LED Display

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Creator:
Spacefelix
Status:
Research
Born On:
14:38, 2 June 2009 (CDT)
Last Updated:
08:53, 30 March 2010 (CDT)

Overview

Use LED Tiles to make a static or moving POV display. A small 10x100 resolution display could be used for simple text; time, date, outside weather, etc. A larger display can display simple low-resolution images, animations and games (pong, space invaders, etc. as the controller permits). Something on the order of 50x100 resolution. An even larger display can operate on a resolution comparable to a computer monitor; CGA (320x200) to SVGA (640x480). A computer could be attached to display the IRC channel, presentations, etc.

Static LED Tile Display

This would simply be a bunch of LEDs mounted to a circuit board. As there are many LEDs required, it is limited to making small monochrome displays.

Size & Cost Estimates

Assuming the tiles are 1" squares, each one is a pixel and cost 50 cents/pixel:

  • 10x100 Display - 0.8'x8.3' for $500 (1,000 pixels)
  • 50x100 Display - 4.2'x8.3' for $2,500 (5,000 pixels)
  • CGA (320x200) Display - 26.7'x16.7' for $32,000 (64,000 pixels)
  • SVGA (640x480) Display - 53.3'x40' for $153,600 (307,200 pixels)

In short, let's just stick with the 10x100 Display

Resizing & Cost Reduction

For the static LED display, I could make a wall-mount monochrome panel that uses the cheapest possible SMLEDs. This will reduce its cost and size while allowing for sufficient resolution.

Moving POV Display

Had a talk with the guys last week. Brimstone mentioned POV as a way to make a big display with a fraction of the LEDs for a static display. Decided that I could make either a vertical-axis cylindrical or conveyor-belt rotating POV display with the LED pixels arranged in a single vertical line. Right now, cylindrical is the easiest mechanically, so I will only consider that design. With the cylindrical configuration, I can have three screens on each third of the sweep of the rotating section. Using surface-mount LEDs (selected for their small profile and their low cost), I can have a compact screen with sufficient resolution while keeping costs low. For each physical pixel on the rotating POV display, the LEDs will be arranged in a line parallel to the direction of rotation. This long arrangement and the motion of the POV may cause pixel color smearing. Therefore, each LED ought to be timed to flash at a specific spot rather than all three flashing at a specific spot.

Size & Cost Estimates

I am looking at the following LEDs from LEDtronics, Inc.:

  • Red - Super Red SMLED in an 805 package, $0.07ea. Link
  • Blue - Super Blue SMLED in an 805 package, $0.42ea. Link
  • Green - Super Lime Green SMLED in an 805 package, $0.25ea. Link / Aqua Green SMLED in an 805 package, $0.50ea. Link

Assuming 1 RGB set per pixel, a pixel will be $0.74ea - $0.99ea.

From the above and using a cylindrical POV with 1/3 screens, I have the following cost and size estimates for various screen resolutions:

Resolution diam x ht (ft(m)) LED Count Cost (for LEDs)
320 x 240 (QVGA) 1.3(0.4) x 1(0.3) 720 $180 - $240
640 x 480 (VGA) 2.5(0.8) x 2(0.6) 1,440 $360 - $480
1280 x 800 (WXGA) 5(1.5) x 3.3(1) 2,400 $600 - $800

Note: Display diameter is determined assuming that each virtual pixel is as wide as each LED line's height for each physical pixel. It is assumed that the pixels are packed as tightly as possible (touching each other).

Simple Moving POV LED Display

Let's start simply. Using some tri-color LEDs, I could make a rotating disc-type POV as a starter project. Akin to the POV clock.

Rotating and Scanning Laser

Thought of a way to mount a mirror on a device that made it scan and rotate (scan would be done by a vibrating piezoelectric and rotate would be a simple shaft and electric motor). Such a device could be made from a supermarket checkout laser scanner and some additional hardware. Would just need to figure out a way to switch the laser to form precise patterns.

From research, this is how it is done DIY-style:

Parts List

  • Super Red SMLED in an 805 package, $0.07ea. Link
  • Super Blue SMLED in an 805 package, $0.42ea. Link
  • Super Lime Green SMLED in an 805 package, $0.25ea. Link / Aqua Green SMLED in an 805 package, $0.50ea. Link

Links

--Spacefelix 16:47, 27 May 2009 (CDT)