In parts 1 and 2, I discussed the important parts of what is going on the PC side with lua. While not 110% detailed I hope it gave you an idea on how the data is processed so the Apple II computer could quickly digest it. Now its time to see what happens at the other end of the serial cable. I am using basic, but its not 100% off the rom Applesoft basic, that would be even slower, so I am using a compiler and a fast graphics driver. Both are from “The Beagle Compiler” which was produced by the ever awesome Beagle Bro’s software company, and though still under copyright, the publishers have given permission for use of their software (within reason I don’t think you will get very far selling it).

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Hackaday reader [Paul] recently shared a simple hack he put together via our Flickr photostream.

It seems that his Magellan GPS unit is pretty finicky when it comes to power supplies. When connected to the Magellan adapter, the GPS unit charged as you would expect. When connected to a PC, it sensed the connection and allowed its file system to be mounted, just as it was intended to do.

However, a problem arose when he tried hooking the Magellan up to a different power supply. The unit still thought it was connected to a PC, and refused to perform any GPS-related functions since its file system was tied up. Not wanting to lug around multiple chargers, he decided to see what the heck was going on with his GPS unit.

He pulled the plug apart and found that the 4th and 5th pins of the USB cable were shorted together. While most devices ignore the 4th pin, the Magellan checks to see if that pin is grounded. If so, it assumes it is connected to its power supply. If not, it assumes that it should act as if it is connected to a PC.

With this information in hand, [Paul] did the same thing as any of us would and hacked together a USB cable with shorted pins. The cable can be attached to any standard USB port or charger, saving him from having to lug around an extra adapter.

The crew at Defcon is hard at work getting things ready for this year’s event, taking place over the first weekend in August. While the typical call for papers has been out for almost two months now, the extra space afforded by the RIO hotel has given the organizers a chance to shake things up a bit and try something new.

Along side the call for papers, they have issued a call for workshops. Since they have about 8 spare rooms on hand, they have decided to allow people who consider themselves a leader, ‘leet hacker, or ninja in their particular field to share their knowledge in a small (30 person) workshop setting.

The organizers are not strict on content, though it should be compelling. They cite examples such as teaching people to build an impenetrable Linux installation, PS3 hacking, or even helping people prep for a Ham radio license exam.

If you have something interesting to share with the community, be sure to swing by the Defcon site and get your application started!

Instructables user [PenfoldPlant] is a big fan of indoor rock climbing, and while watching others make difficult climbs, he has often wondered if he could follow the same route up the wall. Unfortunately, aside from watching the other climbers and hoping to remember the path they have taken, he found there isn’t much you can do to ensure that you have precisely replicated the climb.

He thought awhile and came up with a laser tracking system that can be used to record a climber’s ascent, then replay it any number of times. This allows climbers to be able to replicate other climbers’ paths as well as compete against one another in timed races.

This works much like the “ghost” feature found in most racing games, though the process is half manual/half automated. The initial ascent is recorded by manually tracing the climber’s route with a laser pointer as they climb. The path is recorded and then can be replayed, courtesy of the onboard Arduino.

It really is a neat system, and while it works pretty well already, we think there is still room for enhancement. It wouldn’t be extremely difficult to have the climber wear some sort of light beacon that could be tracked using a web cam or other recording device, taking the manual labor out of the equation. In that case however, we imagine the Arduino would need to be swapped out for something a touch more powerful.

Stick around for a quick video of the tracking system in action.

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Here at Hackaday, we’re not against showing videos of gratuitous destruction just for the sake of it, though we try not to make it a habit. In this case we just couldn’t help ourselves. However, this video technically constitutes a security hack, as it does involve erasing sensitive information from CDs…

…with awesome!

This may be the coolest CD eraser we’ve seen yet. Positioned between two high-voltage transformers, the spinning CD has its data violently stripped off in just a matter of seconds. To be fair, the data isn’t erased per se, but the metallic substrate on which the data is recorded is flaked off by the aggressive application of electricity.

Having destroyed our fair share of AOL CDs in the microwave over the years, we are now a bit sad over the fact that they were disposed of in such a lackluster fashion – if only we had one of these around!

Since we’re on the topic of mindless destruction, you might as well take a few minutes and check out this thermite-roasted Thanksgiving turkey, this self-destructing hard drive, or perhaps this thermic lance built from spaghetti.

You know, for science.

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[Gordon] sent us a tip about this simple laser trip wire system after reading yesterday’s post on a more complicated laser security unit. That build did a lot to provide functionality, such as a system to disarm the trip wire, and a robust light detection circuit. This time around there’s more happening with smoke and mirrors than with electronics.

[The Timmy] built this simpler version based on a laser trip system from Afrotechmods (video of that one is embedded after the break). He had a bag full of small square mirrors which he attached to a wall with some poster putty. A laser module shines a beam of light onto a cadmium sulfide sensor after it bounces around the optical network for a while. That CdS sensor controls an N-channel MOSFET, switching it off when light is detected and on when the intensity of the laser is absent. This example just turns an LED on and off, but since it uses logic-level voltages you can choose to add a microcontroller to the mix if you have other plans in mind.

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[Sean Michael Ragan] built this FM transmitter which shows off its circuitry via a clear plastic dome. The device is electrically identical to one we looked at in September. That version championed a construction method that used small squares of copper clad as solder points which were each super-glued to a large copper-clad platform serving as a ground plane. [Sean] is using a printed circuit board that was laid out by Sonodrome. You can check out their own glass-jar transmitter build where the board artwork is available for download.

One of the tips we enjoyed from [Sean's] step-by-step build is the coil wrapping. He used the threads of a 1/4-20 bolt to guide copper wire as he wrapped a total of four turns. Once the bending is done, just unthread the bolt to separate it from the coil and gently stretch the wire for a 12mm distance between the two leads. Not only is this visually pleasing, but it will help with transmission clarity.

Pop a few aluminum bits into this little RC racer and you’ll have power for around forty minutes. This concept, which has been patented, is the result of a college research project. It uses a chemical reaction between aqueous Sodium Hydroxide and aluminum. The result of that reaction is hydrogen, which is gathered and directed to a fuel cell that drives the car.

Novel? Yes. Interesting? Absolutely. But you should be raising an eyebrow at the dubious choice of fuel that is aluminum.

If you don’t know what we’re talking about let us paint you a picture. Aluminum is a metal that is refined from bauxite ore. It takes an immense amount of electricity to smelt the metal. This is usually justified because aluminum is one of the most recyclable substances on earth, capable of being melted down and reformed countless times. But dissolving it in drain cleaner breaks it down and then it’s gone. So what we have here simply must be the least efficient disposable battery so far developed. It’d probably use less resources to grow and harvest lemons as a power source.

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