Much Faster Cold Brew Through Cavitation

Some coffee snobs might call this sacrilege. Cold brew is supposed to take a long time — that’s part of how it gets its characteristic smoothness. But a group of engineers from the University of New South Wales (UNSW Sydney) have figured out a way to cut the time down from several hours to a mere three minutes, using ultrasonic waves.

Diagram showing the parts of the faster cold brew system -- the portafilter of a Breville espresso machine, plus a transducer and horn.Typically, the cold brew coffee process takes between 12 and 24 hours. Enough time to steep the grounds and extract the flavors without the benefit of hot water. This is how it differs from iced coffee, which is brewed hot and poured over ice.

Interestingly, the UNSW Sydney engineers’ process uses a typical prosumer-grade espresso machine and involves blasting the portafilter with a transducer and a horn. This transforms the coffee basket into a sonoreactor. Sound waves at a frequency of 38.8 kHz are injected at multiple points through the walls, generating acoustic cavitation within. You can read all about it in Ultrasonics Sonochemistry.

That’s not even the most exciting part. The study found that this arrangement is capable of doubling both the extraction yield and caffeine concentration, compared with non-soundblasted samples. The team sent samples of the coffee off to be evaluated on aroma, texture, flavor, and aftertaste. Although the one-minute extraction samples received similar ratings to a 24-hour brew in terms of flavor and aftertaste, they lacked the intensity and dark chocolate aroma of the longer brew. But the three-minute extraction samples scored quite highly in all areas, suggesting that the average cold brew drinker wouldn’t be able to tell the difference.

Would you like to roast your own beans at home? You can use a popcorn popper, but you might get tired of semi-uneven roasts and upgrade to a DIY wobble disk roaster.

Continue reading “Much Faster Cold Brew Through Cavitation”

Tiny Speaker Busts Past Sound Limits With Ultrasound

Conventional speakers work by moving air around to create sound, but tiny speakers that use ultrasonic frequencies to create pressure and generate sound opens some new doors, especially in terms of maximum achievable volume.

A new design boasts being the first 140 dB, full-range MEMS speaker. But that kind of volume potential has less to do with delivering music at an ear-splitting volume and more to do with performing truly effective noise cancellation even in a small device like earbuds. Cancelling out the jackhammers of the world requires parts able to really deliver a punch, especially in low frequencies. That’s something that’s not so easy to do in a tiny form factor. The new device is the Cypress, from MEMS speaker manufacturer xMEMS and samples are aiming to ship in June 2024.

Combining ultrasonic waves to create audible sound is something we’ve seen show up in different ways, like using an array of transducers to focus sound like a laser beam. Another thing ultrasonics can do is cause sensors in complex electronics to become unhinged from reality and report false readings. Neato!

UChaser Follows You Anywhere

If you’ve been making up for lost years of travel in 2023, you might have seen a fellow traveler in the airport terminal or train station walking with their luggage happily careening behind them. [Jesse R] and [Brian Lindahl] wanted more of that. They wanted an open-source, low-cost system that could be put in anything.

The basic principle is that they will have a transmitter that sends both a radio signal and an ultrasonic pulse. The receiver receives the radio signal and uses it as a reference for the two ultrasonic sensors. The time since the radio signal is compared between the two, and a distance and direction are established.

In practice, the radio is an ESP32-S3 using ESP-NOW (which we’ve seen relatively recently on another project), a protocol from Espressif that offers low latency 250 bytes payloads. The ultrasonic transceiver is based on Sparkfun’s HC-SR04. For prototyping purposes on the receiver, they just removed the transmitter to avoid populating the airwaves, as to listen, you had to transmit. The prototype was an electric wheelbarrow that would happily follow you around the yard wherever you go.

With the concept validated, they moved to a custom ultrasonic setup with a custom buffer amp and damp transistor, all centered around 20kHz. The simulations suggested they should have been better than the HC-SR04 from Sparkfun, but the 30-foot (9 meters) range went to 10 feet (3 meters). They ultimately returned to using Sparkfun’s circuit rather than the custom amp.

We’re looking forward to seeing the project continue. There are various challenges, such as variability in the speed of sound, echos and reflections, and ultrasonic line of sight. We love the peak behind the curtain that allows us to see what decisions get made and the data that informs those decisions. All the code and PCB design files are available on GitHub under an MIT and Creative Common license, respectively. This project was submitted as part of the 2o23 Hackaday Prize.

Video after the break.

Continue reading “UChaser Follows You Anywhere”

Listening To Bats As They Search For Food

The range of human hearing goes up to about 20 kilohertz, which is fine for our purposes, but is pretty poor compared to plenty of other animal species. Dogs famously can hear up to about 60 kHz, and dolphins are known to distinguish sounds up to 100 kHz. But for extremely high frequencies we’ll want to take a step into the world of bats. Some use echolocation to locate each other and their food sources, and bats like the pipistrelle can listen in to sounds up to 350 kHz. To listen to them you’ll need a device like the π*pistrelle. (Ed Note: a better explanation is available at the project’s website.)

The original implementation of the bat detector was based on a Raspberry Pi Pico, from which it gets its name. But there have been several improvements on it in the years since it was first developed. The latest can detect bats when it hears their 350 kHz sonar calls thanks to an ultrasonic microphone and op amp. The device then records the bat sounds and then either heterodynes the sound down or time-expands it to human-audible range so the calls can actually be heard. There’s an LED display on the board as well as three input buttons, but an iOS companion app is available to interact with the device as well.

If you want to know for sure which species is flying around at night, you can use machine learning to help figure that out.

Arduino-Powered Missile System Uses Ultrasound To Aim

In the real world, missile systems use advanced radars, infrared sensors, and other hardware to track and prosecute their targets. [Raspduino Uno] on YouTube has instead used ultrasound for targeting for an altogether simpler desktop fire control solution.

This fun build uses a common off-the-shelf USB “missile launcher” that fires foam darts. To supply targeting data for the launcher, an Arduino Uno uses an ultrasonic sensor pair mounted atop a servo. As the servo rotates, the returns from the ultrasonic sensor are plotted on a screen run by a Raspberry Pi. If an object is detected in the 180-degree field of view of the sweeping sensor, a missile is fired using the dart launcher.

It’s a relatively simple build, but nonetheless would serve as a useful classroom demonstration of radar-like targeting techniques to a young audience. Real military hardware remains altogether more sophisticated. Video after the break.

Continue reading “Arduino-Powered Missile System Uses Ultrasound To Aim”

Converting A Sink To An Ultrasonic Cleaner

While ultrasonic cleaning might sound a bit like the “sonic shower” from Star Trek, this is actually one case where the futuristic-sounding technology predates its use in Sci-Fi. Ultrasonic cleaners have been around since the 50s and are used to clean all sorts of oddly-shaped or specialty objects by creating cavitation within a liquid that allows the surface of the object to be scoured. With the right equipment, these cleaning devices are fairly straightforward to build as well.

This ultrasonic cleaner by [Branchus Creations] started off as a standard stainless steel laundry sink, but with the addition of a few transducers it really turns up the volume. They are attached to the underside of the sink with a combination of a bolt and hard epoxy so that the sound is efficiently transmitted to the sink, but they’re not much use without driver boards to power them. These drivers take AC power and convert it to the DC required to generate the ultrasonic frequencies, and this build uses a driver for each of the transducers all wired up to a common control board for ease-of-use.

The results speak for themselves; a test is performed on a sheet of aluminum foil which quickly turns takes on a Swiss cheese appearance after just a couple minutes in the cleaner. It’s also shown cleaning rusty nails and a few other things as well. For other nontraditional cleaning methods, be sure to check out this wet media blast cabinet built from a 55-gallon drum.

Continue reading “Converting A Sink To An Ultrasonic Cleaner”

Walk-Bot Is A Navigation Device For The Vision-Impaired

For the vision impaired, there are a wide variety of tools and techniques used to navigate around in the real world. Walk-bot is a device that aims to help with this task, using ultrasound to provide a greater sense of obstacles in one’s surroundings.

Is trigonometry the most useful high school maths out there? There’s an argument that says yes.

Created by [Nilay Roy Choudhury], the device is intended to be worn on the waist, and features two sets of ultrasonic sensors. One set is aimed straight ahead, while the other points upwards at an angle of 45 degrees. An infrared sensor then points downward at an angle of 45 degrees, aimed at the ground.

The distance readings from these sensors are then collated by a microcontroller, which uses trigonometry to determine the user’s actual distance to the object. When objects are closer than a given threshold, the device provides feedback to the user via a buzzer and a vibration motor. The combination of three sensors looking out at different angles helps capture a variety of obstacles, whether they be at head, chest, or knee height.

It’s unlikely that a complex electronic device would serve as a direct replacement for solutions like the tried-and-tested cane. However, that’s not to say there isn’t value in such tools, particularly when properly tested and designed to suit user’s needs.

We’ve seen some great projects regarding visual impairment before, like this rig that allows users to fly in a simulator. If you’ve been working on your own accessibility tools, don’t hesitate to drop us a line!