A Microcontroller Friendly AR Headset On The Cheap

September 2, 2021 by Tom Nardi 9 Comments

Generating the real-time images required for augmented reality (AR) goggles usually requires a fair amount of processing power, to the point that DIY efforts based around the Raspberry Pi often have trouble keeping up. But what if your AR aspirations don’t require fancy high-resolution graphics? If text and the occasional icon is enough to get the job done, then these lo-fi AR goggles from [bobricius] might be the ideal solution.

As with previous homebrew AR rigs we’ve seen, this one starts with an affordable headset designed to project the display of a smartphone onto a pair of curved optical combiners. But instead of tucking a phone into the headset, [bobricius] is using a custom PCB that holds a pair of ST7789 1.3 inch 240 x 240 IPS displays. Connected over SPI and supported by just about any microcontroller you’d care to use, tossing some textual data over your field of vision can be accomplished in just a few lines of code.

[bobricius] has actually put together a couple different versions of the PCB for this project. One uses his custom ATSAMD21E18-based “ArmaBrain” module that packs the MCU and an array of common components onto a 28 mm square board that can be easily dropped into other projects. If you’d rather roll your own solution, the second version of the board that simply holds the two displays in the appropriate position and routes the SPI lines to a convenient header should do nicely.

We’ve seen augmented reality displays using microcontrollers like the ESP32 before, but those were essentially just remote displays for a more powerful system. We like this simplified approach, as there are plenty of applications where just getting a few lines of text or some low-resolution images would be more than sufficient for the task at hand. Plus, the commercially-made headset this project is based on certainly looks better than some of the other donor goggles we’ve contemplated modifying in the past.

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Upgrade Board Adds GPIO Pins To Your Replica PDP-11

September 1, 2021 by Tom Nardi 10 Comments

Like many Hackaday readers, [Steven Stallion] has had his eyes on the replica PDP-11 created by [Oscar Vermeulen] for some time now, and this summer he finally got the opportunity to build one himself. But while most owners might be content to just watch the Raspberry Pi based faux-retro computer blink away on a shelf, he wanted to explore putting the machine to more practical use. The end result is the PiDP-11 I/O Expander, an add-on that lets the modern minicomputer interact with the world around it.

Developed after some discussion with [Oscar] himself, the Microchip MCP23016 based expander board fits neatly onto the PiDP-11 PCB, and [Steven] has made sure his installation guide meshes well with the replica’s documentation. The Pi’s I2C bus is actually broken out on the original PCB, so you just need to solder a header on and run some jumpers to where the expander is mounted. You’ll need to pull 5 V as well, and the installation guide has a few tips on convenient connection points.

Each expander board gives you 16 GPIO pins which can be accessed over I2C, including support for interrupts which has been connected to GPIO 19 on the Raspberry Pi. [Steven] notes that you should be able to stack multiples of his expander up should you need even more free pins, though some fiddling with pull-up resistors and I2C addresses will likely be necessary.

The PCBs for the expander have been released under the two clause BSD license, so you’re free to spin up your own copies however you see fit. But if you’d like to save some time, [Steven] is offering assembled boards on Tindie.

Since [Oscar] first teased it at the 2015 Hackaday Supercon, we’ve been enamored with his fantastic PDP-11 replica. We’re always glad to see when somebody has picked up one of these wonderful kits, and doubly so when they’ve figured out a way to expand it in unexpected ways.

See The Unseen With This Magnetic Field Visualizer

September 1, 2021 by Tom Nardi 8 Comments

The average Hackaday reader likely knows, at least in the academic sense, what a magnetic field looks like. But as the gelatinous orbs in our skull can perceive only a tiny fraction of the EM spectrum, we have to take those textbook diagrams at face value. That is, unless you’ve got one of these nifty magnetic field visualizers developed by [Dr.Stone].

Using an XMC1100 microcontroller development board and a TLV49 3D magnetic sensor, the device is able to track the poles of a magnet in real-time and produce an approximation of what the field lines would look like on its electronic paper display. Relative field strength is indicated by the size of the visualization, which allows the user to easily compare multiple magnets. Incidentally, [Dr.Stone] notes that the current version of the hardware and software can only handle one magnet at a time; visualizing complex magnetic fields and more than two poles would take an array of sensors and likely a more powerful processor.

Do you need to visualize the field lines around a magnet? Perhaps not. But being able to quickly get an idea of how strong a magnet is and identify where its poles are could certainly come in handy. We’d like to see [Dr.Stone] take the project to the next phase and turn this into a handheld device for convenient workbench use. It would be a lot less messy than some of the previous methods we’ve seen for visualizing magnetic fields, though if you’re only worried about field strength, there’s arguably more straightforward ways to display it.

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So How Does A Rocket Fly Sideways, Anyway?

September 1, 2021 by Tom Nardi 43 Comments

It’s often said that getting into orbit is less about going up, and more about going sideways very fast. So in that sense, the recent launch conducted by aerospace startup Astra could be seen as the vehicle simply getting the order of operations wrong. Instead of going up and then burning towards the horizon, it made an exceptionally unusual sideways flight before finally moving skyward.

As you might expect, the booster didn’t make it to orbit. But not for lack of trying. In fact, that the 11.6 meter (38 feet) vehicle was able to navigate through its unprecedented lateral maneuver and largely correct its flight-path is a testament to the engineering prowess of the team at the Alameda, California based company. It’s worth noting that it was the ground controller’s decision to cut the rocket’s engines once it had flown high and far enough away to not endanger anyone on the ground that ultimately ended the flight; the booster itself was still fighting to reach space until the very last moment.

There’s a certain irony to the fact that this flight, the third Astra has attempted since their founding in 2016, was the first to be live streamed to YouTube. Had the company not pulled back their usual veil of secrecy, we likely wouldn’t have such glorious high-resolution footage of what will forever be remembered as one of the most bizarre rocket mishaps in history. The surreal image of the rocket smoothly sliding out of frame as if it was trying to avoid the camera’s gaze has already become a meme online, arguably reaching a larger and more diverse audience than would have resulted from a successful launch. As they say, there’s no such thing as bad press.

Naturally, the viral clip has spurred some questions. You don’t have to be a space expert to know that the pointy end of the rocket is usually supposed to go up, but considering how smooth the maneuver looks, some have even wondered if it wasn’t somehow intentional. With so much attention on this unusual event, it seems like the perfect time to take a close look at how Astra’s latest rocket launch went, quite literally, sideways.

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Better 3D Scans Through A Slowed Down Turntable

August 31, 2021 by Tom Nardi 6 Comments

3D scanners aren’t cheap, and the last thing you want to see after purchasing one is bad data. But that’s what [Dave Does] and others were getting from their Revopoint POP scanners until some communal brainstorming uncovered the reason: the motorized turntable that came with the Kickstarter edition of the product was spinning too fast for the software to accurately keep track of the object. So he decided to replace the stepper motor controller in his turntable and document the process for anyone else who’s scanner might be struggling.

In the video below, [Dave] pops open the plastic case of the turntable and reveals a pretty sparse interior. There’s an incredible amount of empty space inside, and even some mounting studs to screw down new components, should you want to get into some hardcore upgrades. But for his purposes, a generic stepper motor controller that featured a potentiometer to adjust the speed was enough. He found a suitable board online for around $5 USD, and got to designing a 3D printed bracket that mates up to the existing screw holes on the turntable.

But it’s not exactly a drop-in replacement. For one thing, you’ve got to pop a hole in the side of the enclosure for the potentiometer knob to stick out of. You’ve also got to solder wires coming from the original DC jack and power switch to the new board to get it hooked up, but at least the motor plugs right in. In the video below, you can see [Dave] demonstrate the impressively deep throttle capability of the new driver.

If you’d rather build than buy, we’ve covered some impressive DIY turntables in the past that could fit the bill nicely, from automatic models that handle camera control to fully 3D printed versions that you’ve got to crank yourself.

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Impromptu Metal Detector Built From The Junk Bin

August 30, 2021 by Tom Nardi 12 Comments

Have you ever found yourself suddenly in need of finding a small metal object hidden in the woods? No? Well, neither have we. But we can’t say the same thing for [zaphod], who’s family was hoping to settle a dispute by finding the surveyor stakes that marked the corners of their property. It was a perfect job for a metal detector, but since they didn’t own one, a serviceable unit had to be assembled from literal garbage.

To start with, [zaphod] had to research how a metal detector actually works. After reviewing the pros and cons of various approaches, the decision was made to go with a beat frequency oscillator (BFO) circuit. It’s not the greatest design, it might even be the worst, but it could be built with the parts on hand and sometimes that’s all that matters. After packing a 2N3904 transistor, an LM386 amplifier, and every Hackaday reader’s favorite chip the 555 timer into an enclosure along with some of their closest friends, it was time to build the rest of the metal detector.

The sensor coil was made by salvaging the wire from an old fluorescent lamp ballast and winding it around the lid of a bucket 27 times. This was mounted to the end of a broom handle with some angle pieces made from PVC sheet material, being careful not to use any metal fasteners that would throw off the detector. With the handle of an old drill in the middle to hold onto, the metal detector was complete and actually looked the part.

So did [zaphod] save the day by finding the surveyor stakes and reconnoitering the family’s plot? Unfortunately, no. It wasn’t a technical failure though; the metal detector did appear to work, although it took a pretty sizable object to set it off. The real problem was that, after looking more closely into it, the surveyors only put down one stake unless they are specifically instructed otherwise. Since they already knew where that one was…

If your homemade metal detector can’t find something that was never there, did it really fail? Just a little something to meditate on. In any event, when even the cheapest smart bulb is packing a microcontroller powerful enough to emulate early home computers, we’re always happy to see somebody keep the old ways alive with a handful of ICs.

Raspberry Pi And ESP32-S2 Team Up For MutantC_V4

August 30, 2021 by Tom Nardi 12 Comments

Back in 2019 we first came across the mutantC, an open source 3D printable Raspberry Pi handheld created by [rahmanshaber] that took more than a little inspiration from Sony’s VAIO ultra-mobile PCs (UMPCs) from the early 2000s. It was an impressive first effort, but it clearly had a long way to go before it could really be a practical mobile device.

Well after two years of development and three iterative versions of this Linux powered QWERTY slider, [rahmanshaber] is ready to show off the new and improved mutantC_v4. Outwardly it looks quite similar to the original version, with the notable addition of a tiny thumbstick and a pair of programmable buttons on the right side that can be used for input in addition to the touch screen. But inside it’s a whole other story, with so many changes and improvements that we hardly even know where to start.

Inside the mutantC_v4, showing off the ESP32-S2

Probably the most notable improvement is the addition of an ESP32-S2, specifically a bare ESP-12K module, to the main PCB. Previous versions of the hardware used an Arduino Pro Micro to interface with all the hardware, but the added horsepower of the ESP32 should come in handy with the array of sensors, controls, and NeoPixels that [rahmanshaber] has tasked the chip with. There’s even a buzzer and a coin-style vibration motor in there to provide some feedback to the user. While the board has changed significantly, it still retains compatibility with the Pi Zero, 2, 3, and 4.

Another notable addition is the expansion connector on the bottom of the handheld that has pins for I2C, UART, and 3.3 V. In the video below, [rahmanshaber] mentions that this feature was previously implemented with a standard 2×6 female header block, but is now using a far slimmer female USB-C port. We do wonder if it’s not a bit confusing to have this faux-USB port right next to the real one that’s actually used to charge the system, but with such cramped quarters occasionally you’ve got to make some tough decisions like that.

It’s quite inspiring to see how [rahmanshaber] has honed his skills since releasing the first version of the mutantC. The 3D printed parts and PCBs have matured considerably over the last two years, showing how quickly a dedicated hobbyist can advance their abilities. The most recent version has been entered in the 2021 Hackaday Prize. But the show isn’t over yet, as we hear v5 of this impressive handheld may tackle the Raspberry Pi 4 Compute Module.

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