Sound Card ADCs For Electrocardiograms

Every few years, or so we’re told, [Scott] revisits the idea of building an electrocardiogram machine. This is just a small box with three electrodes. Attach them to your chest, and you get a neat readout of your heartbeat. This is a project that has been done to death, but [Scott]’s most recent implementation is fantastic. It’s cheap, relying on the almost absurd capability for analog to digital conversion found in every sound card, and the software is great. It’s the fit and finish that makes this project shine.

The hardware for this build is simply an AD8232, a chip designed to be the front end of any electrocardiogram. This is then simply connected to the microphone port of a sound card through a 1/8″ cable. For the exceptionally clever, there’s a version based on an op-amp. It’s an extraordinarily simple build, but as with all simple builds the real trick is in the software. That’s where this project really shines, with custom software with graphics, and enough information being displayed to actually tell you something.

We’ve seen a number of sound card ADCs being used for electrocardiograms in the past, including some from the Before Times; it makes sense, sound cards are the cheapest way to get a lot of analog data very quickly. You can check out [Scott]’s demo video out below.

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Toilet Seat Could Save Your Ass

Our morning routine could be appended to something like “breakfast, stretching, sit on a medical examiner, shower, then commute.” If we are speaking seriously, we don’t always get to our morning stretches, but a quick medical exam could be on the morning agenda. We would wager that a portion of our readers are poised for that exam as they read this article. The examiner could come in the form of a toilet seat. This IoT throne is the next device you didn’t know you needed because it can take measurements to detect signs of heart failure every time you take a load off.

Tracking heart failure is not just one test, it is a buttload of tests. Continuous monitoring is difficult although tools exist for each test. It is unreasonable to expect all the at-risk people to sit at a blood pressure machine, inside a ballistocardiograph, with an oximeter on their fingers three times per day. Getting people to browse Hackaday on their phones after lunch is less of a struggle. When the robots overthrow us, this will definitely be held against us.

We are not sure if this particular hardware will be open-source, probably not, but there is a lesson here about putting sensors where people will use them. Despite the low rank on the glamorous scale, from a UX point of view, it is ingenious. How can we flush out our own projects to make them usable? After all, if you build a badass morning alarm, but it tries to kill you, it will need some work and if you make a gorgeous clock with the numbers all messed up…okay, we dig that particular one for different reasons.

Via IEEE Spectrum.

Game Boy Advance Hiding In a Medical Device

It turns out that medical manufacturers also do hacking once in a while. [JanHenrikH] recently tweeted a photo of an ECG-Trigger-Unit that he’d opened up. Inside he found that the LCD screen was that of a Game Boy Advance (GBA) and the reason he could tell was that the screen’s original case was still there, complete with GAME BOY ADVANCE SP written on it.

In the manufacturer’s defense, this device was likely made around the year 2000 when gaming products were some of the best sources for high speed, high quality, small LCDs displays.  This design document for a portable ECG measurement instrument from as recently as 2013 cites reasons for using a GBA as:

  • impressive plotting results,
  • no serious transmission delays, and
  • fine graphics processing capability.

The Verge had even turned up this US patent from 1997 that has the diagnostic medical device be a cartridge for plugging into a Game Boy. At the time, PCs were frequently used for medical displays but this patent cites issues such as the higher cost of PCs, software installation issues, and crashing. However, they talk about the crashing being due to running word processing and spreadsheet software on the same PC, something not likely to happen if the PC is dedicated to bedside monitoring.

But despite all those pros, wouldn’t you feel surprise and alarm when you first glimpse the Game Boy inside the device that’s monitoring your heart? We also have to wonder what licensing these products went through in the countries in which they were used. This particular device was made by German company Medical Imaging Electronics.

Game Boy hacks aren’t limited to the medical industry though. Here on Hackaday, we’ve seen them turned into remote controls for flying drones and we’ve seen Game Boy cartridge emulators that use STM32. Finally, if you’re wondering where you saw [Jan Henrik]’s name before, he was one of the two hackers driving the motorized armchair in a photo in our [Jenny List]’s SHACamp 2017 write-up.

Our thanks to [geonomad] for the tip!

Hackaday Prize Entry: A Complete Suite Of Biomedical Sensors

The human body has a lot to tell us if we only have the instruments to listen. Unfortunately, most of the diagnostic gear used by practitioners is pricey stuff that’s out of range if you just want to take a casual look under the hood. For that task, this full-featured biomedical sensor suite might come in handy.

More of an enabling platform than a complete project, [Orlando Hoilett]’s shield design incorporates a lot of the sensors we’ve seen before. The two main modalities are photoplethysmography, which uses the MAX30101 to sense changes in blood volume and oxygen saturation by differential absorption and reflection of light, and biopotential measurements using an instrumentation amplifier built around an AD8227 to provide all the “electro-whatever-grams” you could need: electrocardiogram, electromyogram, and even an electrooculogram to record eye movements. [Orlando] has even thrown on temperature and light sensors for environmental monitoring.

[Orlando] is quick to point out that this is an educational project and not a medical instrument, and that it should only ever be used completely untethered from mains — battery power and Bluetooth only, please. Want to know why? Check out the shocking truth about transformerless power supplies.

Thanks to [fustini] for the tip.

Wireless Wearable Watches your Vital Signs

Is it [Dr. McCoy]’s long-awaited sickbay biobed, with wireless sensing and display of vital signs? Not quite, but this wearable patient monitor comes pretty close. And from the look of it, [Arthur]’s system might even monitor a few more parameters than [Bones]’ bleeping bed from the original series.

Starting with an automatic blood pressure cuff that [Arthur] had previously reversed engineered, he started adding sensors. Pulse, ECG, respiration rate, galvanic skin response, and body temperature are all measured from one compact, wrist-wearable device. It’s not entirely wireless – the fingertip pulse oximetry dongle and chest electrodes still need to be wired back to the central unit – but the sensors all talk to a Teensy 3.2 which then communicates to an Android app over Bluetooth, so there’s no need to be tethered to the display. And speaking of electrodes, we’re intrigued by the ADS1292 chip [Arthur] uses, which not only senses the heart’s electrical signals but also detects respirations by the change in impedance as the chest wall expands and contracts. Of course there’s also pneumography via radar that could be rolled into this sensor suite.

It’s all pretty cool, and we can easily see a modified version of this app displayed on a large tablet or monitor being both an accurate prop reconstruction and a useful medical device.

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TOBE: Tangible Out-of-Body Experience with Biosignals

TOBE is a toolkit that enables the user to create Tangible Out-of-Body Experiences, created by [Renaud Gervais] and others and presented at the TEI ’16: Tenth International Conference on Tangible, Embedded, and Embodied Interaction. The goal is to expose the inner states of users using physiological signals such as heart rate or brain activity. The toolkit is a proposal that covers the creation of a 3D printed avatar where visual representations of physiological sensors (ECG, EDA, EEG, EOG and breathing monitor) are displayed, the creation and use of these sensors based on open hardware platforms such as Bitalino or OpenBCI, and signal processing software using OpenViBE.

In their research paper, the team identified the signals and mental states which they have organized in three different types:

  • States perceived by self and others, e.g. eye blinks. Even if those signals may sometimes appear redundant as one may directly look at the person in order to see them, they are crucial in associating a feedback to a user.
  • States perceived only by self, e.g. heart rate or breathing. Mirroring these signals provides presence towards the feedback.
  • States hidden to both self and others, e.g. mental states such as cognitive workload. This type of metrics holds the most
    promising applications since they are mostly unexplored.

By visualising their own inner states and with the ability to share them, users can develop a better understating of their own selves as well others. Analysing their avatar in different contexts allows a user to see how they react in different scenarios such as stress, working or playing. When you join several users they can see how each other responds the same stimuli, for example. Continue reading “TOBE: Tangible Out-of-Body Experience with Biosignals”

Retro-Style DIY Polygraph: Believe It Or Not

A polygraph is commonly known as a lie detector but it’s really just a machine with a number of sensors that measure things like heart rate, breathing rate, galvanic skin response and blood pressure while you’re being asked questions. Sessions can be three hours long and the results are examined by a trained polygraph examiner who decides if a measured reaction is due to deception or something else entirely. Modern polygraphs feed data into a computer which analyses the data in real-time.

Cornell University students [Joyce Cao] and [Daria Efimov] decided to try their hand at a more old fashioned polygraph that measures heart and breathing rates and charts the resulting traces on a moving strip of paper as well as a color TFT display. They had planned on measuring perspiration too but didn’t have time. To measure heart rate, electrodes were attached to the test subject’s wrists. To measure breathing they connected a stretch sensor in the form of a conductive rubber cord around three inches long to a shoelace and wrapped this around the test subject’s abdomen.

While the output doesn’t go into a computer for mathematical analysis, it does go to a PIC32 for processing and for controlling the servos for drawing the traces on the paper as well as displaying on the TFT. The circuit between the breathing sensor and the PIC32 is fairly simple, but the output of the heart rate electrodes needed amplification. For that they came up with a circuit based off another project that had a differential amplifier and two op-amps for filtering.

Since parts of the circuit are attached to the body they made some effort to prevent any chance of electrocution. They used 12 volts, did not connect the test subject to power supply chassis ground, and tested the heart rate electrodes with a function generator first. They also included DC isolation circuitry in the form of some resistors and capacitors between the heart rate electrodes and the amplifier circuit. You can see these circuits, as well as a demonstration in the video below. The heart rate output looks a little erratic, no surprise given that the body produces a lot of noise, but the breathing trace looks very clear.

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