Stretching The Flight Time On A Compressed Air Plane

October 15, 2023 by 24 Comments

[Tom Stanton] has been experimenting with compressed air motors on model aircraft for a good few years, but keeping them aloft (and intact) for more than a few seconds has proven a tough nut to crack. His latest design represents a breakthrough — pulling off an impressive 1 minute and 26 seconds flight on 4 liters of compressed air.

The model incorporates an enhanced engine design featuring an expanding seal on the piston, a concept inspired by the old Air Hogs toy plane. For the airframe, he constructed lightweight wings using 3D printed ABS ribs on a carbon spar and reinforcing rods, all of which were wrapped in heat shrink film. Additionally, [Tom] incorporated a thin balsa former along the leading edge of the wing to help maintain its shape. The fuselage is also composed of a carbon fiber tube, and is outfitted with printed fittings to install the wings, V-tail, RC electronics, and soda/air bottles. A hollow nylon bolt holds the two bottles together end-to-end while allowing the motor to be screwed directly onto the front bottle. To conserve weight, each of the two V-tail control surfaces are actuated by single cables linked to servos, with piano wire torsion springs in the hinges to maintain tension

Despite successful flights, [Tom]’s trials were not without challenges. One crash threatened severe damage to his airframe, but thanks to a central 3D printed bracket that absorbed most of the impact, total destruction was avoided. Similarly, a printed shaft saved his expensive carbon fiber propeller from being damaged during multiple landings, an outcome that led [Tom] to devise a readily replaceable consumable connector.

A second video after the break offers a behind-the-scenes insights into this project including some fascinating technical details. For more on this project’s history, take a look at the initial diaphragm engines and his attempts to make them fly.

Continue reading “Stretching The Flight Time On A Compressed Air Plane” →

Burnt Resistor Sleuthing

October 15, 2023 by 7 Comments

You smell smoke and the piece of gear you are working on stops working, probably at an inopportune time. You open it up and immediately see the burned remains of a resistor. You don’t have the schematic, the Internet has nothing to say, and the markings on the resistor are burned away. What do you do? [Learn Electronics Repair] has some advice.

The resistor is probably open, but even if it isn’t, you can’t count on any measurement you make. The burning could easily change the value. The technique comes from comments on one of his earlier videos where he had such a burned resistor but was able to find the correct value. He decided to test the suggestion: cut away the burned resistor and measure the pieces that are left. It probably won’t give you the exact value, but it will get you in the ballpark.

So a rotary tool did the surgery, and you can see it all in the video below. We aren’t sure this method would work on every type of resistor you might encounter, and surface mount will also present special problems. However, if you are stabbing in the dark anyway, it won’t hurt to try.

Everyone knows the smoke that comes out is magic. Sometimes, you cut into components by necessity. Other times, it is for art’s sake.

Continue reading “Burnt Resistor Sleuthing” →

Keeping Badgers At Bay With Tensorflow

October 15, 2023 by 9 Comments

Human-animal conflict is always a contentious issue, and finding ways to prevent damage without causing harm to the animals often requires creative solutions. [James Milward] needed a humane method to stop badgers and foxes from uprooting his garden, leading him to create the Furbinator 3000, a system that combines computer vision with audio deterrents..

[James] initially tried using scent repellents (which were ignored) and blocking access to his garden (resulting in more digging), but found some success with commercial ultrasonic audio repellent devices. However, these had to be manually turned off during the day to avoid annoying activation of the PIR motion sensors by [James] and his family, and the integrated solar panels couldn’t keep up with the load.

This presented a good opportunity to try his hand at practical machine vision. He already had a substantial number of sample images from the Ring cameras in his garden, which he turned into a functional TensorFlow Lite model with about 2.5 hours of training. He linked it with event-activated RTSP streams from his Ring cameras using the ring-mqtt library. To minimize false positives on stationary objects, he incorporated a motion filter into the processing pipeline. When it identifies a fox or badger with reasonable accuracy, it generates an MQTT event.

[James] modified the ultrasonic devices so they would react to these events using an ESP8266-based WeMos D1 Mini Pro development board and added an external 5 V power supply for sustained operation. All development was performed in a Docker container which simplified deployment on a Raspberry Pi 4.

After implementing the system, [James] woke up to the satisfying sight of his garden remaining untouched overnight, a victory that even earned him some coverage by the BBC.

Thanks for the tip [Laurent]!

Compact, Gesture-Based Remote Control Over Bluetooth

October 14, 2023 by 5 Comments

[AlexMiller11] shared a project for a DIY gesture-sensing remote control that acts like a Bluetooth keyboard, capable of controlling media and presentations on a computer with a high degree of accuracy.

The device recognizes eight different gestures and controls a host PC over Bluetooth.

The hardware is a Silicon Labs xG24 dev kit, a small IoT-focused board able to be powered by a CR2032 cell. Part of what makes it all work is the six-axis IMU sensor, but the rest is the software to interpret that data and figure out what motions the user is trying to do. That happens with a Neuton.AI model and SDK, a tiny but effective machine learning framework for small devices.

How does it actually work? The device acts as a Bluetooth HID, and gets connected to a PC in the same was as a regular Bluetooth keyboard. Once that’s done, recognized gestures are printed out the serial port as well as sent via Bluetooth to the host machine. Media can then be played, paused, volume adjusted, presentations controlled, and more. More details are on the project’s GitHub repository. There’s also a demo video that explains exactly what’s going on, embedded below the page break.

Machine learning is a way of using software to solve the kinds of problems humans are not very good at writing programs to solve, and accurate gesture recognition is a good example. Not all such applications require heaps of overheating GPUs, either. We’ve seen the concept of a neural network stripped down to its bare essentials running on an Arduino Uno, for those who would like to better appreciate the fundamentals.

Continue reading “Compact, Gesture-Based Remote Control Over Bluetooth” →

AI-Powered Snore Detector Shakes The Pillow So You Won’t

October 14, 2023 by 18 Comments

If you snore, you’ll probably find out about it from someone. An elbow to the ribs courtesy of your sleepless bedmate, the kids making fun of you at breakfast, or even the lady downstairs calling the cops might give you the clear sign that you rattle the rafters, and that it’s time to do something about it. But what if your snores are a bit more subtle, or you don’t have someone to urge you to roll over? In that case, this AI-powered haptic snore detector might be worth building.

The most distinctive characteristic of snoring is, of course, its sound, and that’s exactly what [Naveen Kumar] chose as a trigger. To differentiate between snoring and other nighttime sounds, [Naveen] chose an Arduino Nicla Voice sensor board, which sports a Syntiant NDP120 deep-learning processor and a built-in MEMS microphone. To generate a model that adequately represents the full tapestry of human snores, a publicly available snoring dataset — because of course that’s a thing — was used for training. Importantly, the training data included samples of non-snoring sounds, like sirens and thunder, as well as clips of legit snoring mixed with these other sounds. The model is trained with an online tool and downloaded onto the board; when it detects the sweet sound of sawing wood three times in a row, a haptic driver board vibrates the pillow as a gentle reminder to reposition. Watch it in action in the brief video below.

Snoring is something that’s easy to make light of, but in all seriousness, it’s not something to be taken lightly. Hats off to [Naveen] for developing a tool like this, which just might let you know you’ve got a problem that bears a closer look by a professional. Although it might work better as a wearable rather than a pillow-shaker.

Continue reading “AI-Powered Snore Detector Shakes The Pillow So You Won’t” →

PCB Repair Is A Sticky Proposition

October 14, 2023 by 9 Comments

What do you do when a PCB is cracked or even broken in two? [MH987] has a plan: superglue the board back and then bridge the traces with solder, solder paste, or wire. The exact method, of course, depends on the extent of the damage.

We’ve had some success with similar techniques, and, honestly, for single-sided boards, we would be tempted to add a thin backer behind the crack. We’ve also used conductive paint to repair traces, but it’s good to have having as many tricks as possible because you never know what will work best for a particular repair. The post mentions that this is easier to do on a single-sided board, but it is certainly possible to do on a two-layer board.

The example repair is a Walkman which — if you are a youngster — was a portable music player that takes cassette tapes. These haven’t been made since 2010, so it is important to repair what you have.

If you can’t repair your Walkman, you could build an updated version. If your board is seriously damaged, you might get hope from this more extreme repair.

2023 Halloween Hackfest: Candy Basket Sees You Coming

October 14, 2023 by 5 Comments

On Halloween, some people can’t or don’t want to open the door for various reasons. Maybe they have a cat that likes to escape every chance it gets, or maybe their favorite TV show is on during prime trick-or-treating time. Whatever the case, we think it’s perfectly acceptable to leave a bowl of candy outside the door, especially if there are electronics involved.

In this case, the bowl detects trick-or-treaters and candy eaters using an LD2410 60 GHz radar sensor and an RP2040. A light pipe shows orange when a person is detected, and switches over to green as they come closer, as if to say you may have candy now.

Nothing happens after that, but now that we think about it, it would be cool to add an MP3 decoder and a speaker to play a little witch cackle or something once they’ve had a chance to stick their hand in the bucket.

[Mike Kushnerik] actually designed the PCB a few months ago for non-Halloween purposes: some home automation projects. But then they were trying to think of something for Halloween, and this delightful light-up bucket came to mind. In addition to the RP2040 chip, there’s a 128 MB flash chip, a WS2812 LED, and a header for communicating with the radar sensor over UART. Be sure to check out the brief demo video after the break.

If you’d like to stand outside and give out candy, at least send it down a light-up slide or something.

Continue reading “2023 Halloween Hackfest: Candy Basket Sees You Coming” →