Polyphony On A Tiny Scale

May 9, 2021 by 4 Comments

Older readers may remember the Stylophone, a small battery powered electric organ using conductive PCB pads and a stylus to create notes. The simple multivibrators in those instruments made them monophonic, but here in 2021 we can do better than that! [Sjm4306] has gone the extra mile with a PCB organ, by making a capacitive-touch instrument that boasts four-note polyphony.

At its heart is an ATmega328p whose software sports four tone generators that each emerge on a different pin. These are summed using a set of 100 Ω resistors and fed to a tiny speaker. Power comes from a CR2032 lithium cell, and he notes that a higher voltage delivers more volume.

The full story is detailed in the video below the break, along with a bit of four-note polyphonic action. We’re guessing that this instrument would sound sensational when hooked up to a reverb unit.

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Fix Your Nokia’s White Screen Of Death

May 9, 2021 by 17 Comments

Today the Nokia brand can be found on a range of well-screwed-together Androind phones and a few feature phones, but as older readers will remember that before their descent into corporate chaos and the Windows Phone wilderness, there was once a time when the Finnish manufacturer dominated the mobile phone landscape and produced some of the most innovative and creative handset designs ever created. It’s for some of these that [Michael Fitzmayer] has done some work providing tools revive the devices from an unfortunate bricking.

The N-Gage was the phone giant’s attempt to produce a handset that doubled as a handheld game console, and though it was a commercial failure at the time it has retained a following among enthusiasts. The flaw comes as its Symbian operating system fills its user partition, at which point the infamous “White Screen Of Death” occurs as the device can no longer reboot. Rewriting the flash chip used to be handled by Nokia service tools, but these can no longer be found. His fix substitutes a “Blue pill” STMF103-based dev board that connects to the Nokia FBus serial port and does its job. It’s possible that it could be used on other Symbian devices, but for now it’s only been tested on the N-Gages.

It’s easy to forget when a smartphone is defined by iOS and Android, that Symbian gave us a smartphone experience for the previous decade. For those of us who still pine for their miniaturised Carl Zeiss Tessar cameras and candybar form factors, it’s good to see them receiving some love.

Thanks [Razvan] for the tip.

A MIDI Controller — From A Twister Mat?

May 9, 2021 by 3 Comments

Twister, the mildly embarrassing but strangely enjoyable floor contortion game that most of us have vague youthful memories of from Christmas parties. Could a Twister mat be used as an input device? [Guy Dupont] took those 24 coloured dots and made just that, after a conversation with a friend.

Wiring up a floor-sized plastic mat isn’t as easy as it might seem, and early experiments with copper foil and capacitive touch sensor chips proved to be a failure. The replacement came in the form of force sensitive resistors, read by a brace of MCP3008 multiplexed analogue-to-digital converters. These are then read by an ESP32 that does all the MIDI magic. We’re treated in the video below the break to full details including the entertaining sight of him playing Twister to a beat, prompted by a robotic-voiced random move generator, and we can see that this devices has some potential.

We’ve not seen another Twister mat before, but force sensitive resistors have made an appearance in a much higher-resolution array. It’s the LED floor game controller that has us going though.

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Calibrating A VNA The Proper Way

May 8, 2021 by 16 Comments

Those of us who have bought cheap TinyVNA devices for our RF experimentation will be used to the calibration procedure involving short-circuit, 50 Ω, and open terminations, followed by a direct connection between ports. We do this with a kit of parts supplied with the device, and it makes it ready for our measurements. What we may not fully appreciate at the level of owning such a basic instrument though, is that the calibration process for much higher-quality instruments requires parts made to a much higher specification than the cheap ones from our TinyVNA. Building a set of these high-quality parts is a path that [James Wilson] has taken, and in doing so he presents a fascinating discussion of VNA calibration and the construction of standard RF transmission line components.

We particularly like the way that after constructing his short, load and open circuit terminations using high-quality SMA sockets, he put a custom brass fitting 3D printed by Shapeways on the end of each to make them easier to handle while preserving their RF integrity. If we’d bought a set of terminations looking like these ones as commercial products we would be happy with their quality, but the real test lay in their performance. Thanks to a friend he was able to get them tested on instruments with much heftier price tags, and found them to be not far short of the simulation and certainly acceptable within his 3 GHz range.

Curious about VNAs at the affordable end of the spectrum? We took a look at the TinyVNA, which while it is something of a toy is still good enough for lower frequency measurements.

Finally An Inexpensive Route To Digital Radio Listening

May 8, 2021 by 30 Comments

An inexorable trend over the last decade or more has been the exodus of AM radio stations from the low frequency and HF broadcast bands. The bandwidth and thus audio quality at these frequencies puts them at a disadvantage against FM and internet streamed services, and the long-distance advantage of HF has been reduced by easy online access to overseas content. The world has largely moved on from these early-20th-century technologies, leaving them ever more a niche service.

Happily for medium- and long-wave enthusiasts there is a solution to their decline, in the form of DRM, or Digital Radio Mondiale, a digital scheme that delivers cleaner audio and a range of other services in the same space as a standard-sized AM channel. DRM receivers are somewhat rare and usually not cheap though, so news of an Android app DRM receiver from Starwaves is very interesting indeed.

DRM uses a licensed encoding scheme from the Fraunhofer Institute, and this product follows on from a line of hardware DRM receivers that Starwave have developed using their technology. It uses the Android device as a front-end for any of a number of SDR receivers, including the popular RTL-SDR series. It supports the VHF variant of DRM, though we’re guessing that since the best chance of finding a DRM channel for experimentation is on HF that an RTL-SDR with the HF modification will be required. We think it’s an interesting development because the growth of DRM is a chicken-and-egg situation where there must be enough receivers in the wild for broadcasters to consider it viable.

Leap Motion Controls Hands With No Glove

May 8, 2021 by No comments

It isn’t uncommon to see a robot hand-controlled with a glove to mimic a user’s motion. [All Parts Combined] has a different method. Using a Leap Motion controller, he can record hand motions with no glove and then play them back to the robot hand at will. You can see the project in the video, below.

The project seems straightforward enough, but apparently, the Leap documentation isn’t the best. Since he worked it out, though, you might find the code useful.

An 8266 runs everything, although you could probably get by with less. The Leap provides more data than the hand has servos, so there was a bit of algorithm development.

We picked up a few tips about building flexible fingers using heated vinyl tubing. Never know when that’s going to come in handy — no pun intended. The cardboard construction isn’t going to be pretty, but a glove cover works well. You could probably 3D print something, too.

The Unity app will drive the hand live or can playback one of the five recorded routines. You can see how the record and playback work on the video.

This reminded us of another robot hand project, this one 3D printed. We’ve seen more traditional robot arms moving with a Leap before, too. Continue reading “Leap Motion Controls Hands With No Glove” →

MIT’s Hair-Brushing Robot Untangles Difficult Robotics Problem

May 8, 2021 by 12 Comments

Whether you care to admit it or not, hair is important to self-image, and not being able to deal with it yourself feels like a real loss of independence. To help people with limited mobility, researchers at MIT CSAIL have created a hair-brushing robot that combines a camera with force feedback and closed-loop control to adjust to any hair type from straight to curly on the fly. They achieved this by examining hair as double helices of soft fibers and developed a mathematical model to untangle them much like a human would — by working from the bottom up.

It may look like a hairbrush strapped to a robot arm, but there’s more to it than that. Before it ever starts brushing, the robot’s camera takes a picture that gets cropped down to a rectangle of pure hair data. This image is converted to grayscale, and then the program analyzes the x/y image gradients. The straighter the hair, the more edges it has in the x-direction, whereas curly hair is more evenly distributed. Finally, the program computes the ratio of straightness to curliness, and uses this number to set the pain threshold.

The brush is equipped with sensors that measure the forces being exerted on the hair and scalp as it’s being brushed, and compares this input to a baseline established by a human who used it to brush their own hair. We think it would be awesome if the robot could grasp the section of hair first so the person can’t feel the pull against their scalp, and start by brushing out the ends before brushing from the scalp down, but we admit that would be asking a lot. Maybe they could get it to respond to exclamations like ‘ow’ and ‘ouch’. Human trials are still in the works. For now, watch it gently brush out various wigs after the break.

Even though we have wavy hair that tangles quite easily, we would probably let this robot brush our hair. But this haircut robot? We’re not that brave.

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