A Binaural Microphone For The Great Outdoors

December 17, 2022 by Jenny List 15 Comments

A binaural recording is designed to mimic as closely as possible the experience of listening through human ears, and thus binaural microphones are often shaped like the human head with the microphone cartridges placed where the ears would be. That’s not the only way to make a binaural microphone though, and the Crown Stereo Ambient Sampling System, or SASS, did the same thing with a pair of pressure zone microphones for outdoor recordings. [Filip Mulier] doesn’t have one of the originals, but he’s done his best to make a SASS-like microphone of his own.

The attractive thing about this design is its simplicity, making use of foam sheets for the main body, with packing board as a rain deflector and a couple of layers of non-woven cloth as a wind filter. Perhaps best of all though are the recordings, in which we hear ambient recording at its finest. Listen with headphones, we suggest the dawn chorus.

If binaural recording and stereo interests you, we’ve taken a closer look in the past.

BBC Micro:Bit As Handheld Synthesizer

December 17, 2022 by Bryan Cockfield 4 Comments

The BBC Micro:bit, while not quite as popular in our community as other microcontroller development boards, has a few quirks that can make it a much more interesting piece of hardware to build a project around than an Arduino. [Turi] took note of these unique features and decided that it was the perfect platform to build a synthesizer on.

The Micro:bit includes two important elements that make this project work: the LED matrix and a gyro sensor. [Turi] built a 5×5 button matrix for inputs and paired each to one of the diodes, which eliminates the problem of false inputs. The gyro sensor is used for detuning, which varies the pitch of any generated sound by a set amount according to the orientation of the device. It also includes a passive low-pass filter to make the sound more pleasant to the ear, especially for younger players of the machine. He’s released the source code on his GitHub page for anyone interested in recreating it.

While this was a one-off project for [Turi], he notes that using MicroPython to program it instead of C led to a lot of unnecessary complications, and the greater control allowed by C would enable some extra features with less hassle. Still, it’s a fun project that really showcases the unique features of this board, much like this tiny Sumo robot we covered over the summer.

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Printed Film Camera Gets 10 Seconds Out Of A 35mm Roll

December 17, 2022 by Jenny List 17 Comments

When the British budget electronics brand Amstrad released their first budget VHS camcorder in the mid 1980s, they advertised it as making a filmmaker out of everyone. Now everyone truly is a filmmaker of sorts with their always-handy mobile phones, even though possessing a camera does not give you the talent of Steven Spielberg.

Such easy access to video hasn’t dimmed the allure of old-style film though, and there is a band of enthusiasts who seek out the older medium. [Joshua Bird] is one, and he’s produced a rather special 3D printed camera that can capture short videos on a standard roll of 35mm camera film. The downside is that, at the going rate, filming your masterpiece comes out to approximately $600 USD for each 10 minutes of footage. Better keep that dense exposition to a minimum.

The two most important mechanisms in a movie camera are the shutter and the film advance. The first is a disc that spins once a frame with an arc-shaped aperture over a section of it to let the light through, while the second is a hook that engages with the film once a frame after the shutter aperture has passed, to advance it to the next frame. Designing these to work in printed form is no easy task, and [Joshua] takes the reader through the various twists and turns in their development. Beyond that he takes a novel approach to a through-the-lens viewfinder, eschewing a split prism for an angled mirror on the shutter disk.

With each frame taking a fraction of the 35mm frame it’s clear from the video below that this doesn’t deliver the highest quality image. But that’s not the point of a device like this, above all it’s a working movie camera that he made himself. Since some of us have interests in that direction, dare we say we’re envious? Meanwhile, this isn’t the first 3D printed movie camera we’ve brought you.

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Citizen-Driven Network Monitors Public Service Radio For Natural Disaster Alerts

December 17, 2022 by Dan Maloney 12 Comments

Time is of the essence in almost every emergency situation, especially when it comes to wildfires. A wind-driven fire can roar across a fuel-rich landscape like a freight train, except one that can turn on a dime or jump a mile-wide gap in a matter of seconds. Usually, the only realistic defense against fires like these is to get the hell out of their way as soon as possible and make room for the professionals to do what they can to stop the flames.

Unfortunately, most people living in areas under threat of wildfires and other natural disasters are often operating in an information vacuum. Official channels take time to distribute evacuation orders, and when seconds count, such delays can cost lives. That’s the hole that Watch Duty seeks to fill.

Watch Duty is a non-profit wildfire alerting, mapping, and tracking service that provides near-real-time information to those living in wildfire country. Their intelligence is generated by a network of experienced fire reporters, who live in wildfire-prone areas and monitor public service radio transmissions and other sources to get a picture of what’s going on in their specific area. When the data indicate an incident is occurring, maps are updated and alerts go out via a smartphone app. Reporters have to abide by a strict code of conduct designed to ensure the privacy of citizens and the safety of first responders.

While Watch Duty’s network covers a substantial area of California — the only state covered so far — there were still a significant number of dead zones, mostly in the more remote areas of the Sierra Nevada Mountains and in the northern coastal regions. To fill these gaps, Watch Duty recently launched Watch Duty Echo, which consists of a network of remote listening posts.

Each station is packed with RTL-SDR receivers that cover a huge swath of spectrum used by the local fire, law enforcement, EMS agencies — any organization likely to be called to respond to an incident. In addition, each station has an SDR dedicated to monitoring ADS-B transponders and air band frequencies, to get a heads-up on incidents requiring aerial support. The listening posts have wideband discone antennas and a dedicated 1090-MHz ADS-B antenna, with either a cellular modem or a Starlink terminal to tie into the Watch Duty network.

Hats off to the folks at Watch Duty for putting considerable effort into a system like this and operating it for the public benefit. Those who choose to live close to nature do so at their own risk, of course, but a citizen-driven network that leverages technology can make that risk just a little more manageable.

DIY Square Guitar Is Anything But

December 17, 2022 by Kristina Panos 3 Comments

One of the greatest things about this place is how y’all constantly feed off of each other. And while this isn’t exactly an example of that, it’s pretty darn close — we feature a square guitar build one day, and get a tip about another way different and perhaps more functional one the next.

[Craig Lindley] had no idea of his luthier powers until an email from StewMac inspired him to build his own guitar. Rather than strip a perfectly good axe or two for all the parts, he bought the hardware and a pre-made neck, and built the body himself. The Bo Diddley-inspired boxy body is an ice cream sandwich of sapele, inlaid with white ash around the perimeter which is quite the classy look. Speaking of looks, [Craig] worried that all-gold hardware would be too flashy, but we think it looks great.

Not hard-mode enough for you? Well, here’s a guitar made from scratch, (more or less). If you’d rather have more of a teaching guitar, behold this LED-laden axe.

Yesterday’s Future Is Brighter Today

December 17, 2022 by Elliot Williams 31 Comments

The demoscene never ceases to amaze. Back in the mid-80s, people wouldn’t just hack software to remove the copy restrictions, but would go the extra mile and add some fun artwork and greetz. Over the ensuing decade the artform broke away from the cracks entirely, and the elite hackers were making electronic music with amazing accompanying graphics to simply show off.

Looked at from today, some of the demos are amazing given that they were done on such primitive hardware, but those were the cutting edge home computers at the time. I don’t know what today’s equivalent is, with CGI-powered blockbusters running in mainstream cinemas, the state of the art in graphics has moved on quite a bit. But the state of the old art doesn’t rest either. I’ve just seen the most amazing demo on a ZX Spectrum.

Simply put, this demo does things in 2022 on a computer from 1982 that were literally impossible at the time. Not because the hardware was different – this is using retro gear after all – but because the state of our communal knowledge has changed so dramatically over the last 40 years. What makes 2020s demos more amazing than their 1990s equivalents is that we’ve learned, discovered, and shared enough new tricks with each other that we can do what was previously impossible. Not because of silicon tech, but because of the wetware. (And maybe I shouldn’t underestimate the impact of today’s coding environments and other tooling.)

I love the old demoscene, probably for nostalgia reasons, but I love the new demoscene because it shows us how far we’ve come. That, and it’s almost like reverse time-travel, taking today’s knowledge and pushing it back into gear of the past.

Say The Magic Word, And The TinySA Goes Ultra

December 17, 2022 by Al Williams 14 Comments

We’ve looked at the TinySA spectrum analyzer in the past. However, the recent Ultra edition offers an increase in range from 800 MHz to 6 GHz. How does it work? [IMSAI Guy] tells us in a recent video that you can watch below. In addition to an increased frequency range, the new device offers a larger display and enhancements to the signal generator and bandpass filtering. It also has an optional LNA. All this, of course, is at a price since the Ultra sells at a little more than twice the original unit’s price. Still, $120 or so for a 6 GHz spectrum analyzer isn’t bad.

For some reason, you have to put a passcode in to enable the Ultra mode, although the passcode appears to be common knowledge and available on the device’s wiki. You can presume they could, at some point, make this feature or others require a paid passcode, but for now, it is just a minor inconvenience. Reminds us of a certain oscilloscope that’s become quite popular in our community.

One thing you should be aware of, however, is that the Ultra mode uses a mixer to downconvert the incoming signal to the ordinary 800 MHz range. That means, as you can see in the video, that the local oscillator puts out some signal at the input. The level is relatively low, but still something to be aware of if you are trying to make a precision measurement.

The video compares the device to an HP 8591E spectrum analyzer. It tops out at 1.8 GHz and runs about $2,500 new. Even on eBay, you can expect to pay between $500 and $1000 for one of these. The results seem to be comparable, for the most part.

We looked at the device’s predecessor back in 2020. We also did a full-blown review a little bit later.

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