A Brief History Of Calculator Watches

December 2, 2024 by 32 Comments

When humans counted on their fingers, everyone had a state-of-the-art (at the time) calculator at all times. But as we got smarter about calculation, we missed that convenience. When slide rules were king, techies were known to carry them around like swords swinging from their belts. These were replaced with electronic calculators, some also swinging from belt loops, but no matter how small they were, they still were not that handy, no pun intended. That changed around 1975. The Time Computer Calculator company produced an amazing calculator watch for Pulsar. At the time, Pulsar was a brand of the Hamilton Watch Company.

A Pulsar calculator watch (photo: The Smithsonian)

There were a few problems. First, the watch was thick. Despite its size, it had tiny keys, so you had to use a little stylus to push the keys — not as handy as you might wish. On top of that, 1975 display technology used power-hungry LEDs. So, the display was prone to turning off quickly, and the batteries died quickly.

Unsurprisingly, Hamilton, in conjunction with Electro/Data, had earlier rolled out the first LED watch in 1972. With an 18-karat gold case, it went for a cool $2,100 — a whole lot of money in 1972. The first calculator watch was also gold and went for almost $4,000. Soon, though, they brought out a stainless and a gold-filled version that came in at under $500.

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Small Feathers, Big Effects: Reducing Stall Speeds With Strips Of Plastic

December 2, 2024 by 18 Comments

Birds have long been our inspiration for flight, and researchers at Princeton University have found a new trick in their arsenal: covert feathers. These small feathers on top of birds’ wings lay flat during normal flight but flare up in turbulence during landing. By attaching flexible plastic strips – “covert flaps” – to the top of a wing, the team has demonstrated impressive gains in aircraft performance at low speeds.

Wind tunnel tests and RC aircraft trials revealed a fascinating two-part mechanism. The front flaps interact with the turbulent shear layer, keeping it close to the wing surface, while the rear flap create a “pressure dam” that prevents high-pressure air from moving forward. The result? Up to 15% increase in lift and 13% reduction in drag at low speeds. Unfortunately the main body of the paper is behind a paywall, but video and abstract is still fascinating.

This innovation could be particularly valuable during takeoff and landing – phases where even a brief stall could spell disaster. The concept shares similarities with leading-edge slats found on STOL aircraft and fighter jets, which help maintain control at high angles of attack. Imitating feathers on aircraft wings can have some interesting applications, like improving control redundancy and efficiency.

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Exploring The Sounds And Sights Of Alien Worlds

December 2, 2024 by 14 Comments

The 20th century saw humankind’s first careful steps outside of the biosphere in which our species has evolved. Whereas before humans had experienced the bitter cold of high altitudes, the crushing pressures in Earth’s oceans, as well as the various soundscapes and vistas offered in Earth’s biosphere, beyond Earth’s atmosphere we encountered something completely new. Departing Earth’s gravitational embrace, the first humans who ventured into space could see the glowing biosphere superimposed against the seemingly black void of space, in which stars, planets and more would only appear when blending out the intense light from the Earth and its life-giving Sun.

Years later, the first humans to set foot on the Moon experienced again something unlike anything anyone has experienced since. Walking around on the lunar regolith in almost complete vacuum and with very low gravity compared to Earth, it was both strangely familiar and hauntingly alien. Although humans haven’t set foot on Mars yet, we have done the next best thing, with a range of robotic explorers with cameras and microphones to record the experience for us here back on Earth.

Unlike the Moon, Mars has a thin but very real atmosphere which permits the travel of soundwaves, so what does the planet sound like? Despite what fictional stories like Weir’s The Martian like to claim, reality is in fact stranger than fiction, with for example a 2024 research article by Martin Gillier et al. as published in JGR Planets finding highly variable acoustics during Mars’ seasons. How much of what we consider to be ‘normal’ is just Earth’s normal?

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Building Experience And Circuits For Lithium Capacitors

December 2, 2024 by 22 Comments

For the cautious, a good piece of advice is to always wait to buy a new product until after the first model year, whether its cars or consumer electronics or any other major purchase. This gives the manufacturer a year to iron out the kinks and get everything ship shape the second time around. But not everyone is willing to wait on new tech. [Berto] has been interested in lithium capacitors, a fairly new type of super capacitor, and being unwilling to wait on support circuitry schematics to magically show up on the Internet he set about making his own.

The circuit he’s building here is a solar charger for the super capacitor. Being a fairly small device there’s not a lot of current, voltage, or energy, but these are different enough from other types of energy storage devices that it was worth taking a close look and designing something custom. An HT7533 is used for voltage regulation with a Schottky diode preventing return current to the solar cell, and a DW01 circuit is used to make sure that the capacitor doesn’t overcharge.

While the DW01 is made specifically for lithium ion batteries, [Berto] found that it was fairly suitable for this new type of capacitor as well. The capacitor itself is suited for many low-power, embedded applications where a battery might add complexity. Capacitors like this can charge much more rapidly and behave generally more linearly than their chemical cousins, and they aren’t limited to small applications either. For example, this RC plane was converted to run with super capacitors.

ESP32 Powers DIY Smart Energy Meter

December 2, 2024 by 20 Comments

Energy is expensive these days. There’s no getting around it. If, like [Giovanni], you want to keep better track of your usage, you might find value in his DIY energy meter build.

[Giovanni] built his energy meter to monitor energy usage in his whole home. An ESP32 serves as the heart of this build. It’s hooked up with a JSY-MK-194G energy metering module, which uses a current clamp and transformer in order to accurately monitor the amount of energy passing through the mains connection to his home. With this setup, it’s possible to track voltage, current, frequency, and power factor, so you can really nerd out over the electrical specifics of what’s going on. Results are then shared with Home Assistant via the ESPHome plugin and the ESP32’s WiFi connection. This allows [Giovanni] to see plots of live and historical data from the power meter via his smartphone.

A project like this one is a great way to explore saving energy, particularly if you live somewhere without a smart meter or any other sort of accessible usage tracking. We’ve featured some of [Giovanni]’s neat projects before, too.
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Stripping GoPros To The Bone For Model Rocketry

December 1, 2024 by 11 Comments

The small size of action cameras has made them a great solution for getting high-quality experimental footage where other cameras don’t fit. GoPros are [Joe Barnard]’s camera of choice for his increasingly advanced rockets, but even the smallest models don’t quite fit where he needs them. They also overheat quickly, so in the video after the break, he demonstrates how he strips and customizes them to fit his required form factor.

[Joe] starts out with a GoPro HERO10 Bones, which is a minimalist version intended for FPV drones. He likes the quality of the 4K 120 FPS video and the fact that he can update the settings by simply holding up a QR code in front of the camera. The case appears to be ultrasonically welded, so careful work with a Dremel is required to get it open. The reveals the control board with an aluminum heat sink plate, and the sensor module on a short ribbon cable. For minimal drag[Joe] wants just the lens to poke out through the side of the rocket, so he uses slightly longer aftermarket ribbon cables to make this easier.

The camera’s original cooling design, optimized for drone airflow, meant the device would overheat within 5 minutes when stationary. To increase the run time without the need for an external heat sink, [Joe] opts to increase the thermal mass by adding thick aluminum to the existing cooling plate with a large amount of thermal paste. In an attempt to increase heat transfer from the PCB, he also covers the entire PCB with a thick layer of thermal paste. Many of the video’s commenters pointed out that this may hurt more than it helps because the thermal paste is really intended to be used as a thin layer to increase the contact surface to a heat sink. It’s possible that [Joe] might get better results with just a form-fitting thermal block and minimal thermal paste.

[Joe] is permanently epoxying three of these modified cameras into his latest rocket, which is intended to fly at Mach 3, and touch space. This may look like a waste of three relatively expensive cameras, but it’s just a drop in the bucket of a very expensive rocket build.

We’ve seen GoPros get (ab)used in plenty of creative ways, including getting shot from a giant slingshot, and reaching the edge of space on a rocket and a balloon.

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Electrostatic Puck: Making An Electret

December 1, 2024 by 27 Comments

You might have heard of electrets being used in microphones, but do you know what they are? Electrets produce a semi-permanent static electric field, similar to how a magnet produces a magnetic field. The ones in microphones are very small, but in the video after the break [Jay Bowles] from Plasma Channel makes a big electret and demonstrates it’s effects.

Electrets have been around since the 1800s, and are usually produced by melting an insulating material and letting it solidify between two high-voltage electrodes. The original recipe used a mix of Carnauba wax, beeswax, and rosin, which is what [Jay] tried first. He built a simple electric field detector, which is just a battery, LED and FET, with an open-ended resistor on the FET’s gate.

[Jay] 3D printed a simple cylindrical mold and stuck aluminum foil to the outer surfaces to act as the electrodes. He used his custom 6000:1 voltage transformer to hold the electrodes at ~40 kV. The first attempt did not produce a working electret because the electrodes were not in contact with the wax, and kept arcing across, which causes the electric charge to drop off. Moving the aluminum electrodes the inner surfaces of the mold eventually produced an electret detectable out to 10 inches.

This was with the original wax recipe, but there are now much better materials available, like polyethylene. [Jay] heated a a block of it in the oven until it turned into a clear blob, and compressed it in a new mold with improved insulation. This produced significantly better results, with an electric field detectable out to 24 inches.

[Jay] also built an array of detectors in a 5×5 grid, which he used to help him visualize the size and shape of the field. He once pulled off a similar trick using a grid of neon bulbs.

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