Hackaday Links: March 22, 2015

[Liam Kennedy] built a wearable space station notifier it’s on Kickstarter, and now the campaign is in its final hours. It’s very cool; doubly so if you don’t have to talk to a crazy lady who doubts the existence of NASA.

[countkillalot] lost a Raspberry Pi. It was in his apartment, and responded to ping, but he couldn’t find it. Turning the Pi into an FM transmitter revealed its location. Relevant bash.org.

If you don’t listen to the Amp Hour podcast, oh man are you in for a treat. This time it’s [Chuck Peddle], father of the 6502, designer of the KIM-1, and someone with at least three hours’ worth of interesting stories.

MakeIt Labs, the Nashua, New Hampshire hackerspace, has done everything right – they have their 501(c)(3), and they’ve been talking to the city about getting a new space. They have the option of moving into a space three times the size as their current one, and it’s cheaper than the current space. They have an indiegogo to raise the renovation funds for the new space. Oh, hackaday.io supports pages for hackerspaces. Just pointing that out.

Speaking of hackerspaces, yours needs this sign.

A 3-DAY DESERT CAMPING AND TECH-FEST WITH BEER. That’s all you need to know about Arduino Day, an event being held next weekend in the Mojave.

Want to hide from the NSA, or whatever governments or corporate interests are listening in on your phone? Stick it in a microwave. [WhiskeyTangoHotel] tested out a Tek RSA306 spectrum analyzer in a microwave, once with the door open, once with the door closed. If you’re exceptionally clever or have access to Wikipedia, you can figure out what frequencies will leak out of a microwave given the size of the holes in the metal mesh.

Here’s a Flintstones toilet paper holder. It would have been a phonograph, but no one could find a cooperative turtle and bird.

It has been brought to our attention that everyone should be aware ucapps.de still exists. If you want something that does everything with MIDI and SID chips, there you go.

A Description of Maddening Battery Terminology

Once again, [Afroman] is here for you, this time breaking down electrolyte and the terminology behind batteries.

Volts and Amps are easy mode, but what about Amp hours? They’re not coulombs per second hours, because that wouldn’t make any sense. An Amp hour is a completely different unit podcast, where a 1Ah battery can supply one amp for one hour, or two amps for 30 minutes, or 500 mA for two hours.

Okay, what if you take two batteries and put them in series? That would double the voltage, but have the same Ah rating as a single cell. Does this mean there is the same amount of energy in two batteries as what is found in a single cell? No, so we need a new unit: the Watt hour. That’s Volts times Amp hours, or more incorrectly, one joule per second hour.

Now it’s a question of the number of cells in a battery. What’s the terminology for the number of cells? S. If there are three cells in a battery, that battery has a 3S rating. You would think that C would be the best letter of the alphabet to use for this metric, but C is entirely different. Nothing here makes any sense at all.

What is C? That’s related to the number of amps a battery can discharge safely. If a 20C battery can discharge 2200mAh, it can deliver a maximum current of 44 A, with 20C times 2.2Ah being 44A.

So there you go. A complete description of something you can’t use logic and inference to reason through. Video below.

Continue reading “A Description of Maddening Battery Terminology”

Hackaday Meetup with [Chris Gammell]

hackaday-meetup-with-chris-gammell

Update: We have it figured out. We’re bringing the awesome at The Blind Donkey in Pasadena, CA at 6pm this evening. Stop in with your hardware and your war stories. Chris Gammell, Mathieu Stephan, and I can’t wait to talk Arduino hardware hacking with you!

I’m getting to meet all kinds of cool people in person this year, and so can you! Well… if you happen to be in Pasadena, California on Wednesday after work and have nothing better to do. [Chris Gammell] — well-known for The Amp Hour and Contextual Electronics — and I are both going to be in town. We’re meeting up for a beer and thought we’d invite you along for the fun.

Details are scarce right now. I’m not sure of time or place (other than Pasadena area) so make sure you follow @Hackaday on Twitter and watch for the #HaD_meetup tag Wednesday afternoon for the details. We’ll also update the Hackaday Projects event page at the time. I’ll bring along some swag; you’d better cart along a piece of hardware to show off in return for a t-shirt or stickers. You’re on your own for food and beverages at this one.

Wondering what I meant about meeting lots of cool people? In addition to the nearly 500 awesome readers who showed up at The Gathering, I met [Brian] and [Eliot] for the first time.

Amp Hour interviews [Joe Grand]

The Amp Hour, a podcast of electronics enthusiasts and professionals alike, just did an epic interview with [Joe Grand]. Along with hosts [Chris Gammell] and [Dave Jones], the discussion runs the gamut of points of interest in the hardware hacking world. The first vignette explores the rise, run, and fall of Prototype This, an engineering-centric TV show that [Joe] did along with a group of various engineers for the Discover Channel. He politely discusses some of the goods and bads of the TV business and how that affected the team’s ability to go into great detail about the projects they were building.

From there the guys discuss the development of Hackerspaces through the years. [Joe] has some concerns about the injection of corporate sponsorships in these DIY spaces and what that may mean in the long run. He then talks about the impending release of his 3-year-long laser range-finder project (we’ve seen a project using a prototype of this sensor). The show is rounded out with discussions about hardware fab houses that [Joe] uses and has used over the years for projects like the Defcon Badges (we loved his Defcon 18 badges).

It’s a great episode so download a copy and set aside about an hour to listen to the whole show.