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== POV display ==
 
== POV display ==
  
''(moved to [[POV display]])''
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I'm building yet another "POV display".
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I plan on putting a few features into my display that I haven't seen in any other so far:
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* bright blue LEDs (even though blue is usually the most expensive color ... although sometimes "true green" is even more expensive than blue).
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* no slip rings -- just pumping energy across an air gap
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* ... and a few other features that I'm keeping hush-hush.
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I want lots of lumens.
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Unfortunately, when I go to pick LEDs out of the catalogs, they're not
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rated in lumens, they're rated in candelas.
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Is it even possible to estimate "lumens" from the catalog information?
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Do you know what the difference is? Does your flashlight really
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produce 10 times the light ( in lumens)? Or does the flashlight merely
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focus its light on a tiny spot, so that that spot gets 10 times as
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many candelas ?
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For example, check out these 2 LEDs:
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$8.75 SSP-LX6144C7UC : 4000 mcd at 120 mA
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$8.75 SSP-LX6144D7UC : 1800 mcd at 120 mA
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From the mcd rating, it appears that the first one is more than 2wice
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as bright -- and it is, if you're directly in front of it when you
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look at it.
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However, if you're even the tiniest bit off-center, the second one is
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much brighter -- in fact, the total lumens that second LED puts out
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(2500 mlm) is slightly more than the total lumens than the first one.
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If you diffuse the light and try to light up a whole room with an
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array of them, the second one will make the room brighter.
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I'm currently planning on using these in my first POV display:
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* $1.32 Telux TLWB7900 : blue : 330 mlm, 231 mcd at 50 mA. (price in ones from http://Newark.com/ )
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Other LEDs I considered using in my POV display (and may re-consider for my next one):
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* $18.89 "Lamina light engine" BL-22B1-0140 : 22000 mlm at 420 mA. (this price includes the required heat sink -- price in ones from http://Digikey.com/ ). This has the most lumens per dollar I've found so far (for blue LEDs).
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* $8.750 Sunbrite LuxLEDs SSP-LX6144D7UC blue: 120 mA, 2500 mlm, 1800 mcd (Odd that the red Sunbrite LuxLEDs are cheaper at Newark, the other colors cheaper at Digikey.) cheapest $/lumen blue LED, except for the "light engine"
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* $2.550 Lumex "DSP LED" 67-1876-ND: blue, 5 mm, 2500 mcd ( DigiKey ) apparently have some kind of internal chip. All colors run at 2.0 V nominal (1.5 V minimum) (rather than running on current like most LEDs. unfortunately, the data sheet doesn't suggest how much current they take -- I presume more than 20 mA).
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* $1.600 Sunbrite "based LED" SSP-01TWB7UWB12 (441-1007-ND) blue 10 mm 20 mA 7000 mcd
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* $5.980 GM5WA06270A SMT RGB (35 mA red, 35 mA green, 35 mA blue) 3000 mcd (full color range -- apparently used for digital camera flash ?) (Digikey)
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Spoke-POV and propeller clocks links:
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* An entire discussion forum devoted to POV displays http://ladyada.net.nyud.net:8090/forums/viewforum.php?f=11
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** In particular, lots of nice pictures http://www.ladyada.net.nyud.net:8090/forums/viewtopic.php?p=4712
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** 'no-microcontroller-programmer-needed' minipov http://ladyada.net.nyud.net:8090/forums/viewtopic.php?t=32
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* LEDtoy on Sourceforge http://ledtoy.sourceforge.net/
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* Ian’s Spoke POV http://www.ianpaterson.org/projects/spokepov20050704/index.htm
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* "Propeller Clock" Mechanically Scanned LED Clock: by Bob Blick http://www.bobblick.com/techref/projects/propclock/propclock.html (I think this is the original)
  
 
== Full-color LED lighting ==
 
== Full-color LED lighting ==

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