Blood Pressure Monitor For Under $1

Medical equipment is not generally known for being inexpensive, with various imaging systems usually weighing in at over a million dollars, and even relatively simpler pieces of technology like digital thermometers, stethoscopes, and pulse oximeters coming in somewhere around $50. As the general pace of technological improvement continues on we expect marginal decreases in costs, but every now and then a revolutionary piece of technology will drop the cost of something like a blood pressure monitor by over an order of magnitude.

Typically a blood pressure monitor involves a cuff that pressurizes against a patient’s arm, and measures the physical pressure of the blood as the heart forces blood through the area restricted by the cuff. But there are some ways to measure blood pressure by proxy, instead of directly. This device, a small piece of plastic with a cost of less than a dollar, attaches to a smartphone near the camera sensor and flashlight. By pressing a finger onto the device, the smartphone uses the flashlight and the camera in tandem to measure subtle changes in the skin, which can be processed in an app to approximate blood pressure.

The developers of this technology note that it’s not a one-to-one substitute for a traditional blood pressure monitor, but it is extremely helpful for those who might not be able to afford a normal monitor and who might otherwise go undiagnosed for high blood pressure. Almost half of adults in the US alone have issues relating to blood pressure, so just getting information at all is the hurdle this device is attempting to overcome. And, we’ll count it as a win any time medical technology becomes more accessible, more inexpensive, or more open-source.

A prosthetic eye anodized green around the edges with a yellow and blue "iris" surrounding an LED center.

Skull Lamp Illuminates The Cyberpunk Future

Cyberpunk is full of characters with cool body mods, and [bsmachinist] has made a prosthetic eye flashlight (TikTok) that is both useful and looks futuristic. [via Reddit]

[bsmachinist] has been machining titanium prosthetic eyes for over five years now, and this latest iteration, the Skull Lamp, has a high brightness LED that he says is great for reading books at night as well as any other task you might have for a headlamp. Battery life is reported as being 20 hours, and the device is switched by passing a magnet (Instagram) near the prosthetic.

We love seeing how prosthetics have advanced in the last few years with the proliferation of advanced tools for makers. Some other interesting prosthetics we’ve covered are this DIY Socket for Prosthetics with a built-in charger and power supply and several different prosthetic projects for kids including these Heroic Prosthetics by Open Bionics, the E-Nable Alliance, and a Kid Who Designed his Own Prosthetic.

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Toothbrush Goes From Mouth-Whitening To Room-Brightening

Some of the hacks we see make us wonder why they aren’t already a commercial product, and this electric toothbrush turned rechargeable flashlight is one of them. Sure, these things exist, but we haven’t seen one with a dedicated charging stand. They usually just take micro USB or whatever, so it’s on you to remember to plug it in. How great would it be to have a fully-charged flashlight always at the ready, especially one in a position to illuminate the room? Although [wannabemadsci] makes it look easy, this conversion took quite a bit of doing.

Perhaps the most amazing part is that [wannabemadsci] found a halfway decent flashlight at the dollar store. Better than average, this thing has a main light, a side light, and takes 3xAAs instead of a couple of AAAs. The only issue is that the toothbrush batteries don’t quite put out enough voltage for the flashlight’s LED, so [wannabemadsci] used a booster board.

Of course, there’s a lot more to this hack than sawing off the USB connector from the boost converter so it fits. The toothbrush handle had to be modified to accept the flashlight guts, and the threads relocated from the flashlight. Since the battery charge indicator shines through the momentary button on the toothbrush, [wannabemadsci] wanted to reuse it, but it required a small board that converts it to a latching push button. Finally, the flashlight bezel had to be painted white. Paint is such an easy thing to do, and this detail makes all the difference in how professional this looks.

There’s a lot you can do with a functioning electric toothbrush as your base, like brute-forcing the pins of a lock with vibration.

Non-Contact Probe Works Better With A Little More Complexity

Non-contact voltage probes have been around a while and some test equipment now has them built-in. This is one of those things that you probably don’t think about much, but surely it isn’t that hard to detect AC voltage. Turns out there are a lot of circuits floating around that can do it and [nsievers51] tried a bunch. Many didn’t work very well, but the best used a 4069 CMOS hex inverter. A dollar store flashlight provided power, a case, and an LED and the result was a good-looking and effective probe.

The circuit came from the Electronics Library website and is fairly complex for this sort of device. The CMOS inverters have a high input impedance so they pick up the weak signal. Instead of directly driving an LED, two inverters form a ring oscillator that generate pulses around 1 kHz. At that frequency, the LED appears to be on, but battery consumption is less severe. A single 2N2222-style transistor drives the LED.

We’ve seen a number of variations on this tool in the past. Many of them only use transistors.

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big LED flashlight

Own The Night With This Ludicrously Bright DIY Flashlight

If you’re a flashlight person, you know that there’s little you would do to get the brightest, most powerful, most ridiculous flashlight possible. You might even decide to build yourself a ludicrously powerful flashlight, like [Maciej Nowak] did.

If you choose the DIY route, be warned that it’s probably not going to be a simple process, at least if you follow [Maciej]’s lead. His flashlight is machined out of aluminum rounds, all turned down on the lathe to form the head of the flashlight. The head is made from three parts, each of which acts as a heat sink for the five 20-Watt CREE XHP70 LED modules. The LEDs are mounted with care to thermal considerations, and wired in series to DC-DC converter that provides the necessary 30 V using a battery pack made from four 21700 Li-ion cells. The electronics, which also includes a BMS for charging the battery and a MOSFET switching module, form a tidy package that fits into the aluminum handle.

The video below shows that the flashlight is remarkably bright, with a nice, even field with no hotspots. Given the 45-minute useful life and the three-hour recharge time, it might have been nice to make it so anywhere from one to five of the LEDs could be turned on at once. Some interesting effects might be had from switching the LEDs on sequentially, too.

Given the proclivities of our community, it’s no surprise that this is hardly the first powerful flashlight we’ve seen. This one broke the 100-Watt barrier with a single COB LED, while this ammo-can version sports an even higher light output. Neither of them looks much like a traditional flashlight, though, which is where [Maciej]’s build has the edge.

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101 Uses For An Everready — Flashlight History

For some reason, I’m always interested in why things are called what they are. For example, I’ve been compelled in the past to research what Absorbine Senior is. Not that it is important, but Absorbine Junior is a smaller size of horse liniment, so you don’t have to buy a drum of ordinary Absorbine just to rub down your sore thumb. So it isn’t a mystery that I would find myself musing over why we call a flashlight a flashlight.

You don’t think of a flashlight as flashing, under normal circumstances, at least. Turns out the answer lies in the history of the device, its poor beginnings, and our willingness to treat imperfect components as though they were much better than they are. That last point, by the way, still has ramifications today, so even if you aren’t a fan of flashlight history, keep reading.

Portable Lighting

Ever since people learned to use fire, there’s been a desire for portable lighting. Torches, candles, and even oil lamps have all had their place. But burning things for light in small cramped spaces leaves a lot to be desired. It isn’t surprising that people quickly turned to electricity when that seemed to be feasible.

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100% Printed Flashlight: Conductive Filament And Melted-in Leads

Conductive filament isn’t an ideal electrical conductor, but it’s a 3D-printable one and that’s what makes [Hercemer]’s 3D-printed flashlight using conductive filament work. Every part of the flashlight is printed except for the 9 volt battery and LEDs. Electrically speaking, the flashlight is a small number of LEDs connected in parallel to the terminals of the battery, and turning it on or off is done by twisting or loosening a cap to make or break the connection.

The main part of the build is a 3D-printed conductive cylinder surrounded by a printed conductive ring with an insulator between them. This disk- or pad-shaped assembly forms not only the electrical connection between the LEDs and battery terminals, but also physically holds the LEDs. To attach them, [Hercemer] simply melts them right in. He uses a soldering iron to heat up the leads, and presses them into the 3D-printed conductive block while hot. The 9 V battery’s terminals contact the bottom when the end cap is twisted, and when they touch the conductive assembly the flashlight turns on.

Anticipating everyone’s curiosity, [Hercemer] measured the resistance of his conductive block and measured roughly 350 ohms when printed at 90% infill; lower infills result in more resistance. You can see a video of the assembly and watch the flashlight in action in the video, embedded below.

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