Human-Powered Laser Gun Makes Battery-Free Target Practice

April 26, 2020 by 15 Comments

[Dirk] shared a fascinating project of his that consists of several different parts coming together in a satisfying whole. It’s all about wanting to do target practice, indoors, using a simple red laser dot instead of any sort of projectile. While it’s possible to practice by flashing a red laser pointer and watching where it lands on a paper target, it’s much more rewarding (and objective) to record the hits in some way. This is what led [Dirk] to create human-powered, battery-free laser guns with software to track and display hits. In the image above, red laser hits on the target are detected and displayed on the screen by the shooter.

Right under the thumb is the pivot point for the lever, and that’s also where a geared stepper motor (used as a generator) is housed. Operating the action cranks the motor.

There are several parts to this project and, sadly, the details are a bit incomplete and somewhat scattered around, so we’ll go through the elements one at a time. The first is the guns themselves, and the star of the show is his 3D printed cowboy rifle design. The rifle paints the target with a momentary red laser dot when the trigger is pressed, but that’s not all. [Dirk] appears to have embedded a stepper motor into the lever action, so that working the lever cranks the motor as a generator and stores the small amount of power in a capacitor. Upon pulling the trigger, the capacitor is dumped into the laser (and into a piezo buzzer for a bit of an audio cue, apparently) with just enough juice to create a momentary flash. We wish [Dirk] had provided more details about this part of his build. There are a few more images here, but if you’d like to replicate [Dirk]’s work it looks like you’ll be on your own to some extent.

As for the target end of things, blipping a red dot onto a paper target and using one’s own eyeballs can do the job in a bare minimum sort of way, but [Dirk] went one further. He used Python and OpenCV with a camera to watch for the red dot, capture it, then push an image of the target (with a mark where the impact was detected) to a Chromecast-enabled screen near the shooter. This offers much better feedback and allows for easier scoring. The GitHub repository for the shot detector and target caster is here, and while it could be used on its own to detect any old laser pointer, it really sings when combined with the 3D printed cowboy rifle that doesn’t need batteries.

Not using projectiles in target practice does have some benefits: it’s silent, it’s easy to do safely, there is no need for a backstop, there are no consumables or cleaning, and there is no need to change or patch targets once they get too many holes. Watch it all in action in the video embedded below.

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Fuel From Water Using Only An Arc Welder

April 26, 2020 by 36 Comments

Water, high currents, blinding balls of plasma, and a highly flammable gas that’s toxic enough to kill you in three minutes if you breathe enough of it. What’s not to love about this plasma-powered water gas generator?

In all seriousness, [NightHawkInLight] is playing with some dangerous stuff here, and he’s quite adamant about this one being firmly in the “Don’t try this at home” category. But it’s also fascinating stuff, since it uses nothing but a tank of water and an electric arc to produce useful amounts of fuel very quickly. It’s easy to jump to the conclusion that he’s talking about the electrolytic splitting of water into the hydrogen-oxygen mix HHO, but this is something else entirely.

Using a carbon electrode torch connected to his arc welder, a setup that’s similar to the one he used to make synthetic rubies, [NightHawkInLight] is able to strike an underwater arc inside a vessel that looks for all the world like a double-barreled bong. The plasma creates a mixture of carbon monoxide and hydrogen which accumulates very rapidly in the gasometer he built to collect the flammable products produced by a wood gasifier.

The water gas burns remarkably cleanly, but probably has limited practical uses. Unless you live somewhere where electricity costs practically nothing, it’ll be hard to break even on this. Still, it’s an interesting look at what’s possible when plasma and water mix.

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A LoRa IM-Me For The End Of The World

April 25, 2020 by 25 Comments

Enshrined in the hacker hall of fame, the IM-Me was an instant messaging toy that turned out to be extremely hackable. You could easily ditch its instant messaging platform to turn it into a little spectrum analyser. Of course what’s old is new again, and in this age where we no longer have the Nokia 3110, the Sidekick, or even Blackberries, how shall we get our fix of those wireless gadgets with physical keyboards?

What would happen if a hacker had a go at creating one of those? [Bobricius]’ Armachat is an instant messaging platform that uses LoRa as its over-the-air protocol, and is powered by a Microchip ATSAMD21x18 ARM Cortex M0 microcontroller alongside an RFM95 LoRa module.

The IM-Me, a free text chat device in the age of per-message charges, was the sweat heart of hardware hacking back in 2010

There are two versions of the device for hand and pocket, both of which come with QWERTY keyboards made with momentary-action switches, 18650 cell power, and LCD screens. The idea is that it could form a robust communication system when many others have failed.

As it stands they have a simple text messaging app in the firmware, but there are other features yet to come. Perhaps the most interesting is a possible store-and-forward meshing system in the future, which would make this a powerful comms tool in so many circumstances. Both of [Bobricius’] devices can be seen in the video below the break — no word from him on the possibility of a pink case option. Meanwhile [Bobricius] has appeared on these pages many times before. With so many to choose from it’s hard to pick one, but his Nixie-like LED display is quite memorable.

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Tired Of Fruit Ninja? Try Vegetable Assassin Using An ESP32 Sword

April 25, 2020 by 2 Comments

In a world where ninjas no longer rule the social hierarchy, where can a ninja-wannabe practice their sword fighting skills? In the popular Introduction to Embedded Systems class at the Massachusetts Institute of Technology, a team of students made their own version of the popular mobile game Fruit Ninja with a twist – you’re fighting your true nemesis, vegetables.

Vegetable Assassin allows single or multi-player mode, with players slicing vegetables on a screen using fake swords with sensors to detect the players’ motion. The web-based game allows swords to communicate their orientation to the game session with a WebSocket connection to a server, with the game generated and rendered using a 3D client JavaScript library. Rather than using MQTT, which also uses a persistent TCP connection as well as lower overhead, WebSocket provided maximum browser support.

An onboard ESP32 microcontroller and IMU track the sword movements. The game begins by calibrating the sword movements within the play area. Information is generated using the Madgwick algorithm, a 9-degrees-of-freedom algorithm that uses 3-axis data from the sword’s gyroscope, accelerometer, and magnetometer and outputs the absolute orientation of the sword.

The sword and browser both connect to the same channel on the server through a WebSocket connection, identified by a session ID similar to how web chat rooms are implemented. A statistics server manages the allocation of session IDs and other persistent game data to track high scores.

As for the graphics, a Three.js WebGL library creates the scene and camera, loading the game into the browser’s animation frame. Other scripts load the 3D models for the fruits and vegetables in the game, update their positions based on the physics engine provided by Cannon.js, and render UI elements within the game.

Curious? The project site has the microcontroller code to build your own sword that you can use to play the demo. If you don’t have an ESP32 and accelerometer handy you can play Vegetable Assassin in your browser instead.

Checking In On Relatives Using Old Android Tablets

April 25, 2020 by 15 Comments

With social distancing it can be harder to stay in touch with our relatives, especially those who are elderly and not particularly tech-savvy. Looking for a solution to that end for his own grandmother, [Steve] came up with the idea of using an inexpensive used tablet and a mobile data plan in order to mail her a “video phone” that works out of the box.

This method requires zero button presses in order to pick up a video call.

Since the tablet is configured to use cellular networks rather than WiFi, it requires no setup process at all to the recipient. And with the Android version of Skype, it’s possible to configure it so that calls are automatically picked up and video chat enabled. That way, whoever gets the tablet after it’s prepared doesn’t have to tap a single button on the screen in order to receive a call.

[Steve] has also developed the simple idea into a full-fledged easy-to-follow tutorial so that just about anyone is able to replicate the process for their own loved ones. And if you’re still having any trouble with it, there’s a team of volunteers right on the website who can help you with tech support. Just remember to disinfect whatever device you’re sending, since viruses can typically stick to surfaces like plastic and glass for longer.

Now, if showing up to your relatives as a disembodied video screen doesn’t cut it for you, then you might want to send them something more substantial like this cute little telepresence robot that can drive around on a desk.

KiCad Panelization Made Easy

April 25, 2020 by 14 Comments

There’s a new Python-based script that will panelize your KiCad circuit boards from the command line. The project by [Jan Mrázek] is called KiKit and works on .kicad_pcb files to arrange them in a grid with your choice of mousebites or v-cuts for separating the boards after production.

When working with smaller boards it’s common practice to group them together into panels. This is done to speed up PCB assembly as multiple boards can have solder paste applied, go through a pick and place machine, and be sent into the reflow oven as a single unit. Often this is done manually, but in many cases this script will save you the time while delivering the results you need.

Let’s say you really wanted to make a whole bunch of those Xling open source Tamagotchi-like key fobs we saw a couple of weeks back. Using KiKit you can gang up six of the boards at a time, using “mousebites” to keep them together during production but make it easy to separate them after all the components are soldered:

/usr/local/bin/kikit panelize grid --space 3 --gridsize 2 3 --tabwidth 3 --tabheight 3 --htabs 2 --vtabs 1 --mousebites 0.5 1 0.25 --radius 1 Xling/hardware/xling.kicad_pcb xling_panel.kicad_pcb

You can see that the parameters let you set space between the boards, number of boards in the grid, width of the tabs, tab dimensions, number of tabs between boards, and even the radius of the curve where the tabs meet the board. These settings were pulled from the examples page, which demonstrates outcomes for many different settings options.

If you want to give this a try, we suggest installing directly from the repository, as improvements are ongoing and the pip3 version didn’t have all of the options shown in the examples. For us this was as easy as sudo python3 setup.py install and then calling the script with the full path /usr/local/bin/kikit.

Results from this board are both impressive and cautionary. You can see the top edge of the design is recessed yet the most up-to-date version of KiKit was still able to make the connection. However, how this affects the USB connector on the bottom of the board design may be something to consider before pulling the trigger on your panel order.

OpenScan 3D Scans All Of The (Small) Things

April 25, 2020 by 22 Comments

The OpenScan project has been updated quite a bit since its inception. OpenScan is an open source, Arduino or Raspberry Pi-based 3D scanner for small objects that uses 3D printed hardware and some common electronic components to create 3D scans using photogrammetry; a process by which a series of still images from different angles are used to create a 3D point cloud of an object, which can then be used to generate a 3D model.

Feature visualization overlays detected features onto the camera preview to help judge quality. Broadly speaking, green is good.

Photogrammetry is a somewhat involved process that relies on consistent conditions, so going through the whole process only to find out the results aren’t up to snuff can be tiresome. Happily, OpenScan offers some interesting new functions such as feature visualization via the web interface, which helps a user judge scan quality and make changes to optimize results without having to blindly cross their fingers quite so much. OpenScan remains a one-person project by [Thomas], who is clearly motivated to improve his design and we’re delighted to see it getting updates.

Embedded below is a video that walks through the installation and web interface. It’s a fairly long and comprehensive, but if you like you can skip directly to [Thomas] demonstrating the interface around the 8:22 mark, or watch it below. Interested in your own unit? [Thomas] has an e-shop for parts and the GitHub repository is right here; the project also has its own subreddit.

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