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Topic: Comparing Light source outputs (LED neopixel) (Read 1 time) previous topic - next topic

DevilWAH

I am trying to work out the actual output of Neopixels compared to Traditional lighting for a fish tank.

So i know for example that a fish tank requires ~1 watt per gallon of water. Different set up need different amounts but this is a good average number.

This is based on fluorescent lamps so my current tank has 80 Watt tubes which make sense.

But I would like to switch to LED's but finding a lot of conflicting information.

I was looking at a strip of nano pixels

5m 16.4FT 150led WS2812B Full Color LED strip 150 LED 150 pixels, which has the following specs

Size: L500cm (5M) x W1.2cm x T0.45cm
Emit Color: Programming control
Protection: IP20 non Waterproof
Working Voltage: 5V DC
LED Quantity: 30eds / m, 5meter / roll
View angle: 120 ° ~ 140 °
Working Temperature: -20 ° to 50 °
350-450mcd/led
Wattage: max 7.5W/meter,
Color Temperature: 3500-7500K

So this suggest is is going to pull 7.5 X 5 = 37.5watts in total or ~7 amps
but 350-450mcd per LED X 150 only = 250 Lumen which seems very low!

And then i read things like this on some Aquarium sites

"
When it comes to lighting your tank, size matters. Most fish tanks need 1 to 3 watts per gallon of water, while those with plants need 2 to 5 watts per gallon. LEDs work differently than traditional lighting options because they're more energy efficient. They often come in 1- and 3-watt options; the more LEDs you use, the higher the overall wattage they produce. For a small tank, 18 1-watt LEDs on a 12-inch heatsink fixture should equate to 175 watts. If there are 24 LEDs on the same fixture, you have 250 watts of light, and 36 LEDs gives you 400 watts. The same number of LEDS on a larger fixture lowers the wattage; for example, 36 LEDs on an 18-inch heatsink bar is equivalent to 250 watts. When purchasing LEDs, read the manufacturer's specifications to determine how many watts the fixture provides.
"


which seems to say 18 X 1Watt LED = 175 Watt?

So how do i make sence of all of this?its a bit like a 7W LED bulb = 40W incandescent.

What is the real number i should be focusing on (lumens?) and what numbers do i need to accurately calculate it from the Specs of the LED's? 

Grumpy_Mike

You have to remember that measuring light output in terms of watts is a bit meaningless when when changing technologies.
This is because the watt is only the amount of power the light producing device consumes, not the amount of light it produces.

In other words you have to take into account the conversion efficiency of the technology or work with a measure of light not power consumption.

DevilWAH

You have to remember that measuring light output in terms of watts is a bit meaningless when when changing technologies.
This is because the watt is only the amount of power the light producing device consumes, not the amount of light it produces.

In other words you have to take into account the conversion efficiency of the technology or work with a measure of light not power consumption.
thanks you.

I came to the conclusion that the real number needed is Lumen. (and for course wave length) when growing plants.

I am guessing the manufacture described Specs is not right as according to with each LED producing <450mcd of utput at 130 degrees (give or take). even if we considered each "pixel" as 3 LED's (red, Green, BLue) its still only translates to ~650 Lumens, less than a 20W incandescent bulb and just from comparing them next to each other this is not the case!

Miss type i think :)

Grumpy_Mike

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just from comparing them next to each other this is not the case!
I think you can't simply do that. You need to measure. There are lots of things you don't take into account by just looking. Things like the emission angle and the light distribution over a surface.

Quote
I came to the conclusion that the real number needed is Lumen.
I think what you actually need is the Lux:-
https://en.wikipedia.org/wiki/Lux

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