First time, trying to learn :)

[sprout]

Hi guys!

I feel so lucky I found my way here. I'm about to start my first grow (other than some small trees in my gecko terrarium years ago ) and I got a 4x4 tent and ventilator from a friend some time ago. I spent a few nights reading here and there is so much info and experience around! My experience with LEDs comes down to some 12V daylight soft strips over my desk I hooked up to a rigged old computer PSU

I just ordered a 20 batch of 4' 90 CRI EB3 strips, I guess that's a lot more than I will need. I would like to use them full cycle for now.
My plan so far is running them all on a HLG-600H-42AB in parallel as soft as possible and my guess is mounted on L-profiles the strips will be safe even if one fails? I will use thermal compound I have lying around anyway for good measure (GD900 is so damn cheap).

Cables and Wagos are all on their way, I just hope I'm right with my choice of driver and wiring. Is it ok or did I miss something? Would I stress my plants without dimming?

Thanks for all the input

[ganjah]

Welcome to the site, sprout. I just got here myself.

I think your plan is solid, and it's very similar to what I'm going to do. Your hlg-600h-42ab driver has two outputs, so I'd build 2 fixtures with 10 strips each. Parallel wiring sounds right afaik, but I'm not an electrician, and the other strips on angle aluminum should take the heat in the event that 1 strip fails. Also, I think there are methods to use the driver's pots to match/limit the voltage to the strips, but you'd have to search around for it.

My only concern about your build is that you want to use thermal grease between the strips and L angle. I've used a ton of Arctic Silver over the years in PC builds. But for strips it doesn't make sense.

Why? Well,

1) it's totally unnecessary because these strips don't have as much concentrated heat output as computer chips, so while you are increasing the dissipation capacity, the strips don't need it and don't benefit that much from it;
2) it's really messy and I can't imagine how many weeks or months it would take to apply that much grease to the strips;
3) if you ever had to take the fixture apart, it would be a real pain;
4) the double sided thermal tape normally used in strip builds + a couple nuts/bolts/plastic washers is plenty to attach the strips to your L angle, and plenty to manage the heat they put out.

You will definitely stress the plants if you don't dim the light and hang high at first. Luckily, you have the ability to dim on the driver or connect a dimming potentiometer to the proper lead from the driver. Get a Kill-A-Watt or similar and dim to half of max wattage for the first week or so, and hang 24" above the plants while doing so. Over the course of a week or two, slowly work your way down in hanging height and up in wattage until your plants show signs of stress, then back it off.

In a 4x4, your build is going to be amazing. I look forward to seeing the finished product!

[LEDG]

Nice post, ganjah. Agree on all counts.

[sprout]

Thanks for your detailed answer ganjah!

I thought about splitting the fixture when I traded millimeters here and there for some side clearance. Getting everything inside the tent will be much easier.

You have some good points on the thermal paste. It would be overkill, but then I'm also a guy who uses liquid metal on mid range CPUs I just thought I might take the stuff I have here anyway, lay one or two thin lines along the backside of each strip and screw them down. Cleaning it off with alcohol works well enough, if I wanted to rearrange the LEDs I'd likely use them on the same profiles anyway.
I consider the tape, I just didn't like it in the past. Some stuff sticks like a brick when the tape was on for long, some tape does not stick at all, which is fine on strips that are screwed in place anyway and if I ever wanted to remove them without fear of braking the PCB I guess. Can you recommend some?

(I'm reading lots about growth by now I got the feeling I might even want to start dimming down further with the lamps closer, save some kWhs. It should work using a PWM signal generator on these drivers. Does that make any sense for the plants?)*

*EDIT: I just found out the HLG series drivers PWM dimming function is just another signal way and there's no PWM output coming from that, same (in)efficiency in lower ranges. So I'll just stick to your advice!

[ganjah]

No problemo sprout. It's cool to have forums to discuss this stuff with other friendly, like-minded people.

If you want to use the thermal grease, use it. If you want to use thermal tape, I agree that it's hit-or-miss when it comes to bonding and you will want to use the nuts/bolts/washers in a couple places to secure them - middle and ends of each strip, at least. Use the thermal tape linked from the DIY builds section of this website (not the forums), or find another brand. I don't know if bigger "name brands" are better.

@greengenes made a video recently and he spoke about thermal tape being unreliable, and I think he's going to try to get some plastic pieces printed to hold the strips. I also think a guy named woodshed13 on IG has printed something similar for strip builds, if you didn't want to drill holes in each rib of your fixture.

Besides the tape/grease decision, I think you have a great build and I'm excited to see it!

[sprout]

Besides the tape/grease decision, I think you have a great build and I'm excited to see it!

I can't wait I got lots of bolts and nuts + washers now and my little Bosch Professional drill will get some 150 holes done in no time

With the thermal paste I look at it this way: those LEDs will run cooler in the long run and if it's just a little. Lower junction temperature will get me slightly better efficiency and longer lifetime. I will avoid air gaps forming compared to adhesive strips. I only use that stuff when I have to, like on graphics cards memory that I have no fitting block for and then I use expensive stuff with at least some W/m*K.
Using GD900 is cheaper (I ordered some extra to be sure I won't run out mid-build and I still came out at half of what the noname/no heat transfer numbers tape from the DIY would have cost me for the build) and it might benefit me in the long run as well. Just one thing, if anyone wants to try it: use gloves, if you don't like soaking your fingers in alcohol

Thanks again for your input ganjah, especially on hanging heights.
I'll post results!

[sprout]

Update: the main supplier for MeanWell drivers in Europe has problems sourcing AB variants for the HLG series for at least two months, likely longer as my seller told me. I changed my order to 2x Meanwell HLG-320H-42A and got a little discount. I'm kind of sad about the missing dimmer but I was going to mount externally anyhow. Guess I'll just have to use the built in potis and be careful.

[sprout]

Got the L-profiles in. Now I wonder: Does it make sense to mount the strips kind of like I layed this out here (less streched)? That should distribute PPFD better in the "x-axis" and prevent some hotspotting in the middle but would it hurt for y-axis? Maybe it's not making a huge difference, just wondering if this makes sense at all.

[bilabong007]

Hi,

Tek linked to a program that allowed you to model ppfd of a fixture. Can't rem what it's called but I will dig through and see if I can find it. Maybe worth having a play with it to fine tune the setup?

ETA - IT's called Dialux

[TEKNIK]

Spacing them closer towards the edges does help spread the light out a little better
You have alot of strips there so it will be pretty even, your hang height to canopy makes a big difference overall and wall reflection changes spread dramatically.