[Clare] isn’t the most musically inclined person, but she can strum a guitar. Thanks to a little help from an Arduino, she doesn’t even have to do that.

She built the strumbot, which handles the strumming hand duties of playing the guitar. While [Claire] does believe in her strumbot, she didn’t want to drill holes in her guitar, so hot glue and double-sided foam tape were the order of the day.

The business end of the strumbot is a micro servo. The servo moves two chopsticks and draws the pick across the strings. The tiny servo surprisingly does a great job getting the strings ringing. The only downside is the noise from the plastic gears when it’s really rocking out.

Strumbot’s user interface is a 3D-printed case with three buttons and three LEDs. Each button activates a different strum pattern in the Arduino’s programming. The LEDs indicate the currently active pattern. Everything is powered by a USB power pack, making this a self-contained hack.

[Clare] was able to code up some complex strum patterns, but the strumbot is still a bit limited in that it only holds three patterns. It’s good enough for her rendition of “Call Me Maybe”, which you can see in the video after the break. Sure, this is a simple project, not nearly as complex as some of the robotic guitar mods we’ve seen in the past. Still, it’s just the ticket for a fun evening or weekend project – especially if you’re introducing the Arduino to young coders. Music, hacking, and modding – what more could you ask for?

In order to get a good cut with a CNC router, the cutting tool speed needs to be properly set. Since his CNC didn’t come with RPM feedback, Troy Barbour came up with his own solution using an Arduino Nano along with an IR emitter/sensor pair.

The spindle was set up with a single reflective surface, enabling it to sense one pulse per revolution that is sent to the Arduino at up to up to 30,000 RPM. To ensure accurate measurement, the device was programmed using an interrupt, meaning that if another process is running, it will temporarily drop what it’s doing and count the incoming pulse.

RPM is displayed on a tiny OLED screen, which shows both an RPM number as well as a dial indicator for quick reference.

Build an optical RPM indicator for your CNC router with an Arduino Nano, an IR LED/IR photodiode sensor and an OLED display for less than $30. I was inspired by eletro18’s Measure RPM – Optical Tachometer Instructable and wanted to add a tachometer to my CNC router. I simplified the sensor circuit, designed a custom 3D-printed bracket for my Sienci CNC router. Then I wrote an Arduino sketch to display both a digital and analog dial on an OLED display.

You can see it in action below, and find build instructions and code on Barbour’s write-up.

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While largely supplanted by more modern forms of printing, dot matrix printers still have their fans. Few, however, are more dedicated than Nikodem Bartnik, who constructed his own model that pulls paper up to 55cm wide and as long as he needs under a gantry that stamps each pixel with a marker.

The device is controlled via an Arduino Uno, which takes input from a Processing sketch running on a computer to obtain the image to be printed.

It uses a pair of stepper motors to advance the paper, as well as a third to position the marker to be stamped. A servo motor pushes the marker down as needed, producing a print that, as seen at 5:15 in the video below, is accurate and stylishly pixellated.

While some fall asleep nearly immediately with no assistance, others need the drone of a fan or a dedicated noisemaker to help them relax. The Fall Asleep Device, also known as “FADing,” by Youz takes a different approach. FADing shines an LED onto the ceiling out via a piece of acrylic, so that you can use it whether you like to sleep on your back or side.

An Arduino Nano controls the nicely-shaped wooden unit, and causes light to fade in and out at a pace that decreases from 11 to 6 pulses per minute, prompting you to regulate and relax your breathing accordingly.

After being started by a button below, FADing is kept on by a relay until it finishes, meaning it uses no power in standby. You can check it out in the video below, and find build instructions and code in Youz’s write-up.

With CNC machines, getting the best results depends on knowing how fast your tool is moving relative to the workpiece. But entry-level CNC routers don’t often include a spindle tachometer, forcing the operator to basically guess at the speed. This DIY optical spindle tach aims to fix that, and has a few nice construction tips to boot.

The CNC router in question is the popular Sienci, and the 3D-printed brackets for the photodiode and LED are somewhat specific for that machine. But [tmbarbour] has included STL files in his exhaustively detailed write-up, so modifying them to fit another machine should be easy. The sensor hangs down just far enough to watch a reflector on one of the flats of the collet nut; we’d worry about the reflector surviving tool changes, but it’s just a piece of shiny tape that’s easily replaced.  The sensor feeds into a DIO pin on a Nano, and a small OLED display shows a digital readout along with an analog gauge. The display update speed is decent — not too laggy. Impressive build overall, and we like the idea of using a piece of PLA filament as a rivet to hold the diodes into the sensor arm.

Want to measure machine speed but don’t have a 3D printer? No worries — a 2D-printed color-shifting tach can work too.

When you play a video game, the controls are normally a compromise between what you have available (a keyboard/mouse) and the actions you’re trying to convey. This, however, wasn’t good enough for Kerbal Space Program enthusiast Hugopeeters, who instead of accepting this limited input method, designed a new control panel using an Arduino Uno as its heart.

Notable features of his build include dual joysticks, a throttle slider, a multi-purpose LCD display, LED bars for fuel gauges, and a beautifully laser-cut enclosure.

Want to construct your own? Find more details on the project in Hugopeeters’ write-up, as well as the Arduino code he used and the KSP plugin necessary to interact with his new hardware.

While video games have grown more and more complex over the last few decades, TWANG takes things in the opposite direction as an Arduino Mega-based 1D dungeon crawler consisting of an RGB LED strip.

The player—a dot—is controlled via an accelerometer mounted to a door spring used as a joystick. With it, the player can move forwards, backwards, and attack by “twanging” the spring to make it vibrate. The LEDs display a wide array of colors, including representations of glowing lava, water, and player disintegration when a mistake is made.

TWANG is inspired by the Line Wobbler game from Robin Baumgarten, and beautifully implemented as shown in the video below by Barton Dring. Code for the build can be found here, and 3D print files for the housing/joystick are also available.

A delightful version of a clever one-dimensional game has been made by [Critters] which he calls TWANG! because the joystick is made from a spring doorstop with an accelerometer in the tip. The game itself is played out on an RGB LED strip. As a result, the game world, the player, goal, and enemies are all represented on a single line of LEDs.

How can a dungeon crawler game be represented in 1D, and how is this unusual game played? The goal is for the player (a green dot) to reach the goal (a blue dot) to advance to the next level. Making this more difficult are enemies (red dots) which move in different ways. The joystick is moved left or right to advance the player’s blue dot left or right, and the player can attack with a “twang” motion of the joystick, which eliminates nearby enemies. By playing with brightness and color, a surprising amount of gameplay can be jammed into a one-dimensional display!

Code for TWANG! is on github and models for 3D printing the physical pieces are on Thingiverse. The video (embedded below) focuses mainly on the development process, but does have the gameplay elements explained as well and demonstrates some slick animations and sharp feedback.

Using a spring doorstop as a controller is neat as heck as well as intuitive, but possibly not quite as intuitive as using an actual car as a video game controller.

Infinity mirrors, which make light appear to stretch to infinity by bouncing light between two mirrors, are incredible to observe. Hacker “Evocate” decided to go the extra mile and not only illuminate the inside of his mirror arrangement, but used an Arduino Uno and a sound sensor to enable it to react to sound.

In addition to this sound sensitivity, a Bluetooth app controls color and brightness, allowing him to customize the device on the fly.

The mirror also has a built-in microphone which detects sound/music and reacts accordingly by generating eye-catching light strobes on the beat of the music! Simply start up the app, connect to Bluetooth and see the magic happen!

If you’d like to build your own, full instructions along with Arduino and app code are available here. Or you can simply check it out in action below!