Add A Little Quindar To Your Comms For That Apollo-Era Sound

If there’s one thing that ties together all the media coming out of the Apollo era, it’s probably the iconic Quindar tones. These quarter-second beeps served as control tones for the globe-spanning communications network needed to talk to the Apollo astronauts, and any attempt to recreate the Apollo-era sound would be glaringly wrong without them. And that’s why [CuriousMarc] whipped up this Quindar tone system.

The video below starts with a detailed treatment of what Quindar tones are and why they were used, a topic we’ve covered ourselves in the past. To recap, Quindar tones are a form of in-band signaling, with a 2,525-Hz pure sine wave intro tone that signaled the transmitters connected to Mission Control in Houston over leased telephone lines to key up. The 2,475-Hz outro tone turned off the transmitters and connected the line to the receivers.

To recreate the sound quality of the original circuitry, and to keep in the retro vibe, [Marc]’s Quindar homage avoided digital circuitry as much as possible, opting instead to generate the two tones with an XR-2206 function generator chip. The chip can rapidly switch back and forth between two frequencies, making it perfect for FSK applications or, in this case, reproducing the two slightly different tones. [Marc] added a dual mono-stable multi-vibrator to pulse the tone, giving the 250-ms pulse, and an audio gate, which uses a MOSFET to switch the tone into an audio stream. All this got soldered up to a piece of perf board and stuffed in the base of a cheap intercom microphone, which while not period accurate still has a cool retro look — and now, a retro sound, too.

Hats off to [CuriousMarc] and his merry band for probing the mysteries of Apollo-era comms and keeping the accomplishments of all those engineers alive. The methods they used are still relevant after all these years, and there seems to be no end to what we can learn from them.

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Making Use Of Stellaris/Tiva Real-Time Clock

If you’re at all like us, or like [Vadim], you’ve got a stash of development boards in a shoebox on a shelf in your closet. If you’re better organized that we are, it might even be labeled “dev boards”. (Ah well, that’s a project for another day.) Anyway, reach into your box and pull one out, and put it to use. Do something trivial if you need to, but a dev board that’s driving a silly blinker is better than a dev board sitting in the dark.

[Vadim]’s good example to us all is going to serve as the brains for an automated plant watering system. That’s a low-demand application where the microcontroller can spend most of the time sleeping. [Vadim]’s first step, then was to get a real-time clock working with the hibernation mode. There’s working code inline in his blog.

“I don’t know, I didn’t go into Burger King.”

If you use Arduino, you’ll feel at home in the Energia ecosystem. But it’s like ordering a Quarter Pounder with Cheese in Paris: Energia is a Royale with Cheese (YouTube) — it’s the little differences. And maybe that’s the point of the exercise; it’s always a good thing to try out something new, even if it’s only minimally different.

So grab that unused dev board off the shelf, struggle through the unfamiliar development environment and/or toolchain, but remember to keep an eye out for the sweet little differences. The more tools that you’re familiar with, the more solutions will spring to mind when you’re hacking on your next project.

Boombox Doorjam Plays Your Theme Song When You Step In The Ring

Although many of us may have had childhood aspirations to be a famous wrestler in the WWE, not very many of us will ever realize those dreams. You can get close, though, if you have your own epic intro music theme that plays anytime you walk into a room. Although it’s not quite the same as entering a wrestling ring, [Matt]’s latest project will have you feeling just as good whenever you enter a room to your own theme song.

The core of the build consists of a boom box with an auxiliary input. The boom box is fed sound via a Raspberry Pi which also serves as the control center for the rest of the project. It runs Node.js and receives commands via websockets from a publicly accessible control server. The Pi is also running Spotify which allows a user to select a theme song, and whenever that user’s iBeacon is within range, the Pi will play that theme song over the stereo.

The project looks like it would be easy to adapt to any other stereo if you’re looking to build your own. Most of the instructions and code you’ll need are available on the project’s website, too. And, if you’re a fan of music playing whenever you open a door of some sort, this unique project is clearly the gold standard. It might even make Stone Cold Steve Austin jealous.