Rifle-Mounted Sensor Shows What Happens During Shot

People unfamiliar with shooting sports sometimes fail to realize the physicality of getting a bullet to go where you want it to. In the brief but finite amount of time that the bullet is accelerating down the barrel, the tiniest movement of the gun can produce enormous changes in its trajectory, and the farther away your target is, the bigger the potential error introduced by anticipating recoil or jerking the trigger.

Like many problems this one is much easier to fix with what you can quantify, which is where this DIY rifle accelerometer can come in handy. There are commercial units designed to do the same thing that [Eric Higgins]’ device does but most are priced pretty dearly, so with 3-axis accelerometer boards going for $3, rolling his own was a good investment. Version 1, using an Arduino Uno and an accelerometer board for data capture with a Raspberry Pi for analysis, proved too unwieldy to be practical. The next version had a much-reduced footprint, with a Feather and the sensor mounted in a 3D-printed tray for mounting solidly on the rifle. The sensor captures data at about 140 Hz, which is enough to visualize any unintended movements imparted on the rifle while taking a shot. [Eric] was able to use the data to find at least one instance where he appeared to flinch.

We like real-world data logging applications like this, whether it’s grabbing ODB-II data from an autocross car or logging what happens to a football. We’ll be watching [Eric]’s planned improvements to this build, which should make it even more useful.

[Leo] Repairs A MIDI Sequencer

We all have that friend who brings us their sad busted electronics. In [Leo’s] case, he had a MIDI sequencer from a musician friend. It had a dead display and the manufacturer advised that a driver IC was probably bad, even sending a replacement surface mount part.

[Leo] wasn’t convinced though. He knew that people were always pushing on the switches that were mounted on the board and he speculated that it might just be a bad solder joint. As you can see in the video below, that didn’t prove out.

The next step was to fire up a hot air gun. Instead of removing the chip, he wanted to reflow the solder anyway. He was a little worried about melting the 7-segment LEDs so he built a little foil shield to protect it. That didn’t get things working, either.

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Amateur Astronomers Spot Meteorite Impact During Lunar Eclipse

According to ancient astronaut theorists, the lunar eclipse this weekend had an unexpected visitor. Right around the time of totality, a meteoroid crashed into the moon, and it was visible from Earth.

Meteoroids crash into the Earth and Moon all the time, although this usually happens either over the ocean (70% of the Earth) where we can’t see it, on the far side of the moon (~50% of the Moon) where we can’t see it, or on the sunlit side of the Moon (another, different 50%), where we can’t see it. These meteoroids range from the size of a grain of sand to several meters across, but only the largest could ever be seen by the human eye. This weekend’s lunar eclipse, the Super Blood Wolf Moon was visible to a large portion of the population, and many, many cameras were trained on the Moon. Several telescopes livestreamed the entire eclipse, and multiple people caught a glimpse of a small flash of light, seeming to come from around Lagrange crater. Because this event was seen by multiple observers separated by thousands of miles, the only conclusion is that something hit the moon, and its impact event was recorded on video.

This is not the first time an impact event has been recorded on the moon. The Moon Impacts Detection and Analysis System (MIDAS) running out of La Hita Observatory has regularly recorded impact events, including one that was comparable to an an explosion of 15 tons of TNT. These automated observatories aren’t running during a full moon, like during a lunar eclipse, because no camera would be able to pick up the flash of light. We were somewhat lucky last weekend’s impact happened during totality, and with dozens of cameras trained on the Moon.

Further investigation will be necessary to determine the size of the meteoroid and obtain pictures of its impact crater, but for a basis of comparison, the LCROSS mission plowed a Centaur upper stage (2.2 tons) into the lunar surface at 2.5 km/s. This should have resulted in a flash visible through binoculars, but it didn’t. The meteoroid that struck the moon last weekend would have been traveling faster (a minimum of about 12 km/s), but the best guess is that this rock might have been of suitable size to have fit in the back of a pickup truck, or thereabouts.

Motorizing An IKEA SKARSTA Table

We’ve been told that standing at a desk is good for you, but unless you’re some kind of highly advanced automaton you’re going to have to sit down eventually no matter what all those lifestyle magazines say. That’s where desks like the IKEA SKARSTA come in; they use a crank on the front to raise and lower the desk to whatever height your rapidly aging corporeal form is still capable of maintaining. All the health benefits of a standing desk, without that stinging sense of defeat when you later discover you hate it.

But who wants to turn a crank with their hand in 2019? Certainly not [iLLiac4], who’s spent the last few months working in conjunction with [Martin Mihálek] to add some very impressive features to IKEA’s adjustable table. Replacing the hand crank with a motorized system which can do the raising and lifting was only part of it, the project also includes a slick control panel with a digital display that shows the current table height and even allows the user to set and recall specific positions. The project is still in active development and has a few kinks to work out, but it looks exceptionally promising if you’re looking to get a very capable adjustable desk without breaking the bank.

The heart of the project is a 3D printable device which uses a low-RPM DC gear motor to turn the hex shaft where the crank would normally go. A rotary encoder is linked to the shaft of the motor by way of printed GT2 pulleys and a short length of belt, which gives the system positional information and avoids the complexity of adding limit switches to the table itself.

For controlling the motor the user is given the option between using relays or an H-Bridge PWM driver board, but in either event an Arduino Nano will be running the show. In addition to controlling the motor and reading the output of the rotary encoder, the Arduino also handles the front panel controls. This consists of a TM1637 four digit LED display originally intended for clocks, as well as six momentary contact tactile switches complete with 3D printed caps. The front panel’s simple user interface not only allows for setting and recalling three preset desk heights, but can even be used to perform the calibration routine without having to go in and hack the source code to change minimum and maximum positions.

We’ve seen all manner of hacks and modifications dealing with IKEA products, from a shelving unit converted into a vivarium to a table doing double duty as a cheap plate reverb. Whether you’re looking for meatballs or some hacking inspiration, IKEA seems to be the place to go.

Color Sensor Demystified

When [millerman4487] bought a TCS230-based color sensor, he was expecting a bit more documentation. Since he didn’t get it, he did a little research and some experimentation and wrote it up to help the rest of us.

The TCS3200 uses an 8×8 array of photodiodes. The 64 diodes come in four groups of 16. One group has a blue filter, one has green and the other has a red filter. The final set of diodes has no filter at all. You can select which group of diodes is active at any given time.

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Howto: Docker, Databases, and Dashboards to Deal with Your Data

So you just got something like an Arduino or Raspberry Pi kit with a few sensors. Setting up temperature or motion sensors is easy enough. But what are you going to do with all that data? It’s going to need storage, analysis, and summarization before it’s actually useful to anyone. You need a dashboard!

But even before displaying the data, you’re going to need to store it somewhere, and that means a database. You could just send all of your data off into the cloud and hope that the company that provides you the service has a good business model behind it, but frankly the track records of even the companies with the deepest pockets and best intentions don’t look so good. And you won’t learn anything useful by taking the easiest way out anyway.

Instead, let’s take the second-easiest way out. Here’s a short tutorial to get you up and running with a database backend on a Raspberry Pi and a slick dashboard on your laptop or cellphone. We’ll be using scripts and Docker to automate as many things as possible. Even so, along the way you’ll learn a little bit about Python and Docker, but more importantly you’ll have a system of your own for expansion, customization, or simply experimenting with at home. After all, if the “cloud” won’t let you play around with their database, how much fun can it be, really?

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The Vectrex Projector We’ve Been Waiting For

Unlike most old consoles, the Vectrex is unique for having a vector-based display. This gives it a very different look to most of its contemporaries, and necessitated a built-in display, as regular televisions aren’t built to take vector signals. Not one to be limited to the stock screen size, [Arcade Jason] decided the Vectrex needed a projection upgrade, and built exactly that.

The build relies on a lens that [Jason] salvaged from an old rear-projection TV. These units used CRTs with big lenses which projected the image onto a screen. That’s precisely what is happening here, with a vector display replacing the CRT used in the original TV. The vector display itself used here is a tube from a small black and white TV set, which [Jason] modified to use a Vectrex yoke, making it capable of vector operation.

Through some modification and careful assembly, [Jason] was rewarded with a wall-sized display for his Vectrex console. This is demonstrated with some beautiful glowing vector demos, accompanied with appropriate bleep-bloop music, as was the style at the time. The Cantina band is a particular highlight.

We’ve seen [Jason]’s vector hacks before, too – like this Asteroids machine modified to display in color. Video after the break.

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