Lego Submarine Gets Balloon Ballast System

September 19, 2021 by Lewin Day 21 Comments

Lego is a fun building block which vast numbers of the world’s children play with every day. However, the mechanical Technic line of Lego building blocks has long offered greater options to the budding engineer. [Brick Experiment Channel] is one such soul, working hard on their latest Lego submarine.

The sub is built inside of a glass food container, chosen for its removable plastic lid with a watertight seal. This keeps all the mechanics dry, as well as the custom electronics built to allow a 27MHz RC controller to send signals to the Lego electronics. This is key as higher frequency radios such as Bluetooth or WiFi can’t penetrate water nearly as well.

A magnetic coupling fitted to a Lego motor is used to drive the propeller in the water without the leaks common when trying to seal a rotating shaft. A second coupling on a Lego servo along with a creative steering arrangement allows the propeller to be turned to steer the craft.

The ballast system is simple. A balloon is filled by a Lego motor running an air pump, capable of 3.0 mL a second and capable of creating a maximum pressure of 2.0 bar. When the balloon is inflated, the buoyancy goes up and the sub rises. Run the motor the other way and the balloon is emptied by a clever clutch and valve arrangement, reducing buoyancy and causing the sub to sink.

The sub isn’t perfect. Maintaining a set depth underwater can be difficult with the rudimentary ballast system, perhaps as the balloon changes shape with varying water pressure. Sometimes, Lego axles slip out of their gears, too, and the radio only works for a few meters under water.

However, simply building a Lego sub of any sort is a remarkable feat. It’s interesting to see the variances in the design compared to earlier projects from [Brick Experiment Channel], too, as we’ve featured their earlier subs before. Video after the break.

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Banish Early Morning Zombification With The Zom-b-gone!

September 17, 2021 by Dave Rowntree 5 Comments

[Applied Procrastination] aka [Simen E. Sørensen] has a simple project to help those of us that struggle with early-morning zombification. By leveraging the backlight optics from a broken LCD monitor, it is possible to create an excellent diffused light source to simulate daylight, before your chosen waking time. The theory is that it is less shocking to the brain to be woken more gradually than an alarm may do. The increasing light level is to prepare the brain with a slowly increasing light level, reminiscent of daybreak, before being properly awoken by an alarm, regardless of the actual light level outdoors. This particularly useful for those of us in more northern regions, such as [Simen]’s native Norway, where mornings are very dark in the winter months.

Daylight is not purely a diffuse source however, it depends on the degree of atmospheric scattering, local reflections and such, but as far as we’re concerned here, we can just aim for as diffuse a light source a possible.

The implementation makes use of the existing LCD metal frame, the light guide panel (usually a big hunk of acrylic covered in etched markings on one side) the diffuser/brightener sheet, and the prism sheet. A white LED strip mounted around the frame edge directs light into the light guide, which with a combination of total internal reflection and scattering on one side only, effectively turns the light through 90 degrees, and spreads it out evenly across that surface. The result of this optical sandwich is flat, even light, exactly what you want for a display, and also for simulating daylight.

Nestled beneath the expected 3D printed frame, is a custom PCB derived by smooshing together the designs from the Adafruit DS3231 RTC module and the Arduino Nano, an additional push button and rotary encoder complete the minimalistic UI, and allow the device to double up as general purpose lamp during the day. Despite a few wobbles with assembling the frame, and some incorrect PCB footprinting, the whole thing came together pretty nicely. This is a perfect thing to do with broken LCD monitors, eeking out a new life and keeping the amount of landfill to a minimum.

For further details of the hardware and codes, see the Zom-b-Gone Github.

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Putting An Afterburner On An Electric Ducted Fan

September 17, 2021 by Lewin Day 30 Comments

Afterburners are commonly agreed to be the coolest feature of military fighter aircraft. Injecting raw fuel into the exhaust stream of a jet engine, afterburners are responsible for that red-hot flaming exhaust and the key to many aircraft achieving supersonic flight. [Integza] wanted to see if the same concept could be applied to an electric ducted fan, and set out to find out.

Of course, building an afterburner for an EDF does add a lot of complication. A flame tube was installed downstream of the EDF, fitted with a brass tube drilled carefully to act as a fuel injector. The flame tube was also fitted with an automotive glow plug in order to ignite the fuel, which was lighter refill gas straight from a can. The whole assembly is wrapped up inside a clear acrylic tube that allows one to easily see what’s happening inside with the combustion.

Results were mixed. While the fuel did combust, but in a rather intermittent fashion. In proper operation, an afterburner would run with smooth, continuous, roaring combustion. Additionally, no thrust measurements were taken and the assembly barely shook the desk.

Thus, if anything, the video serves more as a guide of how to burn a lot of lighter gas with the help of an electric fan. The concept does has merit, and we’ve seen past attempts, too, but we’d love to see a proper set up with thrust readings with and without the afterburner to see that it’s actually creating some useful thrust. Video after the break. Continue reading “Putting An Afterburner On An Electric Ducted Fan” →

Taking A Deep Dive Into SPI

September 16, 2021 by Jim Heaney 9 Comments

With the prevalence of libraries, it has never been easier to communicate with hundreds of different sensors, displays, and submodules. But what is really happening when you type SPI.begin() into the Arduino IDE? In his most recent video, [Ben Eater] explores the Serial Peripheral Interface (SPI) and how it really works.

Most Hackaday readers probably know [Ben] from his breadboard-based computers, such as the 6502 build we featured in 2019. Since then he has been hard at work, adding new and interesting additions to his breadboard computer, as well as diving into different communication protocols to better understand and implement them. For this video, [Ben] set the goal of connecting the BME280, a common pressure, temperature, and humidity sensor with an SPI interface, to his breadboard 6502 computer. Along the way, [Ben] discusses how exactly SPI works, and why there is so much conflicting nomenclature and operations when looking at different SPI devices.

If breadboard computers aren’t your thing, there are tons of other uses for the BME280, such as helping to modernize a Casio F-91W.

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Making A Car Key From A Ratcheting Wrench

September 12, 2021 by Lewin Day 45 Comments

Car keys these days are remarkably complex beasts. Covered in buttons and loaded with security transponders, they often cost hundreds of dollars to replace if you’re unlucky enough to lose them. However, back in the day, keys used to just be keys — a hunk of metal in a mechanical pattern to move some levers and open a door. Thus, you could reshape a wrench into a key for an old car if that was something you really wanted to do.

The concept is simple. Take a 12mm ratcheting wrench, and shape the flat section into a profile matching that of a key for an older car without any electronic security features. The first step is to cut down the shaft, before grinding it down to match the thickness and width of the original key.

The profile of the key is then drawn onto the surface, and a Dremel used with a cutting disc to create the requisite shape. Finally, calipers are used to mark out the channels to allow the key to slide into the keyway, before these are also machined with the rotary tool.

Filing and polishing cleans up the final result to create a shiny, attractive ratchet wrench key. Even better, it does a great job of opening the car, too.

Similar machining techniques can be used to duplicate a key from just a photo (something I did back in 2019 to prank my friend). Alternatively, 3D printing can be great for reproducing even high-security keys. Video after the break.

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Measuring current draw of home shop tools

Using Homebrew Coils To Measure Mains Current, And Taking The Circuit Breaker Challenge

September 12, 2021 by Dan Maloney 21 Comments

Like many hackers, [Matthias Wandel] has a penchant for measuring the world around him, and quantifying the goings-on in his home is a bit of a hobby. And so when it came time to sense the current flowing in the wires of his house, he did what any of us would do: he built his own current sensing system.

What’s that you say? Any sane hacker would buy something like a Kill-a-Watt meter, or even perhaps use commercially available current transformers? Perhaps, but then one wouldn’t exactly be hacking, would one? [Matthias] opted to roll his own sensors for quite practical reasons: commercial meters don’t quite have the response time to catch the start-up spikes he was interested in seeing, and clamp-on current transformers require splitting the jacket on the nonmetallic cabling used in most residential wiring — doing so tends to run afoul of building codes. So his sensors were simply coils of wire shaped to fit the outside of the NM cable, with a bit of filtering to provide a cleaner signal in the high-noise environment of a lot of switch-mode power supplies.

Fed through an ADC board into a Raspberry Pi, [Matthias]’ sensor system did a surprisingly good job of catching the start-up surge of some tools around the shop. That led to the entertaining “Circuit Breaker Challenge” part of the video below, wherein we learn just what it really takes to pop the breaker on a 15-Amp branch circuit. Spoiler alert: it’s a lot.

Speaking of staying safe with mains current, we’ve covered a little bit about how circuit protection works before. If you need a deeper dive into circuit breakers, we’ve got that too.

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Flip-Top Foundry Helps Manage The Danger Of Metal Casting

September 11, 2021 by Dan Maloney 18 Comments

Melting aluminum is actually pretty easy to do, which is why it’s such a popular metal for beginners at metal casting. Building a foundry that can melt aluminum safely is another matter entirely, and one that benefits from some of the thoughtful touches that [Andy] built into his new propane-powered furnace. (Video, embedded below.)

The concern for safety is not at all undue, for while aluminum melts at a temperature that’s reasonable for the home shop, it’s still a liquid metal that will find a way to hurt you if you give it half a chance. [Andy]’s design minimizes this risk primarily through the hands-off design of its lid. While most furnaces have a lid that requires the user to put his or her hands close to the raging inferno inside, or that dangerously changes the center of mass of the whole thing as it opens, this one has a fantastic pedal-operated lid that both lifts and twists. Leaving both hands free to handle tongs is a nice benefit of the design, too.

The furnace follows a lot of the design cues we’ve seen before, starting as it does with an empty party balloon helium tank. The lining is a hydrid of ceramic blanket material and refractory cement; another nice safety feature is the drain channel cast into the floor of the furnace in case of a cracked crucible. The furnace is also quite large, at least compared to [Andy]’s previous DIY unit, and has a sturdy base that aids stability — another plus in the safety column.

Every time we see a new furnace design, we get the itch to start getting into metal casting. And with the barrier to entry as low as a KFC bucket or an old fire extinguisher, why not give it a try? Although it certainly pays to know what can go wrong before diving in.

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