Author: Aaron Beckendorf

69 Articles

An aluminium frame is visible, supporting several connected pieces of chemistry equipment. At the left, there is a tube containing a clear solution, with a tube leading to a clear tube heated by a gas flame, with another tube leading to a clear bottle, which has a tube leading to a bubbling orange solution.

A Miniature Ostwald Reactor To Make Nitric Acid

July 3, 2025 by 13 Comments

Modern fertilizer manufacturing uses the Haber-Bosch and Ostwald processes to fix aerial nitrogen as ammonia, then oxidize the ammonia to nitric acid. Having already created a Haber-Bosch reactor for ammonia production, [Markus Bindhammer] took the obvious next step and created an Ostwald reactor to make nitric acid.

[Markus]’s first step was to build a sturdy frame for his apparatus, since most inexpensive lab stands are light and tip over easily – not a good trait in the best of times, but particularly undesirable when working with nitrogen dioxide and nitric acid. Instead, [Markus] built a frame out of aluminium extrusion, T-nuts, threaded rods, pipe clamps, and a few cut pieces of aluminium.

Once the frame was built, [Markus] mounted a section of quartz glass tubing above a gas burner intended for camping, and connected the output of the quartz tube to a gas washing bottle. The high-temperature resistant quartz tube held a mixture of alumina and platinum wool (as we’ve seen him use before), which acted as a catalyst for the oxidation of ammonia. The input to the tube was connected to a container of ammonia solution, and the output of the gas washing bottle fed into a solution of universal pH indicator. A vacuum ejector pulled a mixture of air and ammonia vapors through the whole system, and a copper wool flashback arrestor kept that mixture from having explosive side reactions.

After [Markus] started up the ejector and lit the burner, it still took a few hours of experimentation to get the conditions right. The issue seems to be that even with catalysis, ammonia won’t oxidize to nitrogen oxides at too low a temperature, and nitrogen oxides break down to nitrogen and oxygen at too high a temperature. Eventually, though, he managed to get the flow rate right and was rewarded with the tell-tale brown fumes of nitrogen dioxide in the gas washing bottle. The universal indicator also turned red, further confirming that he had made nitric acid.

Thanks to the platinum catalyst, this reactor does have the advantage of not relying on high voltages to make nitric acid. Of course, you’ll still need get ammonia somehow.

The top surface of a laptop cooler is visible. It consists of a black plastic mesh with thirteen fans visible behind it, with a blue backlit screen at the bottom of the cooler. There is blue LED backlighting behind each fan, and around the border of the cooler.

Making A Smarter Laptop Cooler

July 2, 2025 by 18 Comments

[Bogdan Micea] uses a laptop cooler, but was a bit annoyed that his cooler would run at the same power no matter how hard the laptop was working. Rather than keep adjusting the cooler’s power manually, he automated it by installing an Arduino Pro Micro as a controller in the cooler and writing a Rust controller application for his computer.

[Bogdan]’s cooler is controlled by four buttons, which can have different functions depending on how long they’re pressed. After mapping out their functionality and minor quirks, [Bogdan] soldered four transistors in parallel with the buttons to let the Arduino simulate button presses; another four Arduino pins accept input from the buttons to monitor their state. The Arduino USB port connects to the cooler’s original USB power input, so the cooler looks superficially unchanged. When the cooler starts up, the Arduino sets it to a known state, then monitors the buttons. Since it can both monitor and control the buttons, it can notify the computer when the cooler’s state changes, or change the state when the computer sends a command.

On the computer’s part, the control software creates a system tray that displays and allows the user to change the cooler’s current activity. The control program can detect the CPU’s temperature and adjust the cooler’s power automatically, and the Arduino can detect the laptop’s suspend state and control power accordingly.

Somewhat surprisingly, this seems to be the first laptop cooler we’ve seen modified. We have seen a laptop cooler used to overclock a Teensy, though, and a laptop’s stock fans modified.

A clear acrylic cylinder is shown, inside of which plants are visible. There is mist inside the tube, and LEDs light it from above. A black plastic cap to the tube is visible.

Preserve Your Plants With An Automated Terrarium

June 30, 2025 by 1 Comment

For those of us who aren’t blessed with a green thumb and who are perhaps a bit forgetful, plants can be surprisingly difficult to keep alive. In those cases, some kind of automation, such as [Justin Buchanan]’s Oasis smart terrarium, is a good way to keep our plants from suffering too much.

The Oasis has an ultrasonic mister to water the plants from a built-in tank, LED grow lights, fans to control airflow, and a temperature and humidity sensor. It connects to the local WiFi network and can set up recurring watering and lighting schedules based on network time. Most of the terrarium is 3D-printed, with a section of acrylic tubing providing the clear walls. Before installing the electronics, it’s a good idea to waterproof the printed parts with low-viscosity epoxy, particularly since the water tank is located at the top of the terrarium, where a leak would drip directly onto the control electronics.

Continue reading “Preserve Your Plants With An Automated Terrarium” →

The underside of the scanner is shown. Four power supply units are visible on the lower side, and assorted electronics are visible on the top side. In the middle, two linear tracks adapted from a 3D printer run along the length of the scanner, and several motors can be seen mounted between the rails.

A Scanner For Arduino-Powered Book Archiving

June 29, 2025 by 4 Comments

Scanners for loose papers have become so commonplace that almost every printer includes one, but book scanners have remained frustratingly rare for non-librarians and archivists. [Brad Mattson] had some books to scan, but couldn’t find an affordable scanner that met his needs, so he took the obvious hacker solution and built his own.

The scanning process starts when a conveyor belt removes a book from a stack and drops it onto the scanner’s bed. Prods mounted on a rail beneath the bed straighten the book and move it into position for the overhead camera to take a picture of the cover. Next, an arm with a pneumatic gripper opens the cover, and a metal bar comes down to hold it in place.

The page-turning mechanism uses two fans: one fan blows from the side of the book to ruffle the pages and separate them, while the other is mounted on a swiveling arm. This fan blows away from the page, providing a gentle suction that holds the page to the arm as it turns the page over. Finally, a glass plate descends over the book to hold the pages flat, the camera takes a picture, the glass plate retracts, and the scanner moves on to the next page.

It is hard to imagine, but have a look at the video in the post if you really want to see it in action.

Continue reading “A Scanner For Arduino-Powered Book Archiving” →

Two clear acrylic tubes are shown in the foreground. Swirls of sawdust are visible on the inside of the tubes, and the tubes are held in place by grey plastic connectors. Below the tubes, there are two clear plastic tubs containing sawdust.

Optimizing Dust Separation For Extreme Efficiency

June 26, 2025 by 15 Comments

[Ruud], the creator of [Capturing Dust], started his latest video with what most of us would consider a solved problem: the dust collection system for his shop already had a three-stage centrifugal dust separator with more than 99.7% efficiency. This wasn’t quite as efficient as it could be, though, so [Ruud]’s latest upgrade shrinks the size of the third stage while increasing efficiency to within a rounding error of 99.9%.

The old separation system had two stages to remove large and medium particles, and a third stage to remove fine particles. The last stage was made out of 100 mm acrylic tubing and 3D-printed parts, but [Ruud] planned to try replacing it with two parallel centrifugal separators made out of 70 mm tubing. Before he could do that, however, he redesigned the filter module to make it easier to weigh, allowing him to determine how much sawdust made it through the extractors. He also attached a U-tube manometer (a somewhat confusing name to hear on YouTube) to measure pressure loss across the extractor.

The new third stage used impellers to induce rotational airflow, then directed it against the circular walls around an air outlet. The first design used a low-profile collection bin, but this wasn’t keeping the dust out of the air stream well enough, so [Ruud] switched to using plastic jars. Initially, this didn’t perform as well as the old system, but a few airflow adjustments brought the efficiency up to 99.879%. In [Ruud]’s case, this meant that of 1.3 kilograms of fine sawdust, only 1.5 grams of dust made it through the separator to the filter, which is certainly impressive in our opinion. The design for this upgraded separator is available on GitHub.

[Ruud] based his design off of another 3D-printed dust separator, but adapted it to European fittings. Of course, the dust extractor is only one part of the problem; you’ll still need a dust routing system.

Thanks to [Keith Olson] for the tip!

A C-shaped wooden frame is shown surrounding a circular tongue drum. The wooden frame holds eight black adjustable arms, at the ends of which are mounted solenoids, positioned just above the surface of the drum.

Giving A Drum MIDI Input With Lots Of Solenoids

June 22, 2025 by 7 Comments

As far as giving mechanical instruments electronic control goes, drums are probably the best candidate for conversion; learning to play them is challenging and loud for a human, but they’re a straightforward matter for a microcontroller. [Jeremy Cook]’s latest project takes this approach by using an Arduino Opta to play a tongue drum.

[Jeremy]’s design far the drum controller was inspired by the ring-shaped arrangement of the Cray 2 supercomputer. A laser-cut MDF frame forms a C-shape around the tongue drum, and holds eight camera mount friction arms. Each friction arm holds a solenoid above a different point on the drum head, making it easy to position them. A few supports were 3D-printed, and some sections of PVC tubing form pivots to close the ring frame. [Jeremy] found that the the bare metal tips of the solenoids made a harsh sound against the drum, so he covered the tips of six solenoids with plastic caps, while the other two uncoated tips provide an auditory contrast.

The Arduino Opta is an open-source programmable logic controller normally intended for industrial automation. Here, its silent solid-state relays drive the solenoids, as [Jeremy]’s done before in an earlier experiment. The Opta is programmed to accept MIDI input, which [Jeremy] provided from two of the MIDI controllers which we’ve seen him build previously. He was able to get it working in time for the 2024 Orlando Maker Faire, which was the major time constraint.

Of course, for a project like this you need a MIDI controller, and we’ve previously seen [Jeremy] convert a kalimba into such a controller. We’ve seen this kind of drum machine at least once before, but it’s more common to see a purely electronic implementation.

A man is shown performing a wheelie on a red bicycle in a classroom. In the background, a projector is displaying a phone screen running an indistinct app.

An Adaptive Soundtrack For Bike Tricks

June 22, 2025 by 7 Comments

If you’ve put in all the necessary practice to learn bike tricks, you’d probably like an appropriately dramatic soundtrack to accompany your stunts. A team of students working on a capstone project at the University of Washington took this natural desire a step further with the Music Bike, a system that generates adaptive music in response to the bike’s motion.

The Music Bike has a set of sensors controlled by an ESP32-S3 mounted beneath the bike seat. The ESP32 transmits the data it collects over BLE to an Android app, which in turn uses the FMOD Studio adaptive sound engine to generate the music played. An MPU9250 IMU collects most position and motion data, supplemented by a hall effect sensor which tracks wheel speed and direction of rotation.

When the Android app receives sensor data, it performs some processing to detect the bike’s actions, then uses these to control FMOD’s output. The students tried using machine learning to detect bike tricks, but had trouble with latency and accuracy, so they switched to a threshold classifier. They were eventually able to detect jumps, 180-degree spins, forward and reverse motion, and wheelies. FMOD uses this information to modify music pitch, alter instrument layering, and change the track. The students gave an impressive in-class demonstration of the system in the video below (the demonstration begins at 4:30).

Surprisingly enough, this isn’t the first music-producing bike we’ve featured here. We’ve also seen a music-reactive bike lighting system.

Thanks to [Blake Hannaford] for the tip!