[Joe Grand’s] Toothbrush Plays Music That Doesn’t Suck

March 27, 2017 by 40 Comments

It’s not too exciting that [Joe Grand] has a toothbrush that plays music inside your head. That’s actually a trick that the manufacturer pulled off. It’s that [Joe] gave his toothbrush an SD card slot for music that doesn’t suck.

The victim donor hardware for this project is a toothbrush meant for kids called Tooth Tunes. They’ve been around for years, but unless you’re a kid (or a parent of one) you’ve never heard of them. That’s because they generally play the saccharine sounds of Hannah Montana and the Jonas Brothers which make adults choose cavities over dental health. However, we’re inclined to brush the enamel right off of our teeth if we can listen to The Amp Hour, Embedded FM, or the Spark Gap while doing so. Yes, we’re advocating for a bone-conducting, podcasting toothbrush.

[Joe’s] hack starts by cracking open the neck of the brush to cut the wires going to a transducer behind the brushes (his first attempt is ugly but the final process is clean and minimal). This allows him to pull out the guts from the sealed battery compartment in the handle. In true [Grand] fashion he rolled a replacement PCB that fits in the original footprint, adding an SD card and replacing the original microcontroller with an ATtiny85. He goes the extra mile of making this hack a polished work by also designing in an On/Off controller (MAX16054) which delivers the tiny standby current needed to prevent the batteries from going flat in the medicine cabinet.

Check out his video showcasing the hack below. You don’t get an audio demo because you have to press the thing against the bones in your skull to hear it. The OEM meant for this to press against your teeth, but now we want to play with them for our own hacks. Baseball cap headphones via bone conduction? Maybe.

Update: [Joe] wrote in to tell us he published a demonstration of the audio. It uses a metal box as a sounding chamber in place of the bones in our head.

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Getting Sparks From Water With Lord Kelvin’s Thunderstorm

March 27, 2017 by 47 Comments

In the comments to our recent article about Wimshurst machines, we saw that some hackers had never heard of them, reminding us that we all have different backgrounds and much to share. Well here’s one I’m guessing even fewer will have heard of. It’s never even shown up in a single Hackaday article, something that was also pointed out in a comment to that Wimshurst article. It is the Lord Kelvin’s Water Dropper aka Lord Kelvin’s Thunderstorm, invented in the 1860s by William Thomson, 1st Baron Kelvin, the same fellow for whom the Kelvin temperature scale is named.  It’s a device that produces a high voltage and sparks from falling drops of water.

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MRRF 17: A Working MakerBot Cupcake

March 27, 2017 by 27 Comments

The Midwest RepRap Festival is the best place to go if you want to see the latest in desktop 3D printing. This weekend, we saw full-color 3D printers, a printer with an infinite build volume, new extruders, a fantastic development in the pursuit of Open Source filament, and a whole bunch of D-bots. If you want the bleeding edge in 3D printing, you’re going to Goshen, Indiana.

Of course, it wasn’t always like this. In 2009, MakerBot released the Cupcake, a tiny printer that ushered in the era of democratized 3D printing. The Cupcake was a primitive machine, but it existed, it was open source, and it was cheap – under $500 if you bought it at the right time. This was the printer that brought customized plastic parts to the masses, and even today no hackerspace is complete without an unused Cupcake or Thing-O-Matic sitting in the corner.

The MakerBot Cupcake has not aged well. This should be expected for a technology that is advancing as quickly as 3D printing, but today it’s rare to see a working first generation MakerBot. Not only was the Cupcake limited by the technology available to hackers in 2009, there are some pretty poor design choices in these printers. There’s a reason that old plywood MakerBot in your hackerspace isn’t used anymore – it’s probably broken.

This year at MRRF, [Ryan Branch] of River City Labs brought out his space’s MakerBot Cupcake, serial number 1515 of 2,625 total Cupcakes ever made. He got his Cupcake to print a test cube. If you’re at all familiar with the Cupcake, yes, this is a hack. It’s a miracle these things ever worked in the first place.

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Low Background Steel — So Hot Right Now

March 27, 2017 by 75 Comments

The nuclear age changed steel, and for decades we had to pay the price for it. The first tests of the atomic bomb were a milestone in many ways, and have left a mark in history and in the surface of the Earth. The level of background radiation in the air increased, and this had an effect on the production of steel, so that steel produced since 1945 has had elevated levels of radioactivity. This can be a problem for sensitive instruments, so there was a demand for steel called low background steel, which was made before the trinity tests.

The Bessemer process pumps air through the iron to remove impurities. shropshirehistory.com

The production of steel is done with the Bessemer process, which takes the molten pig iron and blasts air through it. By pumping air through the steel, the oxygen reacts with impurities and oxidizes, and the impurities are drawn out either as gas or slag, which is then skimmed off. The problem is that the atmospheric air has radioactive impurities of its own, which are deposited into the steel, yielding a slightly radioactive material. Since the late 1960s steel production uses a slightly modified technique called the BOS, or Basic Oxygen Steelmaking, in which pure oxygen is pumped through the iron. This is better, but radioactive material can still slip through. In particular, we’re interested in cobalt, which dissolves very easily in steel, so it isn’t as affected by the Bessemer or BOS methods. Sometimes cobalt is intentionally added to steel, though not the radioactive isotope, and only for very specialized purposes.

Recycling is another reason that modern steel stays radioactive. We’ve been great about recycling steel, but the downside is that some of those impurities stick around.

Why Do We Need Low Background Steel?

Imagine you have a sensor that needs to be extremely sensitive to low levels of radiation. This could be Geiger counters, medical devices, or vehicles destined for space exploration. If they have a container that is slightly radioactive it creates an unacceptable noise floor. That’s where Low Background Steel comes in.

A person is placed into a low background steel container with sensitive equipment to measure the radioactivity of the body, which may be near the background level. Photo from orau.org

So where do you get steel, which is a man-made material, that was made before 1945? Primarily from the ocean, in sunken ships from WWII. They weren’t exposed to the atomic age air when they were made, and haven’t been recycled and mixed with newer radioactive steel. We literally cut the ships apart underwater, scrape off the barnacles, and reuse the steel.

Fortunately, this is a problem that’s going away on its own, so the headline is really only appropriate as a great reference to a popular movie. After 1975, testing moved underground, reducing, but not eliminating, the amount of radiation pumped into the air. Since various treaties ending the testing of nuclear weapons, and thanks to the short half-life of some of the radioactive isotopes, the background radiation in the air has been decreasing. Cobalt-60 has a half-life of 5.26 years, which means that steel is getting less and less radioactive on its own (Cobalt-60 from 1945 would now be at .008% of original levels). The newer BOS technique exposes the steel to fewer impurities from the air, too. Eventually the need for special low background steel will be just a memory.

Oddly enough, steel isn’t the only thing that we’ve dragged from the bottom of the ocean. Ancient Roman lead has also had a part in modern sensing.

Explaining The Operation Of The 74181 ALU

March 27, 2017 by 18 Comments

You will all no doubt be familiar with the 74 series logic integrated circuits, they provide the glue logic for countless projects. If you look back through old listings of the series you’ll find alongside the familiar simple gates a host of now obsolete chips that reveal their roots in the pre-microprocessor computer industry of the late 1960s, implementing entire functions that would now be integrated.

One of the more famous of these devices is the 74181, a cascadable 4-bit arithmetic logic unit, or ALU. An ALU is the heart of a microprocessor, performing its operations. The 74181 appeared in many late-60s and early-70s minicomputers, will be familiar to generations of EE and CS students as the device they were taught about ALUs on, and can now be found in some home-built retrocomputers.

[Ken Shirriff], doyen of the integrated circuit teardown, has published a piece taking a look at the 74181, in particular at its logic functions and the reason for some of them that are rather surprising. As well as the normal logic functions, for example the chip can do “(A + B) PLUS AB“. Why on earth you might think would an ALU need to do that?

The answer lies in the way it performs carrying while adding, a significant speed-up can be achieved over ripple carrying along a chain of adders if it can be ascertained whether a bit addition might generate a carry bit. He explains the function required to perform this operation, and suddenly the unusual extra function makes sense. Addition is transformed from a serial process to a parallel one, with a consequent speed increase.

It’s one of those moments in which you have to salute those logic designers from an era when on-chip real-estate was costly and every ounce of speed had to be teased from their designs. Give it a read, and have a go at the interactive 74181 simulator further down [Ken]’s page. We learned something from the article, and so may you.

We brought you the first part of [Ken]’s 74181 investigations earlier in the year. If you would like to see a 74181 in action, take a look at this 4-bit 74 logic single board computer.

Boost Converter Functionality At Rock-Bottom Prices

March 27, 2017 by 16 Comments

Linear voltage regulators are pretty easy to throw into a project if something in it needs a specific voltage that’s lower than the supply. If it needs a higher voltage, it’s almost just as easy to grab a boost converter of some sort to satisfy the power requirements. But if you’re on a mission to save some money for a large production run, or you just like the challenge of building something as simply as possible, there are ways of getting voltages greater than the supply voltage without using anything as non-minimalistic as a boost converter. [Josh] shows us exactly how this can be done using a circuit known as a charge pump to drive a blue LED.

One of the cool things about AVR microcontrollers is that they can run easily on a coin cell battery and source enough current to drive LEDs directly from the output pins. Obviously enough, if the LED voltage is greater than the voltage of the power supply, this won’t work. That is, unless you have a spare diode and capacitor around to build a charge pump.

The negative charge pump works by charging up a capacitor that is connected to an AVR pin, with the other side between the LED and a garden-variety diode to ground. That results in a roughly (VCC – 0.7) volt difference across the capacitor’s plates. When the AVR pin goes low, the other side of the capacitor goes negative by this same amount, and this makes the voltage across the LED high enough to light up. Not only is this simpler than a boost converter, but it doesn’t need any bulky inductors to work properly.

Will this work for any load? Am I going to start any fires by overdriving the LED? Luckily, [josh] answers all of these questions and more on the project page, and goes into some detail on the circuit theory as well. Granted, the charge pump doesn’t have the fine control over the power supply that you can get out of a buck or boost converter (or any switch-mode power supply). But it does have good bang-for-the-buck.

MRRF 17: Laser Resin Printers

March 26, 2017 by 19 Comments

The Midwest RepRap Festival is the best 3D printer con on the planet. In the middle of Indiana, you’ll find the latest advances for CNC hot glue guns and the processes that make squirting filament machines better, more accurate, and more efficient. There’s more to 3D printing than just filament-based machines, though, and for the last few MRRFs we’ve been taking a look at resin-based machines.

While most of the current crop of resin printers use either DLP projectors or LCDs and a big, bright backlight [Mark Peng]’s Moai printer uses a 150 mW laser diode and galvos. This is somewhat rare in the world of desktop 3D printers, thanks in no small part to the ugliness between Formlabs and 3D Systems. Still, it’s a printer that looks fantastic and produces prints that are far beyond what’s possible with a filament-based machine.

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