Lots of seven segment displays with a single ATtiny

7seg

These days they’ve been replaced with character LCD displays or even brightly colored graphical displays, but if you’re trying to display data on one of your projects, there’s nothing like the classic red glow of a red seven segment display. [five volts] got his hands on a few ancient segmented displays, but controlling even one took up more microcontroller pins than he was ready to spare. The solution to this problem was to use a shift register and control multiple segment displays with an 8 pin microcontroller.

[volts] is using an ATtiny13 to control six seven segment displays. Each display is mounted on a hand-etched board, with a shift register and a handful of resistors soldered to the back. By having the microcontroller shift bits down the line, [volts] created an extremely easy to interface 6-digit segment display, and the entire device can be expanded even more.

The board files and schematics are available on [volt]’s project page. A great project if you’re just starting out to etch your own boards.

Clock display taller than you is just what your living room has been missing

huge-countdown-clock

Sure, it’s time to get the countdown clocks ready to ring in the new year, but why limit it to just one night? If you end up building a six-foot digital display you can count down trivial events; like the remaining seconds of freedom before you have to pimp yourself out in that drab cubicle.

This seven-segment display is homemade and boasts six full-sized digits and two smaller digits with each pair separated by colons. You have probably already guessed that the construction was greatly simplified by using LED strips rather than individual components. This is part of the reason for the size of the display. The strips can be cut, but only down to a minimum of 3 LEDs per segment. That explains the small digits, with their larger siblings doubled in size. But there is a benefit to this constraint, it means that current limiting is already taken care of for you.

The main assembly is a wooden frame surrounding two polycarbonate sheets. The LED strips are sandwiched between those sheets, with segment and digit driver buses exiting a one point on the side. The build doesn’t detail a driver for the display but it shouldn’t be hard to find a multiplexing example that will serve the purpose.

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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