ok i am no expert on leds but if you look on
mouser.com you can find the data sheet provided by Cree for the specific light you are looking at. Of course these data sheets are all available directly from Cree as well. They give you tons of useful technical info on the products.
On the
data sheet for the CREE Xlamp CXB3590 you can find most of what you are asking for. also here is the link to all the info found directly from the manufacturer
cree.com
How do i calcute the loss and efficiency of a CREE Xlamp CXB3590?
i would not worry too much about this, also i don't know to be honest. However here is what i do know.
CXB3590 lamps draw 1.2 amps at 72 Volts (recommended running conditions). the total power expended by the lamp is calculated by P=IV
where I= amps and V= volts so you get 86 Watts of power drawn from the wall.
ok i did some looking around and found the following quote from the
thermal management document that is available on the previous link to cree
Heat generation LEDs generate visible light when current passes across the junction of the semiconductor chip. However, LEDs are not 100% efficient; much of the power running through an LED is output as heat, which thus needs to be dissipated. Cree royal blue XLamp LEDs are over 50% efficient and white XLamp LEDs are over 40% efficient. That is, under normal operating conditions, approximately 50% to 60% of the input power is output as heat, while the rest of the input power is converted to light. To be conservative, assume LEDs convert 25% of the input power to light and output 75% of the input power as heat. This estimate varies depending on current density, brightness and component, but is a good estimate for thermal design. Equation 1 below shows how to calculate the thermal power.
so it looks like about 40+% of the watts that your led driver supplies will actually be radiated as light.
How do i calcute lumens ---> PPFD? (the led information only provides lumens)
This is more interesting i find then the previous question but again i do not honestly know haha. I however will again try to give you the best info i can find. If you look on the data sheet linked above you will find the distribution of relative spectral power for the CXB3590 lamp in cree's 5000k 70cri, 4000k 70cri, 3000k 80cri, and 3000k 90cri varieties. now using the definition i got when i googled PPFD (light that falls between 400-700nm in wavelength) i wold say if you purely want to maximize PPFD go with the 5000k model. As my interpretation of the graph tells me that nearly all the lumens that it promises fall between 400 and 700 nm in wavelength. however, i have also heard that plants prefer the red spectrum (closer to 700nm) that would lead you to the 3000k perhaps. but definitely check out the data sheet and decide for yourself i am claiming no expertise.
How can i find out in witch light spectrum the leds operate?
look at the data sheet it is on there.
Also, can anyone tell me in a single DWC bucket with 5 plants... how can i calculate how much liter the bucket needs to be... and how much oxygen i need to provide to that ammount of liters!
I have nothing to add about DWC really i myself am just starting my first grow DWC style, im just doing one plant in a 5 gallon bucket. i am super nervous about it haha. but from what i have read about dwc you want as much 02 in your water as possible so as many small bubbles as you can manage. and if you have the resources keep the water cool (60 degree F i think) this is because the solubility of 02 in water goes up as the temperature goes down.
Sorry about the length of this response i just like leds a lot haha.
best of luck
