LED display panels are a great way of displaying text and graphics, and aren’t all that hard to program when you know how they work. And most of the single or twin colour panels work pretty much the same way.

The key ingrediant of these panels is the LED matrix module of course, so let’s have a look at what’s inside.

Each LED matrix module consists of 64 LEDs, or 128 if it is a two color matrix. The anode of each LED is connected to the row pin, and the cathode is hooked up to the column pin. To light any given pixel, it’s a matter of grounding the selected row and then connecting the column pin to power. Since the LED matrix is simply that, a matrix, your microcontroller can light any LED of a particular row, or any LED of a specified column. Naturally, we would like to be in a position to light any given LED, so to do that, we need some clever driver circuitry. It must let us select a row and then illuminate the right LEDs. A display is made up of more than one matrix, so it would be better if this circuitry allowed us to connect matrices and panels to one another too.

And so that brings us to the shift register. Drenched in traditional digital electronics, the shift register is a very important part of the display. The 74LS595 is used to create the option of using a couple of microcontroller outputs to manipulate all of the LEDs along a single row. The serial input is pulled high or low, then the clock pin is pulsed to load the value into the shift register. The output of one shift register feeds into the input of the next.

So a shift register allows us to set which LED is on for a given row, but that only gets us a single row. How do we extend this over several rows?

The other vital component is a 3-to-8 line decoder. This accepts 3 inputs, A, B and C, and then pulls one of the 8 outputs low. Normally, the outputs are high. The high output is the one which corresponds to the binary equivalent of the values on the A, B and C pins so setting all pins low will set output zero low. Setting each of A, B and C high will result in setting output 7 low. You can see this allows us control over 8 outputs with only 3 input pins.

The outputs of the decoder are hooked up to mosfets, which permit us to control huge amounts of current very easily. So from our 3 inputs A, B and C we can control 8 rows and each row is connected to ground through the mosfet when the mosfet’s input is pulled low. Excellent! So now we will control which row we mean to use simply by setting the A, B and C inputs and the actual individual LEDs we turn on is set by shifting in low or 1 for each LED position, into the shift register.

As this only illuminates the pixels we care about in one single row, it's a matter of setting the pixel in each row in turn, and when we are done with the last row, beginning again from the beginning. This permits us to control thousands of LEDs, with a low number of control lines.

Embedded Adventures is a good spot to find a lot of different types of LED display panels as well as associated driver hardware and software libraries to make your next exciting microcontroller based project.

How to get a hefty new hard drive for your Mac without making your other gadgets jealous? Iomega is offering up a solution with the fairly elegant Mac Companion Hard Drive, a two or three terabyte external drive designed with Apple computers in mind that adds a high-powered charging port for your peripherals. The drive also packs additional USB and FireWire ports (no Thunderbolt, guys?), plus a set of four LEDs, which let you know how full it is with a glance. The drives are available via Apple at 5 and 5, for 2TB and 3TB, respectively.

Continue reading Iomega Mac Companion Hard Drive offers 3TB of storage and a filling station for your iPad

Iomega Mac Companion Hard Drive offers 3TB of storage and a filling station for your iPad originally appeared on Engadget on Tue, 02 Aug 2011 14:58:00 EDT. Please see our terms for use of feeds.

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If you’ve always dreamed of colorful, glowing accoutrements, or just have some ideas for an upcoming Halloween costume, grab your soldering iron and a sewing needle: Here are a couple of products you can use to get a real 21st-century look.

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If you’re under the impression that robots were all over Google I/O this year, you’d be right — after all, it’s a only small leap from robot to Android. Yesterday we got some hands-on time with iRobot’s Ava mobile robotics platform and came away rather entertained. Ava is an autonomous robot that’s equipped with and array of sensors (two Kinnect-like 2D / 3D cameras, a scanning laser, ultrasonic transducers, and contact bumpers), driven by omnidirectional wheels, and controlled by its own Intel Core-based computer. The base hosts batteries, motors, as well as electronics and supports a telescopic mast that carries a pod containing touch ribbons, speakers, and a microphone. On top of this pod you’ll find a “head” that can tilt / pivot and basically acts as the dock for any Android tablet. Ava is able to navigate a mapped-out space on its own while avoiding obstacles and people along the way — going as far as to “blush” via RGB LEDs in the base if it accidentally bumps into anything or anyone. This autonomous behavior allows the robot to be controlled by simply setting waypoints and letting the onboard computer do all the hard work of coordinating sensors and motors to get it there safely. Google and iRobot have worked together and created APIs that allow Android developers to write apps — from telepresence to roaming testimonials — that control Ava wirelessly from the docked tablet. Both partners are hoping this will spearhead the development of unique new projects which combine the power of robotics and Android devices. There’s no word on pricing or availability at this point, which comes as no surprise given that these machines are still very much prototypes. We’ll leave you to look at our gallery below and watch the robotic ballet in our hands-on video after the break.

Continue reading iRobot Ava mobile robotics platform hands-on at Google I/O (video)

iRobot Ava mobile robotics platform hands-on at Google I/O (video) originally appeared on Engadget on Thu, 12 May 2011 09:13:00 EDT. Please see our terms for use of feeds.

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Toshiba’s focus at CES was glasses free 3D displays, but it highlighted more conventional HDTVs today at an event in Rome. Its new TVs and laptops all tie in to Toshiba Places, which sorts out access to different types of apps for video, social networking, music and other areas and is ready to launch this month. Separating Toshiba from the competition is a slew of new technology and the top of the line 55ZL1 model checks all the boxes: Seven core CEVO CPU for image processing, a Pro-LED512 panel that is the world’s first with 512 zones of dimming among 3,072 LEDs, Personal-TV facial recognition that picks up on which user is watching then personalizes to their preferred settings and active shutter 3D glasses. The edge lit LED VL863 series will come in 47- and 42-inch versions featuring the FPR passive glasses 3D LG is promoting and four pairs of glasses, while the 32- through 46-inch UL863 drops 3D but includes built-in WiFi and Personal-TV then finally the SL863 models are the same minus built-in WiFi. No prices were listed but the new models should be shipping soon, press releases are linked below — no word on the US-bound models yet.

Toshiba shows off 2011 HDTVs with the most local dimming LEDs, facial recognition, 3D and more originally appeared on Engadget on Tue, 05 Apr 2011 21:03:00 EDT. Please see our terms for use of feeds.

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