Light intensity

[Jacob Reitsma]

Hello all,

I made myself an orchid growbox with LED lights and I was wondering which amount of light is right.
My box is 80x70 cm and 1 m high and my LEDs are 4x citizen CLU48 1212 4000k driven with ELG-150-C1050B.

With a potmeter I dimmed it back to 85 watt.

In my box there are tree stages were I did some measurements with my phone,
stage 1 ≈ 6000-7500 lux
stage 2 ≈ 15000 lux
stage 3 ≈ 25000 lux.
So let's say its between 6000 and 30000 lux.

Can someone tell me if this is the right amount of should I give more or less light?

Plants I am growing:
bulbophyllum crassipes
dendrobium catenatum
paphiopedilum gratrixianum
pleurothallis solium
brassia nanboh breeze
sedirea japonica (seedling)
cirrhopetalum frostii (seedling)
dendrobium farmeri (seedling)
phalaenopsis hieroglyphica (seedling)
bulbophyllum neilgherrense
dendrobium kingianum
Restrepia mendozae
Pleurothallis hemirhoda

[rbarata]

I can't help you 'cause I don't grow under lights nor in boxes. Anyway, your "instalation" seems great. Good job.

My only help in this case is to bump it up.

[naoki]

Very nice, Jacob! CLU048 1212 is a very good deal, and gives you very high efficiency for such low price.

If you multiply the lux by 0.01407376 (I haven't digitized CLU048 spectrum, but using Cree 4000K CRI80 spectrum), you'll get the PPFD (micromol/m^2/s). So you are getting 84 - 351 micromol/m^2/s. The optimum PPFD depends on the environment, but in one study of Paph, photosynthesis saturate around 100 micromol/m^2/s. In other words, above that value, increase in photosynthetic rate is minimum. So your lowest level would be good for these lower light orchids. I usually adjust the light to be 100-200 micromol/m^2/s. In your list, there are some higher light plants, but the majority seems to be medium to lower light orchids. So you could turn down the dimer a little bit further.

But if you lower the dimmer too much, the efficiency start to suffer. Here is my measurement of how overalll efficiency (driver + LED) changes with dimming (at the very bottom of the page).

Orchid Borealis: LED Driver

With my combination, I can go down to about 30% or so (15W, and 53.3W is the maximum). But a different combination will respond differently.

Is inside untreated plywood? How are you dealing with the water at the bottom? You might want to paint it with elastomeric paint (or something better), and use a plastic sheet caulked at the bottom.

[Jacob Reitsma]

Thank you Naoki, your blog has been a big inspiration for me for building my light! I am a beginner with both LED and orchids.

I dimmed it back to 80 watt now, that's 50% of the maximum of 160 but only 20% of the maximum of the individual LEDs because they can also be driven at 100watt each if I am right.

I will try to expand my collection with some more higher light orchids, intermediate temperature, but they seem a little harder to find.

The inside is indeed plywood and is treated with epoxy. I will also install a drain soon. So far everything seems very watertight.

[naoki]

That's great! I didn't notice epoxy coating, but now I can see the reflection in the last photo. Epoxy is better than elastomeric paint.

At 525mA, you are getting very high efficacy (175 lm/W). I haven't looked into ELG series driver, but it seems to be a perfect match for 1212. It has high efficiency, and the efficiency stays high even if you dim. You are getting 89% AC/DC conversion efficiency. It's good to know. So overall, the PAR efficacy is around 2.2 micromol/J, and total PAR output is 172 micro mol/J. Basically, this is the same performance as Fluence RAY44, a well regarded grow light (but 1/2 of the cost).

I hope that you'll find nice orchids to grow there!

[Nexogen]

So I've learned from experiments. Perhaps along the way you will change something. If you want to grow orchids personally I do not think you get good results only with 4000K CRI 80 white LED. The light is powerful enough but not much 660nm, probably not even violet.
This is what happened with ELG-150-C1050B.
HLG-80H-C700 could be used (two parallel COB) with the same results but with a better price, however you don’t use more than 60W.

[Tindomul]

Do those lights heat up a lot?
The whole setup looks real good.

[naoki]

Tindo, a lot of cheap LEDs aren't efficient, but Jacob's is one of the most efficient at this point. This means less than 50% of the electricity is converted to heat. I forgot the exact number, but T8 and T5HO is wasting 70-80% of electricity as heat. When I was using T5HO inside of my grow tent, it was becoming too hot (and automatic exhaust kicked in). But with high efficiency COB, I don't have the problem any more, and I can provide much higher light. Solving the heat issue was one of my main reasons to invest on high quality light (and I also wanted to save money in a long term).

Also, unlike HPS, it doesn't "throw" heat forward (i.e. no IR emission).

Here is my new example. Orchid Borealis: Samsung Linear LED module H-series Gen. 3 This is a small grow area for pygmy Drosera. Even if I close the lid completely, there is only 5F raise in the interior temp. It is amazing if you consider the amount of light required for Drosera (Cattleya level or more). The efficiency of Samsung H is similar to Jacob's (actually a little higher, but it is a bit more expensive).

[Jacob Reitsma]

Tindo, I didn't do an exact measurement yet but it seems inside my box it is 1,5 - 2°C warmer than the room when the light are on at half power(80-100watt)

If I would lift the light a little off from the glass the difference would be less than 1°C I think.

[Tindomul]

That's not too bad.