Cannabis Daily Light Integral

[Rahz]

@Rahz I have done a run to try and find the maximum PPFD a strain could handle and was smashing it with up to 3500 PPFD while keeping the ambient temps between 25-30c. As long as the temps were kept in check, the plant can handle it. More relevant is DLI - the plants can handle the high intensity for shorter periods but once they hit their max DLI, damage starts to occur.

Apparently lettuce can handle up to 5000 PPFD in recent research but didn't increase yields.

There is a benefit though, you can use the higher intensity light to reduce your lights on time and increase flower period, which with FR speeds up the flower cycle. Still working on the particulars but I have reduced my lights on down to 6hrs using a 1500-1850 PPFD at the canopy.

Also since you seem fairly smart and a decent vendor, you should go take a look at using PWM current to drive the cobs. Not the PWM dimmer option on meanwells, they still provide stabilized current to the cobs. Do your research into it and see if you are able to source a LED driver with PWM output.

Good info, and not surprising especially with PPFD being measured at the ideal height and more plant matter being located below that plane than above it. I'll take a look at PWM, a quick search does indicate increased efficacy.

Wait, so you're running 6 hrs. on or 6 hrs. at max intensity?

 

[Rahz]

Not really because those par measurements don't include which spectrum is more desirable, HID lights grow better plants cause of IR.

No point in arguing about that. The guy has been using HID for over 10 years and just made the switch. I'm going to check back with him in a couple months to see what he thinks.

 

[Yodaweed]

No point in arguing about that. The guy has been using HID for over 10 years and just made the switch. I'm going to check back with him in a couple months to see what he thinks.

Good luck.

 

[Photon Flinger]

Good info, and not surprising especially with PPFD being measured at the ideal height and more plant matter being located below that plane than above it. I'll take a look at PWM, a quick search does indicate increased efficacy.

Wait, so you're running 6 hrs. on or 6 hrs. at max intensity?

6 hours on with the canopy getting 1500-1850, 18 hours lights off. I can probably still drop the time or PPFD a bit more if I wanted to get super picky about it but this has been working well. Lots of air circulation so no CO2.

3500 PPFD for 12 hours caused some interesting things. I didn't get the 'bleaching' probably because that is more of a heat issue. Contrary actually, the plant reacted by putting out single leaves and went into a massive stretch phase. Tops that were pruned sent shoots out as if it were in veg. It was if the plant was confused between flower and veg which might be the result of the intensity. End product was pretty fluffy but it was dam good stuff.

Went PWM by accident and will never go back

 

[tomate]

@Photon Flinger
Which drivers are you using?

 

[Photon Flinger]

@Photon Flinger
Which drivers are you using?

They are just those generic chinese drivers 45-75V700ma. Turefull, NL, a few other names but they are all just simple buck based boards in a black plastic case. You change the PWM duty cycle with a dial similar to the nobby things on PC fans to adjust the speed.

I mate each one to a Vero 29c and it works very well. Haven't had one go yet but the ones I have are no longer produced so I need another source if I want more lights.

 

[sethimus]

So you never grew with a HID light but somehow think LEDs are better?

Isn't that a little backwards, shouldn't you have first hand experience before ruling something out or anointing something better?

Also why the hell would you continue to use 6 month old bulbs, that just shows your inexperience with HID lights.

did you get molested by a led once? that would explain A LOT.

 

[Randomblame]

They are just those generic chinese drivers 45-75V700ma. Turefull, NL, a few other names but they are all just simple buck based boards in a black plastic case. You change the PWM duty cycle with a dial similar to the nobby things on PC fans to adjust the speed.

I mate each one to a Vero 29c and it works very well. Haven't had one go yet but the ones I have are no longer produced so I need another source if I want more lights.

Can you take a picture for us? So maybe we can find something similar, thank you!

 

[Photon Flinger]

Can you take a picture for us? So maybe we can find something similar, thank you!

No camera sorry, but they are pretty common in a lot of chinese fixture offering.

 

[OneHitDone]

I recently helped someone replace 2 600w HPS with 1120w LED. I let them borrow my par meter and asked them to take readings before and after. The HPS was reading 1022 PPFD 16" below center and 678 PPFD near the side, approximately 16" off center. Readings were also taken 22" below center (752 PPFD) and 22" off center (330 PPFD).

Anyway, this person had one plant that was a late addition and he angled both of his HIDs onto the plant since he didn't need the whole space at the time. Got the biggest buds he's ever gotten. He does run CO2. His light levels at the canopy were likely between 1500 and 2000. Unfortunately I don't have a way to quantify the difference, but he was impressed.

If anyone is curious, the 51% efficient LED that replaced the HID at same reading points were 1408/820 and 1011/605. The bulbs were six months old so they didn't get beaten that badly, but still a major improvement.

Point is, if you hang your lamps too high you're wasting light and loosing yield. I haven't had a chance to play around with HID but one thing I've noticed with LED, especially using 90 degree reflectors is that the center point reading will be somewhat linear while the outer readings will stall for a bit. What I mean by that is for instance you are checking light levels at 12 inches and get maybe 1000 center and 600 side. Move down to 14 inches and your at 850/620 or something similar. Then at 18" it's 700/590. This happens on the side because although the reading is being taken further away which lowers readings it's also further inside the cone which raises readings. This is why you should get your lights as close as they can tolerate within reason. Moving up from 12" to 10 inches in the same example might produce 1200/430 or something similar as the side reading moves outside the cut off point of the reflector cone.

Not interested in the what tech is efficient etc, what in your opinion caused your pal to grow the biggest buds he had ever grown? Spectrum or intensity?

 

[nfhiggs]

when PWM catches on.

Care to elaborate on what you mean here?

 

[Humple]

Not interested in the what tech is efficient etc, what in your opinion caused your pal to grow the biggest buds he had ever grown? Spectrum or intensity?

What matters more to you - bigger buds or higher yield?

 

[Slinging PAR]

Care to elaborate on what you mean here?

PWM or PDC to drive the light source. Reduces heat, produces less wasted light.

 

[OneHitDone]

What matters more to you - bigger buds or higher yield?

High Yields of proper sized dense nugs. No buds the size of your thumb shit!

 

[MichiganMedGrower]

Not interested in the what tech is efficient etc, what in your opinion caused your pal to grow the biggest buds he had ever grown? Spectrum or intensity?

I wish I still had the University of Michigan link but it is in an old device. I can try to search.

They tested metal Halide vs hps for spectrum vs. lumens (intensity) and in every crop lumens showed more growth and barely perceptible quality differences.

For cannabis uv is a variable but they were testing plant growth and yield.

Full spectrum is very effective to keep plants short and bushy. And gives better leaf health. And possibly terpenes but not proven.

Hps will tend to grow bigger more potent buds. The red spectrum promotes stretch and blooming. Some have added 25% blue they grow better quality in my opinion.

 

[Rahz]

Not interested in the what tech is efficient etc, what in your opinion caused your pal to grow the biggest buds he had ever grown? Spectrum or intensity?

Pretty sure it was intensity. Another guy I know used 600s and would get them as close as possible, would get giant main colas directly under the lamp. Calculated the GPW and it was barely 1.

 

[Humple]

High Yields of proper sized dense nugs. No buds the size of your thumb shit!

Well if you have any doubt that LED can grow bats, look at the "From DEs to LEDs" thread by @greengrassgrower1. But personally - though I don't want airy larf - I just can't give a shit about bud size. Does it taste good, and is it effective medicine? That's what counts to me. But I'm not selling, so I don't have to be concerned with bag appeal.

 

[nfhiggs]

Does it taste good, and is it effective medicine?

This. This is what counts.

 

[OneHitDone]

Pretty sure it was intensity. Another guy I know used 600s and would get them as close as possible, would get giant main colas directly under the lamp. Calculated the GPW and it was barely 1.

I think I'd have to lean more to spectrum
Intensity is one thing that led's definitely seem to be bringing to the table, too much in many cases...
Just as in this vid, the QB's whole hype is over high intensities. Yet the HPS side is making larger buds at a lower intensity?

 

[Humple]

I think I'd have to lean more to spectrum
Intensity is one thing that led's definitely seem to be bringing to the table, too much in many cases...
Just as in this vid, the QB's whole hype is over high intensities. Yet the HPS side is making larger buds at a lower intensity?

And if the QBs out-yield the HPS, will you nonetheless consider the HPS to be the winner because of bud size?