Optical Guitar Pickup Works With Nylon Strings

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.

Continue reading “Optical Guitar Pickup Works With Nylon Strings”

Pager Lives Again Thanks To Python And Mastodon

Pagers were a big deal for a while there, even if they never quite made it into the pantheon of excellent sitcom plot devices like answering machines did. Anyway, [Finnley Dolfin] had some pagers and gave them a refresh for the modern era, using them to receive message alerts from Mastodon.

The project is laced together with a bunch of Python code. It uses the Mastodon library for interacting with the social media website. When it detects an incoming direct message, it hooks into DAPNET – the Decentralized Amateur Paging Network.  Via this network, a message is sent out over the airwaves to [Finnley’s] pager, serving as a notification that someone’s reached out to chat on Mastodon.

It’s neat that the amateur radio world is keeping pagers alive, using distributed base stations to share messages. Unfortunately, given the existence of smartphones, we don’t quite see pagers catching on again any time soon. And yet, [Finnley’s] setup has a certain level of old-school cool that no modern phone could match.

We’ve seen only a handful of pager hacks over the years, but they’re still pretty neat. If you’ve got your own cooking up in the workshop, drop us a line, yeah?

Retrotechtacular: The Free Piston Engine

We all know how a conventional internal combustion engine works, with a piston and a crankshaft. But that’s by no means the only way to make an engine, and one of the slightly more unusual alternatives comes to us courtesy of a vintage Shell Film Unit film, The Free Piston Engine, which we’ve placed below the break. It’s a beautiful period piece of mid-century animation and jazz, but it’s also  an introduction to these fascinating machines.

We’re introduced to the traditional two-stroke diesel engine as thermally efficient but not smooth-running, and then the gas turbine as smooth but much more inefficient. The free piston engine, a design with opposed pistons working against compressed air springs and combining both compression and firing strokes in a single axis, doesn’t turn anything  in itself, but instead works as a continuous supplier of high pressure combustion gasses. The clever part of this arrangement is that these gasses can then turn the power turbine from a gas turbine engine, achieving a smooth engine without compromising efficiency.

This sounds like a promising design for an engine, and we’re introduced to a rosy picture of railway locomotives, ships, factories, and power stations all driven by free piston engines. Why then, here in 2024 do we not see them everywhere? A quick Google search reveals an inordinately high number of scientific review papers about them but not so many real-world examples. In that they’re not alone, for alternative engine designs are one of those technologies for which if we had a dollar for every one we’d seen that didn’t make it, as the saying goes, we’d be rich.

It seems that the problem with these engines is that they don’t offer the control over their timing that we’re used to from more conventional designs, and thus the speed of their operation also can’t be controlled. The British firm Libertine claim to have solved this with their line of linear electrical generators, but perhaps understandably for commercial reasons they are a little coy about the details. Their focus is on free piston engines as power sources for hybrid electric vehicles, something which due to their small size they seem ideally suited for.

Perhaps the free piston engine has faced its biggest problem not in the matter of technology but in inertia. There’s an old saying in the computer industry: “Nobody ever got fired for buying IBM“, meaning that the conventional conservative choice always wins, and it’s fair to guess that the same applies anywhere a large engine has been needed. A conventional diesel engine may be a complex device with many moving parts, but it’s a well-understood machine that whoever wields the cheque book feels comfortable with. That’s a huge obstacle for any new technology to climb. Meanwhile though it offers obvious benefits in terms of efficiency, at the moment its time could have come due to environmental concerns, any internal combustion engine has fallen out of fashion. It’s possible that it could find a life as an engine running on an alternative fuel such as hydrogen or ammonia, but we’re not so sure. If new free piston engines do take off though, we’ll be more pleased than anyone to eat our words.

Continue reading “Retrotechtacular: The Free Piston Engine”

High Vacuum Hack Chat

Join us on Wednesday, March 6 at noon Pacific for the High Vacuum Hack Chat with Niklas from Advanced Tinkering!

To the casual observer, there’s not much that goes on in experimental physics that doesn’t require at least a partial vacuum. It makes sense when you think about it; our atmosphere is so thick and so loaded with water vapor and reactive oxygen that it just has to play havoc with experiments. Even when the goal is more applied than empirical, getting rid of all those pesky molecules is often the first step in getting good results.

But pulling a vacuum is rarely an easy task. Sure you can pump out some of the air, but that just makes the rest of the atmosphere try really hard to get back inside and ruin your day. It takes a lot of specialized equipment, a lot of precision-machined stainless steel fittings, and quite a bit of experience not only to pull a vacuum, but to then be able to work within it and do something useful.

join-hack-chatOne place where we’ve seen a lot of high-vacuum action is over on Advanced Tinkering on YouTube. The channel has a wealth of interesting experiments, many of which need a good vacuum to get going. To that end, channel owner Niklas has assembled a nice collection of vacuum gear, and we asked him to drop by the Hack Chat to talk about what he’s learned by embracing the suck.

Our Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, March 6 at 12:00 PM Pacific time. If time zones have you tied up, we have a handy time zone converter.

Luggable Cyberdeck Can Still Be A Luggable PC

In the 80s and early 90s, there existed a class of personal computers that are no longer around today — the luggable. Planted firmly between a desktop and a laptop, these machines were lovingly called so because they were portable, but just barely. Think Kaypro, Osborne, or the Compaq Portable.

First things first — this lovely 1990-era industrial luggable has not been gutted according to [D1g1t4l_G33k]. The chassis, CRT, power supply, and ISA backplane are original and still intact, and they still have all the parts to restore it to its original DOS 3.1 form.

What [D1g1t4l_G33k] did do is replace the 386x-based ISA SBC with a 2005 AMD LX-600 Geode at 366 MHz. Gone are the ISA data acquisition cards and 80 MB SCSI hard drive, replaced with a 32 GB compact flash drive. The floppy drive is functional, too. Now it sits on a cart next to the workbench running AntiX Core 19.5, functioning happily as an AVR development workstation.

Having an old luggable to mess with in the first place isn’t a requirement. We’ve seen a modern take on the luggable, and here’s one with three monitors.

Avi Loeb And The Interstellar Lottery

Except for rare occasions, I don’t play the lottery. Like many of you, I consider state-run lotteries to be a tax paid only by people who can’t do math. That’s kind of arrogant coming from a guy who chose to go into biology rather than engineering specifically because he’s bad at math, but I know enough to know that the odds are never in your favor, and that I’d rather spend my money on just about anything else.

But I’m beginning to get the feeling that, unlike myself and many others, Harvard professor Avi Loeb just might be a fan of playing the lottery. That’s not meant as a dig. Far from it. In fact, I readily concede that a physicist with an endowed chair at Harvard working in astrophysics knows a lot more about math than I do. But given his recent news splashes where he waxes on about the possibility that Earth has been treated to both near misses and direct hits from interstellar visitors, I’m beginning to think that maybe I’m looking at the lottery backward.

Continue reading “Avi Loeb And The Interstellar Lottery”

A screenshot of the drone monitoring application, showing spoofed drones and their coordinates

Can’t Disable DJI Drone ID? Spoof It With An ESP!

We have been alerted to a fun tool, a DJI DroneID spoofer software for ESP8266/ESP32 and some other popular MCUs. Last year, we’ve told you about DJI DroneID — a technology DJI added to their drones, which broadcasts data including the drone operator’s GPS position, which, in turn, appears to have resulted in Ukrainian casualties in the Ukraine war. The announcement tweet states that DJI has added mechanisms from downgrading firmware. Hence, the spoofer.

There’s no other hardware needed, well other than an ESP8266 or ESP32 devboard, anyway. After the break you can find a video tutorial from [Joshua Bardwell] that shows you how to upload the code using Arduino IDE, and even going through coordinate tweaks. If you ever reminisced about the concept of throwies and were wondering what kind of useful, well, there’s your answer: clone the Git repo, compile it, program some interesting coordinates in, and witness the imaginary drones fly.

All in all, we get a lovely addition to our shenanigan toolkits. Surely, someone could use a neural network to distinguish real drones from fake ones, but it’s nothing that can’t be solved with a bit of code. Looking for a less daring hack? Well, you can always add some automation to your DJI drone by poking at the RGB LED signals.

Continue reading “Can’t Disable DJI Drone ID? Spoof It With An ESP!”