Kamis, 01 Desember 2011

Alphanumeric displays

By Ian Harris

You'll be acquainted with the LED display that you have in your clockradio - each digit, of which there are typically 4, is made of 7 segments, or individual LEDs. Frequently in the middle of the display there's a colon symbol, to separate the hours from the minutes. And while you can display some letters, regularly clumsily, often it's only really good for showing numbers.

The problem is fundamentally about letters that have diagonal elements like the letter Y as an example, or X. Those letters are almost impossible to display on a seven segment display. The other set of letters that are troublesome are letters with vertical parts in the middle of the digit - like the letter T.

That is the reason why it will be useful to add more segments to each digit. It doesn't take many - simply by adding 2 vertical segments, breaking the middle horizontal segment in 2, and adding four diagonal segments we are now afforded the ability to produce all of the capital letters in a way that makes them seem natural and in fact, very readable.

The letter Y can be made from one of the new vertical segments and two diagonal ones, the letter Z has a nice, clean look and the letter K becomes possible and the letter R becomes basically readable.

So if you can do all this with a 14 segment display, is there any reason adding any more segments? As it turns out, adding 2 more segments (simply by splitting the top and bottom horizontal segments) lots more things become possible - including a complete alphabet of pretty reasonable lower case letters, and some new punctuation symbols, like squiggly brackets, colons and percent signs.

Moving to what is effectively a graphical display, a LED display panel, or LED matrix display as they are on occasion called, is the next step in effectively adding segments. At this point, not only are you able to display any letter or symbol you like but you can start to use different types of fonts and different sized characters. And as well as letters, you can display graphics! But at that point, you're powering lots more LEDs, with the increased complication of driving thousands of pixels.

So simply by adding a couple more segments to what would have been a common-or-garden 7 segment display, it's easy to get some pretty good looking letters and symbols, without getting to the intricacy of requiring LED display panels.

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