7-Segment Display Is No Small Feat

July 12, 2020 by 13 Comments

The 7-segment display certainly is a popular build, and surprisingly people still come up with new takes on this over a hundred-year-old way to represent numbers. This time [jegatheesan.soundarapandian] is making it big by building a giant 7 feet tall 7-segment display.

Apparently, the plan is to build a giant clock so he started off by making the first digit. To keep it cheap and simple the segments are made from corrugated cardboard which was carefully cut, folded, and then glued together. The light-diffusing lid is simply made from white paper. He used the ubiquitous WS2812B strips to light up the segments, but things turned out to be more complicated as he was not able to get enough strips to fill up all the segments. This forced him to cut up the strip into individual pieces and space them out by reconnecting the LEDs with wires. Cutting, stripping, and soldering 186 wires took him almost 10 hours. An Arduino Uno serves as the brains of the device and there is a nice Android app to control it via Bluetooth.

We are excited to see the complete clock once it is finished. In the meantime let us remember other epic displays like that made from 144 individual 7-segment displays or the giant LED video wall using 1200 ping pong balls.

Video after the break.

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SoftCore CPU Comparison

July 12, 2020 by 19 Comments

Monty Python once did a sketch where people tried to summarize Proust in fifteen seconds. Although summarizing eight FPGA-based CPUs is almost as daunting, [jaeblog] does a nice job of giving a quick sketch of how the CPUs work with the Xilinx Vivado toolchain and the Digilent Arty board.

The eight CPUs are:   VexRiscv, LEON3, PicoRV32, Neo430, ZPU, Microwatt, S1 Core, and Swerv EH1.

The comparison criteria were very practical: A C compiler (gcc or llvm) for each CPU and no CPUs that were tied to a particular FPGA. Two of the CPUs didn’t fit on the Arty board, so their comparisons are a bit more theoretical.  There were other considerations such as speed, documentation, debugging support, and others.

It was interesting to see the various CPUs ranging from some very mature processors to some new kids on the block, and while the evaluations were somewhat subjective, they seemed fair and representative of the things you’d look for yourself. You can also get the test code if you want to try things for yourself.

The winner? The post identifies three CPUs that were probably the top choices, although none were just perfect. Of course, your experience may vary.

If you want an easy introduction to adding things to a soft CPU, this RISC-V project is approachable. Or if you prefer SPARC, check out this project.

Learn The Secrets Of Matching Bottle Cap Threads To One Another

July 12, 2020 by 25 Comments

Do you want to design something to match existing threads on a bottle, or a cap? It turns out there’s an easier way than reaching tiredly for the calipers and channeling one’s inner reverse-engineer. Bottle cap threads — whose industry term is the neck finish — aren’t arbitrary things; they are highly standardized, and [Noupoi] researched it all so that you don’t have to! The Bottle Cap Thread Calculator takes a few key measurements and spits out everything needed to model exact matches. Need some guidance on how exactly to use the information the calculator spits out? There is a handy link to a Fusion360 tutorial on creating bottle threads (YouTube video) to demonstrate.

This all came from [Noupoi] wanting to model an adapter to transfer the contents of one bottle to another, smaller bottle. By identifying which thread was used on each bottle, the job of modeling a matching adapter was much easier. It turns out that the bottle necks were an SP 28-415 (larger) and a 24-415 (smaller), and with that information the adapter was far simpler to design. If you want to check the adapter out, it’s available on Thingiverse.

If truly reverse-engineering bottle threads is needed, here’s a method we covered that involves making a simple cast and working from that.

[via Reddit]

Life-Saving Surgery For A Telescopic Antenna

July 11, 2020 by 19 Comments

Whether it was as an impulsive youth or an impatient adult, there’s probably few among us who haven’t broken a telescopic antenna or two over the years. It doesn’t take much to put a bend in the thin walled tubing, and after that, all bets are off. So [The Amateur Engineer] couldn’t really be too upset when his son snapped the antenna off the transmitter of an old RC truck. Instead, he decided to take it apart and see how it could be repaired.

Taking a thin screwdriver to the antenna’s bottom most segment, he was able to widen up the opening enough to remove the upper sections as well as recover the broken piece and copper locking plates. He cut out the damaged area and drilled new holes for the pins on the copper plates to fit into. Inserting the repaired section back into the lowest segment was no problem, but he says it took a little trial and error before he was able to roll the edge over enough to keep the antenna from falling apart.

Buying a replacement would certainly have been easier, but as the radios in our devices have moved into the higher frequencies, these collapsible antennas have become a bit harder to come by. Modern RC vehicles operate on 2.4 GHz, so they don’t need the long antennas that the older 27 MHz systems utilized. [The Amateur Engineer] did find a few direct replacements online, but none for a price he was willing to pay.

We might have used the broken transmitter as an excuse to switch the RC vehicle over to WiFi control, but we appreciate [The Amateur Engineer] showing how this type of antenna can be disassembled and repaired if necessary.

Detect COVID-19 Symptoms Using Wearable Device And AI

July 11, 2020 by 9 Comments

A new study from West Virginia University (WVU) Rockefeller Neuroscience Institute (RNI) uses a wearable device and artificial intelligence (AI) to predict COVID-19 up to 3 days before symptoms occur. The study has been an impressive undertaking involving over 1000 health care workers and frontline workers in hospitals across New York, Philadelphia, Nashville, and other critical COVID-19 hotspots.

The implementation of the digital health platform uses a custom smartphone application coupled with an Ōura smart ring to monitor biometric signals such as respiration and temperature. The platform also assesses psychological, cognitive, and behavioral data through surveys administered through a smartphone application.

We know that wearables tend to suffer from a lack of accuracy, particularly during activity. However, the Ōura ring appears to take measurements while the user is very still, especially during sleep. This presents an advantage as the accuracy of wearable devices greatly improves when the user isn’t moving. RNI noted that the Ōura ring has been the most accurate device they have tested.

Given some of the early warning signals for COVID-19 are fever and respiratory distress, it would make sense that a device able to measure respiration and temperature could be used as an early detector of COVID-19. In fact, we’ve seen a few wearable device companies attempt much of what RNI is doing as well as a few DIY attempts. RNI’s study has probably been the most thorough work released so far, but we’re sure that many more are upcoming.

The initial phase of the study was deployed among healthcare and frontline workers but is now open to the general public. Meanwhile the National Basketball Association (NBA) is coordinating its re-opening efforts using Ōura’s technology.

We hope to see more results emerge from RNI’s very important work. Until then, stay safe Hackaday.

Interactive CNC Foam Cutter Churns Out Abstract Art

July 11, 2020 by 3 Comments

Foam is certainly an indispensable raw material for various craft and construction projects. Any serious sculptor however, inevitably grows tired of grinding through a foam block using a simple preheated utensil. The next step up, is to assemble a simple but thoroughly effective hot wire cutting contraption, formed out of a thin guitar wire held taut on a “C” shaped mounting frame. Finally, the addition of some electronics to regulate the power delivery makes this simple tool useful for most settings.

[Freddie] has taken this basic idea a step further, by building a complete multi-axis CNC foam cutter intended as an interactive exhibit on computational art. The CNC has the traditional three Cartesian axes but the platform hosting the foam piece can also rotate, introducing an additional degree of freedom. As this is indented to be controlled by attendees, there is no G-code in the mix, rather the inputs of an Xbox controller are applied directly to the work piece.

What is very interesting is how the resulting tool path is visualised and displayed. [Freddie] explains that while the user input tool path could be generated and displayed as equivalent G-code, it does not capture and convey the inherent organic nature of the finished pieces. The solution [Freddie] came up with is to display the toolpath much like a series of musical notes!

We would have loved to have a go at this machine in person, but seeing that isn’t possible in the current circumstances, you can either build a simpler machine we featured earlier or [Freddie] could perhaps fire up a camera and let us control it via the interweb, with a live video feed ofcourse!

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Hack Together Your Own Bat Signal

July 11, 2020 by 27 Comments

Bats use echolocation to see objects in front of them. They emit an ultrasonic pulse around 20 kHz (and up to 100 kHz) and then sense the pulses as they reflect off an object and back to the bat. It’s the same type of mechanism used by ultrasonic proximity sensors for object-avoidance. Humans (except perhaps the very young ones) can’t hear the ultrasonic pulses since the frequency is too high, but an inexpensive microphone in a simple bat detector could. As it turns out bat detectors are available off the shelf, but where’s the fun in that? So, like any good hacker, [WilkoL] decided to build his own.

[WilkoL’s] design is composed primarily of an electret microphone, microphone preamplifier, CD4040 binary counter, LM386 audio amplifier, and a speaker. Audio signals are analog and their amplitudes vary based on how close the sound is to the microphone. [WilkoL] wanted to pick up bat sounds as far away as possible, so he cranked up the gain of the microphone preamplifier by quite a bit, essentially railing the amplifiers. Since he mostly cares about the frequency of the sound and not the amplitude, he wasn’t concerned about saturating the transistor output.

The CD4040 then divides the signal by a factor of 16, generating an output signal within the audible frequency range of the human ear. A bat signal of 20 kHz divides down to 1.25 kHz and a bat signal of up to 100 kHz divides down to 6.25 kHz.

He was able to test his bat detector with an ultrasonic range finder and by the noise generated from jingling his keychain (apparently there are some pretty non-audible high-frequency components from jingling keys). He hasn’t yet been able to get a recording of his device picking up bats. It has detected bats on a number of occasions, but he was a bit too late to get it on video.

Anyway, we’re definitely looking forward to seeing the bat detector in action! Who knows, maybe he’ll find Batman.

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