Dual Power Supply In A Pinch

July 2, 2022 by Chris Lott 14 Comments

Recently I needed a dual voltage power supply to test a newly-arrived PCB, but my usual beast of a lab power supply was temporarily at a client’s site. I had a FNIRSI programmable power supply which would have been perfect, but alas, I had only one. While digging around in my junk box I found several USB-C power-delivery “trigger” boards which I bought for an upcoming project. These seemed almost too small for the task at hand, but after a little research I realized they would work quite well.

The ones I had used the Injoinic IP2721 USB-C power delivery chip, commonly used in many of these boards. Mine had been sold pre-configured for certain output voltages, but they were easy to re-jumper to the voltages I needed, +5 VDC and +20 VDC. The most challenging aspect was physically using them — they are the size of a fingernail. This version had through-hole output pads on 0.1″ centers, so I decided to solder them to the base of a standard MTA pin header. A few crimps later and I was up and running, along with the requisite pair of USB-C cables and power adapters.

For just a few dollars each, these trigger boards are useful to have in your toolbox, both for individual projects and for use in a pinch. We reviewed these modules a couple of years ago, and check out the far more flexible PD Micro that we covered last year.

This Arduino Pen Plotter Is Built For Speed

June 19, 2022 by Dan Maloney 20 Comments

We see a lot of simple pen plotter projects around here, and while we appreciate them one and all, most of them are a little on the slow side. That’s OK — a glacial pace is sometimes all that’s needed, as long as it gets the job done. But there’s nothing wrong with putting the pedal to the metal, so to speak. And that’s exactly what this super-fast Arduino-based plotter is all about.

As the story goes, [IV Projects] felt the need for speed after building an earlier pen plotter project that worked, but failed to excite. With the additional goal of keeping the plotter easy to build with cheap parts, the design centers on a “grit roller drive” for the Y-axis — the one that actually moves the paper back and forth. And move it does, using Dremel tool sanding drums on a lightweight shaft to maximize acceleration. In fact, all the moving parts are kept as lightweight as possible, and the results really show — the three steppers really sing when this plotter is in action.

There are some really clever details in [IV Projects]’ design. We particularly like the way the pen lift mechanism works, and the surprise appearance of a clothespin spring as a belt tensioner was a real treat. Judging by the pile of rejected prototype parts, it took quite a bit of work to get this design right. If you’d like to build your own, STLs are available for the printed parts.

If you’re interested in what the other end of the speed scale looks like, check out this bare-minimum pen plotter.

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Laser Brings Autofocus To Tricked-Out Large Format Film Camera

June 17, 2022 by Dan Maloney 6 Comments

You can’t argue with the results of large-format film cameras — picture the boxy bellows held by a cigar-chomping big-city press photographer of the 1940s — but they don’t really hold a candle to the usability and portability of even the earliest generations of 35mm cameras. And add in the ease-of-use features of later film and digital cameras, and something like a 4×5 Graflex seems like a real dinosaur.

Or maybe not. [Aleksi Koski] has built a large-format camera with autofocus, the “Conflict 45.” The problem with a lot of the large-format film cameras, which tend to be of a non-reflex optical design, is that it’s difficult or even impossible to see what you’re shooting through the lens. This makes focusing a bit of a guessing game, a problem that [Aleksi] addresses with his design. Sadly, the linked Petapixel article is basically devoid of technical details, but from what we can glean from it and the video below, the Conflict 45 is a 4″x5″ sheet-film camera that has a motorized lens board and a laser rangefinder. A short video has a through-viewfinder view showing an LCD overlay, which means there’s some kind of microcontroller on board as well, which is probably used for the calculations needed to compensate for parallax errors during close focusing, as well as other uses.

The camera is built from 3D printed parts; [Aleksi] says that this is just a prototype and that the finished camera will have a carbon-fiber body. We’d love to see more build details, but for now, we just love the idea of an easy-to-use large-format camera. Just maybe not that big.

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Pushing The Limits Of A 16×2 LCD With Bad Apple!!

June 14, 2022 by Dan Maloney 20 Comments

While low-contrast, blue-on-slightly-less-blue 16-character by 2-line LCDs are extremely popular, they really are made specifically for alphanumeric use. They do an admirable job of displaying a few characters, but they don’t exactly spring to mind as a display for non-character purposes. But displaying video on a 16×2 LCD is possible, as long as you’re willing to stretch the definition of “video” a bit and use some imagination while watching.

Normally, a 16×2 display can only display a single character in each spot, chosen from a fixed character set. But [arduinocelantano] was able to leverage the eight custom character slots the display allows to build up images from arbitrary 5×8 pixel bitmaps. After using ffmpeg to scale the original video to a viewport of eight characters, a Python program was used to turn every frame of the scaled video into code to generate the custom bitmaps for each chunk of the viewport. Even with the low refresh rate of the display and the shrunken frame size, the result is a recognizable video, helped no doubt by the choice of the shadow-puppet Bad Apple!! video. Check it out after the break to see how it looks.

We saw a similar rendering of the same video on LCD a while back; that effort was amazing in that it was an EEPROM-only implementation, along with a somewhat bigger LCD with better contrast. That project served as inspiration for [arduinocelantano]’s build here, which in some ways we think looks a bit better — perhaps it’s the inverted pixels. Either way, hats off to both builders for pushing past the normal constraints and teaching us something interesting.

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Bug Zapper Counts And Serenades Its Victims

June 11, 2022 by Sven Gregori 10 Comments

Not many creatures are as universally despised as mosquitoes, whether it’s the harmless kind that, at worst, makes you miss winter, or the more serious ones that can be a real threat to your health. A satisfying way to deal with them is to send them off with a bang using one of those racket-shaped high voltage metal mesh bug zappers. [lmu34] saw big potential for some additional gamification here, and decided to equip his zapper with a kill counter and matching sound effects.

The initial thought was that there has to be a way to detect when a mosquito hits the mesh, and use that to trigger further events — in [lmu34]’s case play a sound file and increment a counter. After taking the zapper apart and doing a bit of research, he put theory into practice using a Digispark Pro board containing an ATtiny167, the DFPlayer module for playing a set of WAV files, and an ambitious four digit 7-segment display to keep track of the “score”. A new 3d-printed cover provided enough space to house all the components, including a charging circuit as he swapped the original two AAA batteries with a rechargeable one, which gave a bit more power for the display.

Of course, with these operation voltages, it would be difficult to detect activity on the high voltage side more than once, so [lmu34] went with current sensing instead. He distinguishes between two different levels here and maps them as normal kill and monster kill for the big zaps respectively, playing different sounds for each. Have a look at the video after the break for some quick demonstration.

All in all, this is a delightfully absurd modification that almost screams for an ESP32 to enable multiplayer mode as next iteration. But if chasing mosquitoes with low-tech gadgets isn’t for you, there’s always lasers and good old torture, although those can’t be repurposed to do some hardware fault injections during the winter months then.

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An Interesting Circular Stewart Platform

June 10, 2022 by Dave Rowntree 9 Comments

Stewart platforms are pretty neat, and not seen in the wild all that often, perhaps because there aren’t a vast number of hacker-friendly applications that need quite this many degrees of freedom within such a restricted movement range. Anyway, here’s an interesting implementation from the the curiously named [Circular-Base-Stewart-Platform] YouTube channel (no, we can’t find the designer’s actual name) with a series of videos from a few years ago, showing the construction and operation of such a beast. This is a very neat mechanism comprised of six geared motors on the end of arms, engaging with a large internal gear. The common end of each arm rides on the central shaft, each with its own bearing. With the addition of the usual six linkages, twelve ball joints, and a few brackets, a complete platform is realised.

This circular arrangement is so simple that we can’t believe we haven’t come across it before. One interesting deviation from the usual Stewart platform arrangement is the use of a central slip-ring connector to provide power, allowing the whole assembly to rotate continuously, in addition to the usual six degrees of freedom the mechanism allows. Control is courtesy of an Arduino Pro Mini, which drives the motors using a handful of Pololu TB6612 (PDF) dual H-bridge driver modules. Obviously, the sketch running on the Arduino will give the thing a fixed motion, but add in an additional data link over that central slip-ring setup (or maybe a wireless link), and it will be much more useful.

We recently saw another 6-DOF actuator design, using flexures, yet another ball-balancing hack, but if you want an actually useful Stewart platform application, checkout this pool-playing robot!

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Unorthodox Toolbox Switcheroo: Barbecue!

June 8, 2022 by Sven Gregori 24 Comments

Despite all the progress in cooking methods over the past millennia, nothing can ever replace the primeval sensation of staring into the embers as your food slowly gets ready. Barbecues are the obvious choice to satisfy this cave nostalgia, and while size might matter in some cases, sometimes you just want the convenience of being able to take your grilling device to the beach, park, or just really anywhere but home. Other times you’re [Laura Kampf] and don’t want to use an old toolbox for storing tools.

It all started with one of those typical three-layer folded cantilever toolboxes that [Laura] really likes for their mechanical construction, but not so much from a usability point of view. Being someone with a knack for turning random stuff into barbecues, this was an intriguing enough device to take apart. After plenty of time spent grinding bolts and paint off, she cut out the tray bottoms to weld metal mesh pieces as grill grates in their place — but you can watch the whole progress in the video below then.

The folding mechanics play out really nicely here. Not only can you access the grill goods by moving them away from the burning coals that are placed in the center bottom part of the box, it also provides you with two different heat layers. The individual lids on each side add even more variety, and this might even work as portable little smoker.

We’ve seen [Laura]’s work a few times before already, and in case you haven’t, go check out her beer keg motorcycle side car, wheelbarrow bicycle trailer, or Zippo lighter turned drill bit storage box.

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