TechyMagThings

The IKEA SKAFTSÄRV is an economical LED accent lamp, but while highly affordable it has only fixed lighting options. [simoneluconi] shows how it can easily be turned into a fully-configurable, WLED-connected, WiFi-enabled RGB lamp with little more than an ESP32-based board.

To do this, the control board of the lamp gets replaced with an ESP32-C3 Super Mini board. Control and automation comes from WLED, open-source software that offers flexible automation and control for LED lights with a wide range of features, including native Android and iOS apps.

Modifying the SKAFTSÄRV lamp is fairly straightforward, but opening the unit does require breaking some glued seams to get inside. Once that’s done, the replacement board fits nicely into the housing and the unit can be closed back up. As far as WLED is concerned, the new lamp has 30 LEDs, WS281x type, GRB color order.

The end result is a stylish accent lamp with built-in diffusor and mount that can be controlled over WiFi with all the features WLED brings, such as easy integration with Home Assistant.

This isn’t the first time IKEA’s LED lighting has been given a powerup. Their pixel-style LED wall-mounted OBEGRÄNSAD, which displays a few canned animations out of the box, got considerably enhanced with a new controller.

Thanks [Crash] for the tip!

After the digital camera rose to prominence, it became a cool hobby to keep taking photos on film. It was even cooler if you did the same with an old motion picture camera. The retro film revival has kept a dedicated bunch of photo labs in business over the years, but it’s still possible to save some cash on development by doing it yourself. If that’s your game, you might try mixing up your own development chemicals. 

As explained by [No Grain No Gain], it’s quite possible to mix up your own ECN-2 chemistry from scratch if you know what you’re doing. ECN-2 is the chemistry you’ll want if you’re trying to develop any of Kodak’s Vision3 films, along with CineStill films.

The problem with traditional methods of making developer is that once it’s mixed up, it doesn’t keep well, and the more you use it, the worse the quality gets. To beat this problem, this method involves producing two stock solutions which can be kept on the shelf for long periods of time. They can then be combined together with a little CD-3 developer on an as-needed basis. This makes it easy to always have fresh developer on hand for the best possible results on every roll processed. To make everything, you’ll need sodium sulfite, potassium bromide, sodium carbonate, sodium bicarbonate, and the specialist CD-3 developing agent. It’s then a simple job to mix up the dry chemicals with a bunch of distilled water to make the two necessary solutions to keep on hand. The video also explains how to deal with RemJet films if you happen to be shooting those.

[No Grain No Gain] estimates that this method can cut the cost of development to as little as 50 cents a roll. There’s plenty of labor involved, but if you want the freshest, best developer on hand for your home lab, it’s a method worth considering.

We’ve explored modern film development techniques before, too. Video after the break.

The vibrobot – a vibrating motor and battery attached to the head of a brush – isn’t truly a robot, since its movement can’t be controlled, but it’s whetted the interest of many future roboticists. With a clever control method, though, it is in fact possible to drive them in any desired direction while using only one motor.

[Namaskar Mitro] based the design of this robot on this research paper; if the vibrating motor is mounted at an angle above the base of the robot, it causes the bot to rotate, and if the motor is mounted off-center from the center of mass, the robot moves in a circle. Crucially, reversing the direction of the motor’s rotation reverses the direction of the robot’s rotation. By rapidly switching the direction of rotation, the bot can move in a series of short, shallow arcs which approximate a straight line.

The robot which [Namaskar] built was based on an ESP-01F microcontroller, which let it be remote-controlled over Wi-Fi. It used a DRF8212 motor driver to control a vibrating pager motor, which was housed inside a 3D-printed enclosure. To move in a straight line, the ESP-01F switches the motor’s direction every 250 milliseconds, which still produces a slightly erratic movement. It can, however, approximately follow a traced path.

This adds to the previous vibrobot control methods we’ve seen: a pair of differentially-driven vibrating motors or a weight-shifting mechanism.

Thanks to [110y6] for the tip!

If you want to maximize the life of your lithium-ion batteries, proper storage voltage is critical. That is, don’t store them empty, and don’t store them completely full either. “Almost fully charged” is a sweet spot for occasional-use devices. Sadly, this is easier said than done. While many devices use integrated rechargeable batteries these days, most provide no method of limiting charge level. That’s where [DaverDavid]’s ChargeCap comes in.

ChargeCap sits between a USB charger and target device, disconnecting when it detects that recharging is 80 to 90 percent complete. This is particularly useful for maximizing the cell life of devices that see only intermittent use.

The way ChargeCap does this is clever, and relies on the fact that all lithium-ion charging curves look the same regardless of cell capacity or cell count. Charge current remains at pretty much the same level for most of the charging process, but tapers off quickly (and in a linear fashion) as cells approach their maximum capacity. That’s because charging a battery is a lot like blowing up a balloon: the first breaths are easy, but once the balloon fills out, every breath needs to push harder than the last.

ChargeCap works by sampling the peak charge current at the beginning of the charge cycle, then detecting when it drops below 50 percent of peak, at which point charging is stopped. The result is a device that reliably charges to 80 to 90 percent of capacity, and no more. ChargeCap uses an ESP32-C3 and a small OLED display that, as a nice touch, inverts colors to signal charge completion. Design files and code are at the GitHub repository.

Lithium-ion cells are fantastic devices, so flesh out your knowledge by reading [Arya Voronova]’s primer on designing them into your own projects, or a more in-depth explanation of how they work.

The Mary Rose was a carrack in the English Tudor Navy of King Henry VIII  that fought in multiple battles during the 16th century before it was sunk in 1545. After its wreck was located in 1971 and raised in 1982 the ship and all the items contained within the partially preserved hull became the focus of intense study. Among these items are the weaponry found, including the canons, but also massive darts that seemed to have been designed for an incendiary payload. Recently [Tod’s Workshop] collaborated with others to test these presumed incendiary darts.

Although fire arrows have been around for a while, seeing what appears to be super-sized versions of these is somewhat unusual, but could make sense in taking out enemy ships of the time. The main questions are how you would even fire them, and how effective they would be. Were the darts thrown by hand from e.g. the crow’s nest, or fired from a canon?

The reproduction darts used are based on the recovered remnants of the original darts, with an incendiary mixture inside a pitch-covered cloth covering. This mixture would be ignited by wooden fuses after a set amount of time, at which point the resulting fire would be basically impossible to put out. Obviously, this also means that if you were to throw one of these darts, it can absolutely not fall onto your own ship.

First tested was throwing the dart by hand, which seems like it would clear the ship. Of course, the three recovered darts were found near a rather special canon that appeared to be both a miscast and angled upwards. Whether that canon was used for launching apparently somewhat experimental darts is hard to say, but it can be tested. Sadly, lacking a full-sized black powder canon a scale model dart was fired using compressed air.

From that scale test it’s clear that at full charge the dart would disintegrate due to the rapid acceleration, but a ‘soft’, or reduced, charge could work against nearby targets. Once the dart lodges itself into the enemy ship’s structure, it would definitely cause severe damage as further tests in the video demonstrate. Having a salvo of these fire darts fired at you from a nearby ship would definitely make for a pretty bad day.

If you’ve watched a Saturn V launch, you’ve probably seen how a large rocket will often jettison a stage on the way up. There are several reasons for this — there is no reason to haul an empty fuel container, for example. However, you can probably imagine how the separation works. You release something — probably explosive bolts — and gravity pulls the old stage away from you as you climb on the next stage’s engines. But what about on the way back? The command module drops the service module before reentry. [Apollo11Space] has a video explaining just how complicated that was to pull off. You can watch it below.

The main problem? The service module has almost everything you need: oxygen, a big engine, fuel, and electrical generation capability. If you’ve ever seen a real command module, they are tiny. Somehow, you need to get the command module prepared to be on its own for the amount of time it takes to land, and get the service module safely away.

In orbit, gravity isn’t a big help in pulling the two pieces apart. For that reason, the mission design called for a very specific orientation for the separation. There are a number of other details you might not have known about.

Landing Apollo 11 successfully depended on some spy tech. We imagine the separation of the LEM had some similar issues, although even the moon’s weak gravity would have helped.