Author: Donald Papp

1343 Articles

Simple, Self-Contained LoRa Repeater In About An Hour

May 2, 2019 by 5 Comments

[Dave Akerman]’s interest in high-altitude projects means he is no stranger to long-range wireless communications, for which LoRa is amazingly useful. LoRa is a method of transmitting at relatively low data rates with low power over long distances.

Despite LoRa’s long range, sometimes the transmissions of a device (like a balloon’s landed payload) cannot be received directly because it is too far away, or hidden behind buildings and geography. In these cases a useful solution is [Dave]’s self-contained LoRa repeater. The repeater hardware is simple, and [Dave] says that if one has the parts on hand, it can be built in about an hour.

The device simply re-transmits any telemetry packets it receives, and all that takes is an Arduino Mini Pro and a small LoRa module. A tiny DC-DC converter, battery, and battery charger rounds out the bill of materials to create a small and self-contained unit that can be raised up on a mast, flown on a kite, or carried by a drone.

The repeater’s frequency and other settings can even be reprogrammed (using a small windows program) for maximum flexibility, making the little device invaluable when going hunting for landed payloads like the one [Dave] used to re-create a famous NASA image using a plastic model and a high-altitude balloon. Check out the details on the GitHub repository for the project and start mashing “add to cart” for parts at your favorite reseller.

Watch These Two Robots Cooperate On A 3D Print

April 20, 2019 by 16 Comments

Putting a 3D printer on a mobile robotic platform is one thing, but two robots co-cooperatively printing a large object together is even more impressive. AMBOTS posted the video on Twitter and we’ve embedded it below.

The robots sport omnidirectional wheels and SCARA format arms, and appear to interact with some kind of active tabletop to aid positioning. The AMBOTS website suggests that the same ideas could be used for other tasks such as pick and place style assembly work, and the video below of co-operative 3D printing is certainly a neat proof of concept.

As a side note: most omni wheels we see (such as the ones on these robots) are of the Mecanum design but there are other designs out there you may not have heard of, such as the Liddiard omnidirectional wheel.

Continue reading “Watch These Two Robots Cooperate On A 3D Print” →

3D Printed Tank Track Pops Together With Plastic BB For Hinge

April 20, 2019 by 20 Comments

3D printing is well-suited to cranking out tank tread designs, because the numerous and identical segments required are a great fit for 3D printing’s strengths. The only hitch is the need for fasteners between each of those segments, but [AlwynxJones] has a clever solution that uses plentiful hard plastic spheres (in the form of 6 mm airsoft BBs) as both a fastener and a hinge between each of the 3D printed track segments.

Each segment has hollows made to snugly fit 6 mm BBs (shown as green in the image here) which serve both as fasteners and bearing surfaces. Assembly requires a bit of force to snap everything together, but [AlwynxJones] judges the result worth not having to bother with bolts, wires, or other makeshift fasteners.

Bolts or screws are one option for connecting segments, but those are heavy and can get expensive. Segments of printer filament have been successfully used in other tread designs, though that method requires added work in the form of either pins, or heat deforming the filament ends to form a kind of rivet. This design may be a work in progress, but it seems like a promising and clever approach.

[via Reddit]

Mini Flickering Torch Effect Uses Neither Wires Nor Solder

April 15, 2019 by 8 Comments
Cross section of pillar model.

[ROBAGON] makes miniature, 3D-printable gaming terrain and features like these stone pillars with flickering torch. His model isn’t free to download (though it’s under $2 at the time of writing), but the part that impressed us was his clever way of using electric tea lights to create a flickering torch effect without needing any soldering or wiring whatsoever.

His solution was to make the base of the pillar large enough to fit an electric tea light, which uses a flickering LED to simulate a candle flame. The molded plastic “flame” is removed from the tea light and placed in the torch sconce, while the tea light itself goes into the base. A short segment of clear acrylic rod is used as a light pipe, running from the tea light’s LED to the base of the torch.

It’s a simple, effective, and economical solution that doesn’t require running or soldering a single wire and you can see it work in the brief video embedded below. Now all that’s missing for those Dungeons & Dragons sessions is this custom calculator.

Continue reading “Mini Flickering Torch Effect Uses Neither Wires Nor Solder” →

See What’s Inside Night Vision, And How To Build Your Own

April 10, 2019 by 26 Comments

[Nick Chen] shared some fascinating and useful details about building a AN/PVS-14 monocular night vision device from parts. It’s not cheap, but the build would be a simple one for most Hackaday readers, at least the ones who are residents of the USA. Since the PVS-14 is export controlled under the International Traffic in Arms Regulations (ITAR), parts are not sold outside of the US. Still, [Nick]’s illustrated build instructions provide a good look at what’s inside these rugged devices.

The build consists of purchasing a PVS-14 parts kit (or “housing kit”) which includes nearly everything except the image intensifier module, which must be purchased separately. Once all the parts are in hand, [Nick] explains how to assemble the pieces into a working unit.

The view through a blemished (or “blem”) image intensifier. Cheaper, and perfectly serviceable as long as the center is clear.

Since the image intensifier is by far the most expensive component, there is an opportunity to save money by shopping for what [Nick] calls “blem” units. These units are functional, but have blemishes or dead spots within the field of view. The good news it that this makes them cheaper, and [Nick] points out that as long as the center region of the tube is clear, they are perfectly serviceable.

How much can one save by building from parts? [Nick] says buying a complete PVS-14 with a Gen 3 tube (sensitive to 450-950 nm) can cost between $2500 to $4000. It’s expensive equipment, no doubt, but deals can be found on the parts. Housing kits can be had for well under $1000, and [Nick] has purchased serviceable image intensifiers for between $500 and $1000. He says searching for “blem tubes” can help zero in on deals.

Knowing the right terms for searching is half the battle, and along with his build instructions (and a chunk of cash) a curious hacker would have all they need to make their own. Heck, build two because the PVS-14 is designed such that two units can be combined to make a binocular unit! Not ready to drop that kind of cash? Check out OpenScope, the open source digital night vision tool.

Giving An Industrial Push Button USB, Elegantly

April 3, 2019 by 38 Comments

[Glen]’s project sounds perfectly straightforward: have a big industrial-style push button act as a one-key USB keyboard. He could have hacked something together in any number of ways, but instead he decided to create a truly elegant solution. His custom PCB mates to the factory parts perfectly, and the USB cable between the button and the computer even fits through the button enclosure’s lead hole.

It turns out that industrial push buttons have standardized components which can be assembled in an almost LEGO-like manner, with components mixed and matched to provide different switch actions, light indicators, and things of that nature. [Glen] decided to leverage this feature to make his custom PCB (the same design used in his one-key keyboard project) fit just like a factory component. With a 3D printed adapter, the PCB locks in just like any other component, and even lines up with the lead hole in the button’s enclosure for easy connecting of the USB cable.

What does [Glen] use the big button for? Currently he has two applications: one provides a simple, one-button screen lock on a Linux box running a virtual machine at his place of work. It first disengages the keyboard capture of the virtual machine, then engages the screen lock on the host. The other inserts a poop emoji into Microsoft documents. Code and PCB design files for [Glen]’s small keyboards are available on GitHub.

Easy Git Repository Summaries With Web-git-sum

March 25, 2019 by 16 Comments

For those hosting their own git repositories there are a number of solutions for creating convenient web-accessible front ends, but [mitxela] wasn’t quite satisfied with any of them. After trying a number of alternatives and reflecting on his requirements, he realized that all he really needed was a summary page listing the latest commits, and a file tree with a list of branches and tags. To accomplish this, he created web-git-sum. It’s a bash script that runs on git’s post-receive hook and generates only two files: a summary page and an index of the repository. You can see a demo of the output at git.mitxela.com.

[mitxela]’s writeup goes into some detail on how git repositories work, how those repositories are served over HTTP, and covers a few of the different options for providing convenient and accessible web front ends. Not all repositories are alike, and what works well for one may not work or scale well for another.

Intrigued by the idea of a private git server? We covered exactly how to set one up (spoiler: it’s really easy.)