What to do with Your Brand New Ultrasonic Transducer

We wager you haven’t you heard the latest from ultrasonics. Sorry. [Lindsay Wilson] is a Hackaday reader who wants to share his knowledge of transducer tuning to make tools. The bare unit he uses to demonstrate might attach to the bottom of an ultrasonic cleaner tank, which have a different construction than the ones used for distance sensing. The first demonstration shows the technique for finding a transducer’s resonant frequency and this technique is used throughout the video. On the YouTube page, his demonstrations are indexed by title and time for convenience.

For us, the most exciting part is when a tuned transducer is squeezed by hand. As the pressure increases, the current drops and goes out of phase in proportion to the grip. We see a transducer used as a pressure sensor. He later shows how temperature can affect the current level and phase.

Sizing horns is a science, but it has some basic rules which are well covered. The basic premise is to make it half of a wavelength long and be mindful of any tools which will go in the end. Nodes and antinodes are explained and their effects demonstrated with feedback on the oscilloscope.

We have a recent feature for an ultrasonic knife which didn’t cut the mustard, but your homemade ultrasonic tools should be submitted to our tip line.

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The M1 NerfBot: When Prototypes Evolve

What do you get when you cross a self-taught maker with an enthusiasm for all things Nerf? A mobile nerf gun platform capable of 15 darts per second. Obviously.

The M1 NerfBot built by [GrimSkippy] — posting in the ‘Let’s Make Robots’ community — is meant to be a constantly updating prototype as he progresses in his education. That being the case, the progress is evident; featuring two cameras — a webcam on the turret’s barrel, and another facing forward on the chassis, a trio of ultrasonic sensors, controlled by an Xbox 360 controller, and streaming video to a webpage hosted on the M1 itself, this is no mere beginner project.

Perhaps most compelling is how the M1 tracks its targets. The cameras send their feeds to the aforementioned webpage and — with a little reorganization — [GrimSkippy] accesses the the streams on an FPV headset-mounted smartphone. As he looks about, gyroscopic data from the phone is sent back to the M1, translating head movement into both turret and chassis cam movement. Check it out!

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Hackaday Links: March 4, 2018

Guess what’s happening next weekend? The SoCal Linux Expo. SCALE is in its 16th year, and is the second greatest convention happening this year at the Pasadena Convention Center. The first, of course, is AlienCon this summer, with a special guest appearance by the guy with the hair on Ancient Aliens. What’s cool at SCALE? Tons of stuff! Tindie and Hackaday will have a booth, you’ll be able to check out the new stuff from System 76, and this is where I first picked up my most cherished possession, a Microsoft (heart) Linux sticker. NEED A TICKET? Cool, use the code ‘HACK’ to get 50% off!

[Muth] over on hackaday.io has been working on a very, very, very cool high voltage display. It’s a ИГГ1-64x64M, or a Gazotron, or something. What is it? It’s a two-color (green and red) 64×64 pixel VFD bitmap display. You want the king of all vacuum-based displays? Here you go. Progress on driving this display is slow, but it’s happening, and it will result in the coolest clock ever created.

Need a pick and place machine? Don’t want to shell out thousands for a Neoden? Here’s an Indiegogo campaign for the Open Placer, a machine that works with OpenPNP software. It’s got vision and a 295x195mm working area.

A few months ago, news came from Havana that the US embassy was under attack. Staffers at the US embassy in Cuba were feeling sick and apparently suffered neurological damage. Explanations ranged from poisoning to some sort of non-lethal weapon. Now, there might be a banal explanation. Researchers at the University of Michigan think it could simply be two ultrasonic sensors placed just the right distance apart. Acoustic interference happens, and that inaudible 35kHz signal becomes a maddening audible signal.

Last week, we had a great talk with OSH Park about PCBs. These Hack Chats are getting out of control, but at least we have a transcript. The biggest takeaway? They’re out of jellybeans, but OSH Park is working on new stickers.

Open Hardware Summit is the greatest con for all things Open Hardware. This year, it’s going to be in Boston. The Summit will be held on September 27th, 2018 at MIT Stratton Student Center. If you’d like to get there a week and a half early, the MIT ham flea market is the third Sunday of the month.

Fail of the Week: The Little Ultrasonic Knife That Couldn’t

We all know the feeling of an idea that sounded great when it was rattling around in our head, only to disappoint when we actually build the thing. It’s a natural consequence of trying new stuff, and when it happens, we salvage what we can and move on, hopefully in wisdom.

The thing that at least semi-defeated [This Old Tony] was an attempt to build an ultrasonic cutter, and it didn’t go well. Not that any blood was shed in the video below, although there seemed like there would be the way [Old Tony] was handling those X-Acto blades. His basic approach was to harvest the transducer and driver from a cheap ultrasonic cleaner and retask the lot into a tool to vibrate a knife rapidly enough to power it through tough materials with ease.

Spoiler alert: it didn’t work very well. We think the primary issue was using a transducer that was vastly underpowered compared to commercial (and expensive) ultrasonic cutters, but we suspect the horn he machined was probably not optimized either. To be fair, modeling the acoustic performance of something like that isn’t easy, so we can’t expect much. But still, it seems like the cutter could have worked better. Share your thoughts on how to make version 2.0 better in the comments.

The video is longish, but it’s as entertaining as any of [Old Tony]’s videos, and packed full of incidental gems, like the details of cavitation. We enjoyed it, even if the results were suboptimal. If you want to see a [This Old Tony] project that really delivers, check out his beautiful boring head build.

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Automating your Door for $20

We love the doors on Star Trek’s Enterprise. We should have known they were human-operated though because they were too smart. They would wait for people, or fail to open when someone was thrown against them during a fight. [SieuweE] has a much more practical automatic door that he calls ArduDoor.

You might guess from the name it uses an Arduino. It also uses a windshield wiper motor which is perfect since it is high-torque and low speed. You might even be able to pick one up for little or nothing if you frequent the junkyards.

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Never Let Your Christmas Tree Run Dry, With Added Ultrasound

Winter in the parts of the Northern Hemisphere for which observing Christmas includes bringing half a forest into the house should really be divided into two seasons. No-spruce-needles-in-the-carpet season, and spruce-needles-doggedly-clinging-to-the-carpet season. Evergreen trees were not designed for indoor use, and for a hapless householder to stand any chance of keeping those needles on the branches there has to be a significant amount of attention paid to the level of the water keeping the tree hydrated.

[Evan] has paid that attention to the problem of Christmas tree hydration, and to address the shortcomings of earlier designs has come up with a low water warning using an ultrasonic rangefinder. Where previous sensor attempts based on conductive probes succumbed to corrosion or dirt build-up, this one has no contact between sensor and water.

Behind the rangefinder is a CHIP board, whose software sends a text message to his phone when the water level gets a bit low. All the software is available in the linked GitHub page, so should you wish to make your tree safe from thirst, you too can give it a try.

SMS texts are a good way to alert a tree owner, but we quite like the sensor that used the tree lights instead.

Listening for Hand Gestures

[B. Aswinth Raj] wanted to control a VLC player with hand gestures. He turned to two common ultrasonic sensors and Python to do the job. There is also, of course, an Arduino. You can see a video of the results, below.

The Arduino code reads the distance from both sensors — one for the left hand and the other for the right. This allows the device to react to single hand gestures that get closer or further away from one sensor as well as gestures involving both hands. For example, raising your left hand and moving it closer or further away will adjust the volume. The right hand controls rewind and fast forward. Raising both hands will start or stop playback.

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