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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Share Bike Surrenders Its Secrets To A Teardown

July 27, 2018 by Jenny List 67 Comments

If you are fortunate enough to live in a tiny settlement of no significance then perhaps you will be a stranger to bike sharing services. In many cities, these businesses have peppered the streets with bicycles secured by electronic locks for which the “open sesame” command comes through a Bluetooth connection and an app, and it’s fair to say they have become something of a menace. Where this is being written there are several competing brands of dubious market viability, to take a trip across town is to dodge hundreds of them abandoned across pavements, and every one of our waterways seems to sport one as jetsam courtesy of our ever-creative late-night drunks.

However annoying they might be, these bikes are electronic devices, and it’s thus interesting to read a teardown of one courtesy of [Electric Dreams]. The bike in question is in Australia and comes from Ofo, and it is very much worth pointing out that it is their property and prying it open is almost certainly a crime.

The bike itself is a fairly unexciting and rugged, with the electronics sitting in a module incorporating a back wheel lock sitting somewhere above where the rear brake might be. Inside is a custom board with GPS, GSM, and Bluetooth, and unexpectedly for an Aussie bike, a Netherlands SIM. Underneath the board is a motor and gearbox to activate the lock, but none of these parts are unexpected. The interesting angle of us comes from the power source, which is a D-sized lithium thionyl chloride cell, a primary cell rather than the expected rechargeable. These cells have a huge energy capacity, but at the expense of a truly nasty electrolyte and a high internal resistance which means they are limited to delivering tiny currents lest they explode. To power the radios and motor in the Ofo, the designer has added a supercapacitor which presumably charges slowly and can then dump the required power when needed.

So bike share bikes have no great surprises in their electronics but a minor one in their power source. Curiosity sated, no need for anyone else to break the law for another look. It’s interesting to see a large lithium thionyl chloride cell in the wild, and it would be even more interesting to know whether Ofo get good life from them. Maybe our commenters will know. Or perhaps someone should ask the Feds.

Thanks [xtra] for the tip.

ESP8266 Internet Controlled LED Dimmer

July 27, 2018 by Tom Nardi 11 Comments

There’s no shortage of debate about the “Internet of Things”, largely centered on security and questions about how much anyone really needs to be able to turn on their porch light from the other side of the planet. But while many of us are still wrestling with the realistic application of IoT gadgets, there’s undoubtedly those among us who have found ways to put this technology to work for them.

One such IoT devotee is [Sasa Karanovic], who writes in to tell us about his very impressive custom IoT LED dimmer based on the ESP8266. Rather than rely on a commercial lighting controller, he’s designed his own hardware and software to meet his specific needs. With the LED strips now controllable by any device on his network, he’s started working on Python scripts which can detect what he’s doing on his computer and react accordingly. For example, if he’s watching a movie the lights will automatically dim, and come back up when he’s done.

[Sasa] has provided all the files necessary to follow in his footsteps, from the Gerber files for his PCB to the Arduino code he’s running on the ESP. The source code is especially worth checking out, as he’s worked in a lot of niceties that we don’t always see with DIY projects. From making sure the ESP8266 gets a resolvable DNS hostname on the network to using websockets which update all connected clients with status info in real-time, he’s really put a lot of work into making the experience as complete as possible.

He’s explains in his blog post what needs to be edited to put this code to work in your own environment, and there’s even some descriptive comments in the code and a helpful debug mode so you can see how everything works. It’s always a good idea to consider that somebody else down the road might be using your code; taking a few minutes to make things clear can save them hours of stumbling around in the dark.

If you need more inspiration for your ESP8266 lighting project, check out this ambient lighting controller for a kid’s room, or this professional under-cabinet lighting controller.