This ESP32 Pico Wristwatch Has Plenty Of Potential

February 12, 2022 by Dave Rowntree 12 Comments

First hand-built prototype. Nurse! isopropyl alcohol, stat!

Prolific hacker [Sulfuroid] is a medical doctor by day, and an electronics hobbyist by night, and quite how he finds the time, we have no idea.

The project we want to highlight is an ESP32 based LED smart watch, which we’ll sure you’ll agree, looks pretty nicely developed so far, and [Sulfuroid] has bigger plans, as you may find, when you dig into the GitHub repo. This analog-style design uses four groups of 0603-sized LEDs, arranged circularly to indicate the passage of time, or anything else you fancy. Since there are four control buttons, a pancake vibration motor, as well as Wi-Fi and Bluetooth, the possibilities are endless.

In order to stand a hope of driving those 192 LEDs from a single ESP32-Pico-D4, it was necessary to use a multiplexed LED driver, courtesy of the Lumissil IS31FL3733 device, which can handle arrays up to 12 x 16 devices. This chip is one to remember, since it has some really nice features, such as global current control to reduce CPU overhead, automatic breathing loops for those fancy fade effects, and even includes a handy open/short detection function, so it can report back assembly problems, assisting in reworking your dodgy soldering!

Power and interfacing are taken care of via USB-C, with a TP4054 single Li-Ion cell charger chip handling the battery. This is a Taiwanese clone of the popular LTC4054, but that chip may be a bit hard to get at the moment. There is the common-as-muck CP2104 USB chip dealing with the emulated serial port side of things, since for some reason, the ESP32 still does not support USB. The Pico-D4 does have RTC support, but [Sulfuroid] decided to use a DS3231M RTC chip instead. We noticed the touch functionality wasn’t broken out – that could be added easily in the next revision!

We’ve covered watches a lot, because who doesn’t want custom geek-wear! Here’s a slick one, a fun one with the brains on display, and finally one using charlieplexing to get the component count down.

Color Dot Puzzle Will Wrinkle Your Brain

February 12, 2022 by Lewin Day 3 Comments

2022 is a good year for puzzles, and if you’re getting tired of Wordle, you might be after a new challenge. This color puzzle from [Sebastian Coddington] could be just what you’re looking for.

[Sebastian] describes the 4×4 Color Dot Puzzle as a sort of combination of the ideas behind the Rubik’s Cube and the 15 puzzle. The aim is to arrange the 16 colored tiles on the board to form four single-colored 2×2 squares in the overall 4×4 board. The puzzle is 3D printed, using 6 colors of filament – black for the body of the puzzle, white for the control sticks, and yellow, green, red, and blue for the individual tiles.

We haven’t seen any mathematical proofs of how to beat the game, but we’re sure [Sebastian] has gotten good at beating the puzzle having designed it himself. According to tipster [Michael Gardi], who knows a thing or two about 3D printing games himself, the puzzle makes for a fun little mind teaser.

If you’re more of a jigsaw person, consider this advanced illuminated build.

The Real World Strikes Back

February 12, 2022 by Elliot Williams 17 Comments

My son was into “Secret Coders“, a graphic novel series wherein a pair of kids discover and thwart a plot to take over the world by learning to program in the LOGO computer language. When I told him that these “turtle bots” were originally actually real physical things, he wanted one. So we built one out of some nice geared DC motors I had lying around.

A turtle bot has essentially three jobs: move forward in a straight line a controlled distance, turn a given number of degrees, and raise and lower a pen. If you’re already screaming “use stepper motors!” at your screen, well, you’re probably right. But I had these nice Faulhaber/Micromo geared motors with encoders that were just collecting dust in the closet, so I used ’em. And because of that, the robot stumbles on two of its three goals in life — the servo pen lifter works just fine.

Perfectly matched DC motors don’t exist. Of course I knew this, because I’ve built bots with DC motors before. But they’ve all had complex control mechanisms and/or feedback that made it moot. Not here. This bot needs to drive perfectly straight without any lines to guide it or more interesting navigation algorithms.

We spent a good half hour driving it around in not-quite-but-almost squares, tweaking each side’s PWMs, running the motors backwards for short bursts to brake the wheels, and generally trying to map degrees of rotation to milliseconds of motor drive. And you know what, my son enjoyed it. The concepts were simple enough for a second grader, and guessing the right PWM values was like a game. When we finally got it good enough, there was a small celebration.

Of course I know that what it really needs is encoder feedback. I installed those encoder gearmotors on purpose after all. But dealing with quadrature and probably a PID loop to control and sync the two sides is not for my son, at least not for another couple years. (They do learn closed-loop control theory in fourth grade these days, right?) I’ll have to do that all offline some night while he’s sleeping.

But I hope he’ll remember the lessons learned from stabbing at it the naive way. Abstractions are great, but no two motors are ever perfectly alike. You’d think you could just calibrate it out, but the motors differ in driven and coasting behavior, so you’ve got a lot more calibrating to do than you think at first. The real world is tough, and although it’s important to have theory and ideas and abstractions to guide you, you’re going to have to tweak to make it work when the wheels hit the floor. But also that it’s fun to do so, and super rewarding when it finally draws a wonky square.

Tutorial Teaches You To Use Neopixels With Micropython

February 12, 2022 by Lewin Day 4 Comments

Addressable LEDs are wonderful things, with products like Neopixels making it easy to create all kinds of vibrant, blinking glowables. However, for those without a lot of electronics experience, using these devices can seem a bit daunting. [Bhavesh Kakwani] is here to help, with his tutorial on getting started with Neopixels using the MicroPython environment.

The tutorial flows on from [Bhavesh’s] Blink example for MicroPython, and is aimed at beginners who are learning for the first time. It explains the theory behind RGB color mixing that allows one to generate all manner of colors with WS2812B-based LED strings, and how to code for the Raspberry Pi Pico to make these LEDs do one’s bidding.

The guide even covers the use of the Wokwi simulation tool. This is a great way for beginners to test their projects before having to play with actual hardware. This is useful for beginners, because it’s a great way to catch mistakes – is there a software problem, or did they push the soldering iron through the microcontroller? It’s also a technique that pays dividends when working on more complicated projects.

Whether you’re entirely new to the embedded world, or just want to learn the intricacies of talking to addressable LEDs and make sense of color mixing theory, this tutorial will serve you well. Before you know it, you’ll be building glowing projects with the best of them!

Simple Dev Board Module Socket

February 12, 2022 by Chris Lott 16 Comments

When you’re building a quick prototype or a one-off project it’s nice to be able to securely mount the various modules and development boards. Sometimes these boards have mounting holes, but often they don’t. As an example from the latter category, digital music instrument maker and performer [DIYDSP] shows us how to build a simple socket to mount an STM32 Nucleo-32 module.

The socket is built on a standard pad-per-hole piece of vector board cut to the desired size. Pairs of female pin header strips are soldered down to the board. The inner pair of headers is for the module, the outer pair is for your interconnections. The headers are connected up with short solder bridges, and [DIYDSP] recommends you extend the outer pair several pins longer than necessary. These extras can be used for additional power or ground points, or on some boards they could connect to the debug header pins. He prefers to use female sockets because that lessens the odds that an accidentally bent pin will short something out.

Final step is to drill your mounting holes in the desired location, and no more development boards free-floating and held up only by wires. Do you have any tips for mounting these kinds of modules, either individually as shown here or onto PCBs? Let us know in the comments.

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Homemade Probe For 3D Printer: $3

February 11, 2022 by Al Williams 38 Comments

You have a few choices if you want to use a probe to level your 3D printer bed. Rarely, you’ll see optical or capacitive probes. More commonly, though, your probe will sense a metal print or uses a physical probe to touch the print bed. [Design Prototype Test] has long used a BLTouch which uses the latter method. However, putting it in a heated build chamber prevented it from working so he set out to make his own simple design using an Allen key.

We’ve seen Allen key sensors before, but usually, they use a microswitch. We’ve also seen microswitches used to directly probe the bed. But, in this case, a 3D printed fan shroud uses an optical sensor to note when the Allen key hits the bed.

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Pyrotechnic Posters Are Fireworks Drawn On Paper

February 11, 2022 by Lewin Day 15 Comments

There’s a deep love many humans feel for fire; it’s often cited as one of the most important discoveries that led to the founding of civilization. The work of French artistic duo [Pinaffo-Pluvinage] definitely hits upon that, combining pyrotechnics with paper to make what are probably the most exciting posters you’ve ever seen, as reported by Heise Online.

The artworks are made with a variety of powders, including those for blue and red flames and one with a special “scintillating” effect.

The posters aren’t huge, measuring 50 cm x 70 cm. However, what they lack in size, they make up for with literal flames. Yes, the posters are laced with a variety of pyrotechnic powders that combust in a variety of designs and patterns to create a dynamic burning artwork once ignited.

Each poster is thus a work of art in both the visual and combustible realms. Different parts of the artwork burn at differnt rates and with different colored flames, adding to the performance when the poster is burned. Impressively, the artworks are not destroyed in the process; the pyrotechnic material burns off with much flame and smoke without destroying the poster itself.

Putting together the posters wasn’t as simple as simply doodling some designs. The duo had to develop their own methods to apply the pyrotechnic material to the paper. Reportedly, the effort took hundreds of experiments to get right.

It’s unclear exactly how the effect is achieved without burning the whole poster down; one suspects some kind of protective layer may be used. It’s quite the opposite of flash paper, which consumes the paper itself in the combustion.

In any case, fireworks experts will likely have some good ideas of the chemicals used to achieve the flaming effects; sound off in the comments if you know what’s what!

The pieces could be interpreted as a commentary on the transience of all things, or the artist’s intention could have been something different entirely. Who can say? Video after the break.

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