Modeling A Guitar For Circuit Simulation

Guitar effects have come a long way from the jangly, unaltered sounds of the 1950s when rock and roll started picking up steam. Starting in large part with [Jimi Hendrix] in the 60s, the number of available effects available to guitarists snowballed in the following decades step-by-step with the burgeoning electronics industry. Now, there are tons of effects, from simple analog devices that would have been familiar to [Hendrix] to complex, far-reaching, digital effects available to anyone with a computer. Another thing available to modern guitarists is the ability to model these effects and guitars in circuit simulators, as [Iain] does.

[Ian] plays a Fender Stratocaster, but in order to build effects pedals and amplifiers for it with the exact desired sound, he needed a way to model its equivalent circuit. For a simple DC circuit, this isn’t too difficult since it just requires measuring the resistance, capacitance, and inductance of the overall circuit and can be done with something as simple as a multimeter. But for something with the wide frequency range of a guitar, a little bit more effort needs to go into creating an accurate model. [Iain] is using an Analog Discovery as a vector network analyzer to get all of the raw data he needs for the model before moving on to some in-depth calculations.

[Iain] takes us through all of the methods of figuring out the equivalent impedance of his guitar and its cabling using simple methods capable of being done largely by hand and more advanced techniques like finding numerical solutions. By analyzing the impedance of the pickup, tone and volume controls, and cable, this deep dive into the complexities of building an accurate equivalent circuit model for his guitar could be replicated by anyone else looking to build effects for their specific guitars. If you’re looking for a more digital solution, though, we’ve seen some impressive effects built using other tools unavailable to guitarists in days of yore, such as MIDI and the Raspberry Pi.

Off-Grid Radio Also Repairable Off-Grid

Low-power radios, often referred to in the amateur radio community as QRP radios, have experienced a resurgence in popularity lately. Blame it on certain parts of the hobby become more popular, like Parks on the Air (POTA) or Summits on the Air (SOTA). These are events where a radio operator operates off-grid at remote parks or mountaintops. These QRP rigs are a practical and portable way to make contacts. You would think that a five- or ten-watt rig running on batteries would be simple. Surprisingly, they can be enormously complex and expensive. That’s why [Dr. Daniel Marks] built the RFBitBanger, a QRP radio designed to not only be usable off-grid but to be built and maintained off-grid as well.

The radio accomplishes this goal by being built out of as many standard off-the-shelf components as possible. It eschews modern surface-mount components in favor of the much more accessible through-hole parts, including the ATMEGA328P at the center of the build. A PCB design is also available, but it can be built on perf board nearly as easily. The radio supports any mode a QRP operator might use, including CW, SSB, RTTY, and a new mode designed explicitly for this radio called SCAMP which is a low bandwidth, low SNR digital mode built into the Arduino-based firmware. It’s a single-band radio, but any band between 20 and 80 meters can be selected with pluggable filters.

As far as bomb-proof radios go, we can’t imagine a better way to live out an apocalypse than with a radio like this. As long as there’s a well-stocked parts drawer around, this radio could theoretically reach around the world without worrying about warranty claims, expensive parts, or even a company going out of business or not stocking parts for old radios anymore. There’s also more information about this build at the Open Research Institute for those interested. And, if you’re wondering how useful any radio could be using only five watts of transmitter power, take a look at this in-depth look at QRP radio operation.

Thanks to [Stephen Walters] for the tip.

Two nearly-identical black and white images of a solar installation on top of a roof in NYC. The left image purports to be from 1909 while the other says it is from 1884. Both show the same ornate building architecture in the background and angle of the panels.

The Mysterious Case Of The Disappearing Inventor

When combing through the history of technological innovation, we often find that pinning down a given inventor of something can be tricky. [Foeke Postma] at Bellingcat shows us that even the Smithsonian can get it wrong when given faulty information.

The mystery in question is the disappearance of inventor [George Cove] from a photograph of his solar panel system from 1909 and its reuse as evidence of the first photovoltaic solar panel by another inventor, [Charles Fritts], around 1884. Questions first arose about this image in 2021, but whether this was an example of photo manipulation was merely speculation at the time.

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Linux, Running On Not A Lot

There are many possible answers to the question of what the lowest-powered hardware on which Linux could run might be, but it’s usually a pre-requisite for a Linux-capable platform to have a memory management unit, or MMU. That’s not the whole story though, because there are microcontroller-focused variants of the kernel which don’t require an MMU, including one for the Xtensa cores found on many Espressif chips. It’s this that [Naveen] is using to produce a computer which may not be the Linux computer with the lowest processor power, but could be the one consuming the least electrical power.

The result is definitely not a Linux powerhouse, but with its Arduino-sourced ESP32 board stacked on an UNO and I2C keyboard and display, it’s an extremely lightweight device. The question remains, though, is it more than a curiosity, and to what can it do? The chief advantage it has over its competitors such as the Raspberry Pi Zero comes in low power consumption, but can its cut-down Linux offer as much as a full-fat version? We are guessing that some commenters below will know the answer.

If you’re curious about the Xtensa version of Linux, it can be found here,

Off-Grid EV Charging

There are plenty of reasons to install solar panels on one’s home. Reducing electric bills, reducing carbon footprint, or simply being in a location without electric service are all fairly common. While some of those might be true for [Dominic], he had another motivating factor. He wanted to install a charger for his electric vehicles but upgrading the electric service at his house would have been prohibitively expensive. So rather than dig up a bunch of his neighbors’ gardens to run a new service wire in he built this off-grid setup instead.

Hooking up solar panels to a battery and charge controller is usually not too hard, but getting enough energy to charge an EV out of a system all at once is more challenging. The system is based on several 550W solar modules which all charge a lithium iron phosphate battery. The battery can output 100 A DC at 48 V which gives more than enough power to charge an EV. However there were some problems getting this much power through an inverter. His first choice let out the magic smoke when it was connected, and it wasn’t until he settled on a Growatt inverter capable of outputting 3.5 kW that the system really started to take shape.

All of this is fairly straightforward, but there’s an extra touch here that makes this project noteworthy. [Dominic] wanted to balance incoming power from the photovoltaic system to the current demands from the EVs to put less strain on the battery. An ESP32 was programmed to only send as much power to the EVs as the solar system is producing at any given time, and also includes some extra logic to make sure the battery doesn’t drain itself from the idle power requirements of the inverter. Right now the system works well but the true test will be when it goes through its first winter. Even though solar panels are more efficient at colder temperatures, if the amount of sunlight or the angle of the panels aren’t ideal there is generally much less production.

Chaos And Camping

In a field somewhere north of Berlin right now, around 5,500 hackers and their family members are blinking, coding, building, giving talks, and simply hanging out. Once every four years, the German hacker scene gathers and gets burned by the day star, despite the ample warnings to apply copious sunscreen.

CCCamp is a must-attend-it-to-get-it type event, but it’s also chock-full of talks on numerous stages, and these you can see from the comfort of your own home without even getting a mosquito bite! We loved [Harald Welte]’s complete guide to the mysterious world of eSIMS, for instance.

What’s most amazing about Camp, though, is that it brings together hackers of all ages and interests. Someone with a tape-measure direction-finding radio, probably participating in the foxhunt, just walked behind another group learning yoga. There is UV tape art and a stinky diesel train. Old greybeards mingle with kids, all playing with the bubble machines. Two folks are playing bocce with old hard drives. I think one camp was working on an autonomous model boat.

Everyone brings what they’re interested in, shares it, and helps anyone else get started if they’re interested. It’s a hacker paradise, even if just for a few days every four years.

New Take On The Camera Obscura Brings Paris Indoors

We haven’t checked, but we’ll go out on a limb here and say this is the first project we’ve featured with a BOM that includes “an apartment in Paris with a breathtaking view of the Eiffel Tower.” We suppose there are other places in the world where a giant camera obscura like this would work too, but you’ve got to admit that the view is pretty spectacular.

Of course, a camera obscura is really just a dark room — that’s literally what it means in Latin — with a small aperture to admit light from the outside world. This projects an inverted image on the opposite wall, which must have looked absolutely magical to pre-technical people and honestly is still pretty stunning today. Either way, it’s a low-tech way of seeing the world in a different light. [Mathieu Stern] decided his camera obscura would turn the traditional design on its head. Literally — he wanted an upright image. Luckily, he found a supplier that makes special optics for camera obscura that do just that. It looks like the optic uses a Dove prism to invert the image, or in this case to turn it back into an upright image.

The real hack here was finding the perfect place with just the right view of the Eiffel Tower — not at all an easy task in a medieval city where streets go where they will and buildings tend to block the sightlines. [Mathieu] eventually managed to find just the right place. With a little aluminum foil to make the rented room really obscura and some strategically positioned sheets to improve the projection surface, he was able to project some beautiful images of the landmark and surrounding cityscape in a panorama on the apartment walls. The video below has some stills and time-lapse sequences that are pretty breathtaking.

We’ve seen other camera obscura before, including this mobile version which may have made things easier for [Mathieu], at the price of giving up a lot of the charm.

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