Great info, thanks for sharing it.
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I’ve seen some specs for individual diodes and fixtures where they’ll say the PPE ranges from 2.7 to 3.0, I assume underdriven is the higher number and maximum is the lower, but I didn’t think about the power supply, that could change too. In general there might be some benefits to running a 600 watt light at 450, it will be cooler, it might last longer.
So get the bigger one if you’re not sure how much light you’ll need 
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Likely. How much that equates to in operating dollars, I don’t recall offhand. I’ve seen the calculations at some point. The difference between 2.7-3.0 is probably not a huge difference to be concerned about unless you’re running lots of fixtures or a looking to squeeze every cent. Where it’s starts to really show up is when we’re talking 2.0 vs 3.0 between different fixtures.
Estimations from Cree:
Fluorescent lamps: approx. 0.7 µmol/J
Current NDL 600W: approx. 1.8 µmol/J
Current NDL 1000W DE: approx. 2.1 µmol/J
Current LED: over 3 µmol/J
There are some reasons to look at the PPE including reducing the heat generation. Fixture price tends to the follow the PPE, though. Figuring out the best bang for the buck is always the trick.
Many power supplies are more efficient at the higher loads. They are usually optimized to be able to produce the max rating and is a design limitation.
Here’s a graph from one of the meanwell current-mode supplies:
In the plot, the efficiency drops significant below 50% load or thereabouts and is fairly flat above that amount.
However, back of the paper evaluation means something less than 50 watt/hr loss from reduction in power supply efficiency.
Today, it’s all about heat. If those small LED packages and surrounding heat sinking could remove all of the heat from the junction, you probably wouldn’t see the efficiency reduction (as illustrated in the plots), until you achieve the theoretical maximums (somewhere > 5 or so I’ve read). And, at that point, the phosphors are ready to produce a spitting volcanic fire or something.
In both cases, rule of thumb is that lower temperatures equates to higher MTBF and less aging effects.
For the Mars fixtures in the op, I don’t have confidence in the PPE (up to 2.8) numbers but, from past evaluation of one of their newer line of fixtures, most of the other numbers were in the ballpark to what they had been advertising.
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Thank you @Northern_Loki this is a fascinating discussion! I’ve been thinking about running an experiment with my new light to test this - thinking I’ll just lay the quantum meter on the floor and take readings at 10% increments on the dimmer, while also charting the power draw on my Killawatt. Should be able to quickly see if the efficiency changes at different wattages.
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That is a lot of information. I’m interested.
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That would be cool. The power supply specific inefficiency loss will likely only be measurable on the DC side of the power supply. The conversion from AC to DC is where the inefficiencies lay and the Killawatt won’t be able to capture only the power supply inefficiency. Rather you’d be measuring a combination of the two, the PPE shift + power supply inefficiency. Either way, it would be neat to see your results. You should be able to look up the specs online for whatever the power supply is on your fixture.
Also FYI, here’s an example what happens when a fixture heats-up (from a Fluence unit we’d measured):
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Thanks for that.
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i also read this before. but never fact checked. so i cant say 100% just wanted to back you up on hearing the same thing
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This was what I was responding to. 300 watts no matter what is drawing it will cost the same to run. Whether it’s a 600 watt lamp dimmed to 300 or a 300 watts lamp running at max power.
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wow, that graph is revealing - so it pays to keep good air movement over your fixture, the light will be slightly brighter. Did you have fans blowing during your test? I’ll have to read up on your test.
This also means I should run my experiment quickly, within a couple minutes, or else let the fixture heat up for 30 minutes beforehand. Yes, it would test the power supply & diodes together, I’m curious about the overall efficiency at different wattages. I’ll have to run a couple experiments w/ temperature too.
For lighting nerds the design lighting consortium website is amazing, they tested the exact Vypr fixture I got from Fluence, most commercial-type fixtures are now on their website, even HLG…Mars Hydro is in there too! impressive results with the FC6500…2.8 umol/J
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No fan. Open air convection.
Either or. Quickly with a cool down period or a dwell period to stabilize.
That would be interesting.
Good resource, I was aware of them but I don’t recall seeing such a comprehensive list being published until now.
FWIW, we’re not too far off with the measurements we had performed here relative to the lab. For the Spydr-2P, they measured 1479.4 μmol/s. We measured 1424 umol / s (at 6 inch distance). For efficiency, the manufacturer states 2.5 uMol/J. They calculated 2.28 uMol/J versus our calculation of 2.14 uMol/J.
| Spectra | Them | Us |
|---|---|---|
| (400-500nm) | 267.02 μmol/s | 240.22 |
| (500-600nm) | 590.8 μmol/s | 564.17 |
| (600-700nm) | 620.34 μmol/s | 674.81 |
They were also running at a different line voltage so the results could be even a better match than expected.
The op’s FC 6500 is on there as well. They actually did measure 2.8 PPE at an astounding 1769 uMols/m^s/s. I’m a bit surprised on that and am thinking vehicle emissions gaming. Might need to revisit at some point.
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This has turned into a fantastic thread. I dont think most delve this far into the technical side of lighting so I am really enjoying all the info being posted. Thanks all.
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vehicle emissions gaming, that’s pretty funny. I’m still driving a VW diesel Jetta btw!
I think it’s good to add in the DLC PAR numbers for 700nm+ (Far Red) to the PPF total too - seems like the consensus is now saying those are useful wavelengths also. DLC is revealing, my Vypr 3P Greenhouse actually tested higher than the Fluence spec. But DLC ran it at 120V, I think Fluence uses 277v for the specs - more likely to be used by greenhouses
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I received a response regarding the tent. They informed me they are sending a tent cover? I didn’t inquire to what this is, but I’m guessing it is what it says. Doesn’t do much for me as I’ve already been draping a dark bed sheet over the door to prevent light from entering during lights out. My pics suck, but this zipper is crap. It is getting worse by the day and impacts the entire front door. I patched pin holes all around each corner seam, as well as a few in the walls, so the zipper is my only current issue.
I didn’t expect, nor ask for a new tent, but not too impressed with Mars’ response considering this tent is less than 2 months old. Even less impressed with the zipper.
Doug—keep me posted on how yours holds up. It’s always possible I simply got a defective model.
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that’s sucks about the “tent cover” not much of a solution! FWIW…I don’t think that’s nearly enough light to disturb the 12/12 cycle. I actually have two 6-inch vent holes covered by nothing but mosquito netting on my flowering tents. Whatever daylight is coming in the bedroom windows gets into the tent a little bit, it’s never affected anything, the plants flower right on time w/o hermi.
The plants are wired to ignore the light of the full moon which is bright. Both my Secret Jardin 4x4 tents have light leaks on the zipper like your pictures.
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Any chance the “tent cover” is the tent minus the floor and poles? That would be acceptable.
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@Muleskinner these pics don’t do any justice. It’s really no bueno. It very well could be a negligible amount of light, but if I get in there zipped up and the light is off, but lights on outside the tent, I can see pretty well. Then again, I may be paranoid. The sheet I have hung over is mitigating the faulty zipper so all is truly well. If I see nanners later, you know the conclusion I’ll draw haha.
@ReikoX that’s the best case scenario and certainly not ruling it out. I’m not going to trash Mars either way. A lot of people like them which also begs the question…did I just get a bit of a lemon? I’ll update here when I receive whatever they are sending. Their customer service has been very engaged with me. That I do want to mention.
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That’s what I’m thinking there sending ya.
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Hey, will do. I am going to assume a tent cover means the skin without the hardware. Otherwise it would mean they manufactured a cover to go over the tent which seems more expensive than handing out another already created shell. Let us know what shows up. Their customer service is definitely very important so really curious how they respond.
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Yeah me too. I built some cardboard baffles to limit it but a little is not a big deal.