Led light questions for beginner

Hi all. Real beginner here. I have 2 x Samsung LM301b (660-665nm-3000k-5000k-730nm ) with meanwell driver 400 watts power consumption. in a 2.2 x 1.1 metre tent. Fully dimmable.
My question is at what height and at what power should i have these lights at the differing stages? IE- Vege- transition and flowering?
As i said i am a true beginner but realy keen to learn how to achieve best results and not damage my plants. There is just so much differing information and opinions.
any help much appreciated.


Good Morning @kiwi9 Welcome to the community. You have come to the right place fo information. Lots of knowledge here. You need to visit with @dbrn32. He is the light expert and I love getting his opinion. Happy growing.

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here is a light chart that posted on my grow journal from another member that answers your question i think.


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i used a phone app too determine DLI, but as it happened, the height from the plant was about halfway thru the range of height recommended by the manufacturer. in other words, manufacturer suggested 15-24 inches from the plant. i ended up at about 20 inches from the plant. there’s a whole universe of info on this subject that can serve to really confuse. i may be off course here, i think the best thing, and what i am doing now is to just watch your plants and let them tell you what they want. if they are getting too much light, you’re gonna get light burn. you will see it if it’s happening. at that point either dim the lights some or move the light higher up. if the plants are trying to stretch, they’re wanting more light. move it closer or turn up the power.

you can buy a light meter, and there are plenty of threads on here about them, but in the end, unless you have money too burn, they aren’t necessarily needed.

oh yeah, welcome aboard!

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Good morning @kiwi9. The Samsung LM301b diodes are a popular choice for led grow lights. At 480 watts of power this should have enough power to cover a 4x4 grow tent. And if you have two of these you may may too much coverage.
Can you include a picture or specifications of the manufacturer and part number of the board?
480 watt input usage should cover a 4’x4’ tent just fine.
Here’s the led grow light I’ve been using.


Depends on size of boards and board spacing for the most part. A small fixture with concentrated light pattern will need to be higher than a large fixture with diffuse light pattern.


Hi Everyone
Thanks for all your feedback. I have included the full technical description for my lights to try and create a better picture. I feel a bit ignorant here but there just seems so much information and opinions to wade through. sometimes its great to just get simple basic advise which is easy to understand.
Samsung 400 Watt LM301B Tech features
High Energy efficiency with 2.7 2.7 umol/j
2 x Meanwell ELG240 Drivers- Fully Dimmable
400 W power consumption
Light coverage- 5Ft x 5 Ft Vege
4Ft x Ft - Flower
Samsung LM301B & Osram Diodes (660-665nm- 3000k-5000k-730nm)
Dimensions- W60cm-x D48cm-x H5.9cm
Hope this all creates a better picture and once again thanks to all who respond with any advice

Thanks for the pictures @kiwi9. That first image looks like a light footprint. If you have metrics for your light that will determine the distance and spread you can expect for a sustainable grow. Here’s a similar boards light footprint with metrics.

Some lights are listed here with metrics of test data.

@LateNightGardner hey I am looking into Bar light hate to ask but what kind is that, are u happy with it, would u recommend it?, looking to cover 4x2 space or little more, started a new thread Bar light vs QB, thanks I’m new and looking to upgrade the right way

Indeed, I am very happy with the HYPHOTONFLUX HPF4000 I purchased from Amazon. I’ll update you on what I’ve heard about these guys on the Bar light vs. quantum board discussion.

HYPHOTONFLUX HPF4000 LED Grow Lights 5x5ft with Samsung LM301B & MeanWell Driver,Full Spectrum Growing Light Plants Grow Lamp,Dimmable Daisy Chain Commercial Grow Lights for Indoor Plants 2.7μmol/J https://www.amazon.com/dp/B08G85XXKG/ref=cm_sw_r_cp_api_glt_fabc_AF8Q2RX3B11MV9D32TC1

“what height and at what power should i have these lights at the differing stages?”

A mfr puts out information based on a standard. Your grow environment most likely does not adhere to their standard. So you have to have a method to translate to your environment. PPFD is a good way to make that translation. That’s what the numbers are in their footprint map.

A specialize PAR meter or a simple $5 app for a smart phone can measure PPFD at the canopy. Various sources recommended slightly different PPFD readings but in general they will be something like this:

Seedling/clone less than 100 (some say 200-400)
Veg 350-500 (some say 400-600)
Flower 400-800 (some say 600-900) see * note below

Using the meter of choice move the light up/down and adjust dimmer up/down until the range is reached for your growth phase and the plants tolerate the adjustment. If you see any signs of light or heat stress readjust.

  • note: When you flip to 12/12 for flower you are providing 50% less daily light (aka DLI) so the adjustment can (should) be increased.

Thanks for the info

thanks. all info and help much appreciated.

thanks. All info and help much appreciated.

Welcome @kiwi9 nice to see another kiwi on here :slight_smile: