New grower. DLI Advice on ppfd and dli.

[Random Tasked User]

Hi everyone, I could do with some advice, I’m almost at the end of completing my setup and I’m struggling with the dli and ppfd. I’ve actually only just stumbled across dli by chance on YouTube and I’m glad I did because otherwise I’d probably been blasting auto flowers on 20/4 or 24/0 at around 900ppfd. Anyway the flower light Ill be using at 8” at 100% has ppfd centre hotspot of 1580, and the lowest corner has ppfd 1020. Would it be safe to assume if I was to run the light at 40% at 8” that would give me a rough ppfd of 662 ? And if that’s the case would the lowest corner of 1020. At 60%less which would give me 408. Be enough ? The DLI would be 57

 

[Random Tasked User]

The DLI would be “57” for the 662 and DLI of “35”for the 408. Also having a light dimmed that much Would it impact the plants in anyway ? I’m new to this forum and any advice would be appreciated many thanks.

 

[Lil Dab]

The problem I have found is the dimmers knobs aren't always accurate and can be very sensitive.... can you download the Photone light meter app on a smart phone? I use that and it gets me in the ball park I assume your using LEDs if so then pay the extra 5.99$ for full spectrum unlock that's what i do then watch so see how the plant reacts and go from there

 

[Random Tasked User]

The problem I have found is the dimmers knobs aren't always accurate and can be very sensitive.... can you download the Photone light meter app on a smart phone? I use that and it gets me in the ball park I assume your using LEDs if so then pay the extra 5.99$ for full spectrum unlock that's what i do then watch so see how the plant reacts and go from there

Thank you !! yes I’m using led I’ve heard about the app before so I’ll definatley try it out.

 

[Olderfart]

IMO, you are better off reducing intensity by lifting the light at full power if you have room. If you lift the full power light until the PPFD at the canopy top is at your target level, you will deliver more light lower in the canopy than you would by turning the light to lower. Counterintuitive, but true. I suspect that when the term "penetration" is used in indoor grows, it refers mostly (yeah, I know, not completely) to this effect.

Having said that, on the whole, I think more light is usually better. Unless you see actual damage from light, I very much doubt that DLI's up to ~~800ppfd/60 DLI would be a problem for anything other than seedlings with less than a couple sets of real leaves. I provide ~400-500ppfd for my babes, and ramp it up to 600-700 after they have a couple sets of leaves. Cannabis in the wild has to put up with ~2000ppfd in direct sun at germination, after all - it may not like it, but it will usually get past it. The main issue (I think) with DLI and LEDs, as long as no damage is done, is efficiency, not horrible damage effects. If you give them more than they need, the plants will not be able to use it all as efficiently, so the power bill will go up more than the yield will. However, that does not mean that the yield will not go up, and that is an important point. It is also true that light intensity affects plant anatomy, less light or less blue light means more height, more light and/or more blue produces a more squat plant. My current grow has kept all my plants short due to a lot of light, and a lot of blue from my screwin led's. Next grow, I will reduce the blue light to get a bit more height.

I don't chase efficiency because I need the heat in the 'drobe anyway. Different strokes and all that. Good luck with it.

 

[Mañ'O'Green]

@STICKYSCISSORS(23) Welcome to AFN If heat in the tent is not a consideration then Seedlings go 20 DLI, Veg 40 - 50 DLI and flower 60 DLI. Like mentioned above 24" to 30" light height will give better coverage.

At today's energy prices running your lights ~ 50% will give you more photons for the buck but it is light fixture dependent as to the savings.

The Photone app is a great tool. I highly recommend it.

 

[Random Tasked User]

IMO, you are better off reducing intensity by lifting the light at full power if you have room. If you lift the full power light until the PPFD at the canopy top is at your target level, you will deliver more light lower in the canopy than you would by turning the light to lower. Counterintuitive, but true. I suspect that when the term "penetration" is used in indoor grows, it refers mostly (yeah, I know, not completely) to this effect.

Having said that, on the whole, I think more light is usually better. Unless you see actual damage from light, I very much doubt that DLI's up to ~~800ppfd/60 DLI would be a problem for anything other than seedlings with less than a couple sets of real leaves. I provide ~400-500ppfd for my babes, and ramp it up to 600-700 after they have a couple sets of leaves. Cannabis in the wild has to put up with ~2000ppfd in direct sun at germination, after all - it may not like it, but it will usually get past it. The main issue (I think) with DLI and LEDs, as long as no damage is done, is efficiency, not horrible damage effects. If you give them more than they need, the plants will not be able to use it all as efficiently, so the power bill will go up more than the yield will. However, that does not mean that the yield will not go up, and that is an important point. It is also true that light intensity affects plant anatomy, less light or less blue light means more height, more light and/or more blue produces a more squat plant. My current grow has kept all my plants short due to a lot of light, and a lot of blue from my screwin led's. Next grow, I will reduce the blue light to get a bit more height.

I don't chase efficiency because I need the heat in the 'drobe anyway. Different strokes and all that. Good luck with it.

Thanks for your reply I did think raising the light would make more sense for more coverage. My only concern with this is Im working out of an 8x8 split down the middle with one half for veg and the other side for flower and my big light is an 8 bar spider farmer so I don’t want too much coverage. but now I got the app Ill raise up my light to the top stick it in full blast and dim if I need too. The higher intensity being on full power would also help bring up my temps which is great. 700 through flowering working well ? what hours are you running ? I’d like to run 20/4 but i worry about using timers. To many wires and plug ins freak me out

 

[Random Tasked User]

@STICKYSCISSORS(23) Welcome to AFN If heat in the tent is not a consideration then Seedlings go 20 DLI, Veg 40 - 50 DLI and flower 60 DLI. Like mentioned above 24" to 30" light height will give better coverage.

At today's energy prices running your lights ~ 50% will give you more photons for the buck but it is light fixture dependent as to the savings.

The Photone app is a great tool. I highly recommend it.

Thanks the welcome !! I’ve learnt so much over the last month using this forum.

 

[Olderfart]

Thanks for your reply I did think raising the light would make more sense for more coverage. My only concern with this is Im working out of an 8x8 split down the middle with one half for veg and the other side for flower and my big light is an 8 bar spider farmer so I don’t want too much coverage. but now I got the app Ill raise up my light to the top stick it in full blast and dim if I need too. The higher intensity being on full power would also help bring up my temps which is great. 700 through flowering working well ? what hours are you running ? I’d like to run 20/4 but i worry about using timers. To many wires and plug ins freak me out

I am on 20/4, and I need a space heater in my 4x4 as well as my diy screw in arrays to keep it at ~27C.

I haven't had any timer problems, so far. For my lights, I use an outdoor Woods timer, and it is still good after about a year's worth of operation.

The main thing with extensions is to monitor them for unusual heat. If they get hot under load, resistance is developing for some reason, perhaps dirty connections, corrosion, broken or loose wire, or bent contacts. There are any number of possibilities, but anything that increases resistance above the nominal level a good cord and connections have will produce heat, and could cause a fire. The problem is that heat caused by resistance will not blow a breaker, so there is no protection other than operator care. Usually once resistance start, it is likely to get worse, maybe to the point of causing fire. Just a bit warm under continuous heavy load is tolerable, but anything beyond that is a warning. Heat anywhere in your wiring run, other than where the work is supposed to be done is always a warning, and sometimes a serious threat of fire.

Being careful with extensions is a good idea, but IMO with care, they do not deserve their bad reputation. Just keep the contacts clean, the wires tight, and monitor for heat where it should not happen. At least that is what I do and I am still getting away with it after more years than I care to remember.

 

[Random Tasked User]

I am on 20/4, and I need a space heater in my 4x4 as well as my diy screw in arrays to keep it at ~27C.

I haven't had any timer problems, so far. For my lights, I use an outdoor Woods timer, and it is still good after about a year's worth of operation.

The main thing with extensions is to monitor them for unusual heat. If they get hot under load, resistance is developing for some reason, perhaps dirty connections, corrosion, broken or loose wire, or bent contacts. There are any number of possibilities, but anything that increases resistance above the nominal level a good cord and connections have will produce heat, and could cause a fire. The problem is that heat caused by resistance will not blow a breaker, so there is no protection other than operator care. Usually once resistance start, it is likely to get worse, maybe to the point of causing fire. Just a bit warm under continuous heavy load is tolerable, but anything beyond that is a warning. Heat anywhere in your wiring run, other than where the work is supposed to be done is always a warning, and sometimes a serious threat of fire.

Being careful with extensions is a good idea, but IMO with care, they do not deserve their bad reputation. Just keep the contacts clean, the wires tight, and monitor for heat where it should not happen. At least that is what I do and I am still getting away with it after more years than I care to remember.

Thanks for your advice it’s been really helpful I’ve downloaded the Photone app used the diffuser and I don’t know wether I’m either terribly bad with a tape measure or doing something wrong but both my lights at the manufacturers distances are way off the mark lol Its definatley something I’m doing wrong so will figure it out tomorow. The seeds are in wet paper towels and I’m looking forward to get this grow started. Your advice has been mega helpful thank you !! Im going to start a new post with my first grow wish me luck bro !!