Controlling High Voltage 7-Segment Displays


The MAX7219 is one of those parts in your bin that has a “done and done” attitude. In case you’re unfamiliar, this chip can be used to control 7-Segment displays, 8×8 Matrix displays, or even a pile of random LEDs. You talk to it via a simple serial interface and it handles the tasks you don’t want to fuss with, such as multiplexing and modulation. Not all displays are alike, however, so [Raj] wrote in to show how he used the MAX7219 to control high voltage 7-segment displays.

The spec on the MAX7219 only allows an input voltage of 5V, which limits the driver output to around 4V and can cause problems when using large displays that series-connect LEDs internally. [Raj’s] solution allows the MAX7219 to control displays with combined forward voltages of up to 24V, and as an added bonus, the circuit maintains compatibility with existing microcontroller libraries. We imagine this could be a nifty trick to keep on hand the next time you need to control large scoreboard displays.

The circuit works with the help of intermediate drivers to essentially level-shift the voltage to the display, which both provides the high voltage and protects the MAX7219’s inputs. One of the drawbacks of this circuit is losing the MAX7219’s constant current feature, requiring that each segment connection includes a current-limiting resistor. We appreciate this design’s attention to default states, because you wouldn’t want all of your LEDs turning ON during boot-up!

Building Mosaic LEGO Lamps


Looking for a throw back to your childhood, or maybe you just appreciate things that light up and look amazing? Well, [Baron] has a really impressive project for you. Not only does it look stunning and incorporate all of the things we love, it’s actually a pretty novel design. These lamps are built completely out of LEGO Technic pieces, the brand of LEGO that have holes drilled through them so you can build more advanced creations.

[Baron] used these parts with the drilled holes to create a dot matrix in which he placed colored transparent LEGO dots in the holes. The method of creating patterns is very similar to the way it’s done on the “Lite-Brite”. We especially love the theme of these lamps and they would match well with your LEGO mystery box. What’s really great about this tutorial is that it lays down the foundation for LEGO-built lamps that could be more interactive, involve more control (like RGB LEDs), or even introduce some LEGO mechanics!

Reverse Engineering the Sony Ericsson Vivaz High Resolution 640 x 360 Cellphone LCD

In our opinion, reverse engineering may be one of the best ways to tease your brain. [Andy] just did that by reverse engineering the Sony Ericsson Vivaz high resolution LCD (cached copy here). In his (very) nicely written article, [Andy] explains all the steps that led him to the result shown in the picture above. He started by finding the repair manual of the Vivaz, to discover that the display could be interfaced with 8080 type parallel signals. That meant that he could use a standard microcontroller without high speed buses to interface with it, in this case the STM32F4. Next in his adventure, [Andy] ordered the appropriate connector and took a more educated guess for the onboard microcontroller. A long Google search brought up the R61523 from Renesas. So he designed his breakout board, got it produced and a few hours later a nice picture was being shown on the LCD. He even took the time to compare the original display with the clone he found on the webs, and modified his graphics library to support this display.

A Video Game with custom LCD characters


[Nakul] wanted to build a video game, and with a few projects worth of Arduino experience decided he could finally attain his goal. He used a character LCD display to make his game, and instead of a text-based adventure, he went with a graphical side scroller.

The display for this space-based side scroller isn’t a graphical display like a CRT or a graphic LCD. Instead, [Nakul] is using the ubiquitous Hitachi HD44780 character LCD display. Normally these are used to display text, but they all have the ability to display custom 5 by 8 pixel characters. The code puts these custom characters – a spaceship, missile, and barrier – into the display’s memory and uses them as the sprites for the video game.

You can grab [Nakul]’s code over on his git or check out the action videos below.

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A very small HDMI display

With dozens of pocket-sized ARM boards with HDMI popping up, we’re surprised we haven’t seen this before. [Elias] made a custom driver board that takes an HDMI input and displays it on a very tiny, high-resolution display from a cell phone.

The display used is the same as what comes stock in the HTC desire HD. With a resolution of 800×480, it’s more than enough for a basic desktop, and while it’s not a 1080p monster from a few flagship phones, it’s more than enough for most uses.

[Elias]’ board consists of a Himax display driver and a TI DVI receiver. Included on the board is an MSP430 microcontroller used for initializing the driver and display. This build was originally intended for the Replicape, a 3D printer driver board for the Beaglebone, but because the only connections to this board are HDMI and an SPI to the ‘430, this also works with the Raspberry Pi.

MacBook Pro Retina display with a normal computer


If you’ve seen one of the fancy, expensive MacBook Pro laptops with a Retina display, you’ll know how awesome having that much resolution actually is. This incredible resolution comes with a price, though: the MBP with a Retina display is about $500 more expensive than the normal resolution MPB model, and it’s very difficult to find a laptop of comparable resolution without cries of fanboyism being heard.

[Daniel] over at Rozsnyo came up with a neat solution that connects one of these fancy 15-inch Retina displays to just about any computer. The build is the beginning of a product that works just like the previous DisplayPort adapter for the iPad retina display, but with the possibility of a few added features such as HDMI input and use of the internal webcam and WiFi antennas.

This build isn’t really a finished product anyone can buy and plug into a replacement Retina display just yet. Even if it were, it’s extraordinarily difficult to find a replacement display for the high-end MacBook for under the price of a really good monitor, anyway. In a few years, though, when the old, busted Retina laptops are traded up for a new, shiny model, though, we’ll be the first to try out this mod and get some serious desktop space.

LED retrofit for vintage edge-lit numeric display modules


This single digit display is an old edge-lit module that [Ty_Eeberfest] has been working with. The modules were built for General Radio Company and have a really huge PCB to control just one digit. [Ty’s] modules didn’t come with that driver board, so he was left with the task of controlling an incandescent bulb for each digit. After a bit of thought he figured it would be much easier to just replace the edge-light bulbs with a set of LEDs.

We’ve seen these exact modules before, referenced in a project that created an edge-lit Nixie tube from scratch. Each digit in the display is made from a piece of acrylic with tiny drill holes which trace out the numerals. The acrylic is bent so that the edge exits out the back of the module where it picks up light from the bulb. [Ty] laid out his circuit board so that each LED was in the same position as the bulb it was replacing. As you can see, his retrofit works like a charm.

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