Listening In On Muscles With The BioAmp EMG Pill

Ever felt like what your MCU of choice misses is a way to read the electrical signals from your muscles? In that case [Deepak Khatri] over at Upside Down Labs has got your back with the BioAmp EMG Pill. Described as an affordable, open source electromyography (EMG) module, based around a TL074 quad low-noise JFET-input opamp. At just over 32×10 millimeters, it’s pretty compact as well.

The onboard opamp ensures that the weak electrical signals captured from the muscles when they move are amplified sufficiently that the ADC of any microcontroller or similar can capture the signal for further processing. Some knowledge of how to set up an EMG is required to use the module, of course, and the TL074 opamp prefers an input voltage between 7-30 V. Even so, it has all the basics onboard, and the KiCad project is freely available via the above linked GitHub project.

In addition, [Deepak] also tweeted about working on an affordable, open source active prosthetics controller (and human augmentation device), which has us very much interested in what other projects may come out of Upside Down Labs before long. After, all we’re no strangers to hacking with biosignals.

The Tube Map, In Glorious 8-Bit!

There was a time when visitors to London would carry an A to Z map to navigate the city’s Undergound railway system, referring to the iconic London Transport map printed on its back as they did so. Now it’s likely they’ll do the same with their smartphones, with apps ranging from simple analogues of the printed version through to fully annotated route planners with up to the minute train information. Is this a new technology, something only possible in the last decade? Serial British rail YouTuber [Geoff Marshall] thinks otherwise, and has programmed a Tube map on a vintage BBC Micro.

We don’t expect anyone to heft a pile of vintage hardware onto the Central Line at rush hour even though in reality he’s running it on an emulator due to his real BBC Micro being kaput. Perhaps someone should drop him a line about capacitor replacement in that power supply. But it does provide an entertaining jaunt back into afternoons in a 1980s school computer lab, with MOVE, DRAW, and PLOT commands as he wrestles with the limited colour palette of MODE 2.  The result only covers Tube Zone 1, or the very centre of London, so to visit London Hackspace you’ll have to remember to take the Bakerloo line northbound out to Zone 4 and disembark at Wembley Central.

Happily as you can see in the video below the break he enlists the help of a friend to run it on real hardware. He posted the code as a comment to the video but it’s really hard to find. Try this direct link and scroll down, it should be the first comment but you need to click “Read more” to unfold the code. We think the Tube Map would make a great test for any retrocomputer, so we look forward to this feat being repeated.

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DRehmFlight: Customizable Flight Stabilisation For Your Weird Flying Contraptions

The availability of cheap and powerful RC motors and electronics has made it possible for almost anyone to build an RC flying machine. Software is usually the bigger challenge, which has led to the development of open-source packages like BetaFlight and Ardupilot. These packages are very powerful, but not easy to modify if you have unconventional requirements. [Nicholas Rehm] faced this challenge while doing his master’s degree, so he created dRehmFlight, a customizable flight controller for VTOL aircraft. Overview video after the break.

dRehmFlight runs on Teensy 4.0 with a MPU6050 or MPU9250 IMU

[Nicholas] has been building unique VTOL aircraft for close to a decade, and he specifically wanted flight stabilization software that is easy to modify and experiment with. Looking at the dRehmFlight code, we think he was successful. The main flight controller package is a single file of fewer than 1600 lines. It’s well commented and easy to figure out, even for an inexperienced programmer. A detailed PDF manual is also available, with full descriptions for all the functions and important variables, and a couple of tutorials to get you started. Libraries for interfacing with accelerometers and RC gear is also included. It runs on a 600 Mhz Teensy 4.0, and all the programming can be done from the Arduino IDE.

[Nicholas] has repeatedly demonstrated the capabilities of dRehmFlight with several unique aircraft, like the belly flopping RC Starship we covered a while ago, a VTOL quad rotor biplane, VTOL F35, and the cyclocopter seen in the header image. dRehmFlight might not have the racing drone performance of BetaFlight, or advanced autopilot features of Ardupilot, but it’s perfect for getting unconventional aircraft off the ground. Continue reading “DRehmFlight: Customizable Flight Stabilisation For Your Weird Flying Contraptions”

A Volume Control From A VCR Drum

The VHS VCR has now passed from widespread use, and can thus be found as a ready supply of interesting parts for the curious hardware hacker. [Clewsy] has a novel use for a VCR head scanning drum, the part that is supposed to be tasked with reading information off of magnetic tape. Instead, it’s reading information from fingers as the knob for a USB volume control. Underneath the drum is an optical encoder disk which is read by an ATmega32U4 for USB interfacing with a host computer.

The helical-scan video recorder was a mechanically complex solution to the problem of recording a high-bandwidth video signal onto a tape that could be made slow-moving enough to be practical. By recording the video in diagonal stripes across the tape from a fast-moving spinning head they avoided the need for huge reels of tape, enabling hours of video to be fitted into a roughly book-size cassette.

While over time the mechanics of a VCR mechanism were simplified and cheapened to a great extent, the heads and drum were the one area that could not be compromised. Thus the VCR head was for a time the most high-precision mechanical device owned by most consumers, and the drums usually have exceptionally nice bearings. All of this makes one a particularly good choice for a volume knob or indeed any other large rotational control, so much so that we’re surprised it hasn’t become a more frequent occurrence. So scour the electronic junk, and you might just find the ultimate in free high quality control hardware.

Of course, this isn’t the only thing a VCR head drum can do.  How about a centrifuge?

Racing Game Crashes Into Its Next Life As A Sound Bender

They say the best things in life are free, but we would loudly argue that a dollar can go a long way, too. It all depends on what you do with it. When [lonesoulsurfer] saw this busted-up handheld racing game at the junk store, he fell in love with the lines of the case and gladly forked over a buck in order to give it a new life as a wicked little sound-bending machine with dancing LEDs.

Here’s how it works: [lonesoulsurfer] records a few seconds of whatever into the mic with the looping function switched off, then turns it back on to start the fun. He can vary the pitch with the speed controller pot, or add in some echo and reverb. Once the sound is dialed in, he works the pause button on the left to make melodies by stopping and restarting the loop, or just pausing it momentarily depending on the switch setting.

The electronics are a mashup of modules mixed with a custom PCB that combines the recording module with an LM386 amplifier and holds the coolest part of this build — those LEDs that dance to the music behind the toy’s original lenticular screen. Like most of [lonesoulsurfer]’s builds, it’s powered by an old cell phone battery that’s buck-boosted to 5 V. Check out the build and bleep-bloop video after the break.

Lenticular lenses are all kinds of fun. Get one that’s big enough, and you can use it to disappear for a while.

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Signal Conditioning Hack Chat This Wednesday

Join us on Wednesday, February 17 at noon Pacific for the Signal Conditioning Hack Chat with Jonathan Foote!

The real world is a messy place, because very little in it stays in a static state for very long. Things are always moving, vibrating, heating up or cooling down, speeding up or slowing down, or even changing in ways that defy easy description. But these changes describe the world, and understanding and controlling these changes requires sensors that can translate them into usable signals — “usable” being the key term.

Making a signal work for you usually requires some kind of signal processing — perhaps an amplifier to boost a weak signal from a strain gauge, or a driver for a thermocouple. Whatever the case, pulling a useful signal that represents a real-world process from the background noise of all the other signals going on around it can be challenging, as can engineering systems that can do the job in sometimes harsh environments. Drivers, filters, amplifiers, and transmitters must all work together to get the clearest picture of what’s going on in a system, lest bad data lead to bad decisions.

To help us understand the world of signal conditioning, Jonathan Foote will drop by the Hack Chat. You may remember Jonathan as the “recovering scientist” who did a great Remoticon talk on virtual modular synthesizers. It turns out that synths are just a sideline for Dr. Foote, who has a Ph.D. in Electrical Engineering and a ton of academic experience. He’s a bit of a Rennaissance man when it comes to areas of interest — machine learning, audio analysis, robotics, and of course, signal processing. He’ll share some insights on how to pull signals from the real world and put them to work.

join-hack-chatOur Hack Chats are live community events in the Hack Chat group messaging. This week we’ll be sitting down on Wednesday, February 17 at 12:00 PM Pacific time. If time zones have you tied up, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.

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The Rotary-X Engine Is A Revolution In Thermodynamics

If you’re running an army, chances are good that you need a lot of portable power for everything from communications to weapons control systems. When it comes to your generators, every ounce counts. The smaller and lighter you can get them, the better.

Connecticut-based company LiquidPiston is developing a high-powered generator for the US Army that uses the company’s own rotary x-engine — a small, light, and powerful beast that sounds like a dream come true. It can run on gasoline, diesel, natural gas, kerosene, or jet fuel, and is scalable from 1 to 1,000 horsepower (PDF).

Co-founder and CEO Alex Schkolnik describes the design as a combination of the best parts of the Otto and Atkinson cycle engines, the Diesel, and the Wankel rotary while solving the big problems of the latter two. That sounds impressive, but it doesn’t mean much unless you understand how each of these engines work and what their various advantages and disadvantages are. So let’s take a look under the hood, shall we?

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