My LED adventure

Hi guys,

I figured I better get on the LED bandwagon before I get left behind. So I bought a bunch of parts and made up something that would fit my cabinet a little better than the air-cooled hood I’ve been using. It was more of a light distribution thing that inspired this. The HID seemed way bright in the center with lots less light in the corners.

Got a heat sink from HeatSinksUSA, a foot wide by 3 feet long. Four hours of marking, drilling and tapping 40 little blind holes. And another hour filing the cheese-grater ends.



After wrestling with the heat sink for a bit, handles seemed like a good idea. This thing weighs about 25 pounds and there just wasn’t a good way to hang on to it. It will be hung up with 4 rope ratchets, when the time comes. I’m hoping to get the LED surface of the fixture within 4 inches of the cabinet’s ceiling. I’m gonna need all the head room I can get…



Seems like whenever I read a writeup about someone firing up an LED fixture for the first time, they always mention how the photo doesn’t do the light justice. This pic does sorta make the light look a little wimpy. But it ain’t. It’s actually really annoying just being in the same room with it. It’s the kind of thing that inspires squinting and holding my hand in front of my eyes. I won’t be running it much until I get it hung up. It’s like trying to arc weld without a helmet.



I still need to sort out the wad of wire nuts. The driver, an HLG 480H-C1750A, doesn’t have a ground wire in its output cable, making things more difficult. The kill-a-watt meter shows the thing is pulling 480 Watts. I’m thinking it’ll need to be turned down a bunch. It will definitely need a fan blowing on it to keep it cool.



1440 individual LEDs. Looks a lot like the pattern on my retinas that lasted for 5 minutes. Apparently the driver has a half second delay before it fires up, just enough time to glance at the LEDs. It’s something one only does once.



The boards seem pretty well constructed.



Still a wad of wire nuts, but now they’re a wad in a pretty box, with a switch.



The T5 (at 75 Watts) is delivering 350 umols to the tops of the reveging plants. The LED is able to supply 350 umols to the same tops at minimum power (200 Watts) from its current height. At the same power, it’s 1000 umols at 12” from the diodes.



Just for fun, I turned up the power so that 3” above the screen was 500 umols. The wall Watts was 440. It was 1000 umols 25” from the light. This would be too much power, as it wouldn’t allow for enough canopy depth. I’m guessing somewhere around 300 watts will be about right, but I’ll have to wait a bit before I can play

Gonna need to make some lampshades with this setup; a couple of removable panels that hang down from the top of the doorways a foot or so. Being around this light is downright annoying.

This light is much more pleasant to be around when it’s below eye level.



Well, guess what… Apparently this thing is so efficient that the heat that I need to make my garden function properly has been just about eliminated from the lighting spectrum. This leaves my leaves too chilly for proper growth. Seems like I need to have a minimum of 82F in the garden for the light to work effectively. I don’t have this and can’t achieve it easily in the cabinet. My “single speed only” fan pulls room air (at 70F) through the cabinet so fast that the difference between the inlet air temp and the temp inside is only 2-3F. With the HID, this difference is 6-7F. This makes a huge difference in the growth rate.


Just for kicks, I cranked up the heater to 75F for the day. This made the cabinet interior 77F and I saw growth again. But between the stifling hot guest house and what would be a crazy electric bill, I decided that doing it this way was out.


Perhaps If the light was in a tent with a variable speed fan, I might have a better chance. Meanwhile, I have grass to watch grow… So, for now, we’re back to this:


OS

 

With the LEDs raise the temps to 75 to 78 and you will get harder larger flowers unless your running CO2 at higher temps.

 

Very clean work Smokey. Love it.

 

Awesome going to start calling you the Doctor that is like a operating room CLEAN SWEET-Bud

 

But is the vent pipe Goblin approved?

 

JCIO, Maybe I'll feel different about the temp when it gets hot around here. Seems like my garden is set up much more to combat the heat than the cold. I was thinking about your idea of using less heatsink, but it's still going to be the same amount of heat for a certain amount of light. As it is now, the heatsink is nice and warm, but all its heat is getting sucked upwards into the fan.

Mr. G, When I fired up the LED over the plant in veg, it pretty much didn't grow at all for a couple of days at 73F. 77F made a huge difference. (I am using CO2 at 1200 ppm.) Seems like I'm real reluctant to raise the lung room/guest house temperature too far above a "people comfy" 70F. My reservoir has to stay cool too.

Thank you, Herb. Hopefully Goblin will approve of it. I hated to remove my mushroom filter to make room for the new light. Needs something to keep the crud out...

Thanks, HeadCase. It's been kind of a wacky long term project. I'm a bit surprised at how well it's worked.

Duc, Thanks! Actually I have been giving that a bit of thought. The fan would be doing an awful lot of starting, I think. It's a 240 CFM fan and the cabinet is only 48 CF. I'd guess with all the restrictions that are in the air flow path, the fan is flowing lots less than it's rated.


After a bowl or three, I started listing all the possibilities to heat up the garden, no matter how goofy or impractical or just plain wrong. (And some of them are way out there.) Here's my list:

1. Restrict the fan outlet.
2. Restrict the fan inlet.
3. Use the 400W baseboard heater in the inlet stream.
4. Reconfigure inlet to pull air off ceiling.
5. incandescent heat lamps?
6. Install new variable speed fan and filter outside the cab. Block off existing fan.
7. Thermostat on/off control of fan.
8. Run the guest house at sauna temps.
9. Get a tent. Keep cabinet HPS.
10. Bypass the air flow around the fan somehow
11. Reverse the direction of airflow through the cabinet.
12. Modify fan wheel for less efficiency.
13. Keep HPS and use QBs as auxiliary lighting on smaller heatsinks
14. Use a thermostatically-controlled diverter valve to bring in outside air to fan.
15. Use a simple manual slide valve to do #14. Would need another light trap and furnace filter.
16. Use a 4” pipe between the light trap on the bottom and the fan inlet box on top. Install a manual valve on it. Basically, partially bypass air around the grow chamber.

I'm now too far into the stretch to do too much playing. But hopefully by next go round...

Anyway, thank you all for your nice comments.

OS

 

Glad to be of help, JCIO.

 

Inspiration...gotta love it.

 

Smokey...is that mushroom filter a carbon scrubber? I've not seen one like that before. Pretty cool.

 

No, Herb, it's a foam particulate filter. The same sort of thing as an air filter for a dirt bike. The manufacturer expects it to be oiled to catch the finer stuff. Unfortunately, the oil that they put on wouldn't stay put. So now it doesn't get oiled. Still works pretty well to keep the dust and hair out of the fan and carbon filter.

They call it a "Dust Shroom."

 

Got ya. Same type of filter they used on older small engines. My wood splitter has one. My carbon scrubber has a pre-filter on it that does the same job. Keeps my cool tube from getting too much dust on the inside of the glass.