Category: Electronics

Repurposing Components from a Broken Air Purifier | May 03 2026, 15:00

The air purifier broke down, so I bought a used one with a new cartridge for the price of a replacement cartridge plus $40. I completely disassembled the old one, extracted the reusable components, and figured out how it works. Just like in school 🙂

Inside, it comprises:

– an ESP32-WROOM-32D controller. But a part of the board responsible for voltage burned out, so it’s trash now.

– a CO sensor MQ-7 (unfortunately soldered to the board, but can be desoldered). Though, it needs a heating cycle for correct operation. First 5V (60 sec) for sensor cleaning, then 1.5V (90 sec) for measurement. But, it can also be used elsewhere.

– Plantower PMS9103M — a high-precision laser sensor for measuring airborne particulate matter concentrations (PM1.0, PM2.5, PM10). Can be connected to Arduino, specification available.

– a microwave motion sensor (radar), model RCWL-0516. Can be connected to Arduino, very simple interface. Detects motion up to 5-7 meters around within 360 degrees.

– 200W Snowfan YY225H310B motor. Also quite simple to connect, but it requires 310V DC plus 15V for speed control. But that’s all.

– a Hall sensor (magnet)

The motor is the most valuable part. It’s priced at $100 on eBay. Though, it should probably be tested first to see if it hasn’t burned out.

NFC Smart Lock Review: Battery Woes and Unexpected Vendor Response | March 13 2026, 18:49

At the beginning of the year, I bought an NFC smart lock for the front door for 170 bucks. Recently, I wrote a review on Amazon stating that the batteries lasted only a month and a half, and if it continues like this, I will end up paying almost the same amount annually. The manufacturer has responded saying they will refund the money. They didn’t ask to remove the review, and I don’t even know if that’s possible.

Unlocking the Mystery: Dual Voltage Needs in Smart Locks | March 07 2026, 22:43

Update: figured it out, looks like the lock needs 6v + 6v for different purposes. Maybe the power part and electronics.

Anyone who knows electronics, help me understand. Red wires are connected to contacts that respond to the tester. A total of 8 batteries. I can’t see a classic snake configuration here. Can’t understand why the lower right ones are responding. I want to connect an external adapter

Exploring ASML’s Advanced Chip-Making Equipment with Veritasium | January 02 2026, 00:47

Veritasium released a very cool report yesterday from ASML about the equipment used to print chips for your little phones, cameras, and laptops.

For those who aren’t familiar with the process. First, a monocrystal is grown from ultra-pure silicon and cut into thin wafers, then multiple layers of thin dielectrics, conductors, and semiconductors are repeatedly applied to the wafer surface, each time shaping the necessary areas using photolithography, etching, and ion doping, eventually creating billions of transistors and connecting metallic paths; finally, the wafer is tested, cut into individual crystals, and packaged into casings, making them into finished microchips.

This process had a limitation – the width of the paths and the distance to the next one are limited by the wavelength of the light used, and reducing it is difficult because there’s nothing to focus such a beam with – lenses simply absorb/reflect everything. In EUV lithography (extreme ultraviolet), the wavelength is 13.5 nm. This is virtually soft X-ray radiation.

The video explains details about the ASML machine costing 400 million dollars. Instead of refracting lenses, highly complex systems of reflecting mirrors are used. These mirrors are the smoothest surfaces ever created by humanity. If the mirror of this machine were enlarged to the size of the Earth, the largest bump on it would not be thicker than a playing card. To enable the mirrors to reflect X-rays, up to 76 alternating layers of tungsten and carbon, each less than a nanometer thick, are applied. All this is done by Zeiss. In addition, this mirror has a controlled curvature—it is constantly adjusted by robots with precision up to picoradians. The precision of the mirror control is so high that if a laser were mounted on it, directed at the Moon, the system could choose on which exact side of a 10-cent coin lying on the moon’s surface to hit with the beam.

But. We don’t have a “light bulb” that emits light in the EUV range.

To generate this light, a laser “shoots” at a droplet of molten tin the size of a white blood cell, traveling at 250 km/h. The first pulse flattens the droplet into a disc, the second and third turn this “disc” into plasma – and all this occurs within just 20 microseconds. When hit by the laser, the droplet heats up to 220,000 Kelvin — approximately 40 times hotter than the surface of the Sun. This plasma emits that very necessary light. And it does so 50,000 times a second. They say it’s been brought up to 100,000. Imagine, at a hundred thousand laser shots per second, it never misses a single one. All this happens in a deep vacuum. To clean the mirrors from tin particles, the chamber is constantly blown with hydrogen at a speed of 360 km/h — faster than a Category 5 hurricane. This process is described by the same formula (Taylor-von Neumann) that describes a nuclear explosion or supernova explosion.

The machine layers the chip with an error margin of no more than five atoms, while the matrix swings back and forth with an overload of 20G.

A single High-NA machine is transported in 250 containers on 25 trucks and seven Boeing 747 aircraft.

Link to the video – in the comments. Or search on YouTube on the channel veritasium.

From Freezer to Fridge: A DIY Cooling Hack | December 19 2025, 00:56

Today I sold a refrigerator. It has a story. The essence of it is that it’s not a refrigerator, although it looks like one. It’s a freezer. And it freezes on average to minus 18 degrees. I bought it second-hand, thinking it was a refrigerator. The buyer also came today thinking it was a refrigerator.

And here I realize that minus 18 degrees is not at all what I need.

Well, I am a Solution Architect. I didn’t want to dig into it, I just drove to Lowe’s and bought a simple blinker. It turns on and off according to schedule whatever is plugged into it. I stuck a radio thermometer inside (I had one) and adjusted the blinking frequency (20 minutes) so that the internal temperature was on average +4 degrees Celsius. The radio thermometer showed that the temperature fluctuations were very small – nominally plus or minus 0.5 degrees from +4, even less. And so it worked for me for some months until I realized that I just didn’t need it.

Sold it today with the adapter. It’s gone to the people.

The Inner Mechanics of Old Rotary Phones | November 25 2025, 00:59

When I was little, I used to take apart old telephones many times, and only now, in my grey years, I realized that I never wondered how they worked. And they worked in a very interesting way.

Let’s start with the dial. The phone is connected to the network by two wires. The dial is a rotary one. When you wind up the disk, the contacts are blocked, and when you release it, the disk returns backward and delivers a series of interruptions/pulses to the line. But how was it made to return at a constant speed (which is 10 pulses per second)?

It operated based on a centrifugal friction governor. The mechanics (gearbox) accelerated the governor’s axle to thousands of revolutions per minute. Two weights with friction pads (consider them brakes) were seated on the axle. The centrifugal force pressed them against the stationary drum, creating a braking effort. This is a direct heir to Watt’s centrifugal governor, allowing the mechanism to work stably regardless of how sharply you released the disk.

Next. The Central Office connected you with a friend. You both speak at the same time, and sound is transmitted there and back through two wires—why two wires and not four, you understand? Well, okay, but why don’t you hear yourself too loudly, since the microphone sends the sound there, from where the “speaker” hears it?

I couldn’t answer quickly. Went googling. So, it turns out that a special differential transformer was responsible for this. There, the current from the microphone branches off: part goes into the line to the friend, and part goes into the “balance circuit” (a chain of a resistor and capacitor inside the phone), mimicking the line resistance. The transformer coils are wound in opposition: the magnetic flows from the current in the line and the current in the balance circuit mutually annihilate themselves in the coil that goes to the speaker. Engineers purposely adjusted the balance not perfectly, leaving a “local effect” – a quiet sound of one’s own voice, so the phone wouldn’t seem “dead.” But the incoming signal from the friend has nothing to unbalance it (silence on your side), so it freely passes to the speaker.

Now about the microphone. At that time there were no transistors in phones, but the signal was loud. The secret is in the design of the microphone, it’s carbon. Essentially, it is a box with carbon powder and a movable diaphragm. The sound from your mouth compresses and decompresses the powder, changing its resistance. The microphone does not generate current but modulates the powerful current coming from the Central Office. Essentially, it worked as an amplifier. Over time, the charcoal compacted, and the audibility dropped—hence the habit of tapping the handset to “shake up” the powder.

The speaker was normal, electromagnetic. Although not quite. If there were only an electromagnet inside (without a permanent magnet), the phone would horribly distort the voice. An electromagnet attracts iron regardless of the polarity of the current. If you supply a sine wave (voice), the diaphragm would be attracted during both the positive and the negative half-waves. Result: the frequency of the sound would have doubled, and you would hear not the voice of a friend, but an unintelligible high-frequency buzzing. The permanent magnet solves this problem: It creates “preload.” The diaphragm is always attracted to the magnet with medium force. When the “plus” of the signal arrives, the magnetic field strengthens and the diaphragm flexes more. When the “minus” arrives, the field weakens and the diaphragm springs back.

In modern speakers, the force strictly depends on the direction of the current. Plus pushes, minus pulls. Therefore, the frequency doubling, which old phone engineers feared, physically cannot occur here. The diaphragm doesn’t need “preload” by a magnet, it just needs to hang in peace.

Interestingly, the principle of old electromagnetic capsules (metal diaphragm + “anchor”) is used now in the most expensive in-ear headphones—google “balanced armature headphones” (prices around $500).

The voltage in the telephone network was negative – minus 48/60 volts. Plus was grounded, and the “live” wire was the minus. Why? It turns out, this is protection against electrochemical corrosion. The cables lie in moist earth. If there were a “plus” (anode) on the wire, upon insulation damage, copper would dissolve (electrolysis) and the cable would rot. With “minus” (cathode), metal ions, on the contrary, tend to settle on the conductor from the soil, which prolonged the cable’s life by decades.

Childhood Curiosity and the Mysteries of Soviet Electrical Engineering | September 23 2025, 17:00

I remember being puzzled as a child by who the idiot was that decided to make the radio plug exactly the same as the one for 220 volts. This radio plug was supposed to go into a radio socket.

As a child, I used to disassemble and “improve” almost everything electrical in the house (I hadn’t graduated to electronics yet). Of course, I got shocked many times by the outlet, but to my surprise, the old Soviet phone could also give a shock. When a call came in, the voltage in the line would jump from 12-60 volts to 120 volts 🙂

I also had an interesting experience with Christmas lights. For a younger schoolchild, it was unclear why Christmas lights could shock you since they used the same bulbs that I connected to a flat “Planeta” battery. I had to learn the technicalities 🙂 By the way, those square flat batteries have disappeared; they used to be everywhere.

Inside the High-Tech World of USB-C Cables: More Than Just Wires | September 22 2025, 22:50

It turns out USB-C cables are sometimes whole computers inside the odd form factor of a wire. Watching a video where guys from Adam Savage’s dissected an Apple Thunderbolt 4 cable ($130) using a CT scanner, explaining its internals, and comparing it to a similar cable for $12.

The cable connector contains a complex system that includes a full-fledged processor, two power supplies, and many other components. The processor splits data into multiple parallel streams and converts them into differential signals that travel through twisted, intertwined pairs of wires. The system sends two signals simultaneously, but in mirror-opposite directions. This helps protect the signal from interference (from vacuum cleaners, mobile phones, etc.). Indeed, the circuit board inside is nine-layered.

On the internal circuit board, there are interesting serpentine/wavy tracks with sizes in fractions of a millimeter. It turns out, Apple engineers intentionally made them longer to match the overall length with the neighboring longer tracks (because they include turns). This is necessary for the signals to reach the processor absolutely simultaneously, down to the nanosecond.

The cable itself inside is made up of many individually shielded smaller coaxial cables. There are more than a dozen of them.

The cheap cable lacks this smart electronics, no active components inside. It just has connectors and wires.

But the coolest thing – the guys post such scans in the video description as a link to a viewing program. There you can rotate and examine everything on your own. I’ll put it in the comments

Switching from Sony to AirPods Max: A Cautionary Tale on Counterfeits | September 22 2025, 20:44

I made a gift for myself yesterday and bought Airpods Max. I already had Sony WH1000XM3, but I didn’t quite grow to like them. They don’t perform well with multiple devices, especially Macs, and although I find the sound quality decent, I prefer the sound in the Airpods, initially thinking it was due to the codecs, which indeed are a bit chaotic. Sony supports all – SBC, AAC, aptX, aptX HD, and LDAC. Apple devices (Mac, iPhone) do not support aptX and LDAC. Of all the advanced codecs available to Sony, the only one Apple devices can utilize is AAC. Exactly the same codec found in Airpods. But the sound to the ear is noticeably different.

Regarding the new ones, I realized I would be earning an eternity plus still, of course, I decided to buy used. For popular items, if you have a lot of time, you’ll definitely find some in excellent condition and for half the price. And here’s what I found out in the process: nine out of ten “half-price” headphones are fakes. The same situation applies to Airpod earplugs. Sometimes they are of very high quality, but like any counterfeit, they have serious flaws, but as many reviews say, the average ear won’t notice the difference, as counterfeiters don’t skimp on the audio path.

Eventually, I watched a ton of videos on how to distinguish fakes from genuine ones, and managed to buy Airpods in perfect condition yesterday for $180 when their price is $500.

Interestingly, checking the serial number on Apple’s website is no longer a cure-all because they’ve learned to reuse serial numbers from stolen ones. Most importantly: never buy a sealed box. Its outer part is counterfeited such that it can only be differentiated by the slightly less neatly wrapped film. In unpacked “ears,” the differences are more noticeable. The main thing – the headphones must pair with the computer using Apple’s proprietary protocol, which the counterfeiters have not yet been able to replicate.

Popup on iPhone upon first connection: Genuine — with a “Connect” button. Fake — no button, connects via Bluetooth settings.

The material of the headphones — should be metal. Fake — plastic, because metal is more expensive to manufacture. Snap your fingers on them, there should be a specific sound (try it in the Apple Store) — but most importantly, it should be the same on both sides. On the fake, it’s different and distinct.

The material inside the box: Genuine — cardboard (possibly recycled). Fake — plastic. Although cardboard is sometimes used too. An unreliable indicator.

Wrapping of the headphones: Genuine — in paper material. Fake — in plastic or without wrapping. Also unreliable.

Case — Interior material: Genuine — soft, changes color when touched, has text. Fake — hard, does not change color. This is quite a reliable aspect, because fakes will not use more expensive leather.

Noise when shaking: Genuine — noiseless. Fake — the button moves, noise is heard. Ear cups: Genuine — strong magnets, do not fall off. Fake — weak magnets, easily detach or fall off. Screws inside the cups: Genuine — dark. Fake — silver or light. This only works if you have seen the genuine ones. The difference is impossible to describe in words.

Noise cancelation (ANC): Genuine — activates only on the head. Fake — works in any position (even on a desk). Of course, it’s also poor, but detecting this is difficult unless you have the fakes on hand.

We must also check for Spatial Audio. It requires an accelerometer inside. Of course, fakes do not install one – it’s almost unused and why unnecessarily make the design more expensive. But in Spatial, it is used (you move your head – the sound shifts back and forth).

In short, when I was traveling yesterday, I was almost sure I wouldn’t buy anything. But — I got lucky.

Speaking of the Airpods themselves, they have some drawbacks that have been known for several years. I’m okay with them. The headphones are heavier than they could be, they don’t fold as they might, they bump against the chin when worn around the neck, and it’s not very comfortable to wear them that way, the price is high (but okay for used), strange case, and the protective case is huge, half the size of a backpack. Among the very important pros for me — support for multiple devices and perfect integration with Apple devices, good noise cancellation (almost like Sony’s), premium materials, and perfect build quality.

Exploring the Evolution of Inflight Entertainment: The Forgotten eXport Connector | September 14 2025, 13:24

We’re taking off. I’m wondering what kind of connector this is. Googling it. About 10 years ago, the Panasonic IFE multimedia system (which seems to have been used on B773ER and A333, I’m on a Boeing 777ER) featured a new port named eXport. It was a 9-pin mini-DIN connector for iPods. You could buy an adapter cable made by Griffin that essentially served as a bridge between the 9-pin mini-DIN and the 30-pin dock connector of iPods. Do you remember such connectors on iPods? And do you remember iPods at all? This cable allowed you to charge the iPod, control it via the IFE system, and transmit media from it to the IFE system. Time flies so fast. Looked up when the airplane was made – 14 years ago. That is, 14 years ago it still made sense to integrate a proprietary connector into the seats that essentially worked only with iPods.

I’m not even writing about RJ-45 above. White-orange orange, white-green blue, white-blue green, white-brown brown

Update from a page that has been gone for ten years, but the archive org remembers everything

And how does all this work? Here are some visual materials for clarity and facts from Panasonic (…about the biggest and highest-flying accessory for iPod in the world (as someone from Apple put it)

1. Allows audio and video signals to be transmitted from a passenger’s iPod to the IFE system, while also providing power and charging the iPod.

2. The eXport solution consists of two main components: the eXport connector (installed in the seat) and the eXport cable (connects the iPod to the eXport connector).

3. The crew will provide the eXport cable to passengers during the flight.

4. The solution is the world’s first Apple-certified Made for iPod” and Made for iPhone” solution, specifically designed for commercial airliners.

5. Natively supports Apple authentication technology.

6. In the near future, Panasonic will introduce additional functionality that will allow two-way communication between the iPod and the IFE system.

7. Supports both iPod and iPhone (in airplane mode”).

The reason a special cable is needed is that Apple does not allow video to be transmitted via USB. The only alternative would be to have three RCA connectors and an AC power socket onboard. But it’s expensive (installing an AC power system) and not worth the extra weight. Plus, it takes up legroom under the seat. Moreover, having three RCA connectors is a lot of ‘ports’ (red, yellow, white), which can confuse passengers (imagine a night flight in a darkened cabin). It only increases the workload on the crew, who are responsible for safety and comfort, not tech support.”