Author: Lewin Day

3334 Articles

How A Failed Video Format Spawned A New Kind Of Microscope

September 23, 2025 by 11 Comments

The video cassette tape was really the first successful home video format; discs just couldn’t compete back in the early days. That’s not to say nobody tried, however, with RCA’s VideoDisc a valiant effort that ultimately fell flat on its face. However, the forgotten format did have one benefit, in that it led to the development of an entirely new kind of microscope, as explained by IEEE Spectrum.

The full story is well worth the read; the short version is that it all comes down to capacitance. RCA’s VideoDisc format was unique in that it didn’t use reflective surfaces or magnetic states to represent data. Instead, the data was effectively stored as capacitance changes. As a conductive stylus rode through an undulating groove in a carbon-impregnated PVC disc, the capacitance between the stylus and the disc changed. This capacitance was effectively placed into a resonant circuit, where it would alter the frequency over time, delivering an FM signal that could be decoded into video and audio by the VideoDisc player.

The VideoDisc had a capacitance sensor that could detect such fine changes in capacitance, that it led to the development of the Scanning Capacitance Microscope (SCM). The same techniques used to read and inspect VideoDiscs for quality control could be put to good use in the field of semiconductors. The sensors were able to be used to detect tiny changes in capacitance from dopants in a semiconductor sample, and the SCM soon became an important tool in the industry.

It’s perhaps a more inspiring discovery than when cheeky troublemakers figured out you could use BluRay diodes to pop balloons. Still fun, though. An advertisement for the RCA VideoDisc is your video after the break.

Continue reading “How A Failed Video Format Spawned A New Kind Of Microscope” →

Automatic Feeder Keeps Fish Sated

September 23, 2025 by 3 Comments

[Noisy Electrons] is a maker who also likes to keep fish. He sometimes needs to travel and keep his fish fed in the meantime, so he created an automated solution to handle that for him.

The build is based around an STM32 microcontroller, paired with a MCP7940N real-time clock to keep time. The microcontroller is hooked up to a few buttons and a small display to serve as an interface, allowing the feeding times and dosage amounts to be configured right on the device. Food is distributed from a 3D printed drum with a hole in it, which is rotated via a stepper motor.  Each time the drum rotates, some food falls through the hole and into the tank. Dosage amount is measured in rotations — the more times the drum rotates, the more food is delivered to the fish.

[Noisy Electron] built three of these devices for three separate tanks. Thus far, it’s been three weeks and all the fish are still alive, so we’ll take that as a vote of confidence in the build. We’ve featured some other great pet feeders over the years, too Continue reading “Automatic Feeder Keeps Fish Sated” →

Heart Rate Measurement Via WiFi, The DIY Way

September 23, 2025 by 13 Comments

A few weeks back, we reported on a research group that figured out how to measure heartrate using perturbations in WiFi signals. [Nick Bild] was interested in this so-called “Pulse-Fi” technique, but noted the paper explaining it was behind a paywall. Thus, he worked to recreate the technology himself so he could publish the results openly for anyone eager to learn.

[Nick] paid for the research paper, and noted that it was short on a few of the finer details and didn’t come with any code or data from the original research team. He thus was left to figure out the finer details of how to measure heart rate via WiFi in his own way, though he believes his method is quite close to the original work.

The basic concept is simple enough. One ESP32 is set up to transmit a stream of Channel State Information packets to another ESP32, with a person standing in between. As the person’s heart beats, it changes the way the radio waves propagate from the transmitting unit to the receiver. These changes can be read from the packets, and processed to estimate the person’s heart rate. [Nick] explains the various data-massaging steps involved to go from this raw radio data to a usable heart rate readout.

It’s a great effort from [Nick] to recreate this research all on his own in his home lab. Files are on GitHub for the curious. If you’re eager to learn more about these innovative measurement techniques, you might like to read our prior reporting on the tech. Also, it’s worth remembering—don’t use your homebrew prototypes for any serious healthcare purposes. Continue reading “Heart Rate Measurement Via WiFi, The DIY Way” →

Building Your Own DVB-S2 Receiver

September 22, 2025 by 9 Comments

Generally, a digital TV tuner is something you buy rather than something you make yourself. However, [Johann] has always been quite passionate about the various DVB transmission standards, and decided he wanted to build his own receiver just for the fun of it.

[Johann]’s build is designed to tune in DVB-S2 signals transmitted from satellites, and deliver that video content over a USB connection. When beginning his build, he noted it was difficult to find DVB reception modules for sale as off-the-shelf commercial parts. With little to nothing publicly available, he instead purchased a “Formuler F1 Plug & Play DVB-S2 HDTV Sat Tuner” and gutted it for the Cosy TS2M08-HFF11 network interface module (NIM) inside. He then paired this with a Cypress CY7C68013A USB bridge to get the data out to a PC. [Johann] then whipped up a Linux kernel driver to work with the device.

[Johann] doesn’t have hardcore data on how his receiver performs, but he reports that it “works for me.” He uses it in South Germany to tune in the Astra 19.2E signal.

We don’t talk a lot about DVB these days, since so much video content now comes to us over the Internet. However, we have still featured some nifty DVB hacks in the past. If you’re out there tinkering with your own terrestrial or satellite TV hardware, don’t hesitate to notify the tipsline!

Robot Balances Ball On A Plate

September 22, 2025 by 26 Comments

Imagine trying to balance a heavy metal ball bearing on a cafeteria tray. It’s not the easiest thing in the world! In fact, it’s perhaps a task better automated, as [skulkami3000] demonstrates with this robotic build.

The heart of the build is a flat platform fitted with a resistive touchscreen panel on top. The panel is hooked up to a Teensy 4.0 microcontroller. When a heavy ball bearing is placed on the touch panel, the Teensy is thus able to accurately read its position. It then controls a pair of NEMA 17 stepper motors via TCM2208 drivers in order to tilt the panel in two axes in order to keep the ball in the centre of the panel. Thanks to its quick reactions and accurate sensing, it does a fine job of keeping the ball centred, even when the system is perturbed.

Projects like these are a great way to learn the basics of PID control. Understanding these concepts will serve you well in all sorts of engineering contexts, from controlling industrial processes to building capable quadcopter aircraft. Continue reading “Robot Balances Ball On A Plate” →

This Device Is A Real Page Turner

September 22, 2025 by 6 Comments

You can read e-books on just about anything—your tablet, your smartphone, or even your PC. However, the interface can be lacking somewhat compared to a traditional book—on a computer, you have to use the keyboard or mouse to flip the pages. Alternatively, you could do what [NovemberKou] did, and build a dedicated page-turning device.

The device was specifically designed for use with the Kindle for Mac or Kindle for PC reader apps, allowing the user to peruse their chosen literature without using the keyboard to change pages. It consists of a thumb wheel, rotary encoder, and an Arduino Pro Micro mounted in a 3D printed shell. The Pro Micro is set up to emulate a USB keyboard, sending “Page Up” or “Page Down” key presses as you turn the thum bwheel in either direction.

Is it a frivolous device with a very specific purpose? Yes, and that’s why we love it. There’s something charming about building a bespoke interface device just to increase your reading pleasure, and we wholeheartedly support it.

Continue reading “This Device Is A Real Page Turner” →

IPhone Air Still Apparently Repairable Despite Its Compact Construction

September 22, 2025 by 13 Comments

Miniaturization is a trend that comes and goes in the cellular phone space. For a while, our phones were all getting smaller, then they started getting bigger again as screens expanded to show us ever more content and advertising. The iPhone air is going back the other way, with a design that aims to sell based on its slimness. [iFixit] reckons that despite its diminutive dimensions, it should still be quite repairable.

“Thinner usually means flimsier, harder to fix, and more glued-down parts, but the iPhone Air proves otherwise,” states Elizabeth Chamberlain for the repair outlet. Much of this comes down to clever design, that makes repair possible at the same time as ensuring compactness. A big part of this is the way that Apple made the bottom half of the phone pretty much just battery. Most of the actual electronic components are on a logic board up by the camera. Segmenting the phone in this way makes it easier to access commonly-replaced parts like the battery without having to pull a lot of other parts out of the way first.

[iFixit] refers to this as flattening the “disassembly tree”—minimizing the number of components you have to touch to replace what you’re there to fix. In this regard, the thinness of the iPhone Air is actually a boon. The phone is so thin, it wasn’t possible to stack multiple components on top of each other, so everything is easier to get to. The design is also reasonably modular, which should make routine repairs like USB C port swaps relatively straightforward.

Whatever smartphone you’re working on, it often helps to have a disassembly guide to ensure you don’t wreck it when you’re trying to fix something. [iFixit] remains a stellar resource in that regard. Continue reading “IPhone Air Still Apparently Repairable Despite Its Compact Construction” →