Hackaday Prize Entry: 8-Bit Arduino Audio for Squares

A stock Arduino isn’t really known for its hi-fi audio generating abilities. For “serious” audio like sample playback, people usually add a shield with hardware to do the heavy lifting. Short of that, many projects limit themselves to constant-volume square waves, which is musically uninspiring, but it’s easy.

[Connor]’s volume-control scheme for the Arduino bridges the gap. He starts off with the tone library that makes those boring square waves, and adds dynamic volume control. The difference is easy to hear: in nature almost no sounds start and end instantaneously. Hit a gong and it rings, all the while getting quieter. That’s what [Connor]’s code lets you do with your Arduino and very little extra work on your part.

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Quickie USB Keyboard Device

There are a ton of applications that we use that can benefit from keyboard shortcuts, and we use ’em religiously. Indeed, there are some tasks that we do so often that they warrant their own physical button. And the only thing cooler than custom keyboards are custom keyboards that you’ve made yourself.

Which brings us to [Dan]’s four-button Cherry MX USB keypad. It’s not really all that much more than four keyswitch footprints and an AVR ATmega32u4, but that plus some software is all you really need. He programs the Arduino bootloader into the chip, and then he’s using the Arduino Leonardo keyboard libraries. Bam! Check out the video below.

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540 LEDs On A Geodesic Sphere

[burgerga] loves attending Music Festivals. He’s also a MechE who loves his LED’s. He figured he needed to put it all together and do something insane, so he build a huge, 15″ geodesic sphere containing 540 WS2812B addressable LED’s. He calls it the SOL CRUSHER. It sips 150W when all LED’s are at full intensity, making it very, very, bright.

As with most WS2812B based projects, this one too is fairly straightforward, electrically. It’s controlled by four Teensy 3.2 boards mounted on Octo WS2811 adapter boards. Four 10,000 mAh 22.2V LiPo batteries provide power, which is routed through a 5V, 30Amp heatsinked DC-DC converter. To protect his LiPo batteries from over discharge, he built four voltage monitoring modules. Each had a TC54 voltage detector and an N-channel MOSFET which switches off the LiPo before its voltage dips below 3V. He bundled in a fuse and an indicator, and put each one in a neat 3D printed enclosure.

The mechanical design is pretty polished. Each of the 180 basic modules is a triangular PCB with three WS2812B’s, filter capacitors, and heavy copper pours for power connections. The PCB’s are assembled in panels of six and five units each, which are then put together in two hemispheres to form the whole sphere. His first round of six prototypes set him back as he made a mistake in the LED footprint. But it still let him check out the assembly and power connections. For mechanical support, he designed an internal skeleton that could be 3D printed. There’s a mounting frame for each of the PCB panels and a two piece central sphere. Fibreglass rods connect the central sphere to each of the PCB panels. This lets the whole assembly be split in to two halves easily.

It took him over six months and lots of cash to complete the project. But the assembly is all done now and electrically tested. Next up, he’s working on software to add animations. He’s received suggestions to add sensors such as microphones and accelerometers via comments on Reddit. If you’d like to help him by contributing animation suggestions, he’s setup a Readme document on Dropbox, and a Submission form. Checkout the SolCrusher website for more information.

Thanks [Vinny Cordeiro], for letting us know about this build.

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Hackaday Prize Entry: The Green Machine

For Hackers, rapid prototyping is made easier using basic building blocks such as the Raspberry Pi, Arduino and the huge variety of add on shields for home brew projects. But we don’t see too many real world Industrial applications or machines built using these off-the-shelf electronics. [SlyScience] built The Green Machine – an industrial grade, automated spray painting device to help coat polycarbonate tubes consistently.

The Green Machine is essentially a linear drive that can move a spray gun across a spinning clear tube and coat it evenly with the desired color. These tubes are used as color filters – they slide over standard T5, T8 or T12 fluorescent lamps – and are used in advertising, special effects, films and similar applications. For almost 10 years prior to this machine, the task was done manually. The HPLV (high pressure, low volume) spray gun used for this process needed skilled hands to get consistent results. It was easy to ruin a tube and cleaning them was not possible. [SlyScience] figured things out on the go – teaching himself and figuring out all of the software and hardware pieces of the puzzle. The welded steel frame is about the only “custom” part in this build. Everything else is COTS. Check out the video of The Green Machine in action below, and if you have any tips to help improve the build, chime in with your comments.

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Multipurpose Robot For the Masses

As the cost of almost every technology comes falling down, from electronics to batteries to even tools like 3D printers, the cost to build things formerly out of reach of most of us becomes suddenly very affordable. At least, that’s what [John Choi] has found by building a completely DIY general purpose robot for around $2000.

OK, so $2000 isn’t exactly “cheap” but considering that something comparable (like Baxter) costs north of what a new car would cost means that [John] has dropped the price for a general-purpose robot by an order of magnitude. And this robot doesn’t skimp on features, either. It has a platform that allows it to navigate rooms, two manipulating limbs with plenty of servos, a laptop “head” that allows for easy interface, testing, and programming, and an Arduino Mega that allows it to interface with any sensors or other hardware with ease. It’s also modular so it can be repaired and transported easily, and it uses open source software and open hardware so it’s easy to build on.

This robot is an impressive piece of work that should help bring this technology to more than just high-end factories and research labs. They’ve already demonstrated the robot watering plants, playing the piano, picking things up, and many other tasks. We’d say that they’re well on their way to their goal of increasing the number of students and hobbyists who have access to this technology. If the $2k price tag is still too steep, though, there are other ways of getting into robotics without diving headfirst into a Baxter-like robot.

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FR4 Machine Shield Is A CNC Milling Machine From FR4 PCB

The people behind the PocketNC heard you like CNC PCB mills, so they milled you a PCB mill out of PCB. They announced their surprising new open source hardware product, a pocket sized 3-axis CNC machine entirely made out of FR4 PCB material, aptly named “FR4 Machine Shield”, at this year’s Bay Area Maker Faire.

UPDATE: The FR4 Machine Shield is now on Kickstarter

fr4_thumbWe know the concept from quadcopters, little robots, and generally things that are small enough to make use of their PCBs as a structural component. But an entire CNC machine, soldered together from a few dozen PCBs certainly takes it to the next level.

There is no doubt that 2mm thick fiber reinforced epoxy can be surprisingly rigid, although the Achilles heel of this method might be the solder joints. However, it looks like all load bearing, mechanical connections of the machine are supported by tightly interlocking “dovetail” finger-joints, which may help protecting all the solder connections from the strain hardening effects of continuous stress and spindle vibrations.

As you might expect, most of the wiring is embedded into the FR4 frame construction, and to squeeze the maximum value out of the PCB material, the motor driver boards interface via card edge connectors with the (currently Arduino based) controller board. In addition to the milling head, which features a brushless DC motor and a tool coupler, the team wants to develop heads for circuit printing, microscopy, pneumatic pick and place, hot air reflow, and 3D printing.

With all those cost-driven design choices, from the one-step manufacturing process of the frame and wiring to the dismissal of screws and nuts from the frame assembly, the “FR4 Machine Shield” could indeed become one of the cheapest CNC machine kits on the market. The team targets an introduction price of $400 during a Kickstarter campaign in June 2016. Can they deliver? [Gerrit] checked Pocket NC out at the Faire and ended up raving about how they run their business.

Enjoy their teaser video below!

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How Does a Buck Converter Work Anyway?

[Great Scott] should win an award for quickest explanation of a buck converter. Clocking in at five and a half minutes, the video clearly shows the operating principles behind the device.

It starts off with the question, what should you do if you want to drop a voltage? Many of us know that we can dim and brighten an LED using the PWM on an Arduino, but a closer inspection with an oscilloscope still shows 5V peaks that would be dangerous to a 3.3V circuit. He then adds an inductor and diode, this keeps the current from dropping too fast, but the PWM just isn’t switching fast enough to keep the coil energized.

A small modification to the Arduino’s code, and the PWM frequency is now in the kHz range. The voltage looks pretty good on the oscilloscope, but a filter cap gets it to look nice and smooth. Lastly, he shows how when the load changes the voltage out looks different. To fix this a voltage divider feeds back the information to the Arduino, letting it change the PWM duty to match the load.

In the last minute of the video he shows how to hook up off-the-shelf switching regulators, whose support components are now completely demystified as the basic principles are understood. Video after the break.

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