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What 4.5 million LEDs looks like Answered

Over in Japan, 4.5 millions LEDs have been lit up for a holiday fantasia that runs through March 8. To see all these LEDs color cycling must be amazing to see in person.

As a matter of fact, I'll probably be out in Japan next year, but not early enough to catch this.

An estimated 4.5 million light-emitting diodes offer an amazing spectacle at the Nabana no Sato theme park in Kuwana, Mie Prefecture, on Saturday. The annual winter light show is scheduled to run until March 8. Kyodo. This year’s theme is flowers. The water illumination is out of this world. Here the beautiful sound of the river with vivid color changing-the-art LED technology enables a production of 64 billion colors. The rapidly changing colors actually look more like the flow of the river in front of our eyes. The pond is located in the heart of the Village but can be seen from all over the place.

Link via Gizmodo


they are cool

Wow. Now, put them in 1 pile.

wow, if each had to have their own resistor, that would increase the cost by %50, that would be a LOT of money... but i don't think they would, i think they just had the same power source that would match their voltage...


9 years ago

Just wow.

I wish I was there...
So I could steal some LED's for my project... :-)

And where the hell did they get all of those LED's!!!!!!!!!!!!!!!!!!!

*Goes to Japan and steals 1 led* Liar! There are 4.499999!

I can't. My camera has no service here in Japan (What?!?)

Then go back to USA with your LED then take a picture.

I can't. I'm gonna be here for 3 years

Can you imagine the power consumption if they were all incandescent bulbs ? Zowie.

Can you imagine the heat if they were all incandecent bulbs? OUCH!!!

Yes, even if they were those tiny little holiday bulbs, that would STILL produce a lot of heat....

And we would burn, especially in the tunnel. Now, imagine that they were Xray bulbs...

or simple microwave tubes....cook your goose good :-)

with LEDs at 30 mA this takes over 1000 amps at 120 volts

That is a heck a lot of power, I wonder what their electric bill would be...

Or imagine if they were M249 Para minimi machineguns all pointed at you with an Apache helicopter gunship behind it shooting running chainsaws.

a led and incandescent of equal wattage produce allmost the same heat

Almost, but the LED still wins (by some factor roughly between 5 and 10).

An incandescent bulb produces all of its light by heating a filament. Only 10% of the energy appears in visible light; the rest is heat.

The LED is more "efficient" (essentially all it's light comes out in the desired visible waveband), so the heat output is just from ohmic resistance, internal to the LED and in the associated circuit. If you have a well-matched power supply, that waste heat should be well below 1%.

incandescent is about 1.5 - 2.5 % efficient not 10 %. small incandescents are less efficient so they are maybe 1 - 1.5 % led is about 7 X as efficient as good incandescent so its max 17 % - which means 83 - 85 % are still converted to heat 99 % and 83 % heat is not that of a difference

Your value of ~2% for incandescent efficiency is correct (if I had read through the full Wikipedia article, I would have seen the additional information). The 10% I quoted was the fraction of total EM output in the visible. Your value properly takes into account all of the other circuit losses.

The internal resistance of an LED (any diode) is fairly small within it's operating range. Note, of course, that the I(V) curve for diodes is exponential,

I = Isat[ exp(V/VkT) -1 ]

(where VkT ~ 26 mV at room temperature), so trying to define a linear "effective resistance" isn't really appropriate. Nevertheless, the LED produces _only_ visible light in a narrow waveband, so all of the input power goes to one of two outputs -- either pure visible light, or resistive heating of the circuit.

I think you must be including back-reflection of the generated light at the diode/air interface. Since the refractive indices are so different, that can be substatial for a "bare" LED. However, the kind normally used for illumination have layered coatings (either the old plastic dome, or more complicated structures) which provide a more gradual transition of the refractive index and thereby reduce the back-reflections substantially.

I would be very interested in a source for your ~17% efficiency value.

good incandescent lamps are 14 - 17 lm/w

leds are 90 - 100 lm/w

that means led = 6 - 7 X incandescent

7 X 2.5% = 17.5 % efficiency


That is so cool...

Looks awesome. Wish I was there.

If only i could be there

to steal a bunch of LEDs

Ya, you could easily take a few hundred and no one would notice.


9 years ago

Instant seizure...

The closest thing done anything like this in my area is a Maize Maze *sigh*

wow i wanna go there.... too bad i cant


9 years ago

As a lot of pepole have said... WOW.

wow (looking at pile of old PCs in the room and thinking of assembly + parallel port + one huge LAN)

This is the single greatest pointless thing ever!

Wow, that's really cool. Imagine how long it must have taken to do all of that.

Yea ! would they all need individual resistors ?


9 years ago

Christmas lights are way up my list of "senseless acts of beauty"! A place by my parents does about 1 million lights over their campus (incandescents, last time I saw them), and that's pretty impressive. 4 times as many would be... worth seeing.