Using Electrolysis For More Than Just Generating Hydrogen

June 5, 2026 by Maya Posch 6 Comments

When the topic of ‘electrolysis’ is mentioned, people typically think of just splitting plain old dihydrogen monoxide (hydric acid: H₂O) into its constituent atoms, but this barely scratches the surface of what is going on during electrolysis. Once you understand the full picture it also becomes obvious how electrolysis can be used for other tasks, including metal refining, flow batteries and more, as covered in a recent video by [NightHawkInLight].

On a fundamental level electrolysis is what it says on the tin: a way to lyse (i.e. split apart) using electrons, which is what the anode and cathode provide or remove. This can be used to break down the bonds between hydrogen and oxygen, but also those of iron ore, like Fe₃O₄. Stripping the oxygen from the iron atoms is commonly done in a reduction process using the CO from coke or hydrogen,

Setup for electrolysing iron ore. (Credit: NightHawkInLight, YouTube) — Setup for electrolysing iron ore.

By instead dissolving the iron ore in acid, electrolysis can then be used to separate the two. In the example, the acid is created by one side of the electrolytic cell, with both electrodes separated by an ion-exchange membrane barrier that prevents the chemical processes on each side of the cell to affect the other side while still enabling the cell to work. How to make these membranes is also demonstrated in the video.

Through a careful arrangement of these membranes and the electrodes, you can guide which reactions can occur where, and which – negative or positively charged – ion can pass through which membrane, giving a lot of control. It can also be used to prevent undesirable reactions from happening, such as in this case the generating of chlorine gas from the NaCl being lysed.

Acidity indicator dye is used to show in great detail how the cell works, including its preparation of getting the acidity just right before the crushed iron ore is mixed with some of the generated acid and the resulting liquid added to the cell. Following this you get a closed-loop chemical process to which only fresh iron ore slush has to be added and electrodes swapped out for fresh ones as the build-up of iron becomes sufficiently thick. In addition to supplying the cell with electricity, naturally, though you can even invert the cell and use it as a chemical battery akin to a lead-acid one if that’s more your thing.

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Big Chemistry: Seawater Desalination

June 16, 2025 by Dan Maloney 42 Comments

For a world covered in oceans, getting a drink of water on Planet Earth can be surprisingly tricky. Fresh water is hard to come by even on our water world, so much so that most sources are better measured in parts per million than percentages; add together every freshwater lake, river, and stream in the world, and you’d be looking at a mere 0.0066% of all the water on Earth.

Of course, what that really says is that our endowment of saltwater is truly staggering. We have over 1.3 billion cubic kilometers of the stuff, most of it easily accessible to the billion or so people who live within 10 kilometers of a coastline. Untreated, though, saltwater isn’t of much direct use to humans, since we, our domestic animals, and pretty much all our crops thirst only for water a hundred times less saline than seawater.

While nature solved the problem of desalination a long time ago, the natural water cycle turns seawater into freshwater at too slow a pace or in the wrong locations for our needs. While there are simple methods for getting the salt out of seawater, such as distillation, processing seawater on a scale that can provide even a medium-sized city with a steady source of potable water is definitely a job for Big Chemistry.

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Slim Tactile Switches Save Classic TI Calculator With A Bad Keypad

September 10, 2024 by Dan Maloney 16 Comments

For vintage calculator fans, nothing strikes more fear than knowing that someday their precious and irreplaceable daily driver will become a museum piece to be looked at and admired — but never touched again. More often than not, the failure mode will be the keypad.

In an effort to recover from the inevitable, at least for 70s vintage TI calculators, [George] has come up with these nice replacement keypad PCBs. The original membrane switches on these calculators have a limited life, but luckily there are ultra-slim SMD tactile switches these days make a dandy substitute. [George] specifies a 0.8 mm thick switch that when mounted on a 1.6 mm thick PCB comes in just a hair over the original keypad’s 2.2 mm thickness. He has layouts for a TI-45, which should also fit a TI-30, and one for the larger keypads on TI-58s and TI-59s.

While these particular calculators might not in your collection, [George]’s goal is to create an open source collection of replacement keypads for all the vintage calculators sitting in desk drawers out there. And not just keypads, but battery packs, too.

Wiggling Screen And DLP Power This Volumetric POV Display

July 1, 2021 by Dan Maloney 25 Comments

It seems like the world is ready for a true 3D display. We’ve seen them in sci-fi for decades now, with the ability to view a scene from any angle and inspect it up close. They’ve remained elusive, but that might just be changing thanks to this open-source persistence-of-vision volumetric display.

If the VVD, as it has been named by its creator [Madaeon], looks somewhat familiar, perhaps it’s because editor-in-chief [Mike Szczys] ran into it back in 2019 at Maker Faire Rome. It looks like it has progressed quite a bit since then, but the basic idea is still the same. A thin, flexible membrane, which is stretched across a frame, is attached to articulated arms. The membrane can move up and down rapidly, fast enough that a 1,000-fps high-speed camera is needed to see it move. That allows you to see the magic in action; a digital light processor (DLP) module projects slices of a 3D image onto the sheet, sending the correct image out for each vertical position of the membrane. Carefully coordinating the images creates the POV illusion of a solid image floating in space, which can be observed from any angle, requires no special glasses, and can even be viewed by groups.

With displays like this, we’re used to issuing the caveat that “it no doubt looks better in person”, but we have to say in the GIFs and videos included the VVD looks pretty darn good. We think this is a natural for inclusion in the 2021 Hackaday Prize, and we’re pleased to see that it made it to the semi-finals of the “Rethink Displays” round.

Need A Small Keyboard? Build Your Own!

April 23, 2019 by Brian Benchoff 72 Comments

If you want keyboards, we can get you keyboards. If you want a small keyboard, you might be out of luck. Unless you’re hacking Blackberry keyboards or futzing around with tiny tact switches, there’s no good solution to small, thin, customization keyboards. There’s one option though: silicone keyboards. No one’s done it yet, so I figured I might as well.

Unfortunately, there is no readily available information on the design, construction, or manufacture of custom silicone keypads. There is a little documentation out there, but every factory that does this seems to have copy and pasted the information from each other. Asking a company in China about how to do it is a game of Chinese Whispers. Despite this, I managed to build a custom silicone keypad, and now I’m sharing this information on how to do it with you.

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Resistance In Motion: What You Should Know About Variable Resistors

September 16, 2016 by Steven Dufresne 42 Comments

Adjusting the volume dial on a sound system, sensing your finger position on a touch screen, and knowing when someone’s in the car are just a few examples of where you encounter variable resistors in everyday life. The ability to change resistance means the ability to interact, and that’s why variable resistance devices are found in so many things.

The principles are the same, but there are so many ways to split a volt. Let’s take a look at what goes into rotary pots, rheostats, membrane potentiometers, resistive touchscreens, force sensitive resistors, as well as flex and stretch sensors.

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Arduino Synth Guitar Really Rocks

February 25, 2015 by Rick Osgood 18 Comments

[Gr4yhound] has been rocking out on his recently completed synth guitar. The guitar was built mostly from scratch using an Arduino, some harvested drum pads, and some ribbon potentiometers. The video below shows that not only does it sound good, but [Gr4yhound] obviously knows how to play it.

The physical portion of the build consists of two main components. The body of the guitar is made from a chunk of pine that was routed out by [Gr4yhound’s] own home-made CNC. Three circles were routed out to make room for the harvested Yamaha drum pads, some wiring, and a joystick shield. The other main component is the guitar neck. This was actually a Squire Affinity Strat neck with the frets removed.

For the electronics, [Gr4yhound] has released a series of schematics on Imgur. Three SoftPot membrane potentiometers were added to the neck to simulate strings. This setup allows [Gr4yhound] to adjust the finger position after the note has already been started. This results in a sliding sound that you can’t easily emulate on a keyboard. The three drum pads act as touch sensors for each of the three strings. [Gr4yhound] is able to play each string simultaneously, forming harmonies.

The joystick shield allows [Gr4yhound] to add additional effects to the overall sound. In one of his demo videos you can see him using the joystick to add an effect. An Arduino Micro acts as the primary controller and transmits the musical notes as MIDI commands. [Gr4yhound] is using a commercial MIDI to USB converter in order to play the music on a computer. The converter also allows him to power the Arduino via USB, eliminating the need for batteries.

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