A Wearable That Jives To The Beat Of Your Heart

We’re always searching for the coolest biohacking projects all over the web, so imagine our excitement when we ran across [marcvila333’s] wearable biometric monitor on Instructables. This was a combined effort between [Marc Vila], [Guillermo Stauffacher], and [Pau Carcellé] as they were wrapping up the semester at their university. Their goal was to develop an integrated device that could modulate the wearer’s heart, and subsequently their mood and stress levels, using music.

Their device includes an LCD screen for user feedback, buttons for user input, an MP3 module, and a heart rate sensor module. The user can measure their heart rate and use the buttons to select the type of music they desire based on whether they would like to decrease or increase their heart rate. The science behind this phenomenon is still unknown, but the general sense is that different music can trigger different chemical signals in your brain, subsequently affecting your mood and other subtle physiological effects. I guess you can say that we tend to jive to the beat of our music.

It would be really cool to see their device automatically change the song to either lower or raise the user’s heart rate, making them calmer or more engaged. Maybe connect it to your tv? Currently, the user has to manually adjust the music, which might be a bit more inconvenient and could possibly lead to the placebo effect.

Either way; Cool project, team. Thanks for sharing!

Hackaday Links: June 7, 2020

For many of us who were in college at the time, the 1989 release of Will Wright’s classic SimCity sounded the death knell of our GPAs. Being able to create virtual worlds and then smite them with a tornado or a kaiju attack was the stuff of a procrastinator’s dreams. We always liked the industrial side of the game best, and took great pains in laying out the factory zones, power plants, and seaports. Those of a similar bent will be happy to know that Maxis, the studio behind the game, had a business simulations division, and one of their products was a complete refinery simulator the studio built for Chevron called, unsurprisingly, SimRefinery. The game, which bears a striking resemblance to SimCity, has been recovered and is now available for download, which means endless procrastination by playing virtual petrochemical engineer is only a mouse click away.

Speaking of time wasters, we stumbled upon another simulation this week that sucked away a couple of hours of productivity. As RTL-SDR.com reports, YouTuber called Information Zulu has a 24/7 live stream showing arrivals and departures at Los Angeles International Airport. That may sound boring, but the cameras used to watch the runways are virtual, and the planes are animated based on ADS-B data being scooped up by an RTL-SDR dongle. We pinged Information Zulu and asked for a rundown of the gear behind the system, but never heard back. If we do, we’ll post a full article on what we learned, because the level of detail is amazing. The arriving and departing planes sport the correct livery for the airline, the current weather conditions are shown, taxiing is shown in real time, and there’s even an audio feed from air traffic control.

If you’re looking to gain back a little of the productivity lost to the last two items, Digi-Key might be able to help with their new PCB Builder service. All you have to do is upload your gerbers and select your materials, and they’ll give you options for a bunch of different quick-turn fabrication houses. Looks mighty convenient.

Steve Mould dropped a video this week about vibration analysis. That might not sound very exciting, but the fascinating bit is how companies are now using motion amplification video techniques to show how and where industrial equipment is moving, even if those motions are too subtle to be seen by the naked eye. It’s frankly terrifying to see how pipes flex and tanks expand and contract, and how pumps and motors move relative to each other. The technique used is similar to the way a person’s pulse can be detected on a video by the subtle color change as blood rushes into capillaries. We’d love to see someone tackle a homebrew version of this so we can all see what’s going on around us.

And finally, we want to remind everyone that the Hackaday Prize is back, and that you should get your entries going. What’s new this year is the Dream Team challenges, where four worthy non-profits organizations will each assemble a three-person team to work on a specific pain-point in their process. The application deadline has been extended to June 9, and there are two $3,000 microgrants, one in June and one in July, for each team member. So look through the design briefs and see if your skills match their needs.

FM Signal Detection The Pulse-Counting Way

Compared to the simple diode needed to demodulate AM radio signals, the detector circuits used for FM are slightly more complicated. Wrapping your head around phase detectors, ratio detectors, discriminators, and quadrature detectors can be quite an exercise. There’s another demodulation method that’s not so common, but thankfully it’s also pretty easy to understand: the pulse counting detector.

As [Allan (W2AEW)] notes in the video below, pulse counting is a bit of a misnomer. Pulse counting works by generating a narrow, fixed-width square wave pulse at a set point in the received FM signal’s waveform, usually at the zero-crossing point. Since the frequency of the modulated carrier changes, the duty cycle of the resulting pulse train varies. That means there will be a fixed number of pulses, but by taking the average voltage of the pulse train, we can tease out the original audio frequency signal.

Simple in theory is often more complicated in practice, and [W2AEW] goes into some detail about those complications, such as needing to use a down-converter to make the peak-to-peak frequency deviation in the pulse train more easily detectable. As is his style, he walks us through a test circuit to prove that the theory works in practice. A simple two-transistor circuit generates the pulses at the zero-crossing point, a low-pass filter cleans up the signal, and a cheap audio amplifier reproduces the original audio. It’s a crude circuit to be sure, relying on the stray capacitance of the breadboard to work, but it proves the point and serves as a jumping-off point for further experiments – perhaps using an Arduino to count the pulses?

We always enjoy [W2AEW]’s videos and learn a lot from them. Not long ago we featured another of his videos talking about the mysteries of RF modulation; SSB, anyone?

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Control Your Web Browser Like It’s 1969

Imagine for a moment that you’ve been tasked with developing a device for interfacing with a global network of interconnected devices. Would you purposely design a spring-loaded dial that can do nothing but switch a single set of contacts on and off from 1 to 10 times? What kind of crazy world would we have to live in where something like that was the pinnacle of technology?

Obviously, such a world once existed, and now that we’ve rolled the calendar ahead a half-century or so, both our networks and our interfaces have gotten more complex, if arguably better. But [Jan Derogee] thinks a step backward is on order, and so he built this rotary phone web browser. The idea is simple: pick up the handset and dial the IP address of the server you want to connect to. DNS? Bah, who needs it?

Of course there is the teensy issue that most websites can’t be directly accessed via IP address anymore, but fear not – [Jan] has an incredibly obfuscated solution to that. It relies on the fact that many numbers sound like common phrases when sounded out in Chinese, so there end up being a lot of websites that have number-based URLs. He provides an example using the number 517, which sounds a bit like “I want to eat,” to access the Chinese website of McDonald’s. How the number seven sounding like both “eat” and “wife” is resolved is left as an exercise to the reader.

And here we thought [Jan]’s rotary number pad was of questionable value. Still, we appreciate this build, and putting old phones back into service in any capacity is always appreciated.

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Simple Ultrasound Machine Shows The Skeleton Lurking Inside Us All

That first glimpse of a child in the womb as a black and white image on a screen is a thrilling moment for any parent-to-be, made possible by several hundred thousand dollars worth of precision medical instrumentation. This ultrasound machine cobbled together from eBay parts and modules is not that machine by a long shot, but it’s still a very cool project that actually gives a peek inside the skin.

The ultrasound transducer used by [stoppi71] in this build has an unusual source: a commercial paint-thickness meter. Cue the jokes about watching paint dry, but coatings measurement is serious stuff. Even so, the meter in question only ran about $40 on eBay, and provided the perfect transducer for the build. The sender needs a 100V pulse at about 5 MHz, so [stoppi71] had some fun with a boost converter and a 74121 Schmitt-trigger one-shot driving a MOSFET to switch the high voltage. On the receive side, the faint echo is sent through a three-stage amp using AD811 op amps before going through an LM7171 op amp acting as a rectifier and peak detector. Echos are sent to an Arduino Due for display on a 320×480 LCD. The resolution isn’t great, but the video below shows that it’s enough to see reflections from the skin of [stoppi71]’s forearm and from the bones within.

[stoppi71] says that he was inspired to tackle this build by Murgen, an open-source ultrasound project. That project got further refined and entered into the “Best Product” category in the 2018 Hackaday Prize. We like that because focusing on turning projects into products is what this year’s Hackaday Prize is all about.

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Arduino Heart Rate Monitor Has Star Trek Chic

Building a real-life version of the Star Trek tricorder has been the goal of engineers and hackers alike since the first time Dr McCoy complained about being asked to work outside of his job description. But while modern technology has delivered gadgets remarkably similar in function, we’ve still got a long way to go before we replicate 24th century Starfleet design aesthetic. Luckily there’s a whole world of dedicated hackers out there who are willing to take on the challenge.

[Taste The Code] is one such hacker. He wanted to build himself a practical gadget that looked like it would be at home on Picard’s Enterprise, so he gathered up the components to build a hand-held heart rate monitor and went in search for a suitable enclosure. The electronics were simple enough to put together thanks to the high availability and modularity we enjoy in a post-Arduino world, but as you might expect it’s somewhat more difficult to put it into a package that looks suitably sci-fi while remaining functional.

Internally his heart rate monitor is using an Arduino Pro Mini, a small OLED screen, and a turn-key pulse sensor which was originally conceived as a Kickstarter in 2011 by “World Famous Electronics”. Wiring is very simple: the display is connected to the Arduino via I2C, and the pulse sensor hooks up to a free analog pin. Everything is powered by 3 AA batteries delivering 4.5 V, so he didn’t even need a voltage regulator or the extra components required for a rechargeable battery pack.

Once everything was confirmed working on a breadboard, [Taste The Code] started the process of converting a handheld gyroscopic toy into the new home of his heart rate monitor. He kept the battery compartment in the bottom, but everything else was stripped out to make room. One hole was made on the pistol grip case so that a finger tip could rest on the pulse sensor, and another made on the side for the OLED screen. This lets the user hold the device in a natural way while getting a reading. He mentions the sensor can be a bid fiddly, but overall it gives accurate enough readings for his purposes.

If you’re more interested in the practical aspects of a real-life Star Trek tricorder we’ve seen several projects along those lines over the years, including a few that were entered into the Hackaday Prize.

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Low-Power Motor Can Run For Years On A Coin Cell

Can you run an electric motor for two years on a single lithium coin cell? [IamWe] figured out how to do it, and even though his donut motor doesn’t look like any motor we’ve ever seen before, it’s a pretty solid lesson in low-current design.

The donut motor is really just a brushless DC motor with a sign-pole stator and a multi-pole rotor. The frame of the motor is built from a styrofoam donut, hence the motor’s name. The rotor is a styrofoam sphere with neodymium magnets embedded around its equator. A sharpened bicycle spoke serves as an axle, and clever magnetic bearings provide near-zero friction rotation. The stator coil comes from an old solenoid and is driven by a very simple two-transistor oscillator. [IamWe]’s calculations show that the single CR2032 coin cell should power this motor for over two years. This one looks easy enough to whip up that it might make a nice project for a long winter’s night. Watch it spin in the video below.

This one seems like a perfect entry for the Coin Cell Challenge contest. Sure, it may not be a coin cell jump starter for your car, but our guess is this motor will still be spinning in 2020, and that’s no mean feat.

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