Dream diodes.... what are they?

Beefbisquit

Beefbisquit

Well-Known Member
JMD said:
"the light is still directional" - it is still a point source of light, which requires optics to function properly in the kind of setup we want. Optics and reflectors will make you loose 10% (or much more for bad quality ones) of your light.
If anything, the HID is omnidirectional - but it's also point source.

I want a large uniform light.
Click to expand...
I'd have to see what the cost of a single high wattage diode would be, and all the components to make it work before I could even guess at an approximation; but the current single panels available that are putting out HID-like numbers aren't feasible for most growers. Maybe cash croppers or commercial growers, but people who don't sell (like me) can find it difficult to set aside an entire spare paycheque or two, just for a light....

The reason I grow is so I can smoke pot, but don't have to deal with criminals. Ironic it makes me a criminal in the process.... lol

It might not be the optimal route using one single diode, but I just don't see how it can't be significantly less expensive. Not everyone wants/can afford a Ferrari, to some a Subaru WRX done-to-the-nuts is good enough... ;)
 
FranJan

FranJan

Well-Known Member
OK I gotta play Devil's advocate on this one. The very nature of LEDs would make a baseball sized crystal, THE SINGLE MOST INEFFICIENT DIODE IN THE UNIVERSE :). First off it's a crystalized semiconductor that emits light throughout the entire cystal, not the surface, so photons would have to travel through a matrix of crystal and not just through air. Now because of the size, the majority of the light inside the diode is going to be trapped by the semiconductor or by the whole package and this is gonna create heat. Lotsa heat. I can't do the math but liquid nitrogen is gonna be involved because as you create bigger diodes efficacy drops and you need more current to get light out of the package. You've forgotten there are escape angles involved with LEDs. There's Auger recombination. All kinds of really crazy math, (Étendue!), that comes into the design. It's just never going to work. At least not in this century.

IMHO what you want is the smallest possible chip putting out the most light at the least amount of watts running at room temperature. Then you put those together on an inverted pyramid with wider angles towards the tip, tighter angles on the base, add in Chinese prices, and an Arduino controller for spectrum and time. Now that's a dream.

http://ledsmagazine.com/features/9/10/10

"Light in the LED is produced at the p-n junction when an electron-hole pair combines and a photon is emitted in the process. Thus, photons are created inside of a material rather than in air – where we would ultimately like them to go. This is a problem because the refractive index of the chip material is high compared to that of air."
 
Bumping Spheda

Bumping Spheda

Well-Known Member
I think a multichip made with 40 of Soraa's GaN on GaN Violet chips + 2700k phosphor, all running at ~400W (~10W per chip) is surprisingly feasible. I wonder how close you could pack the chips, but it should be smaller than an average HPS reflector, the chips can run hot. Heck, I think I've seen 500W LED heat sinks that are passive, even, and those 300-500W multichips aren't that big.
 
Beefbisquit

Beefbisquit

Well-Known Member
FranJan said:
OK I gotta play Devil's advocate on this one. The very nature of LEDs would make a baseball sized crystal, THE SINGLE MOST INEFFICIENT DIODE IN THE UNIVERSE :). First off it's a crystalized semiconductor that emits light throughout the entire cystal, not the surface, so photons would have to travel through a matrix of crystal and not just through air. Now because of the size, the majority of the light inside the diode is going to be trapped by the semiconductor or by the whole package and this is gonna create heat. Lotsa heat. I can't do the math but liquid nitrogen is gonna be involved because as you create bigger diodes efficacy drops and you need more current to get light out of the package. You've forgotten there are escape angles involved with LEDs. There's Auger recombination. All kinds of really crazy math, (Étendue!), that comes into the design. It's just never going to work. At least not in this century.

IMHO what you want is the smallest possible chip putting out the most light at the least amount of watts running at room temperature. Then you put those together on an inverted pyramid with wider angles towards the tip, tighter angles on the base, add in Chinese prices, and an Arduino controller for spectrum and time. Now that's a dream.

http://ledsmagazine.com/features/9/10/10

"Light in the LED is produced at the p-n junction when an electron-hole pair combines and a photon is emitted in the process. Thus, photons are created inside of a material rather than in air – where we would ultimately like them to go. This is a problem because the refractive index of the chip material is high compared to that of air."
Click to expand...

I mean the diameter of a baseball, not the depth! :D Appox 3-4 inches across in other words.
 
Lowdown Lenny

Lowdown Lenny

Active Member
Hey guys, big fan of LED point light source here :)

Most newish LEDs have what's called lambertian radiation, meaning perfect spread. All Crees, Bridgeluxes and some Epistars have it. It simply means the light spreads perfectly unlike older and most chinese diodes which needed secondary optics to correct the weak light at angles.

Move the leds closer to eachother and you get more penetration. By spreading the leds equally over the growing area penetration is lowered, which leads to increasing forward current, which leads to lower amount of total light output (all leds are most efficient at 1w / 350 mA).

For me the dream is a big ~500w ~4x4cm multichip at close to 350mA, suspended from the top of the tent and simply having the plants grow up towards the light. Watercooled with the radiator outside the tent - perhaps a household rad to keep temps up at night (cold-ish climate here) :)
 
You must log in or register to reply here.
Top