Hackaday Prize Entry: Open-source Pulse Oximetry

Chances are pretty good you’ve had a glowing probe clipped to your fingertip or earlobe in some clinic or doctor’s office. If you have, then you’re familiar with pulse oximetry, a cheap and non-invasive test that’s intended to measure how much oxygen your blood is carrying, with the bonus of an accurate count of your pulse rate. You can run down to the local drug store or big box and get a fingertip pulse oximeter for about $25USD, but if you want to learn more about photoplethysmography (PPG), [Rajendra Bhatt]’s open-source pulse oximeter might be a better choice.

PPG is based on the fact that oxygenated and deoxygenated hemoglobin have different optical characteristics. A simple probe with an LED floods your fingertip with IR light, and a photodiode reads the amount of light reflected by the hemoglobin. [Rajendra]’s Easy Pulse Plugin receives and amplifies the signal from the probe and sends it to a header, suitable for Arduino consumption. What you do with the signal from there is up to you – light an LED in time with your heartbeat, plot oxygen saturation as a function of time, or drive a display to show the current pulse and saturation.

We’ve seen some pretty slick DIY pulse oximeters before, and some with a decidedly home-brew feel, but this seems like a good balance between sophisticated design and open source hackability. And don’t forget that IR LEDs can be used for other non-invasive diagnostics too.

The 2015 Hackaday Prize is sponsored by:

Arduboy Classic Plays On Original Game Boy Screen

The Arduboy is a Kickstarter backed, 8 bit video game console that mimics the look of a very tiny Nintendo Gameboy. The Arduboy Classic is actually using the case, button and LCD screen from a classic Game Boy.

[uXe] is using the same brains, an ATMEGA32U4, along with a 328 as a co-processor to handle the classic “creme-n-spinich” gameboy screen. 2K of dual port ram acts as a buffer between the two micro-controllers meaning they can not only run while not being in lock step with eachother, but that each micro can read or write to the ram at the same time.

Currently the whole setup is spread out on a breadboard while all the interfacing is worked out, but it is working quite well. Future plans are to make a drop in motherboard replacement for the classic game system, and there is ample room for all the new electronics on the original footprint.

If you’re unfamiliar with the Arduboy project, check out our interview with it’s creator, [Kevin Bates]. That and the demo of [uXe’s] hack based on the project are both found after the break.

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Beautiful Arduino Fireworks Controller

A lot of designers have the luxury of creating things that aren’t supposed to explode. That’s usually easy. The trick is designing things that are supposed to explode and then making absolutely sure they explode at the right time (and only the right time). [JonBush] recently did a beautiful build of an Arduino-based fireworks controller. Seriously, it looks like a movie prop from a summer blockbuster where [Bruce Willis] is trying to decide what wire to cut.

[Jon] used a mega 2560 because he wanted to do the I/O directly from the device. His code only takes about 8K of the total program storage, so with some I/O expansion (like shift registers) a smaller chip would do the job. The device can control up to 8 sets of fireworks, uses a physical arm key, and has a handheld remote. It is even smart enough to sense igniter failures.

The front panel is a work of art and includes a seven-segment display made from Neopixel LEDs. The whole thing is in a waterproof case and uses optical isolation in several key areas.

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Hackaday Prize Entry: Nuclear Powered Random Number Generator

Random number generators come in all shapes and sizes. Some are software based while others, known as true random number generators, are hardware based. These can be created from thermal noise, the photoelectric effect and other methods. But none of these were good enough for [M.daSilva]. He would base his off of the radioactive decay of Uranium 238, and construct a working nuclear powered random number generator.

diagram

Because radioactive decay is unpredictable by nature, it makes for an excellent source for truly random data. The process is fairly simple. A piece of old fiestaware plate is used for the radioactive source. Put it in a lead enclosure along with a Geiger tube. Then wire in some pulse shaping circuitry and a microcontroller to count the alpha particles. And that’s about it. [M.daSilva] still has to do some statistical analysis to ensure the numbers are truly random, along with making a nice case for his project. But all in all, it seems to be working quite well.

Be sure to check out the video for quick rundown of [M.daSilva’s] project. If randomness is your thing, make sure you check out entropy harvested from uninitialized RAM, and the story behind the NIST randomness beacon.

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Cozy Heat Control with an Arduino

[George Dewar] and his wife live in a typical 1940’s house in New Zealand , which in case you didn’t know, have a little insulation in the ceiling… and nowhere else. Like most, they put up with the cold — but after having a baby, [George] decided it was time to start controlling the heat a bit better.

They have an electric oil radiator which works well, but isn’t very smart. It only has 6 settings — not very useful when you’re trying to stay at a certain temperature. First off, they looked into a plug-in thermostat controller, and found a cheap one called the HeaterMate. Unfortunately it left a lot to be desired. For example, it didn’t seem to have PID control at all — and for an oil radiator, when you turn it off… it’s still going to heat the room for a while. He also found that because of the high current load of a heater … the device would read a few degrees over room temperature when operating. Unperturbed, [George] took this opportunity to design and build his own PID thermostat controller instead.  Continue reading “Cozy Heat Control with an Arduino”

Tiny Robot Shakes Head At You In Disapproval

If you don’t have enough things staring at you and shaking their head in frustration, [Sheerforce] has a neat project for you. It’s a small Arduino-powered robot that uses an ultrasonic distance finder to keep pointing towards the closest thing it can find. Generally, that would be you.

When it finds something, it tries to track it by constantly rotating the distance finder slightly and retesting the distance, giving the impression of constantly shaking its head at you in disappointment. This ensures that you will either unplug it or smash it with a hammer after a very short time, but you should read [Sheerforce]’s code first: it’s a great example of documenting this for experimenters who want to build something that offers more affirmations of your life choices.

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Arduino Radar Watches You Breathe

We’ve all likely watched an episode of “Star Trek” and admired the level of integration on the sick bay diagnostic bed. With its suite of wireless sensors and flat panel display, even the 1960s imagining of the future blows away the decidedly wired experience of a modern day ICU stay. But we may be getting closer to [Dr. McCoy]’s experience with this radar-based respiration detector.

[Øyvind]’s build, which takes the origin of the term “breadboard” to heart, is based on a not-inexpensive Xethru module, which appears to be purpose-built for detecting respiration. The extra-thick PC board seems to house the waveguides internally, which is a neat trick but might limit how the module can be deployed. The module requires both a USB interface and level shifter to interface the 2.8V levels of the module to the 5V Arduino Uno. In the video below, [Øyvind]’s prototype simply lights an RGB LED in response to the chest movement it detects, but there’s plenty of potential for development here. We’ve seen a laser-based baby breathing monitor before; perhaps this systems could be used to the same end without the risk of blinding your tyke. Or perhaps better diagnostics for sleep apnea patients than an intrusive night in a sleep study lab.

Clocking in at $750USD for the sensor board and USB interface, this build is not exactly for the faint of heart or the light of wallet. But as an off-the-shelf solution to a specific need that also has a fair bit of hacking potential, it may be just the thing for someone. Of course if radar is your thing, you might rather go big and build something that can see through walls.

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