Tuning Into Medical Implants With The RTL-SDR

July 11, 2021 by 12 Comments

With a bit of luck, you’ll live your whole life without needing an implanted medical device. But if you do end up getting the news that your doctor will be installing an active transmitter inside your body, you might as well crack out the software defined radio (SDR) and see if you can’t decode its transmission like [James Wu] recently did.

Before the Medtronic Bravo Reflux Capsule was attached to his lower esophagus, [James] got a good look at a demo unit of the pencil-width gadget. Despite the medical technician telling him the device used a “Bluetooth-like” communications protocol to transmit his esophageal pH to a wearable receiver, the big 433 emblazoned on the hardware made him think it was worth taking a closer look at the documentation. Sure enough, its entry in the FCC database not only confirmed the radio transmitted a 433.92 MHz OOK-PWM encoded signal, but it even broke down the contents of each packet. If only it was always that easy, right?

The 433 ended up being a coincidence, but it got him on the right track.

Of course he still had to put this information into practice, so the next step was to craft a configuration file for the popular rtl_433 program which split each packet into its principle parts. This part of the write-up is particularly interesting for those who might be looking to pull data in from their own 433 MHz sensors, medical or otherwise

Unfortunately, there was still one piece of the puzzle missing. [James] knew which field was the pH value from the FCC database, but the 16-bit integer he was receiving didn’t make any sense. After some more research into the hardware, which uncovered another attempt at decoding the transmissions from the early days of the RTL-SDR project, he realized what he was actually seeing was the combination of two 8-bit pH measurements that are sent out simultaneously.

We were pleasantly surprised to see how much public information [James] was able to find about the Medtronic Bravo Reflux Capsule, but in a perfect world, this would be the norm. You deserve to know everything there is to know about a piece of electronics that’s going to be placed inside your body, but so far, the movement towards open hardware medical devices has struggled to gain much traction.

Discount Microfluidics From A $9 Spree At The Dollar Store

July 11, 2021 by 1 Comment

Microfluidics — working with tiny volumes of fluids in tiny channels — isn’t something you’d think would be inexpensive. Unless you read [Alexander Bissells’] post on how he created microfluidic devices using stuff from the dollar store. The channels in these devices can be much smaller than a millimeter and the fluid volumes are sometimes measured in femtoliters. At those scales, fluids don’t work like we intuitively think they will.

The parts list included gel tape, baby droppers, and some assorted containers and tools. Total price at the dollar store $9. One of the key finds in the dollar store was some small spray bottles. They weren’t important themselves, but they contain small lengths of silicone tubing and that was useful. Plastic fresnel lenses along with the tubing and gel tape worked to make “chips.” The gel tape also gets cut to make the channels. An eyedropper with some modifications makes a reasonable syringe.

We aren’t sure what you can practically do with any of these, but the T-junction looked pretty interesting. If you want some ideas on how these devices work in biology, including COVID-19 testing, check out this article. And just last week [Krishna Sanka] hosted a Hack Chat on microfluidics in biohacking, you can find the transcript on the project page. If you need a pump, this one uses 3D printer firmware to control it.

But Does It Run TOOM?

July 11, 2021 by 39 Comments

id Software’s iconic 1993 first-person shooter game Doom was the game to play on your 486 (or fast 386) and was for many their first introduction to immersive 3D environments in gaming. Its eventual release as open-source gave it a new life, and now it’s a rite of passage for newly-reverse-engineered devices: Will it run Doom?

One type of platform that never ran Doom though was the classic arcade cabinet with its portrait-aligned screen. This is something [Matt Phillips] has addressed with Toom, a PC Doom port that — finally — runs on a portrait screen.

To enter the world of a UAC space marine in glorious portrait mode, simply take an installation of Doom 1.9 for DOS, and copy the Toom files from the GitHub repository over the top of it. The minimum spec is a 486 so period hardware will be fine, all you’ll need is a monitor that can be tipped on its side.

Doom consumed far too many hours for gamers of a certain age, and while it may look quaint to modern eyes it can’t be overstated what a giant step it was compared to what had gone before. If any of you install Toom and give it a go, prepare to see its monsters when you close your eyes.

We’ve shown you Doom on all sorts of devices over the years, perhaps the most intriguing is a no-software version in FPGA hardware.

Wing Can Expand To Fly Really Slow For Short Take-Off And Landing

July 10, 2021 by 56 Comments

[Mike Patey] had made a name for himself by building high-performance experimental aircraft. In his latest project, he added a transforming wing that can extend its chord by up to 16 inches for low speed and high angle of attack performance.

The aircraft in question, a bush plane named Scrappy, has been attracting attention long before [Mike] even started building the wings. Designed for extremely short take-off and landing (STOL) performance, only some sections of the fuselage frame remain from the original Carbon Cub kit. The wings are custom designed and feature double slats on the leading edge, combined with large flaps and drooping ailerons on the trailing edge. The slats form an almost seamless part of the wing for normal flying, but can expand using a series of linkages integrated into each precision machine wing rib. Making extensive use of CFD simulations, the slats were designed to keep the center-of-lift close to the center of the wing, even with 50 degrees of flaps. Without the slats, the pilot would need to use almost all the elevator authority to counteract the flaps and keep the aircraft’s nose up.

Leading-edge slats have been around since before WW2, but you don’t see them used in pairs like this. Aircraft like Scrappy will never be commercially viable, but innovation by people like [Mike] drives aviation forward. [Mike]’s previous project plane, Draco, was a large turboprop bush plane built around a PZL-104 Wilga. Sadly it was destroyed during an ill-considered take-off in 2019, but [Mike] is already planning its successor, Draco-X. Continue reading “Wing Can Expand To Fly Really Slow For Short Take-Off And Landing” →

Astronomical Clock Uses Your Spare Clock Motors

July 10, 2021 by 1 Comment

We’ll admit we are suckers for clock projects, and the more unusual, the better. We liked the look of [Peter Balch’s] astronomical clock, especially since it was handcrafted and was a relatively simple mechanism. [Peter] admits that it looks like an astronomical clock, but it isn’t the same as a complex instrument from medieval times. Instead, it uses several standard clock motors modified.

We didn’t quite follow some of the explanations for the rotation of the different elements, but the animated GIF cleared it all up. The inner and outer discs are geared at a 6:5 ratio. It takes 2 hours for the inner disc to make one rotation, meaning that every 12 hours the two discs will be back to where they began relative to one another.

Modifying the motors is fine work, requiring a good bit of disassembly and some glue. The electronics that make it tick are quite interesting. To drive the motors, a very specific pulse train is needed, but you also want to conserve battery as much as possible. A simple oscillator with a hex inverter drew more power than desired and an Arduino, even more so. A PIC12F629, though, could sleep a lot and do the job for a very low current consumption. The final clock should run a year on two AA cells.

Is It A Cyberdeck Or A Vintage Toshiba?

July 10, 2021 by 26 Comments

Cyberdecks, the portable computers notable for a freely expressed form factor, owe much to post-apocalyptic sci-fi. But they are not always the most practical devices. There’s a reason that all laptops share a very similar form factor: it’s a convenient and functional way to make a computer to take anywhere. So for the ideal compromise, why not make a cyberdeck from a vintage laptop? That’s exactly what [Valrum] has done with a non-functioning Toshiba 3100/20, upgrading the display and slipping in a Raspberry Pi 4, along with a handy removable USB e-ink supplementary screen (The red/black rectangle to the right of the main screen).

These older machines were so bulky that once their original hardware is removed there is plenty of space for upgrades. Even the screen enclosure is big enough to hide the LCD driver board behind a modern panel.  It follows a well-worn path for Raspberry Pi builds of using a Teensy as a USB keyboard controller, but unexpectedly the stock keyboard has been entirely replaced with a hand-wired one, which is nicely executed to appear superficially as though it was original. In an amusing twist this machine has no battery, not because it wouldn’t be possible but because the original Toshiba didn’t have one either. The USB ports are brought out to the space where the floppy would once have been.

With a plentiful supply of unexceptional or non functional older laptops to be had it’s clear that there’s a rich vein to be mined in this type of build. It’s something we’ve seen done before, in a more famous Toshiba laptop.

Skin-Mounted Wearable Bend Sensor Gets Close And Personal

July 10, 2021 by 1 Comment

[Mikst] has been working on wearable electronics and sensors for a long time, and shared the results of a different kind of bend sensor that fits directly onto the skin. It’s true that this kind of sensor design isn’t re-usable, but it is also very simple and inexpensive. It’s just a proof of concept right now, but we could see it or some of the other ideas [Mikst] tries, used in niche wearable applications where space is critical, like cosplay.

At its heart the sensor is made from two strands of conductive thread and a small strip of stretchy, conductive fabric common in wearable e-textiles. It is stuck directly to the skin using a transparent, non-woven medical adhesive dressing that is particularly good at conforming to contoured areas of the body. In this case, it is used to stick the stretchy piece of conductive fabric directly onto [Mikst]’s knuckle, where it responds to even small movements. You can watch a multimeter measuring the resistance changes in the video, embedded below.

We’ve seen [Mikst]’s work before in finding unusual solutions to e-textile problems, such as a three-conductor pivoting connection used to mount a wearable hall effect sensor.

Continue reading “Skin-Mounted Wearable Bend Sensor Gets Close And Personal” →