Electric current comes in many forms: current in a wire, flow of ions between the plates of a battery and between plates during electrolysis, as arcs, sparks, and so on. However, here on Hackaday we mostly deal with the current in a wire. But which way does that current flow in that wire? There are two possibilities depending on whether you’re thinking in terms of electron current or conventional current.
In a circuit connected to a battery, the electrons are the charge carrier and flow from the battery’s negative terminal, around the circuit and back to the positive terminal.
Conventional current takes just the opposite direction, from the positive terminal, around the circuit and back to the negative terminal. In that case there’s no charge carrier moving in that direction. Conventional current is a story we tell ourselves.
But since there is such a variety of forms that current comes in, the charge carrier sometimes does move from the positive to the negative, and sometimes movement is in both directions. When a lead acid battery is in use, positive hydrogen ions move in one direction while negative sulfate ions move in the other. So if the direction doesn’t matter then having a convention that ignores the charge carrier makes life easier.
Saying that we need a convention that’s independent of the charge carrier is all very nice, but that seems to be a side effect rather than the reason we have the convention. The convention was established long before there was a known variety of forms that current comes in — back even before the electron, or even the atom, was discovered. Why do we have the convention? As you’ll read below, it started with Benjamin Franklin.
[Kenjo] attended Chicago’s Thotcon this past week and has started hacking the convention badge and detailing what he learned. Thotcon’s badge, designed by [Jedha] and programmed by [John Wallis] of Workshop 88, is packed with the requisite electronic hardware and cryptic clues. There are four NeoPixel LEDs, three pots, and a micro USB, all run by an ATmega32u4.
The stock firmware is a game called tesserHack, a maze game using the three pots for navigation. You can also connect via USB to play through the serial console, and this version includes a map view and help menu.
[Kenjo] who previously hacked the Thotcon 0x6 badge, accidentally deleted the stock firmware on this year’s badge, so he used a Bus Pirate as an ISP to burn the Arduino boot loader back on, and has started mapping out the pots and LEDs. If you’re interested in helping out, check out the project on Hackaday.io. [Thanks, gigawatts]
There are a few interesting Hackaday gatherings going on next weekend. The first is the Bay Area Maker Faire. Most of the Hackaday and Tindie crew will be in San Mateo next weekend, and we’re giving away free tickets to the Faire – a $70 value, free to Hackaday readers. Hackaday is crashing a pub on Saturday night. There’s also a super-secret meetup on Sunday. Don’t tell anyone.
On the other side of the country, there’s an even better convention for people who build stuff.. It’s Hamvention, the largest amateur radio meetup in North America. I’m going to be there. Find me and pick up some Hackaday swag. I’ll be posting to the Hackaday Twitter all weekend.
The main purpose of my visit is to document the immense swap meet. There will be over a thousand vendors hocking their wares, from antique radios to gauges and other electronic paraphernalia. It is the biggest draw to Hamvention, and by every account I’ve heard, it’s impossible to look at everything.
It might be impossible to look at everything, but apparently I’ve very good at separating the wheat from the chaff at ham swaps. During my last visit to the W6TRW swap meet in Redondo Beach, I found an UltraSPARC laptop (!), and a wooden modem from the mid 60s. On Friday, Saturday, and Sunday, it will be my job to document all the oddities of Hamvention.
Depending on how many people I meet at Hamvention, there might be a semi-official Hackaday get together after the show. The US Air Force Museum at Wright-Patterson would be cool, but Ihop or Denny’s would be far more realistic. Look for the guy in the Hackaday hoodie flying a Hackaday flag and he’ll give you some sweet stickers and swag.
[Bunnie] was at Burning Man this year, and to illuminate his camp members in the dark and dusty nights of the playa, he created a blinky badge. This isn’t just any badge stuffed with RGB LEDs; each of the badges were unique by the end of Burning Man. These badges were made unique not by twiddling dials or pressing buttons; all the color patterns were bred with badge sex.
This social experiment to replicate nature’s most popular means of creating more nature is built around a peer to peer radio. Each badge is equipped with a radio, a circle of RGB LEDs, and a bit of code that expresses the pattern of lights on the badge as a sequence of genes. When one badge gives consent to another badge, they ‘breed’, creating a new pattern of lights. If you’re wondering about the specifics of the act, each badge is a hermaphrodite, and each badge transmits a ‘sperm’ to fertilize the other plant’s ‘egg’. There’s even a rare trait included in the genome of the badge; each badge has a 3% chance of having a white pixel that moves around the circle of LEDs. [Bunnie] found this trait was more common after a few days, suggesting that people were selectively breeding their badges.
Of course, finding potential mates is a paramount concern for any sexual organism, and the sex badge has this covered, too. The 900MHz radio listens for other badges in close proximity, and when any are found their owners are displayed on an OLED display. This came in handy for [Bunnie] more than a few times – there’s no phones out there, and simply knowing your friends are within a hundred meters or so is a big help.
The entire badge platform is documented online, along with the code and spec for badge genes. Badges with some sort of wireless communication have been around for a while, but this is the first time that communication has been used for something more than sharing contact information or implementing a chat room. It’s a great idea, and something we hope to see more of in future con badges.
Ah, the heady aroma of damp engineers! It’s raining in Silicon Valley, where the 2010 Embedded Systems Conference is getting off the ground at San Jose’s McEnery Convention Center.
ESC is primarily an industry event. In the past there’s been some lighter fare such as Parallax, Inc. representing the hobbyist market and giant robot giraffes walking the expo. With the economy now turned sour, the show floor lately is just a bit smaller and the focus more businesslike. Still, nestled between components intended to sell by the millions and oscilloscopes costing more than some cars, one can still find a few nifty technology products well within the budget of most Hack a Day readers, along with a few good classic hacks and tech demos…
The registration desk hasn’t opened yet at ShmooCon 2009, but we’re already running into old friends. We found [Larry Pesce] and [Paul Asadoorian] from the PaulDotCom Security Weekly podcast showing off their latest ShmooBall gun. ShmooBalls have been a staple of ShmooCon from the very beginning. They’re soft foam balls distributed to each of the attendees who can then use them to pelt the speakers when they disagree. It’s a semi-anonymous way of expressing your dismay physically. [Larry] has been building bigger and better ways to shoot the ShmooBalls for the last couple years. You may remember seeing the 2008 model. This year the goal was to make the gun part much lighter. The CO2 supply is mounted remotely with a solenoid valve and coiled air line. The pistol grip has a light up arming switch and trigger. The gun is fairly easy to transport: the air line has a quick disconnect and the power is connected using ethernet jacks.
November 1st means that registration for ShmooCon 2009 has opened. The DC hacker convention is entering the fifth year. They’re releasing the tickets in blocks; after today’s are gone the next won’t be available till December 1st. Today is also the closing of first round consideration for their call for papers, but you still have another month before the final deadline.