DIY Pulse Oximeter

May 2, 2010 by 28 Comments

This pulse oximeter turned out very nicely. It is based around a Freescale microcontroller and detects pulse as well as oxygen saturation in your blood. The sensor is made of two wood pieces and allows two wavelengths of light to be shined through your finger. A sensor picks up the light on the other side of your stubby digit and the readings are compared to calculate saturation. Check out the finished project after the break.

We saw an Arduino-based oximeter a few months ago. These kind biometric hacks are rare around here. If you’ve got a well documented project don’t forget to tell us about it.

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Pulse Oximeter

January 6, 2010 by 15 Comments

[youtube=http://www.youtube.com/watch?v=GdN5IRVJOXI]

[Mike] is building his own Pulse Oximeter which uses light to measure the oxygen saturation in blood. One collateral benefit of this measurement is that pulse rate can be calculated from the same data. The parts used for the detector include a red LED, infrared LED, and a TSL230R light intensity measuring chip. As explained in the video above, each LED is shined through the tip of your finger and onto the light sensor. The IR LED is used as a baseline and compared to the red LED, which has some of its intensity absorbed by the red blood in your finger. This is a pretty approachable biometric concept so you may want to start here before moving on to more involved biometric interfaces.

[Thanks Russ]

Pixel Watch 3’s Loss Of Pulse Detection: The Algorithms That Tell Someone Is Dying

March 12, 2025 by 61 Comments

More and more of the ‘smart’ gadgets like watches and phones that we carry around with us these days come with features that we’d not care to ever need. Since these are devices that we strap onto our wrists and generally carry in close proximity to our bodies, they can use their sensors to make an estimation of whether said body is possibly in the process of expiring. This can be due to a severe kinetic event like a car crash, or something more subtle like the cessation of the beating of one’s heart.

There is a fairly new Loss of Pulse Detection (LoPD) feature in Google’s Pixel Watch 3 that recently got US FDA approval, allowing it to be made available in the US after previously becoming available in over a dozen European countries following its announcement in August of 2024. This opt-in feature regularly polls whether it can detect the user’s pulse. If not found, it cascades down a few steps before calling emergency services.

The pertinent question here is always whether it is truly detecting a crisis event, as nobody wants to regularly apologize for a false alert to the overworked person staffing the 911 or equivalent emergency line. So how do you reliably determine that your smart watch or phone should dial emergencies forthwith?

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Pulsed Deposition Points A Different Path To DIY Semiconductors

February 19, 2025 by 1 Comment

While not impossible, replicating the machines and processes of a modern semiconductor fab is a pretty steep climb for the home gamer. Sure, we’ve seen it done, but nanoscale photolithography is a demanding process that discourages the DIYer at every turn. So if you want to make semiconductors at home, it might be best to change the rules a little and give something like this pulsed laser deposition prototyping apparatus a try.

Rather than building up a semiconductor by depositing layers of material onto a silicon substrate and selectively etching features into them with photolithography, [Sebastián Elgueta]’s chips will be made by adding materials in their final shape, with no etching required. The heart of the process is a multi-material pulsed laser deposition chamber, which uses an Nd:YAG laser to ablate one of six materials held on a rotating turret, creating a plasma that can be deposited onto a silicon substrate. Layers can either be a single material or, with the turret rapidly switched between different targets, a mix of multiple materials. The chamber is also equipped with valves for admitting different gases, such as oxygen when insulating layers of metal oxides need to be deposited. To create features, a pattern etched into a continuous web of aluminum foil by a second laser is used as a mask. When a new mask is needed, a fresh area of the foil is rolled into position over the substrate; this keeps the patterns in perfect alignment.

We’ve noticed regular updates on this project, so it’s under active development. [Sebastián]’s most recent improvements to the setup have involved adding electronics inside the chamber, including a resistive heater to warm the substrate before deposition and a quartz crystal microbalance to measure the amount of material being deposited. We’re eager to see what else he comes up with, especially when those first chips roll off the line. Until then, we’ll just have to look back at some of [Sam Zeloof]’s DIY semiconductors.

This Air Particulate Sensor Can Also Check Your Pulse Rate

March 26, 2024 by 7 Comments

The MAX30105 is an optical sensor capable of a great many things. It can sense particulate matter in the air, or pick up the blinking of an eye. Or, you can use it as a rudimentary way to measure your heart rate and blood oxygen levels. It’s by no means a medical grade tool, but this build from [Taste The Code] is still quite impressive.

The MAX30105 contains red, green, and infrared LEDs, and a very sensitive light detector. The way it works is by turning on its different LEDs, and then carefully measuring what gets reflected back. In this way it can measure particles in the air,  such as smoke, which is actually what it was designed for originally. Or, if you press your finger up against it, it can measure the light coming back from your blood and determine its oxygenation level. By detecting the variation in the light over time, it’s possible to pick up your pulse, too.

Getting this data out of the sensor is remarkably easy. One need only hook it up to a suitable microcontroller like the ESP8266 and use the MAX3010X library to talk to it. [Taste The Code] did exactly that, and also hooked up a screen for displaying the captured data. Alternatively, if you want the raw data from the sensor, you can get that too.

It should be noted that this build was done for educational purposes only. You shouldn’t rely on a simple DIY device for gathering useful medical data; there are reasons the real gear is so expensive, after all. We’ve looked at this sensor before, too, not long after it first hit the market. Continue reading “This Air Particulate Sensor Can Also Check Your Pulse Rate” →

Retrotechtacular: A Closer Look At The VT Proximity Fuze

June 9, 2023 by 17 Comments

Here at Hackaday, our aim is to bring you only the freshest of hacks, which carries the burden of being Johnny-on-the-spot with our source material. So if something of obvious interest to our readers goes viral, we might just choose to skip covering it ourselves, figuring you all have probably seen it already. But, if we can dig a little deeper and bring extra value over and above what the viral content provides — well then that’s another story.

That’s pretty much the story behind the excellent video recently released by [Real Engineering] about “The Secret Weapon That Changed World War 2.” It concerns the VT series of proximity fuzes — it’s a legitimate alternate spelling of “fuse” if a somewhat archaic one — that were used for artillery shells and spin-stabilized rockets in World War II. The video gives an excellent overview of the development of the VT, which was used primarily in anti-aircraft artillery (AAA). The details about the development of the American VT fuze are excellent, although curiously there’s no mention that British experiments with a radio proximity fuze were part of the goldmine of information brought to America at great risk by the Tizard mission in 1940. While there has been plenty of contention about the exact role the British work played, it’s fair to say that it at least informed the development and fielding of the American VT fuze.

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A Tale Of Two Pulse Modulators

May 8, 2023 by 7 Comments

In the realm of test equipment, there are a number of items that you don’t know you need until you need one. That’s probably the case with the HP11720A pulse modulator. [Tom] acquired two of these even though, by his own admission, he had “no need for these things.” We’d like to say we don’t get that, but — alas — we do.

The good news, though, is he used one of them to measure the quality of some coax cable and shared the exercise with us in the post and a video, which you can watch below. The device can generate pulses with extremely fast rise and fall times (under 10 nanoseconds) at frequencies from 2 to 18 GHz. These were often used in pulsed radar applications and probably cost quite a bit more new than [Tom] shelled out for them.

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