Heart Rate Measurement Via WiFi, The DIY Way

September 23, 2025 by 10 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” →

Play Capacitor Cupid With The Matchmaker

September 23, 2025 by 5 Comments

Occasionally a design requires capacitors that are much closer to being identical in value to one another than the usual tolerance ranges afford. Precision matching of components from parts on hand might sound like a needle-in-a-haystack problem, but not with [Stephen Woodward]’s Capacitor Matchmaker design.

The larger the output voltage, the greater the mismatch between capacitors A and B.

The Matchmaker is a small circuit intended to be attached to a DVM, with the output voltage indicating whether two capacitors (A and B) are precisely matched in value. If they are not equal, the voltage output indicates the degree of the mismatch as well as which is the larger of the two.

The core of the design is complementary excitation of the two capacitors (the CD4013B dual flip-flop achieves this) which results in a measurable signal if the two capacitors are different; nominally 50 mV per % of mismatch. Output polarity indicates which of the capacitors is the larger one. In the case of the two capacitors being equal, the charges cancel out.

Can’t precision-matched capacitors be purchased? Absolutely, but doing so is not always an option. As [Stephen] points out, selection of such components is limited and they come at an added cost. If one’s design requires extra-tight tolerances, requires capacitor values or types not easily available as precision pairs, or one’s budget simply doesn’t allow for the added cost, then the DIY approach makes a lot more sense.

If you’re going to go down this road, [Stephen] shares an extra time-saving tip: use insulated gloves to handle the capacitors being tested. Heating up a capacitor before testing it — even just from one’s fingers — can have a measurable effect.

[Stephen]’s got a knack for insightful electronic applications. Check out his PWMPot, a simple DIY circuit that can be an awfully good stand-in for a digital potentiometer.

Reviving A Scrapped Sound Blaster 2.0 ISA Soundcard

September 22, 2025 by 4 Comments

What do you do when you find a ISA Sound Blaster 2.0 card in a pile of scrap? Try to repair the damage on it to give it a second shot at life, of course. This is what [Adrian Black] did with one hapless victim, with the card in question being mostly in good condition minus an IC that had been rather rudely removed. The core Creative CT1336A and Yamaha YM3812 ICs were still in place, so the task was to figure out what IC was missing, find a replacement and install it.

The CT1350 is the final revision of the original 8-bit ISA Sound Blaster card, with a number of upgrades that makes this actually quite a desirable soundcard. The CT1350B revision featured here on a card from 1994 was the last to retain compatibility with the C/MS chips featured on the original SB card. After consulting with [Alex] from the Bits und Bolts YT channel, it was found that not only is the missing IC merely an Intel 8051-based Atmel MCU, but replacements are readily available. After [Alex] sent him a few replacements with two versions of the firmware preflashed, all [Adrian] had to do was install one.

Before installation, [Adrian] tested the card to see whether the expected remaining functionality like the basic OPL2 soundchip worked, which was the case. Installing the new MCU got somewhat hairy as multiple damaged pads and traces were discovered, probably because the old chip was violently removed. Along the way of figuring out how important these damaged pads are, a reverse-engineered schematic of the card was discovered, which was super helpful.

Some awkward soldering later, the card’s Sound Blaster functionality sprung back to life, after nudging the volume dial on the card up from zero. Clearly the missing MCU was the only major issue with the card, along with the missing IO bracket, for which a replacement was printed after the video was recorded.

Continue reading “Reviving A Scrapped Sound Blaster 2.0 ISA Soundcard” →

Blue Alchemist Promises Rocket Fuel From Moon Dust

September 22, 2025 by 14 Comments

Usually when an alchemist shows up promising to turn rocks into gold, you should run the other way. Sure, rocket fuel isn’t gold, but on the moon it’s worth more than its weight in the yellow stuff. So there would be reason to be skeptical if this “Blue Alchemist” was actually an alchemist, and not a chemical reactor under development by the Blue Origin corporation.

The chemistry in question is quite simple, really: take moon dust, which is rich in aluminum silicate minerals, and melt the stuff. Then it’s just a matter of electrolysis to split the elements, collecting the gaseous oxygen for use in your rockets. So: moon dust to air and metals, just add power. Lots and lots of power.

Melting rock takes a lot of temperature, and the molten rock doesn’t electrolyse quite as easily as the water we’re more familiar with splitting. Still, it’s very doable; this is how aluminum is produced on Earth, though notably not from the sorts of minerals you find in moon dust. Given the image accompanying the press release, perhaps on the moon the old expression will be modified to “make oxygen while the sun shines”.

Hackaday wasn’t around to write about it, but forward-looking researchers at NASA, expecting just such a chemical reactor to be developed someday, proposed an Aluminum/Liquid Oxygen slurry monopropellant rocket back in the 1990s.

That’s not likely to be flying any time soon, but of course even with the Methalox rockets in vogue these days, there are appreciable cost savings to leaving your oxygen and home. And we’re not biologists, but maybe Astronauts would like to breathe some of this oxygen stuff? We’ve heard it’s good for your health.

Full Scale Styrofoam DeLorean Finally Takes Flight

September 22, 2025 by 13 Comments

It’s 2025 and we still don’t have flying cars — but we’ve got this full-scale flying DeLorean prop from [Brian Brocken], and that’s almost as good. It’s airborne and on camera in the video embedded below.

We’ve written about this project before; first about the mega-sized CNC router [Brian] used to carve the DeLorean body out of Styrofoam panels, and an update last year that showed the aluminum frame and motorized louvers and doors.

Well, the iconic gull-wing doors are still there, and still motorized, and they’ve been joined by a tire-tilting mechanism for a Back To The Future film-accurate flight mode. With the wheels down, the prop can use them to steer and drive, looking for all the world like an all-white DMC-12.

The aluminum frame we covered before is no longer in the picture, though. It’s been replaced by a lighter, stiffer version made from carbon fibre. It’s still a ladder frame, but now with carbon fiber tubes and “forged” carbon fiber corners made of tow and resin packed in 3D printed molds. There’s been a tonne of work documented on the build log since we last covered this project, so be sure to check it out for all the details.

Even in unpainted white Styrofoam, it’s surreal to see this thing take off; it’s the ultimate in practical effects, and totally worth the wait. Honestly, with talent like [Brian] out there its a wonder anyone still bothers with CGI, economics aside.

Thanks to [Brian] for the tip! If you have a project you’ve hit a milestone with, we’d love to see it, even if it doesn’t trigger the 80s nostalgia gland we apparently all have embedded in our brains these days. Send us a tip!

Continue reading “Full Scale Styrofoam DeLorean Finally Takes Flight” →

Building Your Own DVB-S2 Receiver

September 22, 2025 by 5 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 21 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” →