Aussie Growers Thread

reza92

reza92

Well-Known Member
weed-whacker said:
Yeah they are pretty aweaome I agree

As U know the cooler the led the more efficient

That's why I'm driving them at 100-900mA in the 2 strip 40w model

Coz then 120 watts of it will do well in a 2x2

You could flower with 80w sure but as I said earlier 3 units will kill it

As we know veg wattage is irrelevant as it simply dictates the speed of growth plus DLI so depending on light schedule may not need as many watts
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They have almost zero efficiency loss until you start driving them past max current.

For flower lights you’ll need them running at max current or more to get the penetration you’ll want. For veg lights running them bellow 50% max current is a waste. This is from personal experience with gen 2 strips.
 
V

viewer1020

Well-Known Member
reza92 said:
They have almost zero efficiency loss until you start driving them past max current.
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From the datasheets I've looked at, LEDs are always more efficient at lower current. I've never seen an exception, but if you know of one, I'm ready to learn.

For example, if you look at the graph of relative flux vs current on page 9 of the Cree XBD datasheet (PDF warning):

Reading approximate values from the graph of the White LED:
At ~165 mA you get 50% relative luminous flux.
At 350 mA : 100%
At 700 mA : maybe as high as 175%.

Note that if you want to double the relative flux, you have to more than double the current.

This is well below the 1 Amp rating for these chips, and you see the efficiency reducing as the current goes higher, even with a consistent junction temperature.

In practice the savings should be greater than the graph implies, for two reasons:

1. Lower currents are produced by lower voltages, so two chips at 150 mA consume less power than one chip at 300 mA (Watts are equal to Volts times Amps).

2. Lower current produces a lower junction temperature for the same heatsink arrangement. Lower temperature produces higher radiant flux, as shown by the graphs on page 7. For blue and white diodes this effect isn't so extreme, but look at what happens to the efficiency of red diodes when the temperature rises! Below 70% at 50 degrees celcius, well below 50% at 75 degrees C.

I'm not saying you should run your diodes at a lower current (though I do, and if I want more light I add more diodes). I am saying that LEDs do lose efficiency at higher currents, as shown by tests run by the manufacturer.
 
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weed-whacker

weed-whacker

Well-Known Member
reza92 said:
They have almost zero efficiency loss until you start driving them past max current.

For flower lights you’ll need them running at max current or more to get the penetration you’ll want. For veg lights running them bellow 50% max current is a waste. This is from personal experience with gen 2 strips.
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Ok sorry but Ur idea about needing to drive them hard to get through the canopy defies physics

A photon is a photon dont matter how many per watt or at what current they were produced


Can U explain this part of the data sheet please?

Even though I agree it is minimal curve

Consider this is at stable temp
U don't use heatsinks?

Mmm

Here are the averages from test done in a tent with an apogee par meter
 

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klx

klx

Well-Known Member
weed-whacker said:
Ok sorry but Ur idea about needing to drive them hard to get through the canopy defies physics

A photon is a photon dont matter how many per watt or at what current they were produced


Can U explain this part of the data sheet please?

Even though I agree it is minimal curve

Consider this is at stable temp
U don't use heatsinks?

Mmm

Here are the averages from test done in a tent with an apogee par meter
Click to expand...
Only so much you can learn from a datasheet. They are a decent guide but not the be all. The early gen veros loved to be run hard and produced better bigger buds than more chips at lower current. Why would that be? Who knows but its true. But you know this already considering you were "one of the LED gurus" that showed us the way. You would know the vero grower I mean too right? What was your previous handle again ?

Can you share some flower pics of plants that you have grown under your lights? Prove to us that you can flower a 2x2 with 80W lets see your results.
 
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