What Does The Bat Say? Tune In With This Heterodyne Detector

June 27, 2020 by Sven Gregori 29 Comments

Bats are fascinating animals, and despite all the myth and creepiness surrounding them, they really remind one more of a drunk bird lost in the night sky than the blood-sucking creature they’re often made out to be. Of course, some really fall into that category, and unlike actual birds, bats don’t tend to grace us with their singsong — at least not in ways audible for us humans. But thanks to bat detectors, we can still pick up on it, and [Marcel] recently built a heterodyne bat detector himself.

Bat Detector in its enclosure — The bat detector (and an insight to the beauty of German language, where a bat is a *flutter mouse)*

The detector is made with a 555, an MCP6004 op amp, and a 4066 analog switch — along with a bunch of passives — and is neatly packed into a 3D-printed case with a potentiometer to set the volume and center frequency for the detection. The bat signal itself is picked up by a MEMS microphone with a frequency range [Marcel] found suitable for the task. His write-up also goes in all the mathematics details regarding heterodyning, and how each component plays into that. The resulting audio can be listened to through a headphone output, and after putting together an adapter, can also be recorded from his smartphone. A sample of how that sounds is added in his write-up, which you can also check out after the break.

In case you want to give it a try yourself, [Marcel] put all the design files and some LTSpice simulations on the project’s GitHub page. If you are curious about bat detectors in general and want to read more about them, follow [Pat Whetman] down that rabbit hole, or have a look at this one made in Python for something more software-focused.

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Nothing Comes From Nowhere

June 27, 2020 by Elliot Williams 19 Comments

How do you come up with new ideas? As much as it sometimes seems like they arrive in a flash out of the blue, they don’t just come out of nowhere. Indeed, we all have well-stocked mental toolboxes that say “this thing can be used to do that” and “if you want to get there, start here”.

One incredibly fertile generator of “new” ideas is simply putting old ideas next to each other and realizing that a chain of two or three can get you to someplace new. It just happened to me while listening to Mike and myself on this week’s Hackaday Podcast.

Here’s the elevator pitch. You take something like the player-pianoesque MIDI barrel piano that we featured last Thursday, and mix it together with the street-painting bicycle trailer that we featured on Friday. What do you get? A roll of paper that can be drawn on by normal kids, rolled up behind a bicycle, with a tank that they can pressurize with a bike pump, that will spray a pixelated version of their art as they roll down the sidewalk.

Now how can I make this real? One of my neighbors has a scrap bike trailer…

But see what I mean about ideas? I just took two existing ideas and rubbed them together, and in this case, they emitted sparks. And I’ve got a mental catalogue of all of the resources around me, some of which fell right into place. This role as fountain of good proto-ideas is why I started reading Hackaday fifteen years ago, and why it’s still a daily must-read for folks like us everywhere. A huge thank you to everyone who’s sharing! Read more Hackaday!

Recreating Paintings By Teaching An AI To Paint

June 27, 2020 by Maya Posch 9 Comments

The Timecraft project by [Amy Zhao] and team members uses machine learning to figure out a way how an existing painting may have been originally been painted, stroke by stroke. In their paper titled ‘Painting Many Pasts: Synthesizing Time Lapse Videos of Paintings’, they describe how they trained a ML algorithm using existing time lapse videos of new paintings being created, allowing it to probabilistically generate the steps needed to recreate an already finished painting.

The probabilistic model is implemented using a convolutional neural network (CNN), with as output a time lapse video, spanning many minutes. In the paper they reference how they were inspired by artistic style transfer, where neural networks are used to generate works of art in a specific artist’s style, or to create mix-ups of different artists.

A lot of the complexity comes from the large variety of techniques and materials that are used in the creation of a painting, such as the exact brush used, the type of paint. Some existing approaches have focused on the the fine details here, including physics-based simulation of the paints and brush strokes. These come with significant caveats that Timecraft tried to avoid by going for a more high-level approach.

The time lapse videos that were generated during the experiment were evaluated through a survey performed via Amazon Mechanical Turk, with the 158 people who participated asked to compare the realism of the Timecraft videos versus that of the real time lapse videos. The results were that participants preferred the real videos, but would confuse the Timecraft videos for the real time lapse videos half the time.

Although perhaps not perfect yet, it does show how ML can be used to deduce how a work of art was constructed, and figure out the individual steps with some degree of accuracy.

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The Trouble With Tamagotchis…

June 27, 2020 by Jenny List 7 Comments

The must-have toy of a couple of decades ago was the Tamagotchi, a virtual pet in an LCD screen on a keyring, that demanded your attention and which would die were you to neglect it. Fortunately it had a reset button on the back through which it could be resuscitated, but even so it lacked a satisfying tactile experience. [Nadine] has done something about this with her Tamagotchi-style Tribble, an anthropomorphic ball of fluff that demands attention and purrs when it receives some.

Inside the ball of fake fur is an Adafruit Circuit Playground with a capacitive touch pad and a haptic motor. After a random time with no attention it “cries”, and its owner strokes it, after which it responds with a purring vibration. It’s quite cute as you can see in the Twitter video below, and fortunately it won’t multiply and fill up your starship. We wonder whether a small resistive heater to give it a body temperature would complete its appeal as a virtual pet.

Given the popularity of Star Trek TOS among Hackaday readers perhaps it’s surprising that we don’t see more Tribble related projects. They have made a notable appearance as a DEF CON badge though.

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Hinge Brings New Meaning To Flexible PCB

June 26, 2020 by Al Williams 9 Comments

It is not a secret that flexible PC boards can bend. But despite the substrate’s flexibility, you can’t really fold them completely over. That bothered [Carl] so he developed a hinge design so that he can fold a board completely in half. You can watch a video showing an example, FlexBox, below.

Normal boards can fold over, but the copper traces can’t tolerate a very tight bend radius. [Carl’s] trick is to make the folding part have no traces at all. Only a small bridge carries traces between the two halves and it is allowed to bend almost like an interconnecting cable.

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Smart Thermometer Can Tell Flu From Cold

June 26, 2020 by Moritz v. Sivers 20 Comments

Before the outbreak of coronavirus, the seasonal flu was one of the most dangerous infectious diseases, but a lot of people have trouble telling the difference between a flu and a cold by their symptoms alone. This gave [M. Bindhammer] the idea to design a smart thermometer that can distinguish between flu and cold.

Automated medical diagnostics is certainly an important technology of the future. [M. Bindhammer]’s project, named F°LUEX, is the second version of his iF°EVE thermometer. After taking the body temperature it asks the patient a set of questions about his symptoms and then calculates the probability of whether it is more likely to be a flu or a cold. [M. Bindhammer] uses a method commonly used in medical diagnostics based on Bayesian statistics which assigns a probability score to both hypotheses. It takes into account how often a certain symptom occurs when you have a common cold or flu as well as the overall probability of catching one or the other.

The hardware of the project is based on a custom PCB that includes a medical-grade MLX90614 infrared thermometer with an accuracy of ±0.2˚C around the human body temperature. The sensor is being read out by a Teensy 3.2 and information is displayed on a small OLED screen. Everything is housed in a 3D printed enclosure that received a nice finishing by painting with primer and acrylic spray paint. Unfortunately, [M. Bindhammer] project also got delayed by the corona crisis as his order for the temperature sensor got canceled due to the current high demand. But that does make us wonder how useful this could be to discriminate between cold, flu, and COVID-19.

An IR thermometer is something useful to have around not only for medical applications and can also be built without a custom PCB and minimal parts.

Ask Hackaday: What Can Be Done With Your Bootlooping Blu-Ray?

June 26, 2020 by Lewin Day 159 Comments

Last Friday, thousands of owners of Samsung Blu Ray players found that their home entertainment devices would no longer boot up. While devices getting stuck in a power-cycling loop is not uncommon, this case stands out as it affected a huge range of devices all at the same time. Samsung’s support forum paints a bleak picture, with one thread on the issue stretching to 177 pages in just a week.

So what is going on, and what can be done to fix the problem? There’s a lot of conflicting information on that. Some people’s gear has started working again, others have not and there are reports of customers being told to seek in-person repair service. Let’s dive in with some wild speculation on the problem and circle back by commiserating about the woes of web-connected appliances.

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