The Hot And Cold Of Balanced Audio

July 27, 2018 by Dan Maloney 45 Comments

A few summers of my misspent youth found me working at an outdoor concert venue on the local crew. The local crew helps the show’s technicians — don’t call them roadies; they hate that — put up the show. You unpack the trucks, put up the lights, fly the sound system, help run the show, and put it all back in the trucks at the end. It was grueling work, but a lot of fun, and I got to meet people with names like “Mister Dog Vomit.”

One of the things I most remember about the load-in process was running the snakes. The snakes are fat bundles of cables, one for audio and one for lighting, that run from the stage to the consoles out in the house. The bigger the snakes, the bigger the show. It always impressed me that the audio snake, something like 50 yards long, was able to carry all those low-level signals without picking up interference from the AC thrumming through the lighting snake running right alongside it, while my stereo at home would pick up hum from the three-foot long RCA cable between the turntable and the preamp.

I asked one of the audio techs about that during one show, and he held up the end of the snake where all the cables break out into separate connectors. The chunky silver plugs clinked together as he gave his two-word answer before going back to patching in the console: “Balanced audio.”

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Radar In Space: The Gemini Rendezvous Radar

July 26, 2018 by Dan Maloney 37 Comments

In families with three kids, the middle child always seems to get the short end of the stick. The first child gets all the attention for reaching every milestone first, and the third child will forever be the baby of the family, and the middle child gets lost in-between. Something similar happened with the U.S. manned space program in the 60s. The Mercury program got massive attention when America finally got their efforts safely off the ground, and Apollo naturally seized all the attention by making good on President Kennedy’s promise to land a man on the moon.

In between Mercury and Apollo was NASA’s middle child, Project Gemini. Underappreciated at the time and even still today, Gemini was the necessary link between learning to get into orbit and figuring out how to fly to the Moon. Gemini was the program that taught NASA how to work in space, and where vital questions would be answered before the big dance of Apollo.

Chief among these questions were tackling the problems surrounding rendezvous between spacecraft. There were those who thought that flying two spacecraft whizzing around the Earth at 18,000 miles per hour wouldn’t work, and Gemini sought to prove them wrong. To achieve this, Gemini needed something no other spacecraft before had been equipped with: a space radar.

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How—And Why—To Avoid Tolerance Stacking In Your Technical Drawings

July 25, 2018 by Cameron Coward 49 Comments

If you want to have your part designs fabricated, you’re going to need to provide the manufacturer with a technical drawing. Yes, 3D printers and many modern machine tools rely on toolpaths created from 3D models. But, there is a good chance the manufacturer will be recreating the 3D model in their own system, instead of using the one you provided. Or, they may use traditional manual machining and not touch a 3D model at all. More importantly, the technical drawing gives them vital information on how closely they need to adhere to your dimensions in order for you to accept the parts.

On a technical drawing, the dimension that you want is called the nominal. But, no manufacturing is ever perfect, so you have to allow some wiggle room in what you’ll accept. That wiggle room is called tolerance. Maybe your part could be a little longer than specified and it wouldn’t affect the functionality. Maybe it could be a little shorter—or either. Specifying a tolerance is necessary, because it tells the manufacturer exactly how much wiggle room you’re giving them.

But, tolerances can introduce unforeseen consequences if you’re not careful. The wiggle room provided by tolerances is absolutely necessary, but if you don’t use them properly you can easily end up with unusable parts, even if the manufacturer followed your instructions to the letter. That usually happens because you have multiple tolerances being added together, which is called tolerance stacking.

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Learn To Count In Seximal, A Position Above The Rest

July 20, 2018 by Tucker Ervin 42 Comments

Believe it or not, counting is not special. Quite a few animals have figured it out over the years. Tiny honeybees compare what is less and what is more, and their brains are smaller than a pinky nail. They even understand the concept of zero, which — as anyone who has had to teach a toddler knows — is rather difficult to grasp. No, counting is not special, but how we count is.

I don’t mean to toot our own horn, but humans are remarkable for having created numerous numeral systems, each specialized in their own ways. Ask almost anyone and they will at least have heard of binary. Hackaday readers are deeper into counting systems and most of us have used binary, octal, and hexadecimal, often in conjunction, but those are just the perfectly standard positional systems.

If you want to start getting weird, there’s balanced ternary and negabinary, and we still haven’t even left the positional systems. There’s a whole host of systems out there, each with their own strengths and weaknesses. I happen to think seximal is the best. To see why, we have to explore the different creations that arose throughout the ages. As long as we’ve had sheep, humans have been trying to count them, and the systems that resulted have been quite creative, if inefficient.

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Delta Clipper: A 1990s Reusable Single-Stage To Orbit Spaceship Prototype

July 19, 2018 by Steven Dufresne 50 Comments

With all the talk of SpaceX and Blue Origin sending rockets to orbit and vertically landing part or all of them back on Earth for reuse you’d think that they were the first to try it. Nothing can be further from the truth. Back in the 1990s, a small team backed by McDonnell Douglas and the US government vertically launched and landed versions of a rocket called the Delta Clipper. It didn’t go to orbit but it did perform some extraordinary feats.

Origin Of The Delta Clipper

The Delta Clipper was an unmanned demonstrator launch vehicle flown from 1993 to 1996 for testing vertical takeoff and landing (VTOL) single-stage to orbit (SSTO) technology. For anyone who watched SpaceX testing VTOL with its Grasshopper vehicle in 2012/13, the Delta Clipper’s maneuvers would look very familiar.

Initially, it was funded by the Strategic Defence Initiative Organization (SDIO). Many may remember SDI as “Star Wars”, the proposed defence system against ballistic missiles which had political traction during the 1980s up to the end of the Cold War.

Ultimately, the SDIO wanted a suborbital recoverable rocket capable of carrying a 3,000 lb payload to an altitude of 284 miles (457 km), which is around the altitude of the International Space Station. It also had to return with a soft landing to a precise location and be able to fly again in three to seven days. Part of the goal was to have a means of rapidly replacing military satellites should there be a national emergency.

The plan was to start with an “X” subscale vehicle which would demonstrate vertical takeoff and landing and do so again in three to seven days. A “Y” orbital prototype would follow that. In August 1991, McDonnell-Douglas won the contract for the “X” version and the possible future “Y” one. The following is the story of that vehicle and its amazing feats.

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What To Expect When You’re Expecting – A Trademark

July 18, 2018 by Bob Baddeley 18 Comments

A trademark represents a brand, so it can be words like “Apple”, including made up words like “Kleenex”. It can be symbols, like the Nike swoosh. It can also be colors, like UPS brown, and even scents like the flowery musk scent in Verizon stores. Filing a trademark in the United States is surprisingly easy. With a couple hundred dollars and a couple hours, you can be well on your way to having your very own registered trademark and having the right to use the ® symbol on your mark. You don’t need a lawyer, but you should know some of the hangups you might run into. The USPTO has a fantastic primer on trademarks, but we’ll TL;DR it for you. Continue reading “What To Expect When You’re Expecting – A Trademark” →

Let’s Talk About Elon Musk’s Submarine

July 17, 2018 by Tom Nardi 223 Comments

When word first broke that Elon Musk was designing a kid-sized submarine to help rescue the children stuck in Thailand’s Tham Luang cave, it seemed like a logical thing for Hackaday to cover. An eccentric builder of rockets and rocket-launched electric sports cars, pushing his engineering teams and not inconsiderable financial resources into action to save children? All of that talk about Elon being a real life Tony Stark was about to turn from meme into reality; if the gambit paid off, the world might have it’s first true superhero.

With human lives in the balance, and success of the rescue attempt far from assured (regardless of Elon’s involvement), we didn’t feel like playing arm-chair engineer at the time. Everyone here at Hackaday is thankful that due to the heroics of the rescuers, including one who paid the ultimate price, all thirteen lives were saved.

Many said it couldn’t be done, others said even saving half of the children would have been a miracle. But Elon’s submarine, designed and built at a breakneck pace and brought to Thailand while some of the children were still awaiting rescue, laid unused. It wasn’t Elon’s advanced technology that made the rescue possible, it was the tenacity of the human spirit.

Now, with the rescue complete and the children well on their way to returning to their families, one is left wondering about Elon’s submarine. Could it have worked?

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