The board in question, with a Pi Pico soldered on, with old PCBs for macropads being used as captouch electrodes

Give Your Pi Pico Captouch Inputs For All Your Music Needs

March 31, 2024 by 11 Comments

Unlike many modern microcontrollers, RP2040 doesn’t come with a native capacitive touch peripheral. This doesn’t mean you can’t do it – the usual software-driven way works wonderfully, and only requires an external pullup resistor! In case you wanted a demonstration or you have a capacitive touch project in mind, this lighthearted video by [Jeremy Cook] is a must watch, and he’s got a healthy amount of resources for you in store, too!

In this video, [Jeremy] presents you with a KiCad schematic and an PCB design you can use to quickly add whole 23 capacitive touch sensing inputs to a Pi Pico! The board is flexible mechanically, easy to assemble as [Jeremy] demonstrates, and all the pins involved can still be used as regular GPIOs if you’d like. Plus, it’s fully open-source, can easily be assembled on your own, and available on Tindie too!

Of course, such a board doesn’t get created for no reason – [Jeremy] has a healthy amount of musical creations and nifty ideas to show off. We quite liked the trick of using old PCBs as capacitive touch sensing, using copper fills as electrodes – which has helped create an amusing “macropad of macropads”, and, there’s quite a bit more to see.

If capacitive touch projects ever struck a chord with you and you enjoy music-related hacking, [Jeremy]’s got a whole YouTube channel you ought to check out. Oh, and if one of the musical projects in the video caught your eye, it might just be the one we’ve featured previously! Continue reading “Give Your Pi Pico Captouch Inputs For All Your Music Needs” →

ESP-Drone: Building An ESP32-Based Quadcopter For Not Much Cash

March 31, 2024 by 12 Comments

What’s the cheapest quadcopter you can build? As [Circuit Digest] demonstrates with their variant of the ESP-Drone project by Espressif, you only need a minimum of parts: an ESP32 MCU, an inertial measurement unit (IMU) such as the MPU6050, and four MOSFETs to drive the brushless DC motors. As the PCB also forms the structural frame and landing struts for the quadcopter, not even a 3D printer is needed. All told, [Circuit Digest] figures the total BOM comes in at around 1,000 Indian Rupees, or about $12 USD.

The fully assembled ESP-Drone flying around. (Credit: Circuit Digest)
The fully assembled ESP-Drone flying around. (Credit: Circuit Digest)

While this [Circuit Digest] project provides basic IMU functionality, the Espressif project also has a few expansion boards detailed on its hardware page, depending on the base model of the mainboard you pick. The [Circuit Digest] project follows the ESPlane-V2-S2 version with no expansion boards, but the ESP32-S2-Drone V1.2 mainboard can be extended with position-hold, pressure and compass modules, as well as custom boards.

As a derivative of the Bitcraze Crazyflie project, the ESP-Drone firmware also supports the rather nifty cfclient software for remote monitoring, logging and control. This may also be in the [Circuit Digest] firmware, but wasn’t listed among the features.

Continue reading “ESP-Drone: Building An ESP32-Based Quadcopter For Not Much Cash” →

Drop-In Switch Mode Regulators

March 31, 2024 by 30 Comments

Perhaps the simplest way to regulate a DC voltage is using a voltage divider and/or an active device like a Zener diode. Besides simplicity, they have the additional advantage of not being particularly noisy, but with a major caveat: they are terribly inefficient. To solve this problem a switching regulator can be used instead, but that generally increases complexity and noise. With careful design, though, a switching regulator can be constructed to almost completely replicate a linear regulator like this drop-in TO3 replacement. (Google Translate from German)

While the replacement regulator was built by [Mr. Floppy], the units are being put to the test in the linked video below by [root42]. The major problem these solve compared to other switching regulators is the suppression of ripple, which is a high-frequency artifact that appears on the DC voltage. Reducing ripple in this situation involved designing low-inductance circuit traces on the PCB as well as implementing a number of EMI filters on both input and output. The final result is an efficient voltage supply for retrocomputers which has a ripple lower than their oscilloscopes can measure without special tools.

[root42] is not only testing these, but the linked video also has him using the modules to repair a Commodore 1541 which originally had the linear TO3 voltage regulators. It’s definitely a non-trivial task to build a switching power supply that meets the requirements of sensitive electronics like these. Switch mode power supplies aren’t new ideas, either, and surprisingly pre-date the first commercially-available transistor although modern ones like these are much less expensive to build.

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Modular Vacuum Table Custom-Fits The Parts

March 31, 2024 by 3 Comments

[enhydra] needed to modify a bunch of side inserts from some cheap ABS enclosures, and to save time and effort, he created a simple vacuum table with swappable inserts to precisely fit the parts. Suction is provided by a shop vacuum (plugged in near the bottom in the photo above) and it worked very well! Sealing and gaskets weren’t even required.

A vacuum table provides a way to hold workpieces flat and secure while a CNC machine does its thing, and because no clamps are involved, it can really speed up repetitive work. [enhydra]’s solution combines a vacuum table with a jig that ensures every rectangular piece is held exactly where the machine expects it to be, making the whole process of modifying multiple units significantly more efficient.

The whole thing — vacuum table and modular top — was straightforward to CNC cut out of what looks like particle board and worked as-is, no added gaskets or seals required, making this a very economical solution.

Vacuum tables can be pretty versatile and applied in more than one way, so keep that in mind the next time you’re wondering how best to approach a workshop problem. We’ve seen a well-engineered table used to speed up PCB milling, and we’ve also seen a DIY vacuum table combined with a heat gun and plastic plates from the dollar store make a bare-bones thermoforming rig.

A Threat Level Monitor For Everyone

March 31, 2024 by 25 Comments

A TV news pundit might on any given evening in 2024 look at the viewers and gravely announce that we are living in uncertain times. Those of us who’ve been around for a bit longer than we’d like to admit would see that, scratch our heads, and ask “Have we ever not lived in uncertain times?” If all this uncertainty is getting to you though, you can now reassure yourself as [Ian Williams] has, with a threat level monitor which displays the UK’s current level of projected fear threat level.

The build is fairly straightforward in hardware terms, with a Raspberry Pi Zero and a Pimoroni e-paper display pHAT. The software grabs the current level of doom from in this case the UK government’s website with a nifty bit of Python code, and turns it into an easy to read alert level bar.

So if you’re genuinely worried that the sky might fall upon your head you can now gain reassurance from a small piece of electronic hardware. If you feel things are really going south though, how about converting your basement into a fallout shelter?

Playing Chess Against Your Printer, With PostScript

March 30, 2024 by 11 Comments

Can you play chess against your printer? The answer will soon be yes, and it’s thanks to [Nicolas Seriot]’s PSChess. It’s a chess engine implemented in PostScript, of all things. It’s entirely working except for one last hurdle, but more on that in a moment.

What’s it like to play PSChess? Currently, one uses a PostScript interpreter (such as GhostScript) to run it, much like one would use the Python interpreter to run Python code. The user inputs moves by typing in commands like d2d4 (representing a piece’s source coordinate and a destination coordinate on the 2D board). Then the program makes a move, and outputs an updated board state to both the console and a PDF document. Then it’s the user’s turn again, and so on until somebody loses.

The chess parts are all working, but there’s one last feature in progress. The final step of the project is to enable PSChess to be run directly on a printer instead of using GhostScript as the interpreter. Intrigued? You can find the code at the project’s GitHub repository.

So why PostScript? While it is a Turing-complete stack-based interpreted language, it was never intended to be used directly by humans. There are no meaningful development tools to speak of. Nevertheless, [Nicolas] finds PostScript an appealing tool for programming projects and provides tips and techniques for like-minded folks. One of the appeals is working within constraints to solve a problem, just like implementing a chess engine in only 4k, or draw poker in 10 lines of BASIC.

Using Electroadhesion To Reversibly Adhere Metals And Graphite To Hydrogels And Tissues

March 30, 2024 by 6 Comments

The usual way to get biological tissues and materials like gels and metals to stick together is using sutures, adhesives or both. Although this generally works, it’s far from ideal, with adhesives forming a barrier layer between tissues and the hard or impossible to undo nature of these methods. A viable alternative might be electroadhesion using cation and anion pairs, which uses low-voltage DC to firmly attach the two sides, with polarity reversal loosening the connection with no permanent effects. This is what a group of researchers have been investigating for a few years now, with the most recent paper on the topic called Reversibly Sticking Metals and Graphite to Hydrogels and Tissues by [Wenhao Xu] and colleagues published this year in ACS Central Science.

This follows on the 2021 study published in Nature Communications by [Leah K. Borden] and colleagues titled Reversible electroadhesion of hydrogels to animal tissues for suture-less repair of cuts or tears. In this study a cationic hydrogel (quaternized dimethyl aminoethyl methacrylate, QDM) was reversibly bonded to bovine aorta and other tissues, with said tissues functioning as the anionic element. Despite demonstrated functionality, the exact mechanism which made the application of 3-10 VDC (80 – 125 mA) for under a minute (10+ seconds) cause both sides to bond so tightly, and reversibly, is still unknown. This is where the recent study provides a mechanism and expands the applications.

Continue reading “Using Electroadhesion To Reversibly Adhere Metals And Graphite To Hydrogels And Tissues” →