Can Handle Seven Segments on Your Display? Try Using Just Six

While the ubiquity of cheap LCD and OLED screens are making them less common, seven-segment displays have been around for decades and are still used in plenty of products. These contain seven individual segments, usually lit by an LED these days, which can each be lit independently. The reason that there are seven segments is because that’s the minimum number required to show all ten of the decimal numbers clearly. But what if you don’t have enough pins available to drive all seven segments, don’t want to use a shift register, and don’t care about legibility? As Ken Yap demonstrates, you can actually get away with using a mere six segments.

Yap actually isn’t the first person to think of this. Way back in the early days of digital displays, every one of those segments had a real cost. Not only did your display have to have an extra segment, you controller had to have another pin available to control it. You can bet that device manufacturers investigated ways to reduce costs by using the bare minimum number of segments. Yap's project was inspired by a strange calculator from 1969, which had oddly stylized curvy numerals. This calculator’s VFD (Vacuum Fluorescent Display) actually had eight segments per digit, but the weird font resulted in a half-height “0” numeral. Yap realized he could use a similar font, but with only six independent segments.

The display that Yap created to demonstrate this six-segment setup is a bit of a cheat, because each segment is actually made up of multiple LEDs. But those LEDs are controlled together as groups. For all practical purposes, each group of LEDs acts as a single segment. Yap doesn’t provide much detail about what kind of hardware he’s using for this display, but that really isn’t the point. He designed custom PCBs with the LEDs arranged to fit his unique font choice, which doesn’t look anything like what you’d see on a seven-segment display. As Yap himself points out, this was only partially successful. Some of the numbers, like “3” and “5” look quite nice. Others, like “6” and “9” are readable but look a bit strange. And some, like the “4” and “7” are difficult to decipher. The “0” is half-height, just like that Sharp calculator. This proves that six-segment displays are possible — they just aren’t practical.