Lessons Learned From A 1-Day RTL-SDR Enclosure Project

December 14, 2018 by Donald Papp 9 Comments

[ByTechLab] needed an enclosure for his R820T2 based RTL-SDR, which sports an SMA connector. Resolving to design and 3D print one in less than a day, he learned a few things about practical design for 3D printing and shared them online along with his CAD files.

The RTL-SDR is a family of economical software defined radio receivers, and [ByTechLab]’s’ enclosure (CAD files available on GrabCAD and STL on Thingiverse) is specific to his model. However, the lessons he learned are applicable to enclosure design in general, and a few of them specifically apply to 3D printing.

He started by making a basic model of the PCB and being sure to include all large components. With that, he could model the right voids inside the enclosure to ensure a minimum of wasted space. The PCB lacks any sort of mounting holes, so the model was also useful to choose where to place some tabs to hold the PCB in place. That took care of the enclosure design, but it also pays to be mindful of the manufacturing method so as to play to its strengths. For FDM 3D printing, that means most curved shapes and rounded edges are trivial. It also means that the biggest favor you can do yourself is to design parts so that they can be printed in a stable orientation without any supports.

This may be nothing that an experienced 3D printer and modeler doesn’t already know, but everyone is a novice at some point and learning from others’ experiences can be a real timesaver. For the more experienced, we covered a somewhat more in-depth guide to practical 3D printed enclosure design.

[ByTechLab]’s desire for a custom enclosure was partly because RTL-SDR devices come in many shapes and sizes, as you can see in this review of 19 different units (of which only 14 actually worked.)

A Cheat Sheet For Publishing Python Packages

December 13, 2018 by Donald Papp 5 Comments

[Brendan Herger] was warned that the process of publishing a Python package would be challenging. He relishes a challenge, however, and so he went at it with gusto. The exhausting process led him to share a cheat sheet for publishing Python packages with the goal of making the next time smoother, while also letting other people benefit from his experience and get a running start.

[Brendan] describes publishing a Python package as “tying together many different solutions with brittle interchanges.” His cheat sheet takes the form of an ordered workflow for getting everything in place, with some important decisions and suggestions about things like formatting and continuous integration (CI) made up-front.

The guide is brief, but [Brendan] has made errors and hit dead ends in the hopes that others won’t have to. The whole thing came about from his work in deep learning, and his desire to create a package that allows rapid building and iterating on deep learning models.

Deep learning is a type of machine learning that involves finding representations in large amounts of data. [Brendan] used it in a project to automatically decide whether a Reddit post contains Star Wars plot spoilers, and we recently saw it featured in a method of capturing video footage only if a hummingbird is present.

Spring-Loaded Bed For K40 Laser Acts As An Auto-Focus

December 2, 2018 by Donald Papp 12 Comments

Laser engraving and cutting has something in common with focusing the sun’s rays with a magnifying glass: good focus is critical to results. If materials of varying thicknesses are used, focus needs to be re-set every time the material changes, and manual focusing quickly becomes a chore. [Scorch Works] has a clever solution to avoid constant re-focusing that doesn’t involve sensors or motors of any sort. The result is a self-adjusting bed that compensates for material height changes, ensuring that the top surface of the material is always a fixed distance from the laser’s head.

The way [Scorch Works] has done this is to make two spring-loaded clamps from angle aluminum and a few pieces of hardware. When a sheet of material is placed into the machine, the edges get tucked underneath the aluminum “lips” while being pushed upward from beneath. By fixing the height of the top layer of angle aluminum, any sheet stock always ends up the same distance from the laser head regardless of the material’s thickness.

[Scorch Works] shows the assembly in action in the video embedded below, along with a few different ways to accommodate different materials and special cases, so be sure to check it out.

Continue reading “Spring-Loaded Bed For K40 Laser Acts As An Auto-Focus” →

Tiny Drone Racing Gates Use Up Those Filament Scraps

November 27, 2018 by Donald Papp 6 Comments

Drone racing comes in different shapes and sizes, and some multirotor racers can be very small indeed. Racing means having gates to fly though, and here’s a clever DIY design by [Qgel] that uses a small 3D printed part and a segment of printer filament as the components for small-scale drone racing gates.

The base is 3D printed as a single piece and is not fussy about tolerances, meanwhile the gate itself is formed from a segment of printer filament. Size is easily adjusted, they disassemble readily, are cheap to produce, and take up very little space. In short, perfect for its intended purpose.

Races benefit from being able to measure lap time, and that led to DIY drone racing transponders, complete with a desktop client for managing the data. Not all flying is about racing, but pilots with racing skills were key to getting results in this Star Wars fan film that used drones. Finally, those who still feel that using the word “drone” to include even palm-sized racers is too broad of a use may be interested in [Brian Benchoff]’s research into the surprisingly long history of the word “drone” and its historically broad definition.

Watch The Low-Cost Mechatronics Lab Dispense Candy, Sort Cups

November 26, 2018 by Donald Papp 5 Comments

A lot can be done with simple motors and linear motion when they are mated to the right mechanical design and control systems. Teaching these principles is the goal behind the LCMT (Low Cost Mechatronics Trainer) which is intended primarily as an educational tool. The LCMT takes a “learn by doing” approach to teach a variety of principles by creating a system that takes a cup from a hopper, fills it with candy from a dispenser, then sorts the cups based on color, all done by using the proper combinations of relatively simple systems.

The Low Cost Mechatronics Trainer can be built for under $1,000 and is the wonderful work of a team from the Anne Arundel Community College in Maryland, USA. The LCMT is clearly no one-off project; there are complete CAD files and build documentation on the site, as well as a complete lab guide for educators.

A demo video of the assembled system is embedded below, with a walkthrough done by [Tim Callinan]. It’s worth a watch to see how cleanly designed the system is, and the visual learners among you may learn a thing or two just by watching the system go through its motions.

Continue reading “Watch The Low-Cost Mechatronics Lab Dispense Candy, Sort Cups” →

“Yell To Press B” Mod Makes N64 Controller Worse

November 25, 2018 by Donald Papp 8 Comments

There’s probably no reason anyone would actually desire a mod like this. Well, no good reason. But [William Osman] had been pondering what it would be like to play some classic games with inputs other than buttons, and decided to make an audio sensor responsible for pressing the B button on an old N64 controller. This “Yell To Press B” mod was also something unique to show his hosts when he visited the YouTube video game aficionados, [Game Grumps].

[William] acknowledges that the build is a bit of a hack job, but the project page does a good job of documenting his build process and covering the kinds of decisions involved in interfacing to a separate piece of hardware. After all, most budding hackers have sooner or later asked themselves “how do I make my gadget press a button on this other thing?” [William] ends up using a small relay to close the connection between the traces for the B button when triggered by a microphone module, but he points out that it should be possible to do a non-destructive version of the mod. Examples exist of reading the N64 controller’s state with an Arduino, which could form the basis of a man-in-the-middle approach of “Yell To Press B” (or anything else) instead of soldering to the button contacts. A video is embedded below, in which you can watch people struggle to cope with the bizarre mod.

Continue reading ““Yell To Press B” Mod Makes N64 Controller Worse” →

Solar-Powered IoT Sensor Saves Wine Batch From Overheating

November 25, 2018 by Donald Papp 4 Comments

Making wine isn’t just about following a recipe, it’s a chemical process that needs to be monitored and managed for best results. The larger the batch, the more painful it is to have something go wrong. This means that the stakes are high for small vineyards such as the family one [Mare] works with, which have insufficient resources to afford high-end equipment yet have the same needs as larger winemakers. The most useful thing to monitor is the temperature profile of the fermentation process, and [Mare] created an exceptional IoT system to do that using LoRa wireless and solar power.

It’s not enough just to measure temperature of the fermenting liquid; viewing how the temperature changes over time is critical to understanding the process and spotting any trouble. [Mare] originally used a Raspberry Pi, I2C temperature sensor, and a Wi-Fi connection to a database to do the monitoring. This was a success, but it was also overkill. To improve the system, the Raspberry Pi was replaced with a LoRaDunchy board, an STM-based module of [Mare]’s own design which is pin-compatible with the Arduino Nano. It includes a battery charger, power management, and LoRa wireless communication. Adding a solar cell and lithium-polymer battery was all it took to figuratively cut the power cord.

Sensing the temperature of fermentation is done by sealing the temperature sensor into a thin aluminum tube, and lowering that into the vat. There it remains, with the LoRaDunchy board periodically waking up to read the sensor and report the tempurature over LoRa before going back to sleep, all the while sipping power from the battery which in turn gets recharged with solar power.

It’s an elegant system that has already paid off. A 500 litre vat of wine generated an alarm when the temperature rose above 24 Celsius for 10 minutes. An email alert allowed the owner to begin mixing the solution and add ice water to put the brakes on the runaway reaction. The temperature dropped and slow fermentation resumed, thanks to the twin powers of gathering the right data, then doing something meaningful with it.

Vineyards and LoRa have joined forces before, for example in the Vinduino project which aims to enable water-smart farming. If you’re unfamiliar with LoRa in general, the LoRa on the ESP32 project page contains a good primer, and if the antenna on the module shown here looks familiar to you it’s because we recently featured [Mare]’s guide on making DIY LoRa antennas from salvaged wire.