The Smallest Large Display Is Projected Straight Onto Your Retina

April 15, 2020 by 42 Comments

For most of human history, the way to get custom shapes and colors onto one’s retinas was to draw it on a cave wall, or a piece of parchment, or on paper. Later on, we invented electronic displays and used them for everything from televisions to computers, even toying with displays that gave the illusion of a 3D shape existing in front of us. Yet what if one could just skip this surface and draw directly onto our retinas?

Admittedly, the thought of aiming lasers directly at the layer of cells at the back of our eyeballs — the delicate organs which allow us to see — likely does not give one the same response as you’d have when thinking of sitting in front of a 4K, 27″ gaming display to look at the same content. Yet effectively we’d have the same photons painting the same image on our retinas. And what if it could be an 8K display, cinema-sized. Or maybe have a HUD overlay instead, like in video games?

In many ways, this concept of virtual retinal displays as they are called is almost too much like science-fiction, and yet it’s been the subject of decades of research, with increasingly more sophisticated technologies making it closer to an every day reality. Will we be ditching our displays and TVs for this technology any time soon?

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Logging Into Linux With A 1930s Teletype

April 15, 2020 by 47 Comments

Buried deep within all UNIX-based operating systems are vestiges of the earliest days of computing, when “hardware” more often than not meant actual mechanical devices with cams and levers and pulleys and grease. But just because UNIX, and by extension Linux, once supported mechanical terminals doesn’t mean that getting a teletype from the 1930s to work with it is easy.

Such was the lesson learned by [CuriousMarc] with his recently restored Model 15 Teletype; we covered a similar Model 19 restoration that he tackled. The essential problem is that the five-bit Baudot code that they speak predates the development of ASCII by several decades, making a converter necessary. A task like that is a perfect job for an Arduino — [Marc] put a Mega to work on that — but the interface of the Teletype proved a bit more challenging. Designed to connect two or more units together over phone lines, the high-voltage 60-mA current loop interface required some custom hardware. The testing process was fascinating, depending as it did on an old Hewlett-Packard serial signal generator to throw out a stream of five-bit serial pulses.

The big moment came when he used the Teletype to log into Linux on a (more or less) modern machine. After sorting out the mysteries of the stty command, he was able to log in, a painfully slow process at 45.5 bps but still a most satisfying hack. The ASCII art — or is it Baudot art? — is a nice bonus.

We love restorations like these, and can practically smell the grease and the faint tang of ozone around this device. We’re not thrilled by the current world situation, but we’re glad [CuriousMarc] was able to use the time to bring off a great hack that honors another piece of our computing history.

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Buyer Beware: This LED Bulb Sold As Germicidal Doesn’t Emit UV-C

April 15, 2020 by 131 Comments

Germicidal lamps are designed to destroy viruses and bacteria using ultraviolet light. But not just any UV light will work, and I came across an example of a lamp that was advertised as germicidal but a few things just weren’t right about it.

This is an actual UV-C LED made by CEL (PDF) that emits 275nm. Note the clear glass that covers the LED.

I ordered the UV-C germicidal LED lamp on Amazon, and received it a few days ago. It felt the suspicion from the first moment: playing around with a lot of different UV LEDs, I’ve learnt how the parasitic visible light from different UV ranges should look like to human eye. Also, proper UV-C LED lenses like the one shown here are made of quartz glass. Compare that to the image at the top of the article of the bulb I received that has a soft plastic lens, which is possibly opaque and degradable in the far UV range. The most important clue that something was wrong was the price. It’s hard to imagine that a UV-C LED lamp with the 253.7nm wavelength, made of more than 200 LEDs and in such a robust metal case, can cost only $62.99.

Although there was the risk of being unjust, I decided to return the product. In my message I bluffed that I measured the spectra of the lamp with a spectral emission meter, and that its output was not in the UV-C range. The next day I received confirmation that the bluff paid off: the seller replied that they advertised the product according to information from the supplier, and that the incorrect information was caused by their lack of understanding of product information. They also attached the official datasheet with the measured wavelength: it was not 253.7 nm, as advertised, but with the peak at 394.3 nm, and the dominant wavelength at 413.9 nm. It was not in the far UV-C, but in the near UV-A range and not at all useful for destroying germs! The seller promised that the product would be removed from their store, and kept the promise.

If you are thinking about buying a UV-C LED lamp, maybe you should get the good old CFL germicidal lamp. I don’t think that viruses care too much about the new technology.

The Drone That Flies In Any Orientation

April 14, 2020 by 8 Comments

Modern radio-controlled multi-rotor drone can be incredibly agile, but can only make orientation changes around the yaw axis while remaining in approximately the same position. Researchers at ETH Zurich have again built and tested multirotor with controllable motion six degrees of freedom, this time dramatically improving efficiency.

We covered a similar design from ETH Zurich previously which was hexacopter with arms with limited rotation. This new design is also a hexacopter, but with 2 coaxial motors on each rotating arm. Each arm has an increased range of rotation over the previous design, beyond 360 degrees. With the range of rotation and the very complex control system, the drone can efficiently fly in any orientation, while still being able to apply effective torque or linear force in any direction. This opens up a lot of possibilities for tasks that drones can perform, like close-up industrial inspection, using tools or pulling cables while keeping the rotors clear.

The arms do have a limited amount of rotation before winding the motor cable tight, but the control system keeps track of this and can unwind during or after movement. See the video after the break to see it in action. The complete scientific paper is not light reading, but definitely interesting. We’re looking forward to seeing if and when these type designs get used in real-world applications.

There are without a doubt a lot of drones in our future, and probably the most successful project to date is the Zipline fixed-wing drones in Rwanda and Ghana, which have made over 35000 deliveries of emergency medical supplies since 2016.

Thanks [Qes] for the tip!

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Printed Brain Implants Give New Meaning To Neuroplasticity

April 14, 2020 by 4 Comments

3D printing has opened up a world of possibilities in plastic, food, concrete, and other materials. Now, MIT engineers have found a way to add brain implants to the list. This technology has the potential to replace electrodes used for monitoring and implants that stimulate brain tissue in order to ease the effects of epilepsy, Parkinson’s disease, and severe depression.

Existing brain implants are rigid and abrade the grey matter, which creates scar tissue over time. This new material is soft and flexible, so it hugs the wrinkles and curves. It’s a conductive polymer that’s been thickened into a viscous, printable paste.

The team took a conductive liquid polymer (water plus nanofibers of a polystyrene sulfonate) and combined it with a solvent they made for a previous project to form a conductive, printable hydrogel.

In addition to printing out a sheet of micro blinky circuits, they tested out the material by printing a flexible electrode, which they implanted into a mouse. Amazingly, the electrode was able to detect the signal coming from a single neuron. They also printed arrays of electrodes topped with little wells for holding neurons so they can study the neurons’ signals using the electrode net underneath.

This particular medical printing hack is pretty far out of reach for most of us, but not all of them are. Fire up that printer and check out this NIH-approved face shield design.

Robot Arm Sucks In A Good Way

April 14, 2020 by 5 Comments

Building a robot arm is fun, but no longer the challenge it once was. You can find lots of plans and kits, and driving the motors is a solved problem. However, there is always one decision you have to make that can be a challenge: what effector to put on the end of it. If you are [MertArduino] the answer is to put suction at the end. If you need to grab the right things, this could be just the ticket for reliably lifting and letting go. You can see a video of the arm in action, below.

The arm itself is steel with four servo motors and comes in a kit. The video shows the arm making a sandwich under manual control. We suspect he might have put it under Arduino control but there’s no sudo for making sandwiches.

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Capture Device Firmware Hack Unlocks All The Pixels

April 14, 2020 by 7 Comments

According to [Mike Walters], the Elgato Cam Link 4K is a great choice if you’re looking for a HDMI capture device that works under Linux. But the bad news is, it wouldn’t work with any of the video conferencing software he tried to use it with because they expect the video stream to be in a different pixel format. For most people, that would probably have been the end of the story. But you’re reading this on Hackaday, so obviously he didn’t give up without a fight.

Early on, [Mike] found there was a software workaround for this exact issue. The problem isn’t that the Elgato can’t generate the desired format, it’s that the video conferencing programs just don’t know how to ask it to switch modes. The software fix is to create a dummy Video4Linux device and use that to change the format in real-time using ffmpeg. It’s a clever trick if you’ve got a conference call coming up in a few minutes, but it does waste CPU resources and adds some unnecessary hoop jumping.

Putting the device into bootloader mode.

Inspired by the software fix, [Mike] wondered if there was a way he could simply force the Elgato to output video in the desire format by default. He found a firmware dump for the device online, and found where the pixel formats were referenced by searching for their names in ASCII with hexdump. Looking through the source for the Linux USB Video Class (UVC) driver, he was then able to determine what the full 16 byte sequence should be for each video mode was so he could zero out the unwanted ones. Then it was just a matter of flashing his modified firmware back to the hardware.

But there was a problem: with the modified firmware installed, the device stopped working. After investigating the obvious culprits, [Mike] broke out the oscilloscope and hooked it up to the Elgato’s flash chip. It turns out that due to a bug in the program he was using, the SPI erase commands weren’t getting sent during the flash. This lead to corrupted firmware which was keeping the Elgato from booting. After making a pull request with his fixes, the firmware flashed without incident and the capture device now does double-duty as a webcam when necessary.

We could certainly think of easier and quicker was to roll your own webcam, but we’re glad that [Mike] took the time to modify his Elgato Cam Link 4K and document it. It’s a fantastic example of practical firmware hacking, even if you’re not in the market for a new high-definition video conferencing rig.