Optical Guitar Pickup Works With Nylon Strings

March 4, 2024 by Lewin Day 68 Comments

Electric guitar pickups rely on steel strings interfering with a magnetic field, the changes in which are picked up with coils of wire. That doesn’t work with nylon strings, because they don’t tend to perturb magnetic fields nearly as much, beyond some infinitesimal level that some quantum physicist could explain. So what do you do? You follow [Simon]’s example, and build an optical pickup instead.

The concept is simple. You place an LED and a phototransistor in a U-shaped channel, and place it so that the string runs through it. You repeat this for each string. Thus, as a string vibrates, it interrupts the light travelling from the LED to the phototransistor. This generates a voltage that varies with the frequency of the string’s vibration. Funnily enough, this type of pickup will work just fine on both nylon and steel strings, if you were so inclined to try it.

[Simon] designed a nifty PCB with six LED-phototransistor pairs (using off-the-shelf interruptor sensors) for use with a nylon-stringed guitar. He reports that sound from the strings comes through clearly, but that there is some noise that is evident in the pickup’s output, too. Listening to the demo, it seems to capture the sound of the nylon strings well, it’s just a shame that the noise floor is so high.

If you prefer your guitar pickups to be the regular magnetic kind, you can always wind your own from scrap. Demo after the break.

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Cheap Microscope Can Take Amazing Images With Some Simple Upgrades

March 2, 2024 by Lewin Day 12 Comments

[Birdbrain] is trying to make their own microfluidic devices. To aid in this quest, they need a quality microscope to see what they’re doing. Instead of buying one outright, they purchased a cheap microscope and upgraded it to do the job instead.

Usability and performance is greatly improved over the stock unit, which was really only fit for learning purposes.

The cheap education-grade microscope cost around $50 USD, had few features, and wasn’t much chop out of the box. The worst part was the sample stage — which was poorly adjustable in the up-and-down axis and could only track about two centimeters up and down. There was no X or Y axis panning either, and it lacked a proper condensor iris, too. Oh, and the included camera module had a resolution of just 240p.

To fix these problems, the microscope was first outfitted with a fully redesigned X-Y-Z stage built out of old components from a salvaged DVD drive and an additional NEMA stepper motor. Camera-wise, it was hooked up with a 2K Raspberry Pi Camera Module 3 running at 10 to 15 frames per second, which broadcasts video over a local network for easy viewing on an external monitor. It also gained an epi-illumination setup for doing reflected light microscopy.

If you’re eager to build a quality microscope with all the controls you personally dream of, this could be a relevant project for you to study. We’ve featured some other builds along these lines before, too. Video after the break.

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DIY Geophone Build Performs Well

March 2, 2024 by Lewin Day 14 Comments

If you want to know what’s going on with the ground, geologically speaking, a geophone is a great tool to have. It lets you listen in on the rumbles and grumbles beneath your feet, and can give you great insight into matters of seismic importance. [mircemk] has designed a very capable geophone that’s simple enough for you to build at home.

The geophone relies on a mass suspended upon a spring inside a chamber, which as you might imagine, will move when shaken by seismic vibrations. The mass is in fact a plastic rod, fitted with an iron nut and a magnet on the end.

This is mounted above a coil, which is fixed to the base of the chamber. Thus, when the chamber is shaken by seismic activity, the mass moves relative to the coil, with the coil picking up the varying magnetic field as it dances around.

The YouTube video does a great job of explaining the concepts involved and how to practically build the device. [mircemk] has also had some other great projects featured on Hackaday before, too.

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Bluetooth Wearable Becomes Rad Synth Controller

March 1, 2024 by Lewin Day 1 Comment

Once upon a time, a watch was just a watch. These days, though, smartwatches have all kinds of tricks built in, from heartrate sensors, to accelerometers, gyros, and tons of networking capability. Take advantage of just some of that hardware, and you have yourself a pretty nifty controller. And that’s precisely what [Simon Brem] did.

The project is based around the capable PineTime smartwatch, which [Simon] has been using with the InfiniTime firmware. On this platform, he created an app that sends out Bluetooth MIDI commands straight from the watch. It can be used as a motion controller, where waving and angling the watch can be used to control MIDI parameters, or it can be used to sync BPM to the wearer’s heartrate. [Simon] demonstrates an example use case in a demo video, where the watch is used to control filters in pleasant ways.

We’ve seen a lot of neat watch hacks lately, as it turns out! To say nothing of the brilliant MIDI controllers that have come through these doors, as well. Video after the break.

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Educational Arduino Clock Uses Analog Meters For Display

March 1, 2024 by Lewin Day 13 Comments

When it comes to educational electronic projects, it’s hard to go past building a clock. You learn tons about everything from circuit concepts and assembly skills to insights about the very nature of time itself. And you get a clock at the end of it! [hamblin.joe] wanted to do a simple project for kids along these lines, so whipped up a neat design using analog meters to display the time.

The build relies on that old stalwart, the Arduino Uno, to run the show. It’s hooked up to a DS3231 real-time clock module so it can keep accurate time for long periods, as is befitting a clock. Displaying the time is done via the use of two analog meters, each fitted with a custom backing card. One displays hours, the other, minutes. The analog meters are simply driven by the PWM outputs of the Arduino.

It’s not a hugely complex project, but it teaches so much. It provides an opportunity to educate the builders about real-time clocks, microcontroller programming, and even the concepts behind pulse width modulation. To say nothing of the physical skills, like learning to solder or how to assemble the laser-cut enclosure. Ultimately, it looks like a really great way for [hamblin.joe] and his students to dive into the world of modern electronics.

Build Yourself A Little Mangonel, You Deserve One

March 1, 2024 by Lewin Day 17 Comments

If you’re of a certain age, you almost certainly learned about mangonels by playing Age of Empires II. Any intermediate player will tell you they are a powerful siege weapon that nevertheless cannot destroy trees (in game). However, why limit yourself to experiencing this capable siege engine in digital form? With the help of [Arry Koster’s] design, you can build a little mangonel of your very own!

A good-looking siege engine is, more often than not, a well-performing one.

The build is intended for a student or hobbyist audience, and is for a mangonel roughly the size of a shoebox. That’s big enough to have some fun, without being so large as to get you into trouble. The project also comes complete with a useful spreadsheet that lets you simulate the performance of a mangonel hurling a projectile so you can better understand the physics involved.

The mangonel is constructed out of wood, just as medieval examples were. The guide explains how to put the the design together, including the use of graphite to lubricate moving parts — a technique also used historically. Beyond building the siege weapon itself, there are also instructions on how to instrument it with an Arduino to measure its performance accurately.

The only thing this project is missing is a brilliant video of the titchy siege machine in action. We want to see it knocking down some appropriately-sized castles! If you happen to be building your own siege engines, miniature or otherwise, don’t hesitate to drop us a line. Do include some excellent footage of your antics, to boot!