Recently, we published an entry-level Arduino project with a single seven-segment LED display. Although it’s an amazing DIY project, we noted that most of the readers are looking for more advanced ...

Instead of a few displays that can be bought from the usual retailers for a dollar a piece, [Esai] made his own four digit, seven-segment display on some perfboard.

The single-digit seven-segment BD Series LED displays are available in a range of six different digit heights from 0.276 (7 mm) to 1.0 in. (25.4 mm) in 24 different styles and models. Common anode ...

Even so, fitting a two-digit display seemed difficult. We used a Charlieplexed display to arrange the LEDs in the required two-digit, seven-segment format, which would serve our purpose (Fig. 2).