2026-01-19 05:00:18
When [Electron Impressions] used a powerful ultrasonic array to project a narrow beam of sound toward a target, he described it as potentially useful in getting someone’s attention from across a crowded room without disturbing other people. This is quite a courteous use compared to some of the ideas that occur to us, and particularly compared to the crowd-control applications that various militaries and police departments put directional speakers to.
Regardless of how one uses it, however, the physics behind such directional speakers is interesting. Normal speakers tend to disperse their sound widely because the size of the diaphragm is small compared to the wavelength of the sound they produce; just like light waves passing through a pinhole or thin slit, the sound waves diffract outwards in all directions from their source. Audible frequencies have wavelengths too long to make a handheld directional speaker, but ultrasonic waves are short enough to work well; [Electron Impressions] used 40 kHz, which has a wavelength of just eight millimeters. To make the output even more directional, he used an array of evenly-spaced parallel emitters, which interfere constructively to the front and destructively to the sides.
Ultrasound shouldn’t be audible, but sound waves travel slightly faster in high-pressure air than in low-pressure air. Since sound waves are just variations in pressure, this means that at high enough amplitudes, they change their own shape as they travel through air, tending to merge together somewhat into lower-frequency waves. When amplitude modulation is applied to the ultrasonic signal, the air itself demodulates it into audible sound (the audio quality isn’t wonderful, but still recognizable). [Electron Impressions] demonstrated the completed device, and it’s possible to hear a clear difference in intensity when it’s pointed at the microphone. It’s also possible to reflect the sound beam off hard surfaces, though multiple reflections tend to decrease the directivity when used indoors.
The circuit itself is very similar to another which we’ve covered before, down to the 555 timer used in the ultrasonic driver, and the overall approach is very reminiscent of this directional ultrasonic array.
2026-01-19 02:00:11
Professional mountain bike racing is a rather bizarre sport. At the highest level, times between podiums will be less than a second, and countless hours of training and engineering go into those fractions of seconds. An all too important tool for the world cup race team is data acquisition systems (DAQ). In the right hands, they can offer an unparalleled suspension tune for a world cup racer. Sadly DAQs can cost thousands of dollars, so [sghctoma] built one using little more then potentiometer and LEGO.
The hardware is a fairly simple task to solve. A simple Raspberry Pi Pico setup is used to capture potentiometer data. By some simple LEGO linkage and mounts, this data is correlated to the bikes’ wheel travel. Finally, everything is logged onto an SD card in a CSV format. Some buttons and a small AMOLED provide a simple user interface wrapped in a 3D printed case.
Analyzing the data is a rather daunting task. The entire analysis framework is neatly wrapped into a web server. The DAQ can automatically sync with the web interface, and provide suspension metrics in conjunction with action camera footage and a GPS track for further analysis.
However, not all is as it seems when it comes to correlating the suspension data into such a nice UI. A key issue is that with four bar, or even six bar, mountain bike linkage designs, the leverage ratio applied to the shock changes through the wheels travel. That means, when measuring shock travel, it needs to be adjusted to find wheel travel according to manufacturer specifications.
You need to be a bit of a suspension wizard to make sense of the charts. Nevertheless, for the mountain biking hackers out there, everything is available on Github, so if you wish to analyze suspension performance, make sure to check it out!
This isn’t the first time we have seen mountain bike data loggers, make sure to check out this simple Arduino build next!
2026-01-18 23:00:15
In an update video by [Hacker University] to an earlier video on ESP32-C3 Super Mini development boards that feature a Flash-less version of this MCU, the question of adding your own Flash IC to these boards is addressed. The short version is that while it is possible, it’s definitely not going to be easy, as pins including SPIHD (19) and SPICLK (22) and SPIQ (24) are not broken out on the board and thus require one to directly solder wires to the QFN pads.
Considering how sketchy it would be to have multiple wires running off to an external Flash IC, this raises many questions about the feasibility, as well as cost-effectiveness. Some in the comments to the video remark that instead you may as well swap the MCU with a version that does contain built-in Flash, but this is countered with the argument that a new ESP32-C3 Super Mini board with the right MCU costs as much as a loose MCU from your favorite purveyor of ICs.
Ultimately this lends some credence to calling these zero Flash Super Mini boards a ‘scam’, as their use cases would seem to be extremely limited and their Flash-less nature very poorly advertised.
2026-01-18 20:00:47
![[Dr Ali Shirsavar] drawing schematics and equations on the whiteboard](https://hackaday.com/wp-content/uploads/2026/01/Biricha-caps-banner.jpg?w=800)
[Dr Ali Shirsavar] from Biricha Digital runs us through How to Select the Perfect Output Capacitor for Your Power Supply. Your switching-mode power supply (SMPS) will require an output capacitor both to iron out voltage swings due to loading and to attenuate ripple caused by switching. In this video we learn how to calculate the required capacitance, and when necessary the ESR, for your output capacitor.
To begin [Dr Ali] shows us that in order to calculate the minimum capacitance to mitigate voltage swings we need values for Δi, Δv, and Ts. Using these we can calculate the minimum output capacitance. We then need to calculate another minimum capacitance for our circuit given that we need to attenuate ripple. To calculate this second minimum we need to change our approach depending on the type of capacitor we are using, such as ceramic, or electrolytic, or something else.
When our circuit calls for an electrolytic capacitor the equivalent series resistance (ESR) becomes relevant and we need to take it into account. The ESR is so predominant that in our calculations for the minimum capacitance to mitigate ripple we can ignore the capacitance and use the ESR only as it is the feature which dominates. [Dr Ali] goes into detail for both examples using ceramic capacitors and electrolytic capacitors. Armed with the minimum capacitance (in Farads) and maximum ESR (in Ohms) you can then go shopping to find a capacitor which meets the requirements.
If you’re interested in capacitors and capacitance you might enjoy reading about Measuring Capacitance Against Voltage and Getting A Handle On ESR With A Couple Of DIY Meters.
2026-01-18 17:00:19
The fun part about world records is that anyone can take a swing at breaking them, which is what [Luke Maximo Bell] has been doing with the drone speed record for the past years, along with other teams in a friendly competition. After having some Aussie blokes previously smash the record with a blistering 626 km/h, the challenge was on for [Luke] and his dad to reclaim the title. This they did with the V4 of their quadcopter design, adding a range of improvements including new engines, new props and an optimized body to eek out more performance.
In the video we see these changes and the tests in detail. Interestingly, the simulations ran on the computer showed that the new body actually had to be larger, necessitating the use of a larger FDM printer. Fortunately a certain FDM 3D printer company sponsors just about everyone out there, hence the new design was printed on a Bambu Lab H2D, also making use of the dual extruder feature to print combined PETG/TPU parts.
It was also attempted to have a follow camera attached to a second FPV done in the form of a 360 degrees camera, but this turned out to be a bit too complex to get good shots, so this will have to be retried again.
In the end a new world record was set at an average of 657 km/h, which sets the stage for the next team to try and overtake it again. As for where the limit is, propeller airplanes have hit over 800 km/h, so there’s still quite a way to go before details like the sound barrier become a problem.
2026-01-18 14:00:23
Self-hosting a few services on one’s own hardware is a great way to wrest some control over your online presence while learning a lot about computers, software, and networking. A common entry point is using an old computer or Raspberry Pi to get something like a small NAS, DNS-level adblocker, or home automation service online, but the hobby can quickly snowball to server-grade hardware in huge racks. [Dennis] is well beyond this point, with a rack-mounted NAS already up and running. This build expands his existing NAS to one which can host a petabyte of storage out of consumer-grade components.
The main reason for building this without relying too much on server-grade gear is that servers are generally designed to run in their own purpose-built rooms away from humans, and as a result don’t generally take much consideration for how loud that environment becomes. [Dennis] is building a lot of the components from scratch for this build including the case, the backplanes for the drives, and a backplane tester. With backplanes installed it’s time to hook up all of the data connections thanks to a few SAS expanders which provide all of the SATA connections for the 45 drives.
There are two power supplies here as well, although unlike a server solution these aren’t redundant and each only serves half the drives. This does keep it running quieter, along with a series of Noctua fans that cool the rest of the rack. The build finishes off with an LED strip which provides a quick visual status check for each of the drives in the bay. With that it’s ready for drives and to be connected to the network. It’s a ton of wiring and soldering, and great if you don’t want to use noisy server hardware. And, if you don’t need this much space or power, we’ve seen some NAS builds that are a bit on the smaller side as well.
