Display types

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Backlit flat-panel displays

There are roughly two parts of such monitors you can care about: How the backlight works, and how the pixels work.

CCFL or LED backlight






On image persistence / burn-in


larger segments

Vacuum Fluorescent Displays are vacuum tubes applied in a specific way - see Lightbulb_notes#VFDs for more details.


Nixie tubes



Mechanical counter



Split-flap diagram.png


LED segments

7-segment and others

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)
7-segment, 9-segment display, 14-segment, and 16-segment display. If meant for numbers will be a dot next to each (also common in general), if meant for time there will be a colon.

These are really just separate lights that happen to be arranged in a useful shape.

Very typically LEDs (with a common cathode or anode), though similar ideas are sometimes implemented in other display types - notably the electromechanical one, also sometimes VFD.

Even the simplest, 7-segment LED involves a bunch of connectors so are

  • often driven multiplexed, so only one of them is on at a time.
  • often done via a controller that handles that multiplexing for you

Seven segments are the minimal and classical case, good enough to display numbers and so e.g. times, but not really for characters.

More-than-7-segment displays are preferred for that.



LCD character dislays

The idea is the same, the interface different - character displays are basically those with predefined (and occasionally rewritable) fonts.

Classical interface

The more barebones interface is often a 16 pin line with a pinout like

  • Ground
  • Vcc
  • Contrast
usually there's a (trim)pot from Vcc, or a resistor if it's fixed

  • RS: Register Select (character or instruction)
in instruction mode, it receives commands like 'clear display', 'move cursor',
in character mode,
  • RW: Read/Write
tied to ground is write, which is usually the only thing you do
  • ENable / clk (for writing)
  • 8 data lines, but you can do most things over 4 of them

  • backlight Vcc
  • Backlight gnd

So minimal setup is:

  • tie RW to ground
  • tie RS, EN, D7, D6, D5, and D4 to digital outs

I2C and other

Matrix dislays

Small LCDs

These are sometimes called OLED, for reasons I don't yet understand.