Thermal Earring Tracks Body Temperature

If you want to constantly measure body temperature to track things like ovulation, you usually have to wear something around your wrist or finger in the form of a smartwatch or ring. Well, what if you can’t or don’t want to adorn yourself this way? Then there’s the thermal earring.

Developed at the University of Washington, the thermal earring is quite small and unobtrusive compared to a smartwatch. Sure, it dangles, but that’s so it can measure ambient temperature for comparison’s sake.

You don’t even need to have pierced earsĀ  — the earring attaches to the lobe magnetically. And yeah, the earring can be decorated to hide the circuitry, but you know we would rock the bare boards.

The earring uses BLE to transmit readings throughout the day, and of course goes into sleep mode between transmissions to save power. Coincidentally, it runs for 28 days per charge, which is the length of the average menstrual cycle. While the earring at this time merely “shows promise” as a means of monitoring stress and ovulation, it did outperform a smartwatch at measuring skin temperature while the wearers were at rest.

This is definitely not the only pair of earrings we’ve got around here. These art deco earrings use flexible PCBs, and this pair will light up the night.

A Transistor, But For Heat Instead Of Electrons

Researchers at UCLA recently developed what they are calling a thermal transistor: a solid-state device able to control the flow of heat with an electric field. This opens the door to controlling the transfer of heat in some of the same ways we are used to controlling electronics.

Heat management can be a crucial task, especially where electronics are involved. The usual way to manage heat is to draw it out with things like heat sinks. If heat isn’t radiating away fast enough, a fan can be turned on (or sped up) to meet targets. Compared to the precision and control with which modern semiconductors shuttle electrons about, the ability to actively manage heat seems lacking.

This new device can rapidly adjust thermal conductivity of a channel based on an electrical field input, which is very similar to what a transistor does for electrical conductivity. Applying an electrical field modifies the strength of molecular bonds in a cage-like array of molecules, which in turn adjusts their thermal conductivity.

It’s still early, but this research may open the door to better control of heat within semiconductor systems. This is especially interesting considering that 3D chips have been picking up speed for years (stacking components is already a thing, it’s called Package-on-Package assembly) and the denser and deeper semiconductors get, the harder it is to passively pull heat out.

Thanks to [Jacob] for the tip!

Thermochromic Treatment Keeps Solderless Breadboards Smokeless

There’s a point in a component’s thermal regime that’s between normal operation and overloaded to the point of obvious failure. That’s a dangerous region, because the component isn’t quite hot enough to release the Magic Smoke, but hot enough to singe any finger you poke around with the see if everything’s running right. So if you’re looking to keep your fingerprints unmodified, but you don’t want to invest in a thermal camera, you might want to let this thermochromic breadboard point the way to overloaded components.

We’re not sure where this tip came from, but judging by the look of the website it was sometime in the late 90s. We’re also not sure who’s behind this little hack, so we’ll just credit [improwis]. The idea is pretty simple — white acrylic paint is mixed with thermochromic pigment, and the mixture is carefully painted onto the plastic surface of a standard-issue solderless breadboard. Care is taken to apply thin coats, lest the paint gets into the contacts and really muck things up. Once the paint is dry you’re ready to build your circuit. We have to admit we’re surprised at how sensitive the paint is; judging by the pictures, the heat coming off a 1/4-watt resistor dissipating 350 mW is plenty, even when the body of the resistor is well above the surface of the breadboard. We’d imagine the paint would point out not only hot components but probably the breadboard contacts too, if things got really toasty.

This seems like such a great application of thermochromism, one that’s a bit more useful than clocks and Pi Day celebrations. If you’re going to try this yourself, you’ll have to track down your own supply of thermochromic pigment, though — the link in the article is long dead. That’s not a problem, though, as Amazon sells scads of the stuff, seemingly aimed mainly at nail salons. The more you know.

IR Camera Is Excellent Hacking Platform

While there have been hiccups here and there, the general trend of electronics is to decrease in cost or increase in performance. This can be seen in fairly obvious ways like more powerful and affordable computers but it also often means that more powerful software can be used in other devices without needing expensive hardware to support it. [Manawyrm] and [Toble_Miner] found this was true of a particular inexpensive thermal camera that ships with Linux installed on it, and found that this platform was nearly perfect for tinkering with and adding plenty of other features to turn it into a much more capable tool.

The duo have been working on a SC240N variant of the InfiRay C200 infrared camera, which ships with a Hisilicon SoC. The display is capable of displaying 25 frames per second, making this platform an excellent candidate for modifying. A few ports were added to the device, including USB and MicroSD, and which also allows the internal serial port to be accessed easily. From there the device can be equipped with the uboot bootloader in order to run essentially anything that could be found on any other Linux machine such as supporting a webcam interface (and including a port of DOOM, of course). The duo doesn’t stop at software modifications though. They also equipped the camera with a lens, attached magnetically, which changes the camera’s focal length to give it improved imaging capabilities at closer ranges.

While the internal machinations of this device are interesting, it actually turns out to be a fairly capable infrared camera on its own as well. The hardware and software requirements for these devices certainly don’t need a full Linux environment to work, and while we have seen thermal cameras that easily fit in a pocket that are based on nothing any more powerful than an ESP32, it does tend to simplify the development process dramatically to include Linux and a little more processing power if you can.

Continue reading “IR Camera Is Excellent Hacking Platform”

Thermal Camera Plus Machine Learning Reads Passwords Off Keyboard Keys

An age-old vulnerability of physical keypads is visibly worn keys. For example, a number pad with digits clearly worn from repeated use provides an attacker with a clear starting point. The same concept can be applied to keyboards by using a thermal camera with the help of machine learning, but it also turns out that some types of keys and typing styles are harder to read than others.

Researchers at the University of Glasgow show how machine learning can pull details from thermal images like these quickly and effectively.

Touching a key with a fingertip imparts a slight amount of body heat, and that small amount of heat can be spotted by a thermal sensor. We’ve seen this basic approach used since at least 2005, and two things have changed since then: thermal cameras gotten much more common, and researchers discovered that by combining thermal readings with machine learning, it’s possible to eke out slight details too difficult or subtle to spot by human eye and judgement alone.

Here’s a link to the research and findings from the University of Glasgow, which shows how even a 16 symbol password can be attacked with an average accuracy of 55%. Shorter passwords are much easier to decipher, with the system attacking 6 and 8 symbol passwords with an accuracy between 92% and 80%, respectively. In the study, thermal readings were taken up to a full minute after the password was entered, but sooner readings result in higher accuracy.

A few things make things harder for the system. Fast typists spend less time touching keys, and therefore transfer less heat when they do, making things a little more challenging. Interestingly, the material of the keycaps plays a large role. ABS keycaps retain heat far more effectively than PBT (a material we often see in custom keyboard builds like this one.) It also turns out that the tiny amount of heat from LEDs in backlit keyboards runs effective interference when it comes to thermal readings.

Amusingly this kind of highly modern attack would be entirely useless against a scramblepad. Scramblepads are vintage devices that mix up which numbers go with which buttons each time the pad is used. Thermal imaging and machine learning would be able to tell which buttons were pressed and in what order, but that still wouldn’t help! A reminder that when it comes to security, tech does matter but fundamentals can matter more.

Pocket-Sized Thermal Imager

Just as the gold standard for multimeters and other instrumentation likely comes in a yellow package of some sort, there is a similar household name for thermal imaging. But, if they’re known for anything other than the highest quality thermal cameras, it’s excessively high price. There are other options around but if you want to make sure that the finished product has some sort of quality control you might want to consider building your own thermal imaging device like [Ruslan] has done here.

The pocket-sized thermal camera is built around a MLX90640 sensor from Melexis which can be obtained on its own, but can also be paired with an STM32F446 board with a USB connection in order to easily connect it to a computer. For that, [Ruslan] paired it with an ESP32 board with a companion screen, so that the entire package could be assembled together with a battery and still maintain its sleek shape. The data coming from the thermal imagining sensor does need some post-processing in order to display useful images, but this is well within the capabilities of the STM32 and ESP32.

With an operating time on battery of over eight hours and a weight under 100 grams, this could be just the thing for someone looking for a thermal camera who doesn’t want to give up an arm and a leg to one of the industry giants. If you’re looking for something even simpler, we’ve seen a thermal camera based on a Raspberry Pi that delivers its images over the network instead of on its own screen.

A Single-Resistor Radio Transmitter, Thanks To The Power Of Noise

One of the great things about the Hackaday community is how quickly you find out what you don’t know. That’s not a bad thing, of course; after all, everyone is here to get smarter, right? So let’s work together to get our heads around this paper (PDF) by [Zerina Kapetanovic], [Miguel Morales], and [Joshua R. Smith] from the University of Washington, which purports to construct a low-throughput RF transmitter from little more than a resistor.

This witchcraft is made possible thanks to Johnson noise, also known as Johnson-Nyquist noise, which is the white noise generated by charge carriers in a conductor. In effect, the movement of electrons in a material thanks to thermal energy produces noise across the spectrum. Reducing interference from Johnson noise is why telescopes often have their sensors cooled to cryogenic temperatures. Rather than trying to eliminate Johnson noise, these experiments use it to build an RF transmitter, and with easily available and relatively cheap equipment. Continue reading “A Single-Resistor Radio Transmitter, Thanks To The Power Of Noise”