’re slowly ramping up the flight volume as we fly into heavier conditions really to make sure we know the limits of the system. We know its actual reliability and true scaled operations so we can get the confidence that it’s ready to operate for people.

Cass: So you’ve got Platform 2. What’s kind of next on your technology roadmap for any possible platform three?

Wyrobek: Oh, great question. Yeah, I can’t comment on platform three at this time, but. And I will also say, Zipline is pouring our heart into Platform 2 right now. Getting Platform 2 ready for this-- the way I like to talk about this internally is today, we fly about four times the equator of the Earth in our operations on average. And that’s a few thousand flights per day. But the demand we have is for more like millions of flights per day, if not beyond. And so on the log scale, right, we’re halfway there. Three hours of magnitude down, three more zeros to come. And the level of testing, the level of systems engineering, the level of refinement required to do that is a lot. And there’s so many systems from weather forecasting to our onboard autonomy and our fleet management systems. And so to highlight one team, our system test team run by this really impressive individual named Juan Albanell, this team has taken us from where we were two years ago, where we had shown the concept at a very prototype stage of this delivery experience, and we’ve done the first order math kind of on the architecture and things like that through the iterations in test to actually make sure we had a drone that could actually fly in all these weather conditions with all the robustness and tolerance required to actually go to this global scale that Platform 2 is targeting.

Cass: Well, that’s fantastic. Well, I think there’s a lot more to talk about to come up in the future, and we look forward to talking with Zipline again. But for today, I’m afraid we’re going to have to leave it there. But it was really great to have you on the show, Keenan. Thank you so much.

Wyrobek: Cool. Absolutely, Stephen. It was a pleasure to speak with you.

Cass: So today on Fixing the Future, we were talking with Zipline’s Keenan Wyrobek about the progress of commercial drone deliveries. For IEEE Spectrum, I’m Stephen Cass, and I hope you’ll join us next time.

Sometimes extreme procrastination works in your favor. Procrastination certainly played a role in this month’s Hands On, which was 20 years in the making. So, too, did family, and place, and what meaning might be found in bringing silent circuits to life. This then is a story that ends with me watching Interstellar and listening to its soaring soundtrack in glorious high fidelity, but begins with my wife’s childhood in North Carolina.

Regular readers will know that I take particular delight in anything that combines old and new tech. So when my wife and I were newlyweds two decades ago, and my wife’s parents gifted us with an early 1960s General Electric wood-cabinet stereo hi-fi, the wheels started turning in my head. My wife grew up listening to records on this stereo, but now it was 2004, and vinyl was clearly dead and never coming back. Instead, I connected one of our new-fangled iPods via the set of RCA audio inputs at the back (fortunately, these had become standard just a few years before the hi-fi was made). We filled our small New York City apartment with the latest hits from the Black Eyed Peas and Arcade Fire—only to discover that the left-hand stereo channel didn’t work.

Identifying the problem was quick and easy. Peering into the gloom of the cabinet’s sprawling circuitry, I spotted the one vacuum tube not emitting a tell-tale orange glow. But fixing the problem was neither quick nor easy. The years ticked on, and we moved from apartment to apartment, and city to city, taking the hi-fi with us. But it sat silent, a convenient place to display photos and stash bottles of liquor. I made fitful attempts to find a replacement tube, searching eBay and scouring the formidable MIT Radio Society Swapfests.

Perfectionism was a big part of my procrastination, as I hoped to find a matched pair—that is, two tubes that came from the same production batch. Prized among vintage audio enthusiasts, a matched pair would ensure that manufacturing variations didn’t leave one stereo channel with a different frequency response than the other. But I never found a pair, at least not at a price I was willing to pay. About two years ago, I finally gave in and spent US $55 for a single replacement GE 7189A tube from KCA NOS Tubes.

Replacing a blown tube [left] was relatively straightforward, as the stereo was designed to permit their replacement, and many tubes are still easily obtainable online. However, the original wax-paper capacitor used to filter noise from the AC power supply had failed, so I had to splice in a custom-made substitute.James Provost

I popped in the 7189A, tuned in a radio station, and music boomed from both speakers. Yay! Yay? No yay. There was sound, all right, but it was bad sound. A harsh hum bullied its way through the music, the dread drone of 60 hertz. I was hearing the AC power frequency.

This would be a much more involved job than simply pulling a blown tube out of a socket and pushing a new one in. Flashlight in hand, I surveyed the hi-fi’s circuits. It has two chassis, one for the radio tuner and controls and one for the stereo amplifier. As I pondered what it would take to extract them for diagnosis and repair, my flashlight fell on a mysterious behemoth: a tube about 10 centimeters long and 3 cm in diameter that was screwed to a side panel and connected to the amplifier board by four leads. What the heck was this?

It was a wax paper multicapacitor, a very obsolete component combining a 70-microfarad capacitor rated for 400 volts, a 100-μF capacitor also rated at 400 V, and a 70-μF capacitor rated at 25 V, with a common negative terminal. Such a device was typically used to filter noise from AC supplies, and prone to long-term failure. I’d found my culprit.

When it comes to dealing with voltages higher than 24 V, I am a complete wuss, but this is where my years of procrastination paid off. After a few more months of nervous delay, I began researching the problem and discovered that rather than having to cobble together a homebrew multicapacitor, I could turn to the pros!

Thanks to the stability of the analog RCA audio connector standard since the 1950s, it was possible to use modern entertainment technology with the vintage hi-fi’s warm-sounding speakers. The flatscreen accepts digital HDMI signals and outputs audio via an optical-fiber connection. A digital-to-analog converter then creates left- and right-channel audio signals to feed into the hi-fi. A selector on the hi-fi’s front panel (originally reserved for connecting a tape player) pipes the audio through the speakers.James Provost

In the last few years, a number of outfits have cropped up to assist people in the repair of vintage radios, supplying original service manuals and providing drop-in substitutes for components you can’t buy any more. I sent off specs to Hayseed Hamfest, which specializes in replacement capacitors. For $43, I soon had a bespoke replacement in a metal can about half the length of my waxy original. I simply had to excise the old monster and wire in its successor.

And then things stalled again—until my father passed away last November. He had spent decades working as an engineer at the Irish national broadcaster, RTÉ, and in his youth he had helped my grandfather in their radio and television rental shop in Dublin. After his funeral, I glared at the stereo, as it awaited a repair that my father could have once done practically blindfolded.

I took off the back and cut the monster out. Splicing in its replacement without removing the amplifier chassis was tricky, but it turned out to be a perfect application for some Kuject connectors I had knocking around. These connectors are short lengths of transparent heat-shrink tubing with some solder inside. Rather than guddling around inside the confined space with a soldering iron, I was able to twist the ends of my leads together, slide the Kuject connector into place, and give it a short blast with a heat gun. Before I knew it, I was done.

And time had helped in other ways too: Instead of just hooking up an iPod, now I could use HDMI cables to connect an Apple TV and a Blu-ray player to a television—which, thanks to modern flat-screen technology, could now be perched on top of the cabinet—and then feed the television’s optical audio output into a converter box and then on into the stereo’s RCA inputs. I tested everything by listening to the elegiac organ rolls of Interstellar swelling out into our apartment.

And there the hi-fi stands now, more than just a photo stand and more than a way to watch “Stranger Things” in style. It’s a reminder of my wife’s upbringing and family, our recollections of the places we’ve lived our lives together, and there, in the currents and voltages being shunted around the circuitry, the echoes of my family, too, and the memory of the hands that taught me my first lessons in electronics.