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Squeezing the juice out of some AA batteries

[Ray's] breadboard power supply lets you drain the last traces of power from ‘dead’ AA batteries. Electronics that are powered off of disposable alkaline batteries have a cutoff voltage that usually leaves a fair amount of potential within. Since many municipal recycling programs don’t take the disposables (you’re just supposed to throw them in the trash!) we love the idea of squeezing them for prototyping use.

His design uses just one IC, the MCP1640, along with a handful of passive components. The chip is a boost converter with a startup voltage of just 0.65V, which means the batteries themselves – normally starting life above 1.5V – can be used until they drop to about 0.3V each.

Above you can see the kit he is selling. But it’s an open source project and the circuit is so simple we’re sure you can build your own. Add that boost converter chip to your next parts order for around $0.40.

[Ray] made a nice demo video for the device which you can see embedded after the break.

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This image contains a hidden audio track

This image contains a hidden audio track which you’re very familiar with. Well, it used to. We’d bet we messed up the careful encoding that [Chris McKenzie] used to hide data within an image when we resized the original.

He’s using a method called Steganography to hide a message in plain sight. Since digital images use millions of colors, you can mess with that color data just a bit and the eye will not really be able to pick up any difference. Each pixel has had the eight least significant bits swapped out for the data [Chris] is hiding. Since the image uses 24-bit color, the largest possible change (going from 0 to 255) in those bottom eight bits will only result in a color change of about 0.15%. And that’s only for one pixel; in most cases the change will be much less.

He shows his work, both decoding and encoding using Ruby, and even provides a one-liner which lets you playback the audio without downloading anything (just make sure you’ve got all of the dependencies installed). Never gonna give, you, up…

[via Reddit]

Display Twitter on an Arduino

If you ever wanted your name out on the Internet, now is your time to shine. [Chris] hooked up an Arduino to the Internet and is streaming the results of combing through Twitter live to the entire world.

The SocialBot9000, as [Chris] calls his build, is an Arduino Uno connected to an Ethernet shield and an LCD character display. The firmware uses the Twitter API to search for recent posts containing the phrase, ‘socialbot9000.’ A PHP script on the Arduino does all the heavy lifting and with the great Bildr tutorial on getting the Ethernet shield up and running, [Chris] was off to the races.

Because it’s extremely doubtful that everyone on the Internet could manage typing a message into Twitter that would be correctly parsed by the SocialBot9000, [Chris] put a small form up on the build log that will correctly generate the message and take you to your Twitter account for posting. After all that was done, [Chris] decided to have some fun and set up a live feed from a camera in front of the LCD display for the world to watch.

Cheap and easy logic signal generator

While function generators or analog signal generators are ubiquitous in their utility, we haven’t seen much of logic function generators on Hack a Day. Luckily, [Dilshan] sent in a really neat 8-channel signal injector that is amazingly simple to build and comes with a great front end for editing patterns from your computer.

The hardware portion of the build is kept to a minimum with a PIC18F chip, USB socket, and header pins as the only major components. This board serves as the hardware output for the Kidogo software. This software provides a very nice interface to generate 5 volt logic signals on eight separate channels that will immensely help exploring your digital world.

With a great interface and very easy to build hardware, we can easily see the Kidogo hardware finding its way onto workbenches around the world. We’re tempted to build our own version using an AVR, but we would hate to ruin such a simple but useful tool.

Tethering a Kindle for free 3G

[Excelangue] just posted a guide to using the free 3G connection in your Amazon Kindle to browse the Internet on your computer.

The hack requires a Kindle Keyboard 3G and the free worldwide Internet access that comes along with the purchase price. After jailbreaking the Kindle and applying a USB network hack, [Excelangue] managed to connect his laptop to the Internet through his computer. The process of tethering the Kindle’s 3G is remarkably easy, but we expect a one-click solution will pop up on the web sometime this week.

Of course we have to note here that tethering a Kindle is against the Amazon terms & conditions, and the data going through your Kindle is tied to a unique ID. If you do this, Amazon knows who you are and is more than likely willing to brick your device. [Excelangue] is looking into tethering to the Kindle over WiFi so Android and iOS devices can get in on the action, but he’s still in the process of experimenting with his build.

Finally, LaTeX in HTML files

Writing a paper in LaTeX will always result in beautiful output, but if you’d like to put that document up on the web you’re limited to two reasonable options: serve the document as a .PDF (with the horrors involves, although Chrome makes things much more palatable), or relying on third-party browser plugins like TeX The World. Now that [Todd Lehman] has finally cooked up a perl script to embed LaTeX in HTML documents, there’s no reason to type e^i*pi + 1 = 0 anymore.

For those not in the know, LaTeX is a document typesetting language that produces beautiful output, usually in PDF form. Unfortunately, when [Tim Berners-Lee] was inventing HTML, he decided to roll his own markup language instead of simply stealing it from [Don Knuth]. Since then, LaTeX aficionados have had to make do with putting TeX snippets into web pages as images or relying on the [; \LaTeX ;] generated from the TeX The World browser extension.

[Todd Lehman]‘s perl script generates the PDF of his LaTeX file and pulls out all the weird font and math symbols into PNG files. These PNG files are carefully embedded into the HTML file generated from the normal text pulled from the LaTeX file. It’s a ton of work to get these document systems working correctly, but at least there’s a reasonable way to put good-looking LaTeX on the web now.

Visualizing a nanosecond

We’re so glad to have run across this video where [Rear Admiral Grace Hopper] explains how to visualize a nanosecond. Now we had never heard of [Grace Hopper] before, but once you watch the clip (also embedded after the break) you’ll want to know who this person is. We work with divisions of seconds all the time when developing with microcontrollers. But those concepts are so abstract we never had a need to think about them as a physical distance. After all they’re a measure of time, right?

You can’t make it out, but she’s holding a length of wire between her hands. It is 11.8 inches long and represents how far electricity can travel in one nanosecond (one billionth of one second). She goes on to explain that this is a calculation of the distance which light can travel in one nanosecond, then really hits the concept home when she uses it to explain latency in satellite communications. For us, the waste of not putting a chip into sleep mode when it’s just stuck in the loop waiting for an interrupt is where we made the connection.

So back to the woman herself. We think you’ll really enjoy reading through her Wikipedia biography page. [Grace] was a computer science pioneer. She is credited with writing the very first computer compiler. She postulated and articulated the concepts that led to the development of COBOL, and popularized the term ‘debugging’. In short, she is one of the giants whose shoulders we all stand upon.

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