Auto Strummer Can Plectrum The Whole Flat-Strumming Spectrum

Playing the guitar requires speed, strength, and dexterity in both hands. Depending on your mobility level, rocking out with your axe might be impossible unless you could somehow hold down the strings and have a robot do the strumming for you.

[Jacob Stambaugh]’s Auto Strummer uses six lighted buttons to tell the hidden internal pick which string(s) to strum, which it does with the help of an Arduino Pro Mini and a stepper motor. If two or more buttons are pressed, all the strings between the outermost pair selected will be strummed. That little golden knob near the top is a pot that controls the strumming tempo.

[Jacob]’s impressive 3D-printed enclosure attaches to the guitar with a pair of spring-loaded clamps that grasp the edge of the sound hole. But don’t fret — there’s plenty of foam padding under every point that touches the soundboard.

We were worried that the enclosure would block or muffle the sound, even though it sits about an inch above the hole. But as you can hear in the video after the break, that doesn’t seem to be the case — it sounds fantastic.

Never touched a real guitar, but love to play Guitar Hero? There’s a robot for that, too.

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A $50 CNC

In theory, there’s isn’t much to building a CNC machine. Hook a bit to a motor and move the motor around with some lead screws and stepper motors. Easy. But, of course, the devil is in the details. [DAZ] made a nice-looking and inexpensive rig that probably isn’t the most precise CNC in the world, but it looks like it does a good enough job and he claims he spent about $50 on it. The video below shows some of the work it has done, and it doesn’t look bad.

This isn’t a rainy afternoon project. You’ll need to cut some wood and 3D print many parts. The drives use M8 threaded rod. Electronics is just an Arduino running standard software.

The steppers looked pretty light duty, and we wondered if it would have been worthwhile to trade them out for beefier ones instead of modifying the ones used for bipolar operation. Still, the results did look good for $50. The 775 spindle is another place you could probably spend a little more and get something better. Non-printed linear rails, and a better screw? The point is that you’ve got a basis to build from.

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Stepper Motor Analyzer Reveals All

In theory, you really don’t need much to work with electronics. A scope ought to do everything. However, for special purposes, it is handy to have meters, logic analyzers, and other special-purpose instruments. If you work on motion systems like 3D printers and CNC machines, you ought to have a way to look at stepper motors. You don’t? [Zapta] has a great Simple Stepper Motor Analyzer and [Teaching Tech] has a great video (see below) that shows some of the great things it can do.

What can it do? It analyzes the motor in place and can visualize what’s happening during stepping, microstepping, and other operating modes. Connecting the instrument is easy since you just use a four-pin pass-through connector.

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You Need An Automated Overhead Camera Assistant

It’s 2021. Everyone and their mother is filming themselves doing stuff, and a lot of it is super cool content. But since most of us have to also work the video capture devices ourselves, it can be difficult to make compelling footage with a single, stationary overhead view, especially when there are a lot of steps involved. A slider rig is a good start, but the ability to move the camera in three dimensions programmatically is really where it’s at.

[KronBjorn]’s excellent automated overhead camera assistant runs on an Arduino Mega and is operated by typing commands in the serial monitor. It can pan ±20° from straight down and moves in three axes on NEMA-17 stepper motors. It moves really smoothly, which you can see in the videos after the break. The plastic-minimal design is interesting and reminds us a bit of an ophthalmoscope phoropter — that’s that main rig at the eye doctor. There’s only one thing that would make this better, and that’s a dedicated macro pad.

If you want to build your own, you’re in luck — there’s quite a lot of detail to this project, including a complete BOM, all the STLs, code, and even assembly videos of the 3D-printed parts and the electronics. Slide past the break to check out a couple of brief demo videos.

Not enough room for a setup like this one? Try the pantograph version.

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Stepper Motors Quick And Simple

If you want a simple and easy introduction to stepper motors, check out the [IMSAI Guy]’s short video where he designs a very basic stepper motor controller and packs in a lot of quick lessons along the way. (Embedded below.)

He first goes over the fundamentals of a stepper motor in a practical, hands-on approach, and also shows us how to ring out the connections if the pinout is unknown. Next he demonstrates stepping the motor manually and then makes a simple FET driver circuit. Just when you’re expecting a small microcontroller to appear, the [IMSAI Guy] instead digs deep into his junk box and explains how to drive the motor with a 22V10 GAL (an electrically erasable PAL) and a 555 timer module. Based on a clearly-explained logic table for driving the coils, a sneaky way to introduce Karnaugh maps, he proceeds to write the output equations in WinCUPL.

Mature Readers will recall the “Happy PAL” Character

WinCUPL is the modern version of CUPL (Compiler for Universal Programmable Logic) originally written by a company called Assisted Technology, now owned by Altium. CUPL and peers like PALASM from Monolithic Memories, Inc. (MMI) and ABEL from Data I/O Corporation were basic Hardware Description Languages specifically designed for PALs, GALs, and CPLDs. PALs were small arrays of logic gates with fusible interconnections, and your design is “burned” into the fuses much like a (EE)PROM. When designing with PALs, you could clearly visualize the connections in your mind, something that has since been remedied by the advent of modern FPGAs.

Alas, he cuts out the part where the source code is compiled and the 22V10 is programmed, and jumps directly into testing the circuit on a breadboard. Spoiler alert — it does work. Zooming in close and squinting, the nifty 555 timer breadboard module that he points out is called a TP353, which you can find from your favorite online supplier.

There is a lot to learn in this tutorial, and the [IMSAI Guy] does a great job at making the subject approachable to hobbyists and novices. We also covered another of his tutorials a couple of weeks ago on image sensors. Thanks to [itsevilbert] for the tip.

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Totally Useless Coffee Dispenser Is Anything But

Good coffee is nice to have, sure, but frankly, caffeine is caffeine and we’ll take it any way we can get it. That includes freeze-dried, if that’s all you’ve got. We won’t judge anyone for their taste in caffeinated beverages, and to call this coffee dispenser ‘totally useless’ is just patently untrue. It clearly has a use, and even if you don’t like freeze-dried coffee, you could sacrifice one jar worth of Nescafe and fill it with Skittles or anything else that will fit in the little collector basket.

In this machine, the cup is the trigger — the 3D-printed plate underneath activates a micro switch embedded in the scrap wood base, and this triggers a micro:bit around back to actuate the stepper motor that twirls the collector basket around. Although [smogdog] has provided all the files, you’d have to come up with your own connector to suspend the thing over the cup and carve your own base.

We love it when we can see what a machine is doing, so not only is it useful, it’s beautiful. And it worked, at least for a little while. For some reason, it keeps burning out stepper motors. Check it out in proof-of-concept action after the break.

We’ve seen the Micro:bit do a lot, and this pinball machine is among the most fun.

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TV Turned Automatic Etch A Sketch With Raspberry Pi

Considering one of the biggest draws of the original Etch a Sketch was how simple it was, it’s always interesting to see the incredible lengths folks will go to recreate that low-tech experience with modern hardware. A perfect example is this giant wall mounted rendition of the iconic art toy created by [Ben Bernstein]. With a Raspberry Pi and some custom electronics onboard, it can even do its own drawing while you sit back and watch.

At a high level, what we’re seeing here is a standard Samsung LCD TV with a 3D printed Etch a Sketch shell mounted on top of it. That alone would be a pretty neat project, and had [Ben] just thrown some videos of designs getting sketched out onto the display, he could have achieved a similar end result with a lot less work. But where’s the fun in that?

It took hundreds of hours to print the shell.

To make his jumbo Etch a Sketch functional, [Ben] spent more than a year developing the hardware and software necessary to read the user input from the two large 3D printed knobs mounted under the TV. The knobs are connected to stepper motors with custom PCBs mounted to their backs that hold a A4988 driver chip as well as a AS5600 absolute magnetic rotary encoder. This solution allows the Raspberry Pi to not only read the rotation of the knobs when a person is using the Etch a Sketch interactively, but spin them realistically when the software takes over and starts doing an autonomous drawing.

Several Python scripts pull all the various pieces of hardware together and produce the final user interface. The software [Ben] wrote can take an image and generate paths that the Etch a Sketch can use to realistically draw it. The points that the line is to pass through, as well as variables that control knob rotation and pointer speed, are saved into a JSON file so they can easily be loaded later. Towards the end of the Imgur gallery [Ben] has created for this project, you can see the software working its way through a few example sketches.

We’ve seen several projects that motorize an Etch a Sketch to draw complex images, but this may be the first example we’ve seen where everything was done in software. This digital version doesn’t need to follow the traditional “rules”, but we appreciate that [Ben] stuck to them anyway. Incidentally this isn’t the first Etch a Sketch TV conversion to grace these pages, though to be fair, the other project took a radically different approach.

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