Author: Bryan Cockfield

1708 Articles

Blood Pressure Monitor For Under $1

June 20, 2023 by 22 Comments

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.

Modular Keyboard And Custom Game Controller

June 20, 2023 by 3 Comments

Most video games, whether on console or PC, have standardized around either a keyboard and mouse or an analog controller of some sort, with very little differences between various offerings from the likes of Sony, Microsoft, Nintendo, or even Valve. This will get most of us through almost all video games, but for those looking to take their gameplay up a notch or who are playing much more complex games, certain specialized controllers are available, but they might not meet everyone’s specific needs. Thanks to this custom, modular keyboard anyone should be able to make exactly the controller they need.

The device features a grid of 15 interfaces where modules like buttons, potentiometers, encoders, and joysticks can be placed. Each module can be customized to a significant extent on their own, and they can be placed anywhere on the grid. The modules themselves can be assigned to trigger keyboard presses or gamepad motions depending on the needs of the user. A Raspberry Pi handles the inputs and translates them to the computer, so in that regard it functions no differently than a standard keyboard or gamepad would. Programming is done by sending commands via a USB serial port, with the ability to save various configurations as well.

The modular controller is open-source in terms of hardware and software, with easy assembly using through-hole components and a customizable 3D printed cover for anyone looking to make their own. The project’s creator [Daniel] had flight simulators in mind when designing the device, which often benefit from having more specialized controllers, but any game with lots of specific inputs from Starcraft to League of Legends could benefit from a custom controller or keyboard like this. Flight simulators are more often the targets of specialized and unique controls, though, like this custom yoke or this physical control panel.

Bringing Back The Minitel

June 19, 2023 by 16 Comments

If you didn’t live in France in the 80s or 90s, it’s likely you missed out on one of the most successful computer networks in existence prior to the modern Internet. Known as Minitel, it was an online service available over existing phone lines that offered a connected computer terminal for users to do most things we associate with the modern world, such as booking travel, viewing news, looking up phone numbers, and plenty of other useful activities. While a lot of the original system was never archived, there are still some efforts to restore some of its original functionality like this MiniMit.

The build requires either an original or a recreation of a Minitel terminal in all its 80s glory, but pairs an ESP32 to support modern network connectivity. The ESP32 interfaces with the Minitel’s DIN socket and provides it with a translation layer between WiFi and the networking type that it would have originally expected to see from the telephone lines. Two of the original developers of Minitel are working on restoring some of the services that would have been available originally as well, which means that the entire system is being redeveloped and not just the original hardware.

We’ve mentioned that this system was first implemented in the 80s, but the surprising thing is that even well after broadband Internet would have been available to most people in France, the Minitel system still had widespread use, not being fully deactivated until 2012. They remain popular as inspiration for other projects as well, like this one which was brought a little more up-to-date with the help of a modern display and Raspberry Pi.

Rock Tumbler Doubles As Ice Cream Maker

June 19, 2023 by 13 Comments

When working with limited space or even with limited funding, finding a tool that can do many things for less space or cost than its separate counterparts is a tempting option. The most common downside is that these tools often can’t perform as well as the single-purpose tools they replace, with the obvious example being a pocket-sized multitool or Swiss Army knife. Even things like combination drill and driver tools, adjustable crescent wrenches, or even a kitchen stand mixer can’t quite perform as well as their dedicated counterparts. So when we find a tool that can do two things equally well, like this rock tumbler that can also make a delicious bowl of ice cream, it’s definitely noteworthy.

The project comes to us by way of [North_Stordeur] whose main goal was to create a delicious bowl of ice cream but was deterred by the cost of purpose-built ice cream makers. Making ice cream isn’t a particularly complex process, though, and [North_Stordeur ] realized that grinding down ice for ice cream shares similarities with tumbling and polishing rocks. Normally, the rocks to be polished are placed in a drum with grit and a liquid, then the drum is placed on the tumbler and spun, which causes the rocks to bounce around inside the drum with the grit and smooth out relatively quickly. Replacing sugar for grit, ice for rocks, and milk for the liquid, the ice eventually is worn all the way down, creating an excellent bowl of ice cream.

Truly, the only downside we could see with a build like this is that the drum in the National Geographic rock tumbler that [North_Stordeur] chose for this project looks like it would only make a single serving at a time. However, with picky eaters around who like their own additions to ice cream, this might be a perk as everyone can make exactly the style they like with their own choice of flavors. It’s an excellent discovery for anyone already grinding and polishing rocks or someone who has already built a DIY ball mill for any number of other uses.

Using Sonar To Measure Traffic Speeds

June 19, 2023 by 21 Comments

One of the most common ways of measuring the speed of a vehicle is by using radar, which typically involves generating radio waves, directing them at a moving vehicle, and measuring the various ways that they return to the device. This is a tried-and-true method, but can be expensive and technically complex. [GeeDub] wanted an easier way of measuring vehicles passing by his home, so he switched to using sonar instead to measure speeds based on the sounds the cars generate themselves.

The method he is using is similar to passive sonar in submarines, which can locate objects underwater based on the sounds they produce. After a false start attempting to measure Doppler shift, he switched to time correlation using two microphones, essentially using stereo audio input to detect subtle differences in arrival times of various sounds to detect the positions of passing vehicles. Doing this fast enough and extrapolating the data gathered, speed information can be calculated. For the data gathering and calculation, [GeeDub] is using a Raspberry Pi to help keep costs down, and some further configuration of the microphones and their power supplies were also needed to ensure quality audio was gathered.

With the system in place in a window, it detected around 9,000 vehicles over a three-day period. The software generates a normal distribution of vehicle speeds for this time, with the distribution centered on around 35 MPH, slightly above the posted speed limit of 30. As long as there’s a clear line of sight to the road using this system it’s just as effective as some other passive systems we’ve seen to measure vehicle speed. Of course, active speed measurement systems are not out of the realm of possibility if you’re willing to spend a little more.

Too Much Git? Try Gitless

June 18, 2023 by 48 Comments

Git has been a powerful tool for software development and version control since the mid ’00s, gaining widespread popularity since then. Originally built by none other than Linus Torvalds for handling Linux kernel development, it’s branched out for use with all kinds of other projects. That being said, it is not the easiest thing to learn how to use, with tons of options, abstract ideas, and non-linear workflows to keep track of. So if you’re new to the system or don’t need all of its vast swath of features, you might want to try out an alternative like Gitless.

Thanks to the fact that the original Git is open source, it’s free to modify and use as any user sees fit, and there are plenty of options available. This one aims to simplify many of the features found in the original Git, implementing a tracking system which somewhat automates commits. It also includes a simplified branching system, making it easier to switch between branches and keep better track of all that’s happening in a project. The command line interface is simplified as well, and the entire system is backwards-compatible with Git which means that if you find yourself needing some of the more advanced tools it’s possible to switch between them with relative ease.

For those of us keeping track of our own software projects, who don’t necessarily need the full feature set that the original Git has to offer, this could be a powerful tool that decreases the steep learning curve that Git is known for. It’s definitely a system work diving into, though, regardless of whichever implementation you choose. It’s an effective tool for everything from complex, professional projects to small hobby projects on the Arduino.

Ham Pairs Nicely With GMRS

June 17, 2023 by 37 Comments

Ignoring all of the regulations, band allocations, and “best amateur practices,” there’s no real fundamental difference between the frequencies allocated to the Family Radio Service (FRS), the General Mobile Radio Service (GMRS), the Multi-Use Radio Service (MURS), and the two-meter and 70-centimeter bands allocated to licensed ham radio operators. The radio waves propagate over relatively short distances, don’t typically experience any skip, and are used for similar activities. The only major difference between these (at least in the Americas or ITU region 2) is the licenses you must hold to operate on the specific bands. This means that even though radios are prohibited by rule from operating across these bands, it’s often not too difficult to find radios that will do it anyway.

[Greg], aka [K4HSM], was experimenting with a TIDRADIO H8 meant for GMRS, which in North America is a service used for short-range two-way communication. No exams are required, but a license is still needed. GMRS also allows for the use of repeaters, making it more effective than the unlicensed FRS. GMRS radios, this one included, often can receive or scan frequencies they can’t transmit on, but in this case, the limits on transmitting are fairly easy to circumvent. While it isn’t allowed when programming the radio over Bluetooth, [K4HSM] found that programming it from the keypad directly will allow transmitting on the ham bands and uses it to contact his local two-meter and 70-cm repeaters as a proof-of-concept.

The surprising thing about this isn’t so much that the radio is physically capable of operating this way. What’s surprising is that this takes basically no physical modifications at all, and as far as we can tell, that violates at least one FCC rule. Whether or not that rule makes any sense is up for debate, and it’s not likely the FCC will break down your door for doing this since they have bigger fish to fry, but we’d definitely caution that it’s not technically legal to operate this way.

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