LED - PPF settings

[voidpainter]

PPF: 1600umol/s
EFFICACY: 2.7 umol/J

SETTINGS: 0 - 25% (150W) - 50% (300W) - 75% (450W) - 100% (600W).

Used in a 4’ x 4’ (1.2m x 1.2m ) space.

No CO2.

My math is very weak, what would be the ideal setting for:

- 10 days established solocup clones
- stretch
- mid flower to end flower?

What would be the PPF value for each setting?

400 - 800 - 1200 - 1600?

In a 4x4 space.

Any help is much appreciated. Stay safe all!

 

[voidpainter]

Also what canopy height would be optimal for different plant stages?

Here are the test results:

- 15cm, average PPFD 1000umol/m2/s
- 30cm, average PPFD 900umol/m2/s
- 50cm, average PPFD 700umol/m2/s

 

[SuperBadGrower]

edit: Oops, I put wrong numbers, I'll elaborate again later.

ppf → ppfd: ppf / area in m²

You can set your system ppf at 1440. (Since that is what you tested, 1600 is a pointless number)
For 30cm hanging height, remove 10%, for 50cm remove 30%

i.e. How much PPFD at 75%, 50cm?

1440 ppf * 0.75 = 1080 ppf (the dimming)
1080 ppf * 0.7 = 756 ppf (take off 30%, to account for the hanging height)
756 ppf / 1.44 m² = 525 ppfd at 75%, 50 cm.

Using that calculation should be able to get you anything

veg 200-450
Flower 600-850

 

[SuperBadGrower]

Even if it sucks to calculate, write the results down and you'll only do it once
There isn't really a set lighting intensity recipe, there is always an interaction effect w/ the environment. If I tell you to hit them with 900 ppfd and the temps get to 65F nobody is gonna have a good time. Just remember at the max temperature you can go for maximum lighting. 80-86 F ambient temps. Cheers

 

[voidpainter]

Edit: Ok I understand, since 15cm test came out at 1000umol/m2/s then PPF is 1440 right?

I’m confused as how you got 1440?

Light spec sheet says it’s PPF is 1620umol/s. I rounded it down to 1600 for less confusion for me when attempting math. I guess im missing something here?

How did you get the subtraction % for hanging heights?

Thank you for your time man

 

[SuperBadGrower]

Hi mate,

To go from PPFD (PPF/m²) you simply multiply by m² again. That is, m² of the area that you calculated the PPFD in. PPFD is a measurement of: µmol/s/m² (PPF is simply total µmol/s)

So 1000 ppfd at 15cm * 1.44 m² gives 1440 PPF total system output. (This assumes 15cm distance)

1600 is probably accurate. However this is the system PPF measured in a sphere (hopefully) which is designed to capture all the light with as little bouncing as possible. You, in reality, are dealing with lots of bounces, and walls which are not 100% reflective, nor spherical.

The hanging heights you listed were 1000, 900, 700. To go from 1000 to 900 you take off 10%, to go from 1000 to 700 you'd take off 30%.

1000 * 0.9 = 900
1000 * 0.7 = 700



If you think of the sun as a grow light to be sold, it would have uncountable PPF, but what arrives here at earth is 1500 or 2000 ppfd max. (Inverse square law)

 

[GMT]

Is there a beginners guide to this somewhere? I don't even know what the letters stand for.
I guess I should try to keep up with modern lingo.

 

[voidpainter]

Is there a beginners guide to this somewhere? I don't even know what the letters stand for.
I guess I should try to keep up with modern lingo.

This explained a lot to me:

https://fluence.science/science-articles/horticulture-lighting-metrics/

 

[voidpainter]

Hi mate,

To go from PPFD (PPF/m²) you simply multiply by m² again. That is, m² of the area that you calculated the PPFD in. PPFD is a measurement of: µmol/s/m² (PPF is simply total µmol/s)

So 1000 ppfd at 15cm * 1.44 m² gives 1440 PPF total system output. (This assumes 15cm distance)

1600 is probably accurate. However this is the system PPF measured in a sphere (hopefully) which is designed to capture all the light with as little bouncing as possible. You, in reality, are dealing with lots of bounces, and walls which are not 100% reflective, nor spherical.

The hanging heights you listed were 1000, 900, 700. To go from 1000 to 900 you take off 10%, to go from 1000 to 700 you'd take off 30%.

1000 * 0.9 = 900
1000 * 0.7 = 700



If you think of the sun as a grow light to be sold, it would have uncountable PPF, but what arrives here at earth is 1500 or 2000 ppfd max. (Inverse square law)

Fucking nice, I understand it now. Thanks!!

 

[Mars Hydro Led]

edit: Oops, I put wrong numbers, I'll elaborate again later.

ppf → ppfd: ppf / area in m²

You can set your system ppf at 1440. (Since that is what you tested, 1600 is a pointless number)
For 30cm hanging height, remove 10%, for 50cm remove 30%

i.e. How much PPFD at 75%, 50cm?

1440 ppf * 0.75 = 1080 ppf (the dimming)
1080 ppf * 0.7 = 756 ppf (take off 30%, to account for the hanging height)
756 ppf / 1.44 m² = 525 ppfd at 75%, 50 cm.

Using that calculation should be able to get you anything

veg 200-450
Flower 600-850

This is very helpful.