Hacked Ultrasonic Sensors Let You See With Sound

December 6, 2024 by Dan Maloney 13 Comments

If you want to play with radar — and who could blame you — you can pretty easily get your hands on something like the automotive radar sensors used for collision avoidance and lane detection. But the “R” in radar still stands for “Radio,” and RF projects are always fraught, especially at microwave frequencies. What’s the radar enthusiast to do?

While it’s not radar, subbing in ultrasonic sensors is how [Dzl] built this sonar imaging system using a lot of radar principles. Initial experiments centered around the ubiquitous dual-transducer ultrasonic modules used in all sorts of ranging and detection project, with some slight modifications to tap into the received audio signal rather than just using the digital output of the sensor. An ESP32 and a 24-bit ADC were used to capture the echo signal, and a series of filters were implemented in code to clean up the audio and quantify the returns. [Dzl] also added a downsampling routine to bring the transmitted pings and resultant echoes down in the human-audible range; they sound more like honks than pings, but it’s still pretty cool.

To make the simple range sensor more radar-like, [Dzl] needed to narrow the beamwidth of the sensor and make the whole thing steerable. That required a switch to an automotive backup sensor, which uses a single transducer, and a 3D printed parabolic dish reflector that looks very much like a satellite TV dish. With this assembly stuck on a stepper motor to swivel it back and forth, [Dzl] was able to get pretty good images showing clear reflections of objects in the lab.

If you want to start seeing with sound, [Dzl]’s write-up has all the details you’ll need. If real radar is still your thing, though, we’ve got something for that too.

Thanks to [Vanessa] for the tip.

Automatic Garbage Can Keeps Cooking Cleaner

July 23, 2024 by Bryan Cockfield 30 Comments

Over the last decade or so, we’ve been inundated with appliances with wireless or “smart” technology that is often of dubious utility. No one really needs a tablet in their refrigerator or Wi-Fi on their coffee maker. A less glamorous kitchen appliance that actually might benefit from some automation and connectivity is the garbage can, or “bin” for those speaking the Queen’s English, and [Mellow_Labs] is here to show off just how to get that done with this automatic garbage can lid.

As he explains, the real impetus behind this build is to not have to touch a dirty lid while cooking to avoid having to take time to wash one’s hands again afterwards. There are a few other design criteria as well; it has to be roommate-approved so nothing permanently attached to the lid, overly complicated, or with an unnecessary amount of wires or other fixtures. A servo with an extension sits on the lid itself, and when activated forces the lid open. A distance sensor provides basic gesture recognition and a microcontroller with wireless connectivity controls both and provides home automation integration as well. With a 3D printed case that includes a quick disconnect function for easy cleaning of the lid, the build was ready to be put into service.

The first iteration used an infrared distance sensor, but placing it by an open window caused it to continuously open and close since sunlight has the same wavelengths of light the sensor is tuned for. A quick swap with an ultrasonic sensor solved the problem, and the garbage can is working flawlessly in the kitchen now. Another appliance that is generally not targeted by off-the-shelf automation solutions is the range fume hood, but another build tackled that problem a while back.

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Much Faster Cold Brew Through Cavitation

May 8, 2024 by Kristina Panos 27 Comments

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.

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.

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Tiny Speaker Busts Past Sound Limits With Ultrasound

November 27, 2023 by Donald Papp 15 Comments

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

August 15, 2023 by Matthew Carlson 16 Comments

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.

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Listening To Bats As They Search For Food

July 14, 2023 by Bryan Cockfield 14 Comments

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

June 13, 2023 by Lewin Day 14 Comments

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.

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