Sub-mm Mechanical 3D Scanner With Encoders And String

July 1, 2021 by Danie Conradie 29 Comments

[Scott Rumschlag] wanted a way to precisely map interior spaces for remodeling projects, but did not want to deal with the massive datasets created by optical 3D scanning, and found the precision of the cost-effective optical tools lacking. Instead, he built a 3D cable measuring device that can be used to map by using a manual probe attached to a cable.

The cable is wound on a retractable spool, and passes over a pulley and through a carbon fiber tube mounted on a two-axis gimbal. There are a few commercial machines that use this mechanical approach, but [Scott] decided to build one himself after seeing the prices. The angle of rotation of each axis of the gimbal and the length of extended cable is measured with encoders, and in theory the relative coordinates of the probe can be calculated with simple geometry. However, for the level of precision [Scott] wanted, the devil is in the details. To determine the position of a point within 0.5 mm at a distance of 3 m, an angular resolution of less than 0.001° is required on the encoders. Mechanical encoders could add unnecessary drag, and magnetic encoders are not perfectly linear, so optical encoders were used. Many other factors can also introduce errors, like stretch and droop in the cable, stickiness of the bearings, perpendicularity of the gimbals axis and even the spring force created by the encoder wires. Each of these errors had to accounted for in the calculations. At first, [Scott] was using an Arduino Mega for the geometry calculations, but moved it to his laptop after he discovered the floating point precision of the Mega was not good.

[Scott] spend around 500 hours building and tuning the device, but the end result is really impressive. There are surprisingly few optical machines that can achieve this level of precision and accuracy, and they can be affected by factors like the reflectivity of an object.

If you do want to get into real 3D scanning, definitely take the time to read [Donal Papp]’s excellent guide to the practical aspects of the various technologies. Most of us already have a 3D scanner in our pocket in the form of a smartphone, which can be used for photogrammetry.

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Pi Pico Game Boy Flash Cart Gets Slim RP2040 Upgrade

July 1, 2021 by Tom Nardi 10 Comments

The story for this one starts a few months ago, when [John Green] released his PICO-GB project. His code allowed the Raspberry Pi Pico to stand in for a Game Boy cartridge, complete with a simple text menu that let the user select between ROMs that had been baked into the microcontroller’s firmware. The project was particularly notable for the fact that it was entirely a software solution; while a custom breakout cartridge made for a handy temporary solution, you could have permanently wired the Pico’s pins directly to the Game Boy’s cartridge connector if you wanted to.

PICO-GB running on the full-size Pi Pico

Then in early June, the RP2040 chip that powers the Pi Pico went up for sale in single unit quantities. That opened up the possibility of building the PICO-GB functionality into a cartridge small enough to actually fit inside the Game Boy. So [Martin “HDR” Refseth] got to work creating the slick cartridge PCB you’re seeing now.

The RP2040 is joined by a trio of Texas Instruments TXB0108 level shifters, and there’s a spot for adding a SPI flash chip. The RP2040 supports a maximum of 16 MB of external flash, but given the size of Game Boy games were generally measured in kilobytes, that shouldn’t pose much of a problem.

Looking ahead, the original PICO-GB documentation mentions enhancements like loading ROMs from SD card, as well as hardware additions like a real-time-clock for the more advanced games that supported it. We assume those concepts will become part of [Martin]’s PCB eventually, but these are still early days.

We’ve seen Game Boy cartridge emulation with a microcontroller in the past, but we’re exited to see how the unique capabilities of the Raspberry Pi Foundation’s custom silicon can improve the state-of-the-art.

[Thanks to Itay for the tip.]

Smart Camera Based On Google Coral

June 30, 2021 by Bryan Cockfield 8 Comments

As machine learning and artificial intelligence becomes more widespread, so do the number of platforms available for anyone looking to experiment with the technology. Much like the single board computer revolution of the last ten years, we’re currently seeing a similar revolution with the number of platforms available for machine learning. One of those is Google Coral, a set of hardware specifically designed to take advantage of this new technology. It’s missing support to work with certain hardware though, so [Ricardo] set out to get one working with a Raspberry Pi Zero with this smart camera build based around Google Coral.

The project uses a Google Coral Edge TPU with a USB accelerator as the basis for the machine learning. A complete image for the Pi Zero is available which sets most of the system up right away including headless operation and includes a host of machine learning software such as OpenCV and pytesseract. By pairing a camera to the Edge TPU and the Raspberry Pi, [Ricardo] demonstrates many of its machine learning capabilities with several example projects such as an automatic license plate detector and even a mode which can recognize whether or not a face mask is being worn, and even how correctly it is being worn.

For those who want to get into machine learning and artificial intelligence, this is a great introductory project since the cost to entry is so low using these pieces of hardware. All of the project code and examples are available on [Ricardo]’s GitHub page too. We could even imagine his license plate recognition software being used to augment this license plate reader which uses a much more powerful camera.

MIT’s Knitted Keyboard Is Quite A Flexible MIDI Controller

June 30, 2021 by Kristina Panos 7 Comments

There are only so many ways to make noise on standard instruments such as acoustic pianos. Their rigidity and inputs just don’t allow for a super-wide range of expression. On the other hand, if you knit your interface together, the possibilities are nearly endless. MIT’s new and improved knitted keyboard is an instrument like none other — it responds to touch, pressure, and continuous proximity, meaning that you can play it like a keyboard, a theremin, and something that is somewhere in between the two. Because it’s a MIDI interface, it can ultimately sound like any instrument you’ve got available in software.

The silver keys of this five-octave interface are made of conductive yarn, and the blue background is regular polyester yarn. Underneath that is a conductive knit layer to complete the key circuits, and a piezo-resistive knit layer that responds to pressure and stretch. It runs on a Teensy 4.0 and uses five MPR121 proximity/touch controllers, one per octave.

The really exciting thing about this keyboard is its musical (and physical) versatility. As you might expect, the keyboard takes discrete inputs from keystrokes, but it also takes continuous input from hovering and waving via the proximity sensors, and goes even further by taking physical input from squeezing, pulling, stretching, and twisting the conductive yarns that make up the keys. This means it takes aftertouch (pressure applied after initial contact) into account — something that isn’t possible with most regular instruments. And since this keyboard is mostly yarn and fabric, you can roll it up and take it anywhere, or wrap it around your neck for a varied soundscape.

If you’re looking for more detail, check out the paper for the previous version (PDF), which also used thermochromic yarn to show different colors for various modes of play using a heating element. With the new version, [Irmandy Wicaksono] and team sought to improve the sensing modalities, knitted aesthetics, and the overall tactility of the keyboard. We love both versions! Be sure to check it out after the break.

Want to play around with capacitive touch sensors without leaving the house for parts? Make your own from paper and aluminum foil.

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Installing Linux Like It’s 1989

June 30, 2021 by Bryan Cockfield 34 Comments

A common example of the sheer amount of computing power available to almost anyone today is comparing a smartphone to the Apollo guidance computer. This classic computer was the first to use integrated circuits so it’s fairly obvious that most modern technology would be orders of magnitude more powerful, but we don’t need to go back to the 1960s to see this disparity. Simply going back to 1989 and getting a Compaq laptop from that era running again, while using a Raspberry Pi Zero to help it along, illustrates this point well enough.

[befinitiv] was able to get a Raspberry Pi installed inside of the original computer case, and didn’t simply connect the original keyboard and display and then call it a completed build. The original 286 processor is connected to the Pi with a serial link, so both devices can communicate with each other. Booting up the computer into DOS and running a small piece of software allows the computer into a Linux terminal emulator hosted on the Raspberry Pi. The terminal can be exited and the computer will return back to its original DOS setup. This also helps to bypass the floppy disk drive for transferring files to the 286 as well, since files can be retrieved wirelessly on the Pi and then sent to the 286.

This is quite an interesting mashup of new and old technology, and with the Pi being around two orders of magnitude more powerful than the 286 and wedged into vacant space inside the original case, [befinitiv] points out that this amalgamation of computers is “borderline useful”. It’s certainly an upgrade for the Compaq, and for others attempting to get ancient hardware on the internet, don’t forget that you can always use hardware like this to access Hackaday’s retro site.

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Machine-Vision Archer Makes You The Target, If You Dare

June 30, 2021 by Dan Maloney 6 Comments

We’ll state right up front that it’s a really, really bad idea to let a robotic archer shoot an apple off of your head. You absolutely should not repeat what you’ll see in the video below, and if you do, the results are all on you.

That said, [Kamal Carter]’s build is pretty darn cool. He wisely chose to use just about the weakest bows you can get, the kind with strings that are basically big, floppy elastic bands that shoot arrows with suction-cup tips and are so harmless that they’re intended for children to play with and you just know they’re going to shoot each other the minute you turn your back no matter what you told them. Target acquisition is the job of an Intel RealSense depth camera, which was used to find targets and calculate the distance to them. An aluminum extrusion frame holds the bow and adjusts its elevation, while a long leadscrew and a servo draw and release the string.

With the running gear sorted, [Kamal] turned to high school physics for calculations such as the spring constant of the bow to determine the arrow’s initial velocity, and the ballistics formula to determine the angle needed to hit the target. And hit it he does — mostly. We’re actually surprised how many on-target shots he got. And yes, he did eventually get it to pull a [William Tell] apple trick — although we couldn’t help but notice from his, ahem, hand posture that he wasn’t exactly filled with self-confidence about where the arrow would end up.

[Kamal] says he drew inspiration both from [Mark Rober]’s dart-catching dartboard and [Shane Wighton]’s self-dunking basketball hoop for this build. We’d say his results put in him good standing with the skill-optional sports community.

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