My first DIY LED grow


This actually is my first light. I’m a big fan of the buy good shit once and it’ll last you a long time so I went with making my own. According to my guess i’m sitting at about 440W at full blast. Considering it hurts to look inside my tent at half power on the dimmers I’m guessing i’m right.

Thanks for the suggestion about the light meter, been messing around with fan speeds and dimmer settings to check temperatures in the tent before I get seedlings into the tent. I’ll look for a light meter and hopefully be able to fine tune my dimmer for each stage. To answer your question, yes this is going to my light from seedling to harvest. I already have a dimmer on each light so I’ll just mess with height and power to control how much light I put on my plants.


Thanks. It shockingly wasn’t too bad, but I did do a lot of research prior to buying and I’m pretty handy. Got the seeds germinating now and plan to manifold the two plants and mess around with different levels of defoliating to see how things turn out. I’ll make sure to keep this updated with pictures and whatnot.


As long as your pot is a true 100k ohm you should be right about the 440.

You won’t need it anytime soon, but you should you want a little more, you can open the dimmer circuit. The hlg will usually run about 105% of rated current when dimmer is open.


Thanks. Was thinking of basically to start gradually increasing the dimmer as it progresses from seedling through veg. Based on what you’re saying would you recommend keeping the dimmer below 100%, at say like the 75% range?

Also @Countryboyjvd1971 , any suggestions on how to use a cell phone light meter (or link to a guide)? The readings are all in lx and i’m not sure how to convert that to PAR which is what my brain is wired for right now.

Ultimately I need to figure out a moderately reliable way to set height/intensity for my plant. I’ve seen a lot of watt per sq foot and PAR maps based on height, but since this is DIY I don’t have the benefit of fancy PAR plots without buying a PAR meter (which i’m not doing now).

Appreciate suggestions. Currently the ladies are germinating so I got a while before I really need to worry about this, but rather have it solved now than be a week or so from now when I really need it.

Oh and on a completely different side note, how do you guys manage watering schedules and travel? Got a few trips planned and I know I can water before I leave and when I get back with everything else on timers but just curious what you all do.


@Rugar89 just built a pretty neat auto watering system. Otherwise blumats are good power free option. There looked to be a few powered options available on amazon too.

You can run the light higher at higher power or lower at lower power. Since every light and space are a little different, there’s really no right answer. You just have to get a feel for it. Right now, you can save on the electric bill and probably run them at 20-30% And probably 30-36" above your seedlings.

You’ll just have to kind of watch from there. Assuming you’ll be checking on them regularly, if you start to notice them stretch just lower light or increase power. Once they start getting a couple of nodes, you can gradually increase the light intensity. You should probably end up about +/- 16" above your canopy at close to full power. If you harden them well, you could probably get a little closer and run a little less power. You just have to remember that you’re dealing with a lot of light intensity, and will be different than the typical Chinese made grow light.


Well its been a bit since my last update…here’s the skinny. Failed to germ my first two seeds properly… sucks but I learned. I’m fairly certain I over watered and got too impatient. I started them in shot glasses of tap water and after 24 hours I dropped them into some rockwool. After another 2 days I didn’t see any growth and so ripped apart the rockwool and tried to just drop them into some soil. I’m assuming at this point they were nonviable since after another 3 days of sitting in some soil I got nothing.

Well after this failure I started over using a glass of water and then paper towel. Worked like a charm and the taproots popped within 48 hours. Instead of messing with rockwool I did a 50/50 mix of Fox Farm Ocean Forest and coco. I dropped the two lil ladies into about a 1/2" hole threw a plastic bag around them and dropped them in my tent with the lights running at about 25% on my dimmer. Running some basic numbers i’m assuming that my dimmer is going to put out the following as I reduce the resistance.

Dimmer turn - Output
closed - 210W
1/4 turn - 268W
1/2 turn - 330W
3/4 turn - 382W
open - 440W

So until I get some sets of leaves I figure i’d keep it between full dimm and 1/2 turn. I’ll watch to make sure its not stretching and if so i’ll increase the power a lil bit. After that i’ll just keep playing with the power as the grow more and more. @dbrn32 that sound like a good plan or have any better suggestions to manage their light?

Figure i’d throw you guys some initial shots of the two ladies. Since all things deserve names…here’s smokey and bandit. I figure these cups will be there home for a while. I plan to do a Nebula Manifold and probably won’t mess with transplanting them until after I have the 8 colas.


You are running an external dimmer right? Should be 100k pot, 0-10vdc, or pwm?

Those numbers don’t look right at all. How did you come up with them?


I lie for a fact lol, forgot you had 2 drivers. That may be the issue. Assuming you’re using a potentiometer, you should have a 50k ohm pot and a 5k ohm resistor. Or 2 100k ohm pots each with a 10k ohm resistor. Either setup should allow you to dim down to about 10% or roughly 50 watts.

And as a side note, you don’t ever want to close the dimming circuit, or short the leads.


@middlecoast, my nursery box uses a “300” watt Meizhi for my seedlings from germination up until they’re about 1 foot or so tall, and that light starts out 2 feet from my seedlings and draws 125 actual watts at the wheels, so to speak lol. You could probably shut down 1 driver for the first 6 weeks or so and save money.


So the reason I got the numbers is that using the potentiometer the driver ranges current from 700mA to 1400mA, or at least that’s how I read the spec for the driver. If that assumption is wrong the rest of my math is also wrong.

Also, I don’t have the wires shorted. Both are connected to the dimmers I got from RapidLED. Not sure the resistance and didn’t feel like pulling out the multi-meter to check.


Thanks for the tip. I’ll probably end up dimming both down instead of trying to turn one off completely since I want to have even coverage in my tent.


@middlecoast need to remove the link only amazon ,and dealers are aloud
Just heads up


The a series drivers that have internal pots dim from 50-100%. B series with dimming leads are different. I’ll check and see what rapid sells.


Ok @middlecoast, Mike said he believes they are slightly over 100k, and have no resistor installed. So they should swing from 0 ohms to 100k ohms.

If that’s true, the dimming feature should be fairly close to linear. 100% output on one end, and close to zero on the other. I don’t think the hlg-240 is rated as dim to off, so don’t turn it all the way down if it goes to zero ohms. That’s why most install the 10k ohm resistor, it represents the 10% output as minimum. Otherwise like i said, it should be about linear. Close to 80% at 80k ohms 70% at 70k, and 25% at 25k ohms.


Thanks for the info. After re-reading the spec sheet I realized the 700mA to 1400mA was for the A model. I’ll try out my light meter app tomorrow to see if I can’t figure out some kinda metric to help understand the resistance and how much power i’m getting depending on the potentiometer.


No problem amigo. I need to go back through the data sheets too. For the last couple years the information we were given was that dimming to off could cause driver failure. But it’s looking like at least some of the newer models are offering dim to off capability. Not a huge deal, but I like to have and share the most accurate information possible.

Once you get the dimmers figured out, you should be plenty good germinating in the 50-100 watt range. If you have a hard time getting it dialed in, perhaps picking up a killawatt would help.


so using my phone took some lx meters and was able to confirm what you had said. sorry about the confusion in my terminology, I didn’t mean that the dimmer would go to off, just swung all the way to either side. New estimations for my dial are:

start position - 40W
1/4 turn - 112W
1/2 turn - 264W
3/4 turn - 364W
open - 440W

at some point i’ll snag a killawatt, just trying to avoid as many of the lil $10-$15 purchases that have snuck up on me. Got the lights dialed in at about 1/4 turn right now about 20" from the plant.


@middlecoast - We named our two “Mary” and “Jane”.


Day 3


Have u seen any good guides on how much time to expect between nodes? I know there are a lot of factors at play but curious if I should expect a new node each week or something.