ESP32 LED Eyes Help Keep Toddler In Bed

November 19, 2022 by 14 Comments

We’ve seen a lot of custom clocks here at Hackaday, many of which have pushed the traditional definition of the timepiece to its absolute limit. But for all their wild designs, most of them do have something in common: they assume you can actually read a clock and understand the concept of time. But what if you’re developing a clock for a toddler who’s only just coming to terms with such heady ideas?

The answer, at least for [Riley Parish] is a set of 3D printed eyes that are illuminated with either yellow or green LEDs depending on whether or not it’s time to get out of bed. More than just the color of the light, the eye design (which is embedded into the rear of the front panel) switches between wide-open and tightly shut depending on the time of day.

Internally the device is very simple, with the 5 mm LEDs and their associated resistors connected directly to the digital out pins on an ESP32 development board. While the dual-core microcontroller is admittedly pretty overkill for flipping some LEDs every 12 hours or so, the firmware does at least pull the current time from NTP — plus the powerful MCU offers plenty of room to grow. A web front-end to configure the device or check its current status would only be a few more lines of code.

As it so happens, this isn’t the first toddler timepiece to grace these pages. Perhaps unsurprisingly, those previous examples also used changing color to help indicate the passage of time.

solenoid wound pickup coil next to a selection of bolts and a steel rod

The Barkhausen Effect: Hearing Magnets Being Born

November 19, 2022 by 21 Comments

The Barkhausen effect — named after German Physicist Heinrich Barkhausen — is the term given to the noise output produced by a ferromagnetic material due to the change in size and orientation of its discrete magnetic domains under the influence of an external magnetic field. The domains are small: smaller than the microcrystalline grains that form the magnetic material, but larger than the atomic scale. Barkausen discovered that as a magnetic field was brought close to a ferrous material, the local magnetic field would flip around randomly, as the magnetic domains rearranged themselves into a minimum energy configuration and that this magnetic field noise could be sensed with an appropriately arranged pickup coil and an amplifier. In the short demonstration video below, this Barkhausen noise can be fed into an audio amplifier, producing a very illustrative example of the effect.

One example of practical use for this effect is with non-destructive testing and qualification of magnetic structures which may be subject to damage in use, such as in the nuclear industry. Crystalline discontinuities or impurities within a part under examination result in increased localized mechanical stresses, which could result in unexpected failure. The Barkhausen noise effect can be easily leveraged to detect such discontinuities and give the evaluator a sense of the condition of the part in question. All in all, a useful technique to know about!

If you were thinking that the Barkhausen is a familiar name, you may well be thinking about the Barkhausen stability criterion, which is fundamental to describing some of the conditions necessary for a linear feedback circuit to oscillate. We’ve covered such circuits before, such as this dive into bridge oscillators.

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DIY Robotic Platform Aims To Solve Walking In VR

November 18, 2022 by 32 Comments

[Mark Dufour]’s TACO VR project is a sort of robotic platform that mimics an omnidirectional treadmill, and aims to provide a compact and easily transportable way to allow a user to walk naturally in VR.

Unenthusiastic about most solutions for allowing a user to walk in VR, [Mark] took a completely different approach. The result is a robotic platform that fits inside a small area whose sides fold up for transport; when packed up, it resembles a taco. When deployed, the idea is to have two disc-like platforms always stay under a user’s feet, keeping the user in one place while they otherwise walk normally.

It’s an ambitious project, but [Mark] is up to the task and the project’s GitHub respository has everything needed to stay up to date, or get involved yourself. The hardware is mainly focused on functionality right now; certainly a fall or stumble while using the prototype looks like it would be uncomfortable at the very best, but the idea is innovative. Continue reading “DIY Robotic Platform Aims To Solve Walking In VR” →

Scramblepad Teardown Reveals Complicated, Expensive Innards

November 18, 2022 by 28 Comments

What’s a Scramblepad? It’s a type of number pad in which the numbers aren’t in fixed locations, and can only be seen from a narrow viewing angle. Every time the pad is activated, the buttons have different numbers. That way, a constant numerical code isn’t telegraphed by either button wear, or finger positions when punching it in. [Glen Akins] got his hands on one last year and figured out how to interface to it, and shared loads of nice photos and details about just how complicated this device was on the inside.

Just one of the many layers inside the Scramblepad.

Patented in 1982 and used for access control, a Scramblepad aimed to avoid the risk of someone inferring a code by watching a user punch it in, while also preventing information leakage via wear and tear on the keys themselves. They were designed to solve some specific issues, but as [Glen] points out, there are many good reasons they aren’t used today. Not only is their accessibility poor (they only worked at a certain height and viewing angle, and aren’t accessible to sight-impaired folks) but on top of that they are complex, expensive, and not vandal-proof.

[Glen]’s Scramblepad might be obsolete, but with its black build, sharp lines, and red LED 7-segment displays it has an undeniable style. It also includes an RFID reader, allowing it to act as a kind of two-factor access control.

On the inside, the reader is a hefty piece of hardware with multiple layers of PCBs and antennas. Despite all the electronics crammed into the Scramblepad, all by itself it doesn’t do much. A central controller is what actually controls door access, and the pad communicates to this board via an unencrypted, proprietary protocol. [Glen] went through the work of decoding this, and designed a simplified board that he plans to use for his own door access controller.

In the meantime, it’s a great peek inside a neat piece of hardware. You can see [Glen]’s Scramblepad in action in the short video embedded below.

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Faceless Clock Makes You Think Twice About How It Works

November 18, 2022 by 23 Comments

We love projects that make you do a double-take when you first see them. It’s always fun to think you see one thing, but then slowly realize everything is not quite what you expected. And this faceless analog clock is very much one of those projects.

When we first saw [Shinsaku Hiura]’s “Hollow Clock 4,” we assumed the trick to making it look like the hands were floating in space would rely on the judicious use of clear acrylic. But no, this clock is truly faceless — you could easily stick a finger from front to back. The illusion is achieved by connecting the minute hand to the rim of the clock, and rotating the whole outer circumference through a compact 3D printed gear train. It’s a very clever mechanism, and it’s clear that it took a lot of work to optimize everything so that the whole look of the clock is sleek and modern.

But what about the hour hand? That’s just connected to the end of the minute hand at the center of the clock’s virtual face, so how does that work? As it is with most things that appear to be magical, the answer is magnets. The outer rim of the clock actually has another ring, this one containing a pair of neodymium magnets. They attract another magnet located in the very end of the hour hand, dragging it along as the hour ring rotates. The video below shows off the secrets, and it gives you some idea of how much work went into this clock.

We’re used to seeing unique and fun timepieces and other gadgets from [Shinsaku Hiura] — this up-flipping clock comes to mind, as does this custom RPN calculator — but this project is clearly a step beyond.

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Tiny RC Truck And Trailer Motors Around Tabletop

November 18, 2022 by 17 Comments

Most RC cars replicate real-world race cars or fantastical off-road buggies for outdoor escapades. [diorama111] is an expert at building tiny desk-roaming models, though, and built this exquisite micro semi-truck and trailer.

Based on a 1/150 scale truck and trailer model, the build starts with the tractor unit. It’s disassembled, and its plastic wheels are machined on a tiny lathe so they can be fitted with grippy rubber tires carved out of O-ring material. The front wheels are given hubs and mounted to a motor-driven screw-type steering assembly. A photodetector is used to aid in self-centering. The rear axle is fitted with a geared drivetrain, running off a small DC motor. Multiple gear stages are used to give the build plenty of torque for pulling the trailer. Remote control of the model is achieved over Bluetooth, with an ATtiny3217 tucked inside with motor drivers to run the show.

The microcontroller also runs a full set of driving, tail, and indicator lights. The trailer is fitted with an infrared receiver and a battery of its own. It receives signals from an infrared LED on the tractor unit, which tell the trailer when to turn on the taillights and indicators.

There aren’t too many modelers working in the RC space at the 1:150 scale. [diorama111] has form here, though, and we’ve featured a previous Toyota Crown build before.

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Word Tour Map of High Altitude Balloon Launched at Hackaday Supercon.

Supercon Balloon W6MRR-26 Continues Its World Tour

November 18, 2022 by 16 Comments

[Martin Rothfield] and other amateur radio operators from San Francisco High Altitude Ballooning (SF-HAB) treated conference attendees to the 2022 Hackaday Supercon to the launch of two High Altitude Balloons (HABs). On the morning of November 6th, the two balloons were launched from a park across the street from Supplyframe DesignLab in Pasadena, California.

Seven days after its launch from Southern California, one of the balloons was over Tajikistan cruising eastward at an altitude of 42,000 feet (12,800 meters). Balloon W6MRR-26 was already approaching China where it will continue its wonderful world tour to parts unknown. The second balloon (call sign W3HAC-11) landed in northern Arizona where it has continued transmitting whenever it receives power from the sun.

Each balloon carries a tiny payload — a printed circuit board powered only by small photovoltaic cells. The board includes a microcontroller, a GPS module, and a Weak Signal Propagation Reporter (WSPR) radio transmitter.  The transmitted operates on the 20 meter amateur radio band at around 14 MHz.

WSPR beacons can provide time, altitude, and location information.  The WSPR telemetry is then relayed via WSPRgates using Automatic Packet Reporting System (APRS) onto the Internet. The collected information can be viewed and mapped on websites such as aprs.fi.

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