Display types

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

https://nl.wikipedia.org/wiki/CCFL

VFD

• 

  larger segments

• 

  dot matrix VFD

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

Lighting

Nixie tubes

Mechanical

Mechanical counter

https://en.wikipedia.org/wiki/Mechanical_counter

Split-flap

https://en.wikipedia.org/wiki/Split-flap_display

LED segments

7-segment and others

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

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 in one position.

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.

https://en.wikipedia.org/wiki/Seven-segment_display

DIY

LCD character dislays

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

The minimal, write-only setup is:

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

Small LCDs

These are sometimes incorrectly referred to OLED, which is a confusion with the small displays which are OLED (but usually monochrome).