An LED Heartbeat Display You Can Wear On Your Sleeve

April 30, 2021 by Zoe Skyforest 3 Comments

There are a few different ways to take a person’s pulse, with varying utility depending on the categories said patient fits in to. [Nitin Nair]’s method doesn’t really have a medical application, but it’s certainly a neat example of what you can do with modern sensors.

The build combines an EmotiBit sensor platform with an Adafruit Feather and accompanying Charlieplexed LED module. The EmotiBit packs a PPG, or photoplethysmogram sensor, otherwise known as a pulse oximeter, which uses optical methods to detect changes in blood volume beneath the skin. From this data, a pulse rate can be derived, and the LEDs flashed with a heart graphic in concert with the rhythm of the wearer’s heart. The benefit of the PPG in the EmotiBit is that it can be worn on the wearer’s arm, or other location with suitable vascularization. This allows the wearer to place the sensor on the arm, and thus wear their heart on their sleeve.

It’s a cool concept, and we’d love to see it neatly packaged with a smoothly animated fade as a sports accessory. It’d be an easy way to signal how fast your heart rate recovers on a run with friends – the device could brag about your fitness for you. Alternatively, if pulse oximetry isn’t enough for you, go ahead and build an ECG instead!

An Attempt At 3D Printing A Hybrid Rocket Engine

April 29, 2021 by Zoe Skyforest 6 Comments

Liquid fuelled engines are throttleable and monstrously powerful, but highly complex. Meanwhile, solid rocket engines are simple and cheap, but once you light them, they’re going full-bore until burnout. Hybrid rocket engines offer perks from both worlds, with simple solid fuel and the ability to throttle down by regulating oxidizer flow. Naturally, [Integza] decided he should try and 3D print one.

The build came about somewhat by accident, as the 3D printed casing of one of [Integza’s] liquid-fuelled rockets continued burning once the fuel was turned off. This prompted the realization that he could 3D print rocket fuel, and simply supply oxygen, creating a hybrid rocket. Thus ensued much experimentation, going so far as to create custom sugar-loaded resin for more power and experimenting with ABS as a potential fuel.

Most of the rockets self-destructed within a few seconds and thrust was minimal, but the basic concept should be a goer. As always, [Integza] is struggling with the thermal limitations of plastics, but we fully expect he’ll one day get to a flight ready engine. His previous experiments show he certainly doesn’t give up. Video after the break.

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Solar And Wind Could Help Support Ethiopia’s Grand Dam Project

April 29, 2021 by Zoe Skyforest 22 Comments

Ethiopia is in the midst of a major nation-building project, constructing the Grand Ethiopian Renaissance Dam (GERD). Upon completion, GERD will become the largest hydropower plant in Africa, providing much needed electricity for the country’s growing population.

The project dams the Blue Nile, a river which later flows into neighbouring Sudan, where it merges with the White Nile and then flows on to Egypt. Like all rivers that flow across political boundaries, concerns have been raised about the equitable management of the water resources to the benefit of those upstream and down. Too much water dammed upstream in GERD could have negative effects on Egyptian agriculture reliant on river flows, for example. Efforts are ongoing to find a peaceful solution that suits all parties. Recently, suggestions have been made to supplement the dam’s power output with solar and wind to minimise disruption to the river’s users.

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Print Your Own Wireless 2.1 Speaker System

April 29, 2021 by Zoe Skyforest 18 Comments

Buying a set of stylish bookshelf speakers is a perfectly reasonable thing to do, and remains legal in most free countries around the world. However, if you really want to impress with a pretty pair to crank out your tunes, you might consider designing and printing your own. [EH_Design] did just that with a stylish 2.1 Bluetooth audio system.

The 2.1 designation refers to the use of two stereo channels plus a subwoofer. It’s a popular setup as human perception means it’s not as necessary to have stereo imaging for low frequency content. The build uses a Texas Instruments TPA3116D2 Class D amplifier with a Bluetooth input, with the efficient design allowing the build to be more compact without the need for as much heat sinking. A 24 V supply delivering up to 3 A is specified, providing plenty of volume when needed. The speakers themselves consist of 3″ drivers mounted in attractive 3D-printed shells, with the “subwoofer” consisting of a pair of 5″ woofers paired up in a special isobaric enclosure that enables a smaller volume to acoustically act like one double the size.

The result is a futuristic-looking set of bookshelf speakers that remind us of some of the fancier high-end sets often seen in hi-fi magazines. Of course, if 3D printing enclosures isn’t enough for you, you could always consider 3D printing the actual speaker driver itself. When you do, let us know how it goes!

RC Ekranoplan Uses LIDAR To Fly In Ground Effect

April 29, 2021 by Zoe Skyforest 33 Comments

Ekranoplans are a curious class of vehicle; most well known for several Soviet craft designed to operate at sea, flying just above the waves in ground effect. [rctestflight] had accidentally come across the ground effect flight regime himself years ago, and decided it was time to build an ekranoplan of his own.

I want to see little ekranoplans in at least three top 10 pop film clips by summer’s end. Please and thank you.

While ground-effect flight can be quite stable for a heavy, human-scale craft, the smaller RC version suffered more from minor perturbations from the wind and such. Thus, a Pixracer autopilot was installed, and combined with a small LIDAR device to accurately measure altitude above the ground. With some custom tweaks to the Ardupilot firmware, the craft was able to cleanly fly along barely a foot off the ground.

The final effect is almost mesmerizing; it appears as if the craft is hovering via some heretofore unknown technology rather than just flying in the usual sense. It’s still sensitive to breezes and sudden drops in the terrain lead to a temporary escape from the ground effect region, but the effect is nonetheless impressive. It’s a nerve wracking video at times, though, with quite a few near misses with traffic and children. Regardless of the nature of your experimental craft, be cognisant of your surroundings. We’ve seen [rctestflight]’s Ardupilot experiments before, too. Video after the break.

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How Best To Get Your Project On Hackaday

April 27, 2021 by Zoe Skyforest 34 Comments

We’re blessed to have such a great community at Hackaday. Our tipline often overfloweth with all manner of projects and builds of all stripes. We see it all here, from beginners just starting out with their first Arduino to diehard hackers executing daringly complex builds in their downtime, and everything in between.

If you’re sitting there in the grandstands, watching in awe, you might wonder what it takes to grace these hallowed black pages. In life, nothing is guaranteed, but I’ve been specially authorised to share with you a few tips that can maximise your chances of seeing your project on Hackaday.

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Blocking Out The Sun: Viable Climate Countermeasure Or Absolute Madness?

April 26, 2021 by Zoe Skyforest 155 Comments

If there’s one thing humans hate, it’s exercising willpower. Whether its abstaining from unhealthy foods, going to bed early, or using less energy and reducing greenhouse gas emissions, we’re famously bad at it. Conversely, if there’s one thing humans love, it’s a workaround. Something that lets us live our lives as the carefree hedonists we are, and deals with the sticky consequences so we don’t have to.

One such workaround for the issue of climate change is a doozy, though — blocking out the sun’s rays in order to cool our warming planet.

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