What ppfd values and height should I hang my leds at?

[d0773d]

Tent: 4 x 8
LIght: Growcraft X6 – 660W LED Grow Light Dimmable

I'm only using one 4 x 4 section of the tent. The light is dimmable. I won't be using C02. Will height be relevant since my light is dimmable? Information I gathered is:

Seedlings, clones, mother plants: 200-400 PPFD
Vegetation Stage: 400-600 PPFD
Flowering Stage: 600-900 PPFD

PPFD value credit from: Garden Talk with Mr. Grow it video How Much PAR For Plants in PPF & PPFD!

 

[Badfinger]

I follow those same PPFD numbers. IMO, you adjust DIM or height to meet those PPFD numbers.
I think the nice thing about having the ability to dim the lights, really comes into play if you start running into height issues in your tent. Also, a dimmed down LED light will use less electricity.

 

[olbobcat]

I am one for dimming and keeping the same height from plants for the most part. Saves money. There was a study which I looking for because I can't remember where I saw it that said in late flower they need less DLI. Remember in nature get less light and fewer hours of light in fall as well as less intense. Now with autos, it might be different. So the DLI reflects how much daily light. So that would take into consideration your PPFD and amount of hours running the lights. So since I run 24/7 I turn the lights to 75-80 percent in flower. If I get brave some time I might try to reduce them more the last week or two of flower to more like 60%.

 

[RiseAboveTheFlame]

Hey fellas. I'm on my first grow and trying to button up my environment conditions for my 2x4.

Do you guys use a PPFD Meter app? I think I found a decent one, but I'm reluctant to calibrate it. I don't really have a good set point for ppfd aside from mfr data, which i don't trust in the first place.

You guys think any of these apps are reliable?

Tia.

 

[Olderfart]

I use an actual par meter. The apps work reasonably well, but ONLY if calibrated for your specific light. If you don't have anything else, the mfr specs will be the best you can do. Keep in mind that you need to be calibrating in the same size space as the mfr used in measuring the PPFD from their light. Ideally, get your mitts on a par meter and use that to calibrate, or find someone else that has already done that. Bottom line is that the app must be calibrated to your exact light spectrum.

Good luck with it.

 

[Olderfart]

Oops, forgot to mention on the dim vs. height thing. Stronger light from further away makes for better "penetration" into a developed canopy. The lower parts of the canopy will get more light, potentially a lot more, by achieving the same PPFD at the top of the canopy from further away rather than by dimming from a closer distance.

With my setup, the extra cost of running lights at full output is zero because my 'drobe needs the heat. Even with the lights on full, a small space heater comes on periodically to keep it at temp, in my case ~27C. If you don't need the heat, your calculations may be different.

Good luck with it.

 

[Rasterman]

I don't have a ppfd meter and had a lot of trouble getting the height perfectly every time, until I realized the plant can tell you. So this system works for me:

1. Put the light at a height that won't hurt your plants.
2. Every day, check to see if your plants are praying (see below). If they're not, lower the light again. If they are, you should raise the light about four clicks if you need more coverage in the tent. But leave it alone if it's only one plant and it's getting good coverage.

Cannabis plants pray when they're getting an abundance of light. My favorite level is the one that causes the plant's leaves to cant upwards at a 15° angle. It's my thinking that the plant angles its leaves to reduce the amount of light.

If the plant is praying, it's getting more light than it needs (so it's thankful and prays). You can use that information to provide the best light possible in the tent. The higher the light is, the more coverage it gives. So if I'm in a tent with several plants and need coverage, I will raise the light just until the plants stop praying. But if I have one plant under the light, I'm going to drop the light down until I get that 15% upward cant.

Anyway, that's what I think I have learned. Do with it what thou wilt.

 

[Delps8]

Hey fellas. I'm on my first grow and trying to button up my environment conditions for my 2x4.

Do you guys use a PPFD Meter app? I think I found a decent one, but I'm reluctant to calibrate it. I don't really have a good set point for ppfd aside from mfr data, which i don't trust in the first place.

You guys think any of these apps are reliable?

Tia.

I've done a fair amount of poking around in this and decided to go with a PAR meter. Not cheap but it is accurate.

I tested Photone about a year ago (it was called Korona back then) and my results were not what I was expecting but, based on emails between myself and the programmer), my sense is that Photone will get you in the ballpark.

Some growers use a LUX meter. That's fine for taking pictures but, seeing that a lux meter/light meter measures a different spectrum, a lux meter is going to be very inaccurate. Some manufacturers publish data that you can use to convert the reading from a lux meter to a reading of PAR. If you've got a light for which that data is available, that could be a cost effective approach.

Next step is to go to a PAR meter. I decided against the "budget priced" PAR meters on Amazon and, based on comments I've read in the intervening year, I'm glad that I did. I ended up getting an Apogee and have been able to take advantage of most of its features but, looking at the market today, the PAR meter that Shane is selling on his site (migrolight.com) seems to be a good buy. You get a lot of features for the extra $$ (the Apogee is about $600 vs <$300 for Shane's meter) but they may not be worth the extra funds.

 

[Delps8]

Tent: 4 x 8
LIght: Growcraft X6 – 660W LED Grow Light Dimmable

I'm only using one 4 x 4 section of the tent. The light is dimmable. I won't be using C02. Will height be relevant since my light is dimmable? Information I gathered is:

Seedlings, clones, mother plants: 200-400 PPFD
Vegetation Stage: 400-600 PPFD
Flowering Stage: 600-900 PPFD

PPFD value credit from: Garden Talk with Mr. Grow it video How Much PAR For Plants in PPF & PPFD!

Check out YouTube videos by Dr Bugbee and you might want to run through the research done a U Miss - Google "cannabid Chandra" and download the PDF. There's a graph in Chandra that shows the curves of photosynthesis vs PPFD for a different temperatures. It's very revealing.
Based on what I've read (and watched), my environment during veg and flower is at least 25° C and at least 700 µmols on as much of the canopy as possible. One of the advantages of growing autos is that you can push the DLI really high.
All of the DLI values that I've seen for "max DLI" in flower appear to be based on 900 µmols for the 12 hour lights on period of a photoperiod plant. Autos don't have the 12 hours of darkness requirement so you can hit them with significant amounts of light for the 18/6 or whatever light cycle you're using. Per Bugbee, cannabis will make use of huge amount of light (how about a DLI of 65 mols!) and, even at 24¢ per kWh, I'm all for giving them as much light as possible,

 

[d0773d]

Check out YouTube videos by Dr Bugbee

I've watched so many videos by Dr Bugbee and interviews with Dr Bugbee. He is the reason why I splurged on a
MQ-500: FULL-SPECTRUM QUANTUM METER. I still have sooooo much more to learn.