As the folks at Hack A Day recently noted, there really is nothing like the classic (and comforting) red glow of a red seven segment display.
And that is probably why a Maker by the name of “Five Volts” wanted to get his hands on a few ancient segmented displays. Unfortunately, controlling even one took up way too many microcontroller pins. The solution? Use a shift register.
“The principle is to control the display with four wires: vcc, ground, shift in clock [and] data in. To get a simple module, I developed a tiny PCB to plug in the LED display and at the back of it the shift register with current limitation resistors,” Five Volts wrote in a blog post.
“The challenge is to fit all these components on such small area, and to get these modules stackable. Then, it allows building a one to N seven segments display.”
Essentially, Five Volts uses a single ATtiny13 to control a total of six 7-segment displays.
“Each display is mounted on a hand-etched board, with a shift register and a handful of resistors soldered to the back,” Hack A Day’s Brian Benchoff explained.
“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 [even] be expanded.”
Interested in learning more? Both the board files and schematics are available here.