PPFD drop rate....?

[MrNice]

Hry Guys

Does any one know any rough calculations of PPFD drop off rate for LED lights from dead centre of the light being the highest reading what the drop off rate may be i.e every two inchs you lose 100 umols or 200 umols

As i dont have a Quantum PAR Meter to measure the light I thought they may be a chart or a rule of thumb so to speak


Any info would be very helpful

[Minty]

Hey MrNice Buddy,

I did a little research before getting my Awesome Invisible Sun LED's. and apparently, If you have an Android phone you can use the built in light sensor to get a good approximation of PAR (un-confirmed by me) using the following Lux Light Meter Free by Doggo and adjusting the results depending on the spectrum of LED light being used.

There are different calibrations depending on the LED Spectrum e.g.

3500K (Doggo App Reading / 100) = PAR Reading
4000K (Doggo App Reading / 90) = PAR Reading

There are more reading etc, and each light has to use a different algorithm to get the final PAR reading but something to go on at least without chipping out for a full Spectrum Par Meter.

I have not tried it yet myself, and heard about it from Shane (MiGro) on YouTube:-

'Light lux meter App to PAR meter hack | Android Smartphone PAR meter hack'

Seems better than nothing so will be giving it a go once my build is ready. Give it a watch if you haven't already.

I will fire up the lights tomorrow and see what sort of reading I get. Totally, forgot about the app until you just mentioned PPFD.

Will post figures soon, but it would be helpful to have some comparisons if anyone else has Android and would be willing to measure the output of lights etc. If we accumulate enough stats we can approximate how accurate it is.



Hopefully, Helpful, mate ;o)

[MrNice]

Thanks Minty
Yeah ive stuck it on the phone and will give it ago later thanks againfor the badger thing is good seems your a very good tech guy quite envious of your BMS grow room setup Mmmm very cool

Many thanks for your reply

[Minty]

I use that app to set my lights too. Accuracy is anyone's guess really I suppose it depends on the phones chipset.

App works well though

I assume it mostly depends on the actual sensors embedded in the devices and these sensors would differ between different phones but that datasets should be available to show the accuracy etc. The way tech is evolving I would say most would be adequate for at least a rough approximation. The trick is having the known constant to compare it against which would involve buying a full spectrum sensor which of course makes using the app redundant.

Thanks Minty
Yeah ive stuck it on the phone and will give it ago later thanks againfor the badger thing is good seems your a very good tech guy quite envious of your BMS grow room setup Mmmm very cool

Many thanks for your reply

Your welcome ;o) I do love my tech especially if it can make things easier

[MrNice]

Hey Minty


Got an old samsung phone off a mate to test the app but got some low readings 18" below light dead centre got between 14806 Lux 15000 Lux seems way off if you use his conversion ratios compaired to invisble sun s PAR map for this light should be 801 umols below dead centre 18"








3500K spectrum:
Divide App reading by 1.4 for accurate lux
Divide App reading by 100 for PAR My light say 15000Lux/100 = 150 PAR ....? with the app

4000K spectrum:
Divide App reading by 1.25 for accurate lux
Divide App reading by 90 for PAR

HPS spectrum:
Divide App reading by 1.2 for accurate lux
Divide App reading by 90 for PAR

Any one else like to test and feed back some results on how there phones perform the samsung i used says the sensor has a max of 3000Lux so dont know how its reading 15000 or so lux from the light then...?

[MrNice]

is a pretty tough calculation to get the par off lux, lux is what we see, par 400nm-700nm is what plants use, to determin this off a phone camera is not gonna be accurate in the slightest. The rate of drop off will depend on many aspects including the quality of the leds , are they high powered or mid powered ?, the concentration of led placement, the power the leds are driven at will have a factor and also the reflective walls and so forth.

As a rule of thumb I would suggest with our lights that if you are running the lights at a current of 2100mA in flower then positions them 21 inches away , if you are running them half power at 1050mA then you could get to 11inches.

This changes a bit for veg, if you were at 1050mA id keep the light at 21inches , or if running at 2100mA increase to 30inches.

So in flowering you could roughly say that for every 100mA of current you reduce your light by you could move it an inch closer

[MrNice]

Thanks Invisible Sun

Ok I take it then that all meanwell drivers out the box potentiometer wise are set to max output
so at max output with the meanwell ELG150 48A 3y driver and your ISH 150 board you will get 2100mA which in turn as stated on your PAR map you will get 801 umols dead centre at 18" canopy height is that correct....?



So then at a hanging height of 24" above canopy you may get 500 umols to 600 umols dead centre ive asked GMO and Nanook what height they hang their lights and every one is different
I have noticed that if you go lower then 18" to the canopy you can get fox tailing freaking the plant out so too much light .

Looks like between 600 umols 800 umols is good for the plants just looking to optimize my grow light for the ladies treat them nice and they will treat you.

I have a fluke multi meter so ill have to check if the board is drawing 2100mA to see if its on max setting then or take your word the driver works streight out the box for 2100mA

Also with the app it says it doest use the cam for the lux readings it uses a light sensor I did go out side today and test it in the sun max reading of 200.000 lux and average of 65.000 Lux which is about right so dont think the app is wrong but i understand about LEDs lights and full spectrum you really need a PAR meter for readings

[Minty]

Hey Minty


Got an old samsung phone off a mate to test the app but got some low readings 18" below light dead centre got between 14806 Lux 15000 Lux seems way off if you use his conversion ratios compaired to invisble sun s PAR map for this light should be 801 umols below dead centre 18"

I still need to do mine but having other issues at the min. Will feedback soon mate.

[Beef]

I have 150 ish type r... i didnt check if it was set to full before switch on tbh...ill check tomorrow and let you know....

ive got mine at approx 16 inches from canopy at present on day 39

[MrNice]

Im going to check with my multi meter tommrow see how many amps the board is pulling im gussing their set to max out the box