Automatic guitar tuning robot

Handheld Bot Takes The Tedium Out Of Guitar Tuning

Even with fancy smartphone apps and custom-built tuners, tuning a guitar can be a tedious process, especially for the beginner. Pluck a string, figure out if the note is sharp or flat, tighten or loosen accordingly, repeat. Then do the same thing for all six strings. It’s no wonder some people never get very far with the guitar.

Luckily, technology can come to the rescue in the form of this handy open-source automatic guitar tuner by [Guyrandy Jean-Gilles]. The tuner has a Raspberry Pi Pico inside, with a microphone attached to the ADC. The program running on the Pico listens for the sound of a plucked string and determines whether the note is sharp or flat. The Pico then drives a small DC gear motor in the appropriate direction, which turns the peg the right way to bring the string into tune. The tuner makes ample use of 3D-printed parts, STLs for which are included in the project repo. [Guyrandy] has also made some updates to the project to make the tuner a little easier to use.

While there’s an affordable commercial version of this — upon which [Guyrandy] based his design — we really like the fact that he rolled his own here, and made the design freely accessible to everyone. We also like the idea that guitarists who can’t use tuners requiring visual feedback can use this, too — just like this one.

[via r/raspberry_pi]

Open-Source Grinder Makes Compression Screws For Plastic Extruders Easy

In a world that’s literally awash in plastic waste, it seems a pity to have to buy fresh rolls of plastic filament to feed our 3D-printers, only to have them generate yet more plastic waste. Breaking that vicious cycle requires melding plastic recycling with additive manufacturing, and that takes some clever tooling with parts that aren’t easy to come by, like the compression screws that power plastics extruders.

This open-source compression screw grinder aims to make small-scale plastic recyclers easier to build. Coming from the lab of [Joshua Pearce] at the Michigan Technological University in collaboration with [Jacob Franz], the device is sort of a combination of a small lathe and a grinder. A piece of round steel stock is held by a chuck with the free end supported by bearings in a tailstock. On the bed of the machine is an X-Y carriage made of 3D-printed parts and pieces of electrical conduit. The carriage moves down the length of the bed as the stock rotates thanks to a pulley and a threaded rod, carrying a cordless angle grinder with a thick grinding wheel. A template attached to the front apron controls how deep the grinder cuts as it tracks along the rod; different templates allow the screw profile to be easily customized. The video below shows the machine in action and the complicated screw profiles it’s capable of producing.

We’ve seen lots of homebrew plastic extruders before, most of which use repurposed auger-type drill bits as compression screws. Those lack the variable geometry of a proper compression screw, so [Joshua] and [Jacob] making all the design documents for this machine available should be a boon to recycling experimenters.

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Unconventional Drone Uses Gas Thrusters For Control

You’ve got to hand it to [Tom Stanton] – he really thinks outside the box. And potentially outside the atmosphere, to wit: we present his reaction control gas thruster-controlled drone.

Before anyone gets too excited, [Tom] isn’t building drones for use in a vacuum, although we can certainly see a use case for such devices. This is more of a hybrid affair, with counter-rotating props mounted in a centrally located duct providing the lift and the yaw control. Flanking that is a triangular frame supporting three two-liter soda bottle air reservoirs, each of which supplies a down-firing nozzle at each apex of the triangle. Solenoid valves control the flow of compressed air from the bottles to the nozzles, providing thrust to stabilize the roll and pitch axes. As there aren’t many off-the-shelf flight control systems set up for reaction control, [Tom] had to improvise thruster control; an Arduino watches the throttle signals normally sent to a drone’s motors and fires the solenoids when they get to a preset threshold. It took some tuning, but [Tom] was eventually able to get a stable, untethered hover. And he’s right – the RCS jets do sound amazing when they’re firing, as long as the main motors are off.

This looks as though it has a lot of potential, and we’d love to see it developed more. It reminds us a bit of this ducted-prop drone, another great example of stretching conventional drone control concepts to the limit.

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Benchtop Lathe Gets An Electronic Leadscrew Makeover

The king of machine tools is the lathe, and if the king has a heart, it’s probably the leadscrew. That’s the bit that allows threading operations, arguably the most important job a lathe can tackle. It’s a simple concept, really – the leadscrew is mechanically linked through gears to the spindle so that the cutting tool moves along the long axis of the workpiece as it rotates, allowing it to cut threads of the desired pitch.

But what’s simple in concept can be complicated in reality. As [Clough42] points out, most lathes couple the lead screw to the spindle drive through a complex series of gears that need to be swapped in and out to accommodate different thread pitches, and makes going from imperial to metric a whole ball of wax by itself. So he set about building an electronic leadscrew for his lathe. The idea is to forgo the gear train and drive the leadscrew directly with a high-quality stepper motor. That sounds easy enough, but bear in mind that the translation of the tool needs to be perfectly synchronized with the rotation of the spindle to make threading possible. That will be accomplished with an industrial-grade quadrature encoder coupled to the spindle, which will tell software running on a TI LaunchPad how fast to turn the stepper – and in which direction, to control thread handedness. The video below has some great detail on real-time operating systems on microcontrollers as well as tests on all the hardware to be used.

This is only a proof of concept at this point, but we’re looking forward to the rest of this series. In the meantime, [Quinn Dunki]’s excellent series on choosing a lathe should keep you going.

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Reaction Wheels Almost Control This Unusual Drone

When you think about all the forces that have to be balanced to keep a drone stable, it’s a wonder that the contraptions stay in the air at all. And when the only option for producing those forces is blowing around more or less air it’s natural to start looking for other, perhaps better ways to achieve flight control.

Taking a cue from the spacecraft industry, [Tom Stanton] decided to explore reaction wheels for controlling drones. The idea is simple – put a pair of relatively massive motorized wheels at right angles to each other on a drone, and use the forces they produce when they accelerate to control the drone’s pitch and roll. [Tom]’s video below gives a long and clear explanation of the physics involved before getting to the build, which results in an ungainly craft a little reminiscent of a lunar lander. The drone actually manages a few short, somewhat stable flights, but in general the reaction wheels don’t seem to be up to the task. [Tom] chalks this up to the fact that he’s using the current draw of each reaction wheel motor as a measure of its torque, which is not exactly correct for all situations. He suggests that motors with encoders might do a better job, but by the end of the video the little drone isn’t exactly in shape for continued experimentation.

Of course, dodgy reaction wheels don’t only cause problems with drones. They can also be a problem for spacecraft when the Sun gets fussy too.

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Microcontroller And IMU Team Up For Simple Flight Sim Controls

Classes are over at Cornell, and that means one thing: the students in [Bruce Land]’s microcontroller design course have submitted their final projects, many of which, like this flight control system for Google Earth’s flight simulator, find their way to the Hackaday tips line.

We actually got this tip several days ago, but since it revealed to us the previously unknown fact that Google Earth has a flight simulator mode, we’ve been somewhat distracted. Normally controlled by mouse and keyboard, [Sheila Balu] decided to give the sim a full set of flight controls to make it more realistic. The controls consist of a joystick with throttle, rudder pedals, and a small control panel with random switches. The whole thing is built of cardboard to keep costs down and to make the system easy to replicate. Interestingly, the joystick does not have the usual gimbals-mounted potentiometers to detect pitch and roll; rather, an IMU mounted on the top of the stick provides data on the stick position. All the controls talk to a PIC32, which sends the inputs over a serial cable to a Python script on the PC running Google Earth; the script simulates the mouse and keyboard commands needed to fly the sim. The video below shows [Sheila] taking an F-16 out for a spin, but despite being a pilot herself since age 16, she was curiously unable to land the fighter jet safely in a suburban neighborhood.

[Bruce]’s course looks like a blast, and [Sheila] clearly enjoyed it. We’re looking forward to the project dump, which last year included this billy-goat balancing Stewart platform, and a robotic ice cream topping applicator.

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Ask Hackaday: How Do You DIY A Top-Octave Generator?

One of the great joys of Hackaday are the truly oddball requests that we sometimes get over the tip line. Case in point: [DC Darsen] wrote in with a busted 1970s organ in need of a new top-octave generator, and wondered if we could help. He had found a complicated but promising circuit online, and was wondering if there was anything simpler. I replied “I should be able to get that done with a single Arduino” and proceeded to prove myself entirely wrong in short order.

So we’re passing the buck on to you, dear Hackaday reader. Can you help [DC Darsen] repair his organ with a minimum amount of expenditure and hassle? All we need to do is produce twelve, or maybe thirteen, differently pitched square waves simultaneously.

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