Reliability Check: Consumer And Research-Grade Wrist-Worn Heart Rate Monitors

April 7, 2020 by 12 Comments

Wearables are ubiquitous in today’s society. Such devices have evolved in their capabilities from step counters to devices that measure calories burnt, sleep, and heart rate. It’s pretty common to meet people using a wearable or two to track their fitness goals. However, a big question remains unanswered. How accurate are these wearable devices? Researchers from the Big Ideas Lab evaluated a group of wearables to assess their accuracy in measuring heart rate.

Unlike other studies with similar intentions, the Big Ideas Lab specifically wanted to address whether skin color had an effect on the accuracy of the heart rate measurements, and an FDA-cleared Bittium Faros 180 electrocardiogram was used as the benchmark. Overall, the researchers found that there was no difference in accuracy across skin tones, meaning that the same wearable will measure heart rate on a darker skin-toned individual the same as it would on a lighter skin-toned. Phew!

However, that may be the only good news for those wanting to use their wearable to accurately monitor their heart rate. The researchers found the overall accuracy of the devices relative to ECG was a bit variable with average errors of 7.2 beats per minute (BPM) in the consumer-grade wearables and 13.9 BPM in the research-grade wearables at rest. During activity, errors in the consumer-grade wearables climbed to an average of 10.2 BPM and 15.9 in the research-grade wearables. It’s interesting to see that the research-grade devices actually performed worse than the consumer devices.

And there’s a silver lining if you’re an Apple user. The Apple Watch performed consistently better than all other devices with mean errors between 4-5 BPM during rest and during activity, unless you’re breathing deeply, which threw the Apple for a loop.

So, it seems as if wrist-worn heart rate monitors still have some work to do where accuracy is concerned. Although skin tone isn’t a worry, they all become less accurate when the subject is moving around.

If you’d like to try your own hand with fitness trackers, have a look at this completely open project, or go for the gold standard with a wearable DIY ECG.

Help Save The National Videogame Museum

April 6, 2020 by 16 Comments

The National Videogame Museum in Sheffield, UK, houses a unique collection celebrating all decades of video games and their culture, and as the lockdown has brought with it a crisis threatening its very existence, has launched a crowdfunding campaign with a video we’ve placed below the break. As a relatively young organisation, they have yet to build up the financial buffer that a more established one would have. It’s important that this and other heritage sites live to open again another day, so we’d urge you to take a look.

On their website they’re providing a page of activities for the bored youngster in your life, but to whet your appetite should you wish to visit them in the future they also have a selection of pages about the rest of their exhibition.

One of the sad features of living through  a pandemic comes in knowing that some of the businesses and organisations we hold dear might not make it through the crisis. We’ve put in a few orders to smaller suppliers over the last week or two to shove a bit of extra business their way, and no doubt you have too. What is not so easy however, is when the threatened organisation is a visitor attraction; we can’t make the trip during a lockdown. The NVM is unlikely to be the only such attraction facing the pinch, so we’d urge you to look out for those that are close to you as well.

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Compiling C To PowerPoint

April 6, 2020 by 5 Comments

If you have worked for a large company — or even a small one — it might seem that you spend more time writing PowerPoint charts than programming. [Tom Widenhain’s] video asks the question: Can we compile C into PowerPoint? Watch the video below to find out the answer. Would it surprise you to know that [Tom] wanted to simulate the x86? It surprised us, too, and we had to note the video appeared on April 1. It does look workable, though, other than it is a bit unwieldy.

Instead of a Turing machine, this builds a set of clever logic gates. Unsurprisingly, [Tom] is the guy who put together a Turing machine in Excel. Surprisingly, he isn’t the first one to attempt a C to PPT compiler. The University of Chicago had a similar idea over a year ago, based on [Tom’s] earlier work and executed program using inefficient Turing machines.

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Flexible Build Platforms Work For FDM, How About SLA?

April 6, 2020 by 6 Comments

Flexible steel sheets as the foundation for build platforms are used to great advantage in FDM 3D printers. These coated sheets are held flat by magnets during printing, and after printing is done the sheet (with print attached) can be removed and flexed to pop the prints free. This got [Jan Mrázek] thinking. He was pretty sure the concept could extend to the build platform on his Elegoo Mars resin printer. With a flexible build platform, troublesome prints could be more easily removed, so he non-destructively modified his printer to have a similar system. [Jan] is clear that this is only a proof of concept, but the test results were good! He printed several jobs that were known to be trouble, and they were all a piece of cake to remove.

[Jan]’s mod consists of a 3D printed, two-piece unit that encapsulates the normal build platform and contains a few strong magnets. A thin sheet of steel sticks flat to this new piece, held in place by the magnets within, and becomes the new build platform. After a print is done, the sheet is removed and [Jan] reports that its flexibility is a big help in removing otherwise troublesome prints, such as the 3D printed solder stencil we covered recently.

[Jan] provides his CAD model but doesn’t really recommend using it for anything other than development work. Results were promising, but there are a number of drawbacks to the prototype. For one thing, it makes the build platform thicker and the Z-axis limit switch needs to be physically lowered in order to zero the unit. Also, the thicker build platform means the volume of resin the build tank can hold is reduced. Still, the idea clearly has merit and shows there absolutely is value in hardware having a hackable design.

Subwoofer Gets Arduino Brain Transplant

April 6, 2020 by 15 Comments

The Samsung PS-WTX500 subwoofer is designed to be used as part of a 5.1 channel home theater system, but not just any system. It contains the amplifiers for all the channels, but they’ll only function when the subwoofer is connected to the matching receiver. [Alejandro Zarate] figured there must be some way to unlock the system’s full functionality without being limited to the original receiver, he just needed to reverse engineer how the subwoofer worked.

All the wires tuck underneath the Arduino

The result is a fantastically well documented write-up that covers the whole process, starting with how [Alejandro] identified and researched the Pulsus PS9829B Digital Audio Processor (DAP). Documentation for this particular chip seems hard to come by, but he was able to find a similar chip from the same manufacturer that was close enough to put him on the right track. From there, he started studying the SPI communications between the DAP and the subwoofer’s S3P70F4 microcontroller.

After analyzing the communication between the two chips, [Alejandro] pulled the S3P70F4 off the board and wired an Arduino Pro Mini 328 in its place. The Arduino was quite a bit larger than the original microcontroller, but with some careful wiring, he manged a very professional looking installation. Short of coming up with a custom PCB adapter, we don’t think it could look much better.

With some relatively straightforward code and a listing of the captured byte sequences, the Arduino was able to power up the PS-WTX500’s amplifiers and handle the incoming audio signal as a stand-alone device.

In the past we’ve seen a similar trick done with the ESP8266, which had the added benefit of enabling WiFi control of the speakers. We’re all for adding modern functionality to older hardware, even if you’ve got to hang it off the back as an external module.

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Offline Dinosaur-Jumping Becomes A Real Workout

April 6, 2020 by 16 Comments

It’s great to see people are out there trying to find fun ways to exercise amid the current crisis. Although jumping up and down isn’t great for the knees, it does give decent cardio. But if you don’t have a rope or a puddle, we admit that jumping can lose its bounce pretty fast.

Quarantine has been a game-filled time for [fridaay]. Somewhere between a handful of FPS games, he decided to try to play Google’s offline dinosaur-based side scroller game by making the dinosaur spring over the saguaros whenever he physically jumps in the air. (Video, embedded below.)

Here’s how it works: [fridaay] holds a transmit circuit that consists of an Arduino UNO, an accelerometer module, and an nRF24L01 transceiver, all running on a 9 V battery. Whenever [fridaay] jumps, the accelerometer reads the change in Z and sends it to the receiving circuit, which is just another UNO and nRF. The receiving UNO is connected to a laptop and configured to press the space bar so the dinosaur canters over the cacti.

We’ve never been able to stay alive long enough in the game to see this happen, but apparently you need to crouch at some point in the game. [fridaay] has yet to implement a control for that, but we’re sure he’ll think of something. Jump past the break to see the video, and hit him up if you need the code.

If you have a lot of parts at your disposal, why not make a physical version?

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Getting To Space Is Even Harder During A Pandemic

April 6, 2020 by 3 Comments

At this point, most of us are painfully aware of the restrictions that COVID-19 social distancing protocols have put on our daily lives. Anyone who can is working from home, major events are canceled, non-essential businesses are closed, and travel is either strongly discouraged or prohibited outright. In particularly hard hit areas, life and commerce has nearly ground to a halt with no clear end date in sight.

Naturally, there are far reaching consequences for this shutdown beyond what’s happening on the individual level. Large scale projects are also being slowed or halted entirely, as there’s only so much you can do remotely. That’s especially true when the assembly of hardware is concerned, which has put some industries in a particularly tight spot. One sector that’s really feeling the strain is aerospace. Around the world, space agencies are finding that their best laid plans are suddenly falling apart in the face of COVID-19.

In some cases it’s a minor annoyance, requiring nothing more than some tweaks to procedures. But when the movements of the planets are concerned, a delay of weeks or months changes everything. While things are still changing too rapidly to make an exhaustive list, we already know of a few missions that are being impacted in these uncertain times.

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