The Incredible Mechanical Artistry Of François Junod

June 29, 2021 by Danie Conradie 16 Comments

The art of building purely mechanical automatons has dramatically declined with the arrival of electronics over the past century, but there are still a few craftsmen who keep the art form alive. [François Junod] is one of these masters, and the craftsmanship and intricacy on display in his automata is absolutely amazing.

[François]’ creations are all completely devoid of electronics, and are powered either by wound-up springs or weights. The mechanics of the automata are part of the display, and contain a vast array of gears, linkages, belts and tracks. Many of them also include their own soundtrack, which range from simple bells and chimes to complete melodies from mechanized wind instruments, as demonstrated in Le Champignonneur below. He also collaborates with craftsman like jewelers on works like La Fée Ondine, which we thought was CGI when we first saw it in the video after the break.

Very few people have the time, skill and patience to make these creations, but we are glad there are still a few around. Some builds, like [Patelo]’s flightless drone aren’t quite as complex, but are no less inspiring. If you don’t quite have the time and fabrication skills, you can still create mesmerizing automatons with 3D printing like [gzumwalt]. Continue reading “The Incredible Mechanical Artistry Of François Junod” →

Ball CVT Drives Robot From A Constant Speed Motor

June 29, 2021 by Danie Conradie 13 Comments

[James Bruton] is experimenting is a series of interesting mechanical mechanisms, the latest being a CVT transmission system which uses a tilting sphere to get a variable speed output from a constant speed input. Video after the break.

In [James]’ proof of concept RC vehicle, a single powered disc is mounted on top, at 90 degree to the wheels. A rotating sphere makes contact with both the driven disc and the wheel. When the rotation axis of the sphere is at 45° between the disc and the wheel, it provides a one 1:1 transmission ratio. As the axis is tilted, the contact points on the sphere shift, changing the relative circumference at the contact points, and therefore changing the transmission ratio. It can also reverse by tilting the sphere in the opposite direction, and disconnected from the output wheel by aligning it with the hole in the bottom of the sphere. [James]’ simple two-wheel RC car concept quite well, driving around his kitchen with the transmission spheres being tilted by servos.

Thanks to the response time, CVT gearboxes are generally not needed for electric motors, but on internal combustion engines that which run best within a certain RPM range they can be very useful. One possible weak point of a design like this is it’s dependence on friction to transfer torque, which makes it vulnerable to wear and slipping.

This build is a spin-off of his spherical omni-wheels and the robot chassis he developed around them. For another interesting robot mechanism, check out is gyroscope balancing system. Continue reading “Ball CVT Drives Robot From A Constant Speed Motor” →

PetBot: Turn PET Bottles Into Filament

June 29, 2021 by Danie Conradie 44 Comments

Recycling plastic into filament normally involves chopping it into tiny pieces and pushing it through a screw extruder. [JRT3D] is taking a different approach with PetBot, which cuts PET bottles into tape and then turns it into filament. See the videos after the break.

Cutting the tape and extrusion happens in two completely separated processes on the same machine. A PET bottle is prepared by cutting off the bottom, and the open rim is pushed between a pair of bearings, where a cutter slices the bottle into one long strip, as a driven spool rolls it up. The spool of tape is then moved to the second stage of the machine, which pulls the tape through a hot end very similar to that on a 3D printer. While most conventional extruders push the plastic through a nozzle with a screw, the PetBot only heats up the tape to slightly above its glass transition temperature, which allows the driven spool to slowly pull it through the nozzle without breaking. A fan cools the filament just before it goes onto the spool. The same stepper motor is used for both stages of the process.

We like the simplicity of this machine compared to a conventional screw extruder, but it’s not without trade-offs. Firstly is the limitation of the filament length by the material in a single bottle. Getting longer lengths would involve fusing the tape after cutting, or the filament after extrusion, which is not as simple as it might seem. The process would likely be limited to large soda bottle with smooth exterior surfaces to allow the thickness and width of the tape to be as consistent as possible. We are curious to see the consistency of the filaments shape and diameter, and how sensitive it is to variations in the thickness and width of the tape. That being said, as long as you understand the limitations of the machine, we do not doubt that it can be useful. Continue reading “PetBot: Turn PET Bottles Into Filament” →

Listen To The RF Around You

June 27, 2021 by Danie Conradie 21 Comments

These days, we are spoiled for choice with regard to SDRs for RF analysis, but sometimes we’re more interested in the source of RF than the contents of the transmission. For this role, [Drew] created the RFListener, a wideband directional RF receiver that converts electromagnetic signal to audio.

The RF Listener is built around a AD8318 demodulator breakout board, which receives signals using a directional broadband (900 Mhz – 12 Ghz) PCB antenna, and outputs an analog signal. This signal is fed through a series of amplifiers and filters to create audio that can be fed to the onboard speaker. Everything is housed in a vaguely handgun shaped enclosure, with some switches on the back and a LED amplitude indicator. [Drew] demonstrates the RFListener around his house, pointing it at various devices like his router, baby monitor and microwave. In some cases, like with a toy drone, the modulation is too high frequency to generate audio, so the RF listener can also be switched to “tone mode”, which outputs audio tone proportional to the signal amplitude.

The circuit is completely analog, and the design was first done in Falstad Circuit Simulator, followed by some breadboard prototyping, and a custom PCB for the final version. As is, it’s already an interesting exploration device, but it would be even more so if it was possible to adjust the receiver bandwidth and frequency to turn it into a wideband foxhunting tool.

Electric RC Plane Flies For Almost 11 Hours

June 27, 2021 by Danie Conradie 45 Comments

Electric RC aircraft are not known for long flight times, with multirotors usually doing 20-45 minutes, while most fixed wings will struggle to get past two hours. [Matthew Heiskell] blew these numbers out of the water with a 10 hour 45 minute flight with an RC plane on battery power. Condensed video after the break.

Flight stats right before touchdown. Flight time in minutes on the left, and miles travelled second from the top on the right.

The secret? An efficient aircraft, a well tuned autopilot and a massive battery. [Matthew] built a custom 4S 50 Ah li-ion battery pack from LG 21700 cells, with a weight of 2.85 kg (6.3 lbs). The airframe is a Phoenix 2400 motor glider, with a 2.4 m wingspan, powered by a 600 Kv brushless motor turning a 12 x 12 propeller. The 30 A ESC’s low voltage cutoff was disabled to ensure every bit of juice from the battery was available.

To improve efficiency and eliminate the need to maintain manual control for the marathon flight, a GPS and Matek 405 Wing flight controller running ArduPilot was added. ArduPilot is far from plug and play, so [Matthew] would have had to spend a lot of timing tuning and testing parameters for maximum flight efficiency. We are really curious to see if it’s possible to push the flight time even further by improving aerodynamics around the protruding battery, adding a pitot tube sensor to hold the perfect airspeed speed on the lift-drag curve, and possibly making use of thermals with ArduPilot’s new soaring feature.

A few of you are probably thinking, “Solar panels!”, and so did Matthew. He has another set of wings covered in them that he used to do a seven-hour flight. While it should theoretically increase flight time, he found that there were a number of significant disadvantages. Besides the added weight, electrical complexity and weather dependence, the solar cells are difficult to integrate into the wings without reducing aerodynamic efficiency. Taking into account what we’ve already seen of [rcflightest]’s various experiments/struggles with solar planes, we are starting to wonder if it’s really worth the trouble. Continue reading “Electric RC Plane Flies For Almost 11 Hours” →

Mechanical 7-Segment Display Uses A Single Motor

June 27, 2021 by Danie Conradie 29 Comments

Seven-segment displays have been around for a long time, and there is a seemingly endless number of ways to build them. The latest of is a mechanical seven-segment from a master of 3D printed mechanisms, [gzumwalt], and can use a single motor to cycle through all ten possible numbers.

The trick lies in a synchronized pair of rotating discs, one for the top four segments and another for the bottom three segments. Each disc has a series of concentric cam slots to drive followers that flip the red segments in and out of view. The display can cycle through all ten states in a single rotation of the discs, so the cam paths are divided in 36° increments. [gzumwalt] has shown us a completed physical version, but judging by CAD design and working prototype of a single segment, we are pretty confident it will. While it’s not shown in the design, we suspect it will be driven by a stepper motors and synchronized with a belt or intermediate gear.

Another 3D printed mechanical display we’ve seen recently is a DIY flip dot, array, which uses the same electromagnet system as the commercial versions. [gzumwalt] has a gift for designing fascinating mechanical automatons around a single motor, including an edge avoiding robot and a magnetic fridge crawler.

Continue reading “Mechanical 7-Segment Display Uses A Single Motor” →

Raspberry Pi Pico Oscilloscope

June 26, 2021 by Danie Conradie 47 Comments

As you dive deeper into the world of electronics, a good oscilloscope quickly is an indispensable tool. However, for many use cases where you’re debugging low voltage, low speed circuits, that expensive oscilloscope is using only a fraction of its capabilities. As a minimalist alternative for these use cases [fhdm-dev] created Scoppy, a combination of firmware for the Raspberry Pi Pico and an Android app to create a functional oscilloscope.

As you would expect, the specifications are rather limited, capturing a maximum of 100 kpts at a speed of 500 kS/s shared between the two channels. Without some additional front end circuitry to protect the Pico, the input voltage is limited to 0-3.3 V. Neither the app nor the firmware is open source, and getting access to the second channel and removing ads requires a ~$3 in-app purchase. Even so, we can still think of plenty of practical uses for a ~$7 oscilloscope. If you do decide to add some front-end circuitry to change to voltage range, you can set them in the app, and switch between them by pulling certain GPIO pins high or low. The app has most of the basic oscilloscope features covered, continuous and single shot capture, adjustable trigger settings and a scalable waveform display.

Simple, cheap oscilloscopes like these have their place, but you start to understand why the “real” ones are so expensive when you see what goes into developing a high performance oscilloscope.