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What is your favorite electronic display?

October 11, 2019 article

I have always found displays one of the most fascinating things about electronics. There are so many interesting and creative ways to visualize data! In this week's article we will take a look at a lot of different displays, just so see what's out there. Many of these display technologies are quite old and no longer in use. All the more reason to take a look! And who knows, maybe you will come across on of these displays :)

This article has a lot of chapters. In each chapter we will talk about a specific kind of display and briefly list its main properties as well as advantages and disadvantages. Then there are a few example images. When you click on them you will find some additional text as well as the source for the image (if I could find it).

Seven-segment LED displays

LEDs, arranged in a particular format with seven segments, are perhaps the best known example of electronic displays.

  • relatively cheap
  • available in many different colors and sizes
  • high power consumption
  • limited character space (only numbers and a few letters)

LED matrix displays

Arranging individual LEDs in a matrix of 5×7 allows the user to display more complicated characters and symbols.

  • relatively cheap
  • available in many different colors, sizes, and resolutions
  • high power consumption
  • readability is not always guaranteed, especially with non-Latin characters (Chinese, Arabic)

Mechanical displays (flip dot)

Seven-segment displays as well as matrix displays can also be realized using a mechanism where colored discs (or segments) are flipped in and out. The mechanical motion is usually triggered by electromagnets.

  • high visibility even in direct sunlight
  • low power consumption
  • mechanism is subject to wear and tear
  • no direct control of segments, can only toggle
  • quite expensive

Edge-lit displays and lightguide displays

Edge-lit displays use a transparent carrier into which a symbol is etched or carved. Upon illumination of the edge of that carrier the light is reflected off of the etches symbold and makes it visible. Nowadays we are used to seeing those displays in shop windows or on exhibitions, but in the 1960's and 1970's this was a viable way to display characters and numbers in mostly scientific instruments.

  • low power consumption when retrofitted with LEDs
  • poor readability
  • small viewing angle
  • glass can break easily
  • rather large

Projection displays

As curious little devices, projection displays contain of a set of stencils each illuminated by an individual lamp. The lamp casts a shadow on the screen and thereby displays a symbol. Some of these projection displays contain lenses and other optical components to improve the visibility.

  • good readability
  • aesthetic fonts possible
  • not very bright
  • rather large

Liquid crystal displays (LCDs)

LCDs are passive displays. When an electric field is applied to a certain type of liquid crystal, the molecules arrange differently and alter the polarization of the light that passes through. In combination with a polarization filter placed behind the LCD screen a partof the light can be filtered out and creates the illusion of an illuminated segment.

  • very low power consumption
  • available in any shape, size, or form
  • cheap
  • readability not always good
  • passive display technology
  • monochrome
  • glass may break

Vacuum fluorescent displays (VFDs)

Vacuum fluorescent displays are vacuum tubes. The heater (filament) emits thermal electrons. When they are accelerated towards a digit, which in turn is coated in a phosphorescent material, they cause that digit to glow in a desired color. These displays are usually multiplexed and may contain hundreds of individual segments.

  • available in any shape, size, or form
  • great readability
  • many different colors available
  • filament is sensitive to mechanical stress
  • glass may break

Incandescent displays (numitrons)

These nifty little devices contain segments made of filaments. Each filament glows when a voltage is applied, just like a tiny light bulb. The segments combine to form letters and numerals.

  • small size
  • relatively cheap
  • quite bright
  • high current consumption
  • filament is sensitive to mechanical stress
  • get rather warm during operation
  • no longer manufactured

Gas discharge displays (Nixie tubes)

Nixie tubes are glow lamps. They are filled with a mixture of the noble gases neon and argon. A positive high voltage is applied to the anode (the mesh around the digits). When a digit is connected to ground, electrons leave that digit and cause the adjacent gas to glow, which creates the illusion of a letter forming in thin air.

  • low power consumption
  • great readability
  • aesthetic display
  • cold cathode technology (does not get warm)
  • many different sizes and characters possible
  • rather expensive
  • required high voltage
  • no longer manufactured
  • can be rather large

Planar gas discharge displays (Panaplex)

Panaplex tubes work similarly to Nixie tubes, they just come in a planar form factor.

  • small form factor
  • great readability
  • rather bright
  • require high voltage
  • no longer manufactured

Cathode ray displays (NIMO tubes)

In a way this curious vacuum tube is very similar to the projection display mentioned above: electrons are accelerated through a stencil that is shaped like a digit or symbol. The electrons that make it through reach the front part of the tube which is coated in a phosphorescent material. The impinging electrons cause the phosphor to glow and form the shadow of a number.

  • quite bright
  • nice aesthetics
  • short life span, burn-in
  • require high voltage
  • historic curiosity, no longer manufactured

Thyratron displays

These are perhaps the most bizarre display device I have seen (yet). Each segment is a thyratron (a tube filled with gas) that in turn causes a phosphorescent segment to glow if a high voltage is applied. Thyratron displays basically contain several NIMO tubes, one for each segment.

  • very bright
  • relatively small form factor
  • average readability
  • requires rather extreme operating voltages
  • historic curiosity, no longer manufactured

Final thoughts

As you can see: there are myriads of different display devices out there! I am sure I forgot to mention a lot of them. If so, please get in touch and tell me about your favorite display device!

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Tag Cloud

  • electronic display
  • seven-segment LED
  • LED matrix
  • flip dot
  • edge-lit
  • lightguide
  • IEE projection
  • LCD
  • VFD
  • Numitron
  • Nixie tube
  • Panaplex
  • CRT
  • NIMO tubes
  • thyratron