Wiring up a lot of LED segment displays

One look at this display and you know there’s a whole lot of pins that need to be wired up. Now look at what those display modules are mounted on. That’s right, [Kemley] is using point-to-point soldering to rig up this big display. It sports four sixteen segment modules on top for alpha-numeric information, and eight large seven segment modules for displaying numbers only.

We’re not certain as to how the electronics are arranged. When talking about the 16-segment modules he mentions that all four are in parallel with NPN transistors to switch the common anode of each. That’s easy enough to understand. But when you get a look at the transistor board you’ll see 24 of them in use. He’s included a 150 ohm resistor on the collector of each transistor. It must be set up to only allow one segment of each group to switch on at a time? We’d guess that each segment is divided into two (upper and lower pins are multiplexed separately), which would explain the double set of transistors. As for date and time, an Arduino board monitors a DS1307 RTC and manages the scanning of the display.

4″ seven segment displays make a fine scoreboard

[Blark] took a few parts and turned them into a simple scoreboard. The centerpiece of the build is a set of 4″ seven-segment displays. With those in hand it was just a matter of choosing a controller to feed them data, and developing a user interface.

He seems to have had some issues as he mentions having blown up two PIC chips while soldering. He transitioned to an ATtiny24 chip and everything seems to work quite well now. The user interface depends on two buttons, each increments the score for one half of the display and pushing both at once zeros the game score. The displays use shift registers to store data so they’re quite easy to control with AVR chips. Check out the demo video after the break.

The only problem here is that someone needs to be on the sidelines to increment the score. We’ve seen some more intricate designs that let you use a remote control or even a smart phone.

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Start thinking 4th dimensionally with a time circuit tutorial

When [Phil Burgess] showed off a few I2C – controlled seven-segment displays on adafruit’s weekly vlog, the comments immediately turned to the time circuits featured in everyone’s second-favorite time machine, the Back to the Future DeLorean. The time circuits are now active, so now you can easily add a temporal display to your car well before a hover conversion.

[Phil] used these LED displays, conveniently controlled by a four-wire I2C bus. Although the displays are addressable independently, it’s only possible to assign each display to one of 8 I2C addresses. [Phil] figured out a neat way to control the 9 displays of the time circuit with the help of a 74HC138 3-to-8 line decoder.

The case was constructed out of clear acrylic lasercut in adafruit’s shop and spray painted with faux-metal paint. After installing the seven-segment displays, a Teensy, ChronoDot, and a few AA batteries finished up the build.

With any luck, the design files for the laser cut case should be available shortly, so get those I2C displays while they’re still in stock.

A glorious mechanical seven segment display

If you’ve ever wondered why you’ve never seen a mechanical seven-segment display, now you know. They’re fairly complicated and most likely absurdly expensive, especially when a few light bulbs or LEDs would do the same job equally well. This didn’t stop [kiu] from completing his mechanical seven-segment clock he calls SevenBlocks, and for that we are thankful.

Each of the 28 segments in [kiu]‘s clock is made of three layers of acrylic and a short section of a rack gear. Unlike every seven-segment display you’ve ever seen, tiny hobby servos provide the indication for each segment. For the electronics, An ATMega8 is used for the brains of the outfit with a 74HC595 shift register to expand the number of I/O lines. A DS1307 RTC module provides accurate timekeeping, and the dozens of servo outputs visible in the ‘guts shot’ makes you realize why you’ve never seen a mechanical seven segment display before – they’re really friggin’ complex.

If you want to build your own mechanical seven-segment clock, [kiu] put all the files up on Github. Everything is there, from the .DXF files ready to feed to a laser cutter to the schematic and board files for each of the three PCBs. A video showing this clock in action is sort of necessary, so you can check that out after the break.

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Display made out of hundreds of seven segment LEDs

While huge LED panels are a relatively common project du jour for people wanting to flex their engineering muscle, we’re taken aback by the sheer beauty of [Skot9000]‘s huge LED display made of seven-segment displays. He calls the build DigitGrid, and it’s a wondrous display the likes of which we’ve never seen.

To build a display based on seven-segment LEDs, [Skot] went with a modular approach in designing the DigitGrid. To power and control all these seven-segment displays, [Skot] used a Texas Instruments TLC5920 to run four 4-digit displays as a single module. Four of these modules connect together to form a row of 32×2 digits, and eight rows of digits come together to make a 512-digit display. With seven LEDs for each digit, that works out to 3,584 4,096 individual LEDs for the entire panel.

To power and control this gigantic array of LED displays, each row uses a PIC16F microcontroller which, in turn, is controlled by an FPGA. After several hours of writing Verilog, [Skot] had a reasonably good hunk of software that allowed him to send frames from his computer to the display. The results, quite simply, are amazing. [Skot] managed to put up a short film showing off the animation capabilities of his new display, and it’s a wonder to behold. You can check that video out after the break.

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Counting down to the New Year

[Rod] is in a position to provide a community service on New Year’s Eve. He spends the evening at a relative’s house next to the beach. There are fireworks at midnight, but the crowd has no communal way to count down to the deadline. This year, he build his own count-down display so that everyone can join in during the last few seconds.

This is a temporary build so each digit is housed in a cardboard box. [Rod] first drew the outline of the seven segment digit on the front, then added holes for three LEDs in each segment. He’s feeding the segments with 12V and therefore is able to run the LEDs in series, along with a resistor, switching each segment with one transistor. He chose an Arduino to drive the display, and since he had two sitting around, used both instead of grabbing a shift register as port expander.

If you’re looking for a more permanent solution, we really like the digit displays designed for this scoreboard. But you’re going to have to etch the boards yourself if you want them done in time for the festivities.

 

HEX Out reveals the secrets your data bus holds

[Quinn Dunki] is looking to augment the tools she has available at her electronics bench and built the HEX Out as a mock-logic sniffer. The device reads 8 or 16-bit inputs, showing the current state of those connections on a 7-segment display. This requires that you’re comfortable reading Hex codes, but if you’re not it’s almost like studying flash cards; before long you’ll be able to read them without thinking about it.

She’s blogging about the design and build process in three parts. The link above is the first installment where she shares the development process for the top layer which hosts the display hardware. The other two parts should be up for your enjoyment in the next couple of weeks.

You’ll notice her design on this portion of the project still requires a lot of point-to-point soldering, even though she etched her own circuit boards. We didn’t look too closely, but it seems this would be worth going to the trouble of etching a double-sided board if you can.

UPDATE: Part Two is now available

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