LED bulb distance from plants?

[HuffnPufferfish]

"Seedling: 15-20 inches| 38.1 -

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or get em out of that heatsink (black buckets) and repot/cover the soil/keep it from drying out, doesnt seem like too much light

whats the boxy thing u made?

 

[Athos]

BReal.

See how they stretch in the picture? That's your cue that the light intensity is too low, not the other way around. How tall are those seedlings?

If you give us more info we could help you more.

Age of plants
Light period
Temperatures and humidity during light on and lights off
Have you fed them or just plain water? What water source (Tap / RO / bottled water)? What was the pH and ppm / EC?
What was the pH and ppm / EC of the run off?
Days between last few waterings / feedings?

 

[BReal]

BReal.

See how they stretch in the picture? That's your cue that the light intensity is too low, not the other way around. How tall are those seedlings?

If you give us more info we could help you more.

Age of plants
Light period
Temperatures and humidity during light on and lights off
Have you fed them or just plain water? What water source (Tap / RO / bottled water)? What was the pH and ppm / EC?
What was the pH and ppm / EC of the run off?
Days between last few waterings / feedings?

If the light intensity is too low than I see it as something strange because I was observing this thread https://www.icmag.com/ic/showthread.php?t=284309 and my setup is actually a little bit more powerfull than Bueno's beggining setup. However light spectrum looks a little bit different - more blue and red as it is 90 CRI cob. Bueno had 80 CRI.

On the picture plants have about 8 days - on this stage they should be a little bit bigger.
Light period 24/24
Only crane water after 24h - maybe I water plants a little bit too often, ground is still moist.
ph and humidity unknown
using vent with carbon filter ~190m3/h (probably a little bit less)

As I mentioned before this is my 1st indoor. I've never had problems with germinating and 1st weeks of the grows of outdoor strains but they were sitting on the windowsill taking energy from the sun. That's why I doubt that it's problem of bad ph, humidity etc. I haven't been using any nutrients yet. Actually... they look pretty fine: I would say acceptable - normal darker green color and these brown little dots on the tips of the leafs are literally microscopic. You won't see them right away so maybe it's not a problem at all. As I have no indoor experience I thought that light intensity may be too strong but now I'm starting to think that it's the opposite actually The real problem is that they grow up to slowly. I'm using 3000k leds btw. - which is not the best option for vegetative grow. I'm aware of it. But once again: Bueno had better results with almost identical setup. That's why this is so strange

Edit: I moved them back closer to the led - back to ~60cm. We will see if it will accelerate their growth. I'm planning to add the second CXB3590 cob (80 CRI) in the near future and this will be the final setup.

 

[doams]

this is a bit too close /10w screw in led/

but agree that 3-5inch is better

 

[repuk]

Doam that girl looks cooked... LEDs are not CFLs, they have much more penetration, no need to put them so close to the canopy.

BReal, I'm afraid you're like killing flies with an RPG...

Douglas.Curtis already explained canopy distance for LEDs is determined by:

1- Kind of LED chips (max watts)
2- Wattage the chips are run at.

A CXB3590 is 137W COB LED chip, way overpowered for your grow space height, even if ran at 50W (remember there's more efficiency).

For low height tents the best option are 11W E27 LED bulbs. LED chips on these look like 1.5-3W each (on philips 11W), so 8" is a good distance to canopy, which will allow you to make better use of the space available.

If I were in your situation, I'll get a 11W 5000-6500K LED bulb, place it at 15-20" over the seedling and use that for them. You'll save power and worries.

I'm afraid COB requires same or even more headroom in height than an 600/1000W HPS, not really suitable for your grow space height.

 

[HuffnPufferfish]

none of those smd run anywhere near 3 watts, theyll melt off the pcb

most miliamps ive seen was 72 and 152, and around 40ish volt, abuot 3v per chip
https://www.saving-star.com/smd-led-comparison/

 

[Parallax]

I keep mine approximately 8 inches from the tops, which is the distance from your thumb to your little finger when you stretch your hand.

 

[repuk]

none of those smd run anywhere near 3 watts, theyll melt off the pcb

most miliamps ive seen was 72 and 152, and around 40ish volt, abuot 3v per chip
https://www.saving-star.com/smd-led-comparison/

I wasn't referring to the watts they're run at, but the LED chip "sizing", which looks to me to be 1.5-3W by their individual LED chip size. This is the first criteria for canopy distance, wattage they're actually driven at coming second (from my experience).

There's 17 LED chips in the 11W bulb, cannot be 3W each as it won't match the math drawing 11W/94mA overall... each is run at around 0.6W.

The point I'm trying to make is two given same wattage bulbs (say 11W) can have different number of LED chips, e.g. one 17 and the other 10 (and bigger) LED chips.

Even both bulbs being 11W, the 17 chip one could be placed closer to the canopy than the 10 chip LED one, whose individual LED chip wattage rating will be higher, even if each individual LED chip on the 17 chip bulb is actually driven harder than the 10 chips one.

 

[HuffnPufferfish]

so its all about the intensity(miliamps) we all know that

 

[repuk]

nope, not just mA. A led chip driven @ say 50mA may cook your canopy at 8", whereas another driven at the same 50mA may not, depending of kind on led chip, more specifically, max wattage and efficiency, thats the point I was trying to make.

 

[exploziv]

It's all about wattage & lens angle. Simplified, it's power over surface.

 

[HuffnPufferfish]

nope, not just mA. A led chip driven @ say 50mA may cook your canopy at 8", whereas another driven at the same 50mA may not, depending of kind on led chip, more specifically, max wattage and efficiency, thats the point I was trying to make.

wich in 99% of the cases is the same; the cheapest chip they could find

the way these bulbs are build is almost identical to the next, they all use the same pbc setup, just the components differ from continent to continent, one at 50ma will be 99% the same as the next at 50ma

you realize you can swap their drivers and it still works?

nothing should be able to cook anything from 8 inches away.. even my cobs dont

 

[exploziv]

But it's not just mA, you also need to factor in volts, hence Watts is a better way of comparing power between led chips.

 

[HuffnPufferfish]

the majority runs 3.x volts, all put in a string, hence why most drivers are 40ish volts, really its not as complicated as people think