A Beginner’s Guide To Magnetometers

July 14, 2011 by Mike Nathan 9 Comments

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The folks over at LoveElectronics recently published an article that explains some of the ins and outs of magnetometers for those who are interested in trying one out, but might not understand how to use them.

A good part of the article focuses specifically on how to manipulate the HMC5883L magnetometer from Honeywell, but a lot of the information can be applied to other makes/brands of compass sensors. They start out discussing in very basic terms how the compass works, then delve into some specifics on how to interface the chip with an Arduino, courtesy of a breakout board that they sell. The breakout board is actually quite simple, so any number of custom iterations could be built for your own testing purposes.

They walk through the use of an HMC5883L-specific Arduino sketch they produced, making it easy for beginners to start getting useful data from the compass units. While a pre-made sketch might seem like a bit of a cop out, it at least gives the curious/motivated beginner a chance to look at some completed code in order to see how things work.

If you are interested in cutting your teeth on some additional beginner concepts, check out these other how-to articles and tutorials.

Electronics Tutorial Two-fer: Soldering Skills And Wires

July 5, 2011 by Mike Nathan 27 Comments

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There is a plethora of electronics tutorials scattered about online. Sometimes it can be hard to separate the good ones from the bad, and the enlightening from the misinformed. We recently came across a pair that we found helpful, and thought they would appeal to anyone starting off in electronics.

In this video tutorial, [Dave Jones] at the EEVblog covers soldering, detailing good practices and common mistakes to avoid when working with through-hole components. As the second video in a series he picks up where part one left off, excitedly demonstrating the ins and outs of good soldering skills.

Hackaday reader [grenadier] is working on a series of beginner’s electronics tutorials, and this week’s entry covers wiring. He discusses wire types, gauges, and even provides a nifty self-computing chart that calculates power loss based on the length and gauge of the selected wire. Before wrapping things up, he briefly touches on fuses and the pitfalls of choosing wire that’s not up to the task at hand. While you’re over there looking over his tutorial, be sure to check out the Junkbox, there’s plenty of awesome stuff to be had!

PLL 101

June 21, 2011 by Kevin Dady 14 Comments

[Jeri Ellsworth] and former Commodore Computer engineer and current full time tinkerer [Bil Herd] have a little chat on skype covering the 101’s of Phase Lock Loops in this hour long video. PLL’s are handy for many applications, but their basic use is to keep clock signals in sync.

Topics covered include: Why we care, a basic explanation for the CD4046, capture ranges, and meta stability. Examples from analog tv, to clock recovery, finding falling edges and FPGA’s. This thing is jam packed full of information.

With talks of future episodes and a quick tour of [Bil’s] bench this is something to not miss. Join us after the break for the video!

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ChipKIT Sketch: Mini Polyphonic Sampling Synth

June 8, 2011 by Phil Burgess 20 Comments

In our hands-on review of the Digilent chipKIT Uno32, we posed the question of what the lasting appeal might be for a 32-bit Arduino work-alike. We felt it needed some novel applications exploiting its special features…not just the same old Arduino sketches with MOAR BITS. After the fractal demo, we’ve hit upon something unique and fun…

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Stripping DRM From OverDrive Media Console EBooks

June 7, 2011 by Mike Nathan 18 Comments

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[Armin Tamzarian’s] local library recently started lending eBooks via the OverDrive Media Console system. He checked out a couple of books, which got him thinking about how the copy protection scheme was implemented. He wondered what recourse users had if they wanted to view a book they have already checked out on a different, or unsupported piece of hardware.

His research centers around Adobe’s ADEPT digital rights management scheme, which is used to protect the books offered on loan by OverDrive. The topic is broken down into three parts, starting with an introduction to the EPUB file structure, the OverDrive Media Console, as well as the aforementioned ADEPT DRM scheme.

The second part takes a close look at the OverDrive Media Console itself, where he uses the ineptkey and ineptepub utilities written by [I♥CABBAGES] to pull the RSA cipher keys from the EPUB data he uncovered. When he then tries to strip the ADEPT DRM layer from his books however, he discovers that OverDrive is using a non-compliant version of the ADEPT standard, which renders existing tools useless.

The final part of [Armin’s] discussion digs even deeper into the OverDrive Console’s inner workings, where he finds that the OverDrive Media Console stores quite a bit of information in an SQLite database. After a bit of digging, he finds all the data he needs to strip the DRM from his books. [Armin] also took the time to wrap all of his findings up into a neat little tool called OMCStrip, which as you may have guessed, strips the DRM from ADEPT-protected eBooks with ease.

Cheap And Cheerful Arduino Breadboard Basics

June 1, 2011 by Jesse Congdon 8 Comments

For those less experienced folks looking to move their Arduino projects to more permanent installations, this is just for you! [Martyn] Posted a three part series, VeroBoardUino, over at his blog about moving your Arduino project to a soldered breadboard.

Part one kicks off with the appropriate breadboard requirements, modifications, and a simple 7805 power supply. In the guide [Martyn] is using strip board, so copper connections will have to be broken using a drill or just by scraping with a hobby knife. Strip board also saves a bit of wire routing in the end. Part two handles the reset button, serial connection and chip socket (Part 2.5 has also been added to include schematics of the breadboard). Finally, part three installs the crystal and connects your Atmega chip to power and ground.

Next post he will be covering more on the software end of things, burning the bootloader and uploading programs to your new board so stay tuned for updates!

Automated Hose Keeps Cats From Watering You

May 25, 2011 by Jesse Congdon 50 Comments

Commenter [TheCreator] reminded us of this fantastic video from [Craig Turner] who you may recognize from SBS’s Top Gear Australia Video Competition. You see, [Craig] has been struggling for some time with the problem of neighborhood cats relieving themselves pretty much all over his stuff. Through surveillance he identified (and named) around 9 separate cats sauntering into his yard during the wee hours of the night. The only issue now was to humanely discourage them from entering his yard.

The best solution, in this case, was a simple spray from the garden hose, but who is going to stay up all night to watch for cats? [Craig]’s ’75 Galant happens to have aftermarket door locks. These typically contain a simple powerful 12V actuator that will push or pull when given current. The actuator is strong enough, and has enough travel, to depress your typical garden sprayer handle. The lock actuators even include enough mounting hardware to tack everything together. The only irreversible part of the hack appears to be the hole drilled into the sprayer’s handle.

The job of cat detection is handled with a PIR sensor (sourced from his home security system) and a paper towel tube to narrow the detector’s field of view. Placed at animal height the PIR detector works like a trip line, and flips a relay connected to an array of devices: A bright LED lamp, a DSLR set to take several quick photos of the victim, An HD video camera, and the sprayer solenoid. This whole rig is placed at a convenient choke point and hilarity ensues! A schematic is included in the video but is pretty difficult to interpret, we transcribed it for you. Some details are unclear but essentially a few relays are stapled together to provide either high or low switching signals.

Check out the video, [Craig]’s schematic, and our interpretation of [Craig]’s schematic after the jump!

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