Reverse Engineering With Sandpaper

November 29, 2018 by Brian Benchoff 34 Comments

Every once in a while, and more so now than before, you’ll find a really neat chip with zero documentation. In [David]’s case, it’s a really cool USB 3.0 eMMC/ SD MMC controller. Use this chip, attach a USB port on one end, and some memory on the other, and you have a complete bridge. There are drivers, too. There are products shipping with this chip. The problem is, there is no data sheet. Wanting to use this chip, [David] turned to sandpaper to figure out the pinout of this chip.

The best example of a product that came with this chip is a simple board from the hardkernel store that happily came with fairly high resolution product photos. While waiting for these boards to be delivered, [David] traced the top layer of copper. This was enough to get an idea of what was going on, but the real work started when the boards arrived. These were placed in a flatbed scanner and carefully photographed.

The next step was to desolder all the parts, taking care to measure and catalog each component. Then, it’s off to sanding with 200 and 600 grit wet sandpaper. Slowly, the soldermask is removed and the top copper layer appears. After that, it’s just a matter of sanding and scanning, stacking all the layers together with your image processing software of choice.

There are a few caveats to hand-sanding a PCB to reverse-engineer the copper layers. First, it makes a mess. This is wet/dry sandpaper, though, and you can and should sand with water. Secondly, even pressure should be applied. We’re not sure if [David] was holding the sandpaper or not, but the best technique is to actually hold the board itself.

Despite a few problems, [David] did get the pictures of each copper layer. After assembling these images, he could make an Eagle part for an eMMC reader for his Nintendo Switch.

Overlooked Minimalism In Assistive Technology

November 23, 2018 by Brian McEvoy 27 Comments

If your eyes are 20/20, you probably do not spend much time thinking about prescription eyeglasses. It is easy to overlook that sort of thing, and we will not blame you. When we found this creation, it was over two years old, but we had not seen anything quite like it. The essence of the Bear Paw Assistive Eating Aid is a swiveling magnet atop a suction cup base. Simple right? You may already be thinking about how you could build or model that up in a weekend, and it would not be a big deal. The question is, could you make something like this if you had not seen it first?

Over-engineered inventions with lots of flexibility and room for expansion have their allure. When you first learn Arduino, every problem looks like a solution for that inexpensive demo board and one day you find yourself wearing an ATMEGA wristwatch. Honestly, we love those just as much but for an entirely different reason. When all the bells and whistles are gone, when there is nothing left but a robust creation that, “just works,” you have created something beautiful. Judging by the YouTube comments of the video, which can be seen below the break, those folks have no trouble overlooking the charm of this device since the word “beard” appears 95 times and one misspelling for a “bread” count of one. Hackaday readers are a higher caliber and should be able to appreciate its elegance.

The current high-tech solution for self-feeding is a robot arm, not unlike this one which is where our minds went when we heard about an invention about eating without using hands, and we will always be happy to talk about robot arms.

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PLA Foils Homemade Tachometer

November 22, 2018 by Al Williams 19 Comments

[Integza] built a Tesla turbine and wanted to know how fast it was spinning. However, he didn’t have a tachometer, and didn’t want to buy one. After a false start of trying to analyze the audio to measure the speed, he decided to use a tried-and-true method. Let the wheel break an infrared (IR) optointerruptor and count the spokes of the wheel as they go by. If you know the spacing between the spokes, you can compute the speed. There was only one problem: it didn’t work.

Turns out, PLA is at least somewhat transparent to IR. Knowing that it was a simple matter to fix some tape to the wheel that would block IR and that made things work much better. If you missed the video where he built the turbine, you might want to watch it first.

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Simulating A Speaker

November 20, 2018 by Al Williams 21 Comments

Speakers are one of those components that are simple to use, but difficult to simulate. Most of us have used a simple resistor to do the job. But a speaker’s response is much more complex, and while that might be enough for a simple simulation the fidelity is nowhere near close. [Sourav Gupta] recently shared his technique for modeling speakers and it looks as though it does a credible job.

[Sourav] shows how a simple resistor and an inductor can do the job, but for better fidelity you need more components to model some mechanical effects. The final model has six components which keeps it easy enough to construct but the problem lies in finding the values of those six components. [Sourav] shows how to use the Thiele-Small parameters to solve that problem. Speaker makers provide these as a guide to low frequency performance, and they capture things such as Q, mass, displacement, and other factors that affect the model.

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Scratch-Building A Supersized Laser Cutter

November 20, 2018 by Tom Nardi 9 Comments

Now that 3D printers have more or less hit the mass market, hackers need a new “elite” tool to spend their time designing and fiddling with. Judging by the last couple of years, it looks like laser cutters will be taking over as the hacker tool du jour; as we’re starting to see more and more custom builds and modifications of entry-level commercial models. Usually these are limited to relatively small and low powered diode lasers, but as the following project shows, that’s not always the case.

This large format laser cutter designed and built by [Rob Chesney] is meticulously detailed on his blog, as well as in the in the video after the break. It’s made up of aluminium profile and a splattering of ABS 3D printed parts, and lives in an acrylic enclosure that’s uniquely isolated from the laser’s internal gantry. All told it cost about $2,000 USD to build, but considering the volume and features of this cutter that’s still a very fair price.

[Rob] carefully planned every aspect of this build, modeling the entire machine in CAD before actually purchasing any hardware. Interestingly enough his primary design constraint was the door to his shed: he wanted to build the largest possible laser cutter that could still be carried through it. That led to the final machine’s long and relatively shallow final dimensions. The design was also guided by a desire to minimize material waste, so when possible parts were designed to maximize how many could be cut from a one meter length of aluminum extrusion.

The laser features a movable Z axis that’s similar in design to what you might see in a Prusa-style 3D printer, with each corner of the gantry getting an 8 mm lead screw and smooth rod which are used in conjunction to lift and guide. All of the lead screws are connected to each other via pulleys and standard GT2 belt, but as of this version, [Rob] notes the Z axis must be manually operated. In the future he’ll be able to add in a stepper motor and automate it easily, but it wasn’t critical to get the machine running.

He used 3D printed parts for objects which had a relatively complex geometry, such as the laser tube holders and Z axis components, but more simplistic brackets were made out of cut acrylic. In some components, [Rob] used welding cement to bond two pieces of acrylic and thereby double the thickness. Large acrylic panels were also used for the laser’s outer enclosure, which was intentionally designed as a separate entity from the laser itself. He reasoned that this would make assembly easier and faster, as the enclosure would not have to be held to the same dimensional tolerances as it would have been if it was integrated into the machine.

[Rob] gives plenty of detail about all the finer points of water cooling, laser control electronics, aligning the mirrors, and really anything else you could possibly want to know about building your own serious laser cutter. If you’ve been considering building your own laser and have anything you’re curious or unsure about, there’s a good chance he addresses it in this build.

Short of having the fantastically good luck to find a laser cutter in the trash that you can refurbish, building your own machine may still be the best upgrade path if you outgrow your eBay K40.

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High Voltage Measurement Is Shockingly Safe

November 17, 2018 by Bryan Cockfield 9 Comments

With the right equipment and training, it’s possible to safely work on energized power lines in the 500 kV range with bare hands. Most of us, though, don’t have the right equipment or training, and should take great care when working with any appreciable amount of voltage. If you want to safely measure even the voltages of the wiring in your house there’s still substantial danger, and you’ll want to take some precautions like using isolated amplifiers.

While there are other safe methods for measuring line voltage or protecting your oscilloscope, [Jason]’s isolated amplifier method uses high voltage capacitors to achieve isolation. The input is then digitized, sent across the capacitors, and then converted back to an analog signal on the other side. This project makes use of a chip from TI to provide the isolation, and [Jason] was able to build it on a perfboard while making many design considerations to ensure it’s as safe as possible, like encasing high voltage sections in epoxy and properly fusing the circuit.

[Jason] also discusses the limitations of this method of isolation on his site, and goes into a lot of technical details about the circuit as well. It probably wouldn’t get a UL certification, but the circuit performs well and even caught a local voltage sag while he was measuring the local power grid. If this method doesn’t meet all of your isolation needs, though, there are a lot of other ways to go about solving the problem.

Arduino Provides Hands-Free Focus For Digital Inspection Scope

November 12, 2018 by Dan Maloney 6 Comments

With surface-mount technology pushing the size of components ever smaller, even the most eagle-eyed among us needs some kind of optical assistance to do PCB work. Lots of microscopes have digital cameras too, which can be a big help – unless the camera fights you.

Faced with a camera whose idea of autofocus targets on didn’t quite coincide with his, [Scott M. Baker] took matters into his own hands – foot, actually – by replacing mouse inputs to the camera with an outboard controller. His particular camera’s autofocus can be turned off, but only via mouse clicks on the camera’s GUI. That’s disruptive while soldering, so [Scott] used an Arduino Pro Micro and a small keypad to mimic the mouse movements needed to control the camera.

At the press of a key, the Arduino forces the mouse cursor up to the top left corner of the screen, pulls down the camera menu, and steps down the proper distance to toggle autofocus. The controller can also run the manual focus in and out or to take a screenshot. There’s even a footswitch that forces the camera to refocus if the field of view changes. It looks really handy, and as usual [Scott] provides a great walkthrough in the video below.

Like it or not, if shrinking technology doesn’t force you into the microscope market, entropy will. If you’re looking for a buyer’s guide to microscopes, you could do worse than [Shahriar]’s roundup of digital USB scopes. Or perhaps you’d prefer to dumpster dive for yours.

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