Horticultural Lighting

[photonwave]

I actually have most of my interest in LEDs for getting mankind into space, but we need food and HID is just too wasteful and power-hungry for our current technology. So, along with many others, I have jumped into the horticultural lighting field, in the hopes that improving what we do on the ground will give us better success in space colonization.

Now, more than just LEDs could be used in space, at least for horticultural purposes. The trick is to providing the proper light and getting it to the plant. "Full Spectrum" lighting is actually a wasteful thing in this application. Plants don't really react to or use green, yellow, and most of the infrared and ultra-violet. Green and yellow actually act as inhibitors and regulators, and if added, should only be added in very, very, very tiny amounts. IR and UV can be harmful to plants, though some investigation is going into IR for triggering or promoting fruiting into crops that do very well in areas where they receive fair amounts of IR exposure (like tomatoes and peppers.)

Anyways, I've been working on developing my own lights (my avatar is a small shot of some of my own.) I have a couple of prototypes assembled and currently being tested, and of course, upon finding success, I'll likely try marketing these to interested parties (ESA/NASA/JAX, hydroponics stores, horticultural greenhouses, kitchens that produce their own herbs in-house fresh, etc.) if this hobby really bears fruit, literally.

Anyways, I'll give you a couple of pics. I'm currently working with 20W of LEDs, 1W each. 3.0 typical forward voltage, 350mA typical current, maker unknown. If I had the equipment, I'd give you the more exacting actuals, but alas, I do not, nor do I have the money to purchase said equipment. Medical bills SUCK!

These are African Basils in the picture. A little spicier than your typical sweet basil variety.

http://imgur.com/kmXJw.jpg - direct link to image so I'm not spamming with HUGE pics - I have to keep these pics large for the purposes of detail in my data gathering.

http://imgur.com/3hlBA.jpg - without the flash.

So yes, two T8 fluorescent form-factor tubes, two feet each, ten diodes each. Regular tail-through LEDs, 7mm (I think) with 160-degree optics. 7:3 blue:red, blues at 465 and reds at 660. Good for a basic light, it's doing the same job as my 216W T5HO array, so far, minus a tiny bit of internodal stretching.

I need to provide a more thorough mix of targeted wavelengths. I know exactly which ones I need the most, sadly those particular LEDs are hard to find, and expensive, especially in the SMD form factor I really want as opposed to tail-through. Also, output is essential, and since we're not dealing with lumens, but photon flux density, it's hard to spec out decent diodes. Not all 1W are equal, by any means!

Questions? Thoughts? Ideas? Help mankind get out into space, or at least keep our planet greener and cleaner!

 

[DM51]

You posted this in a really obscure part of the forum where to the best of my knowledge nobody has ever posted a thread before, lol.

It was in theory a reasonable enough place to put it, but it was unlikely anyone would ever see it there, so I'm moving it to Fixed Lighting for you.

 

[photonwave]

Ahh, thank you. I figured my topic was obscure enough that it probably belonged in there, but here works as well!

 

[photonwave]

I know it has been a while since I posted much of anything, mainly because travel without a laptop is a pain (GRRR HP SUCKS!)

Anyways, I just concluded a little test grow with 20w of LED. You saw the start in the picture links above, here's the finale (two plants got damaged from an earthquake knocking my air compressor off of the shelf.)



[over-size image replaced by link - DM51]

 

[DM51]

photonwave, your photo is much too large - please resize it to comply with Rule 3.

Edit: 2 days later, no response; image replaced by link.

 

[blasterman]

I actually have most of my interest in LEDs for getting mankind into space,

You are aware that NASA is already on this, correct?

I like how you use fluorescent fixtures as a base form factor.

Right now I've been building growth rigs for friends and my own plants using 3watt Satistronics LEDs. Red:blue 3:1. I tore down a corn plant that was growing up to my ceiling, and the cuttings have been growing like crazy under the intense red light. You don't realize how bright 3watt RED leds are until you have seven of them in your living room on a single brick.

 

[purduephotog]

You are aware that NASA is already on this, correct?

I like how you use fluorescent fixtures as a base form factor.

Right now I've been building growth rigs for friends and my own plants using 3watt Satistronics LEDs. Red:blue 3:1. I tore down a corn plant that was growing up to my ceiling, and the cuttings have been growing like crazy under the intense red light. You don't realize how bright 3watt RED leds are until you have seven of them in your living room on a single brick.

Don't scare me. I'm going to have about 20 soon

 

[Illum]

You are aware that NASA is already on this, correct?

I bet NASA knows nothing about the blooming capabilities of scoop away

very impressive by the way!:twothumbs
care to show us pictures of the fixture with the lights off?

 

[blasterman]

Don't scare me. I'm going to have about 20 soon

Just to remind you again, if you're using Satistronics LEDs you have to be real carefull with current regulated sources like Xitaniums, Bucks, etc. I've blown every single one on a 700mA Xitanium, and half on a 350mA driver when mixed with Crees. I've never lost a single one on a fixed voltage source at 700mA; aka laptop brick, etc.

 

[photonwave]

I bet NASA knows nothing about the blooming capabilities of scoop away

very impressive by the way!:twothumbs
care to show us pictures of the fixture with the lights off?

I most certainly can. Sorry for late reply, had to wait for my laptop to come back from service (actually, it's a new laptop, total upgrade!)

The actual 'fixture' is just T8/T12 low-profile endcaps screwed down in to a piece of 2x4, with a lamp cord wired directly to the caps. All electronics are inside of the tube, attached to the heat sink.

 

[photonwave]

Here's a close-up for you:

 

[Illum]

:wow: ...I havent seen side emitters being used in a couple years oo:

this is certainly an impressive use of existing technology. I take it ou removed the ballast for the existing florescent fixture and simply wired a AC-DC driver of some sort to the sockets?

 

[photonwave]

:wow: ...I havent seen side emitters being used in a couple years oo:

this is certainly an impressive use of existing technology. I take it ou removed the ballast for the existing florescent fixture and simply wired a AC-DC driver of some sort to the sockets?

Yea, I had leaned away from using dispersion optics until I had found some great polycarbonate ones.

All controlling electronics, including driver, are inside the tube under the heat sink. Just wire ac-power to the end caps, plug, and go.

 

[blasterman]

Can you flip it over so we can see the heatsink side?

Thermal issues are limiting all my current high power designs. I'd like the see the heat-sink side to see how it deals with the issue.

 

[Illum]

Can you flip it over so we can see the heatsink side?

Thermal issues are limiting all my current high power designs. I'd like the see the heat-sink side to see how it deals with the issue.

When working with LEDs for fixed lighting. Its good to keep in mind that proper heatsinking is the extent to which a fixture, on for any duration of time, can safely be handed by your hand without incurring a first degree burn, which the heatsink should not, under any nominal ambient temperature exceed 120F. This is important for fixtures mounted were you can reach or touch under normal activities.

LED junctions will fry at 150C, or about 302F, so even if it feels too hot to touch, theres plenty of space between the "idea" and "thermal runaway." Care has to be given that the temperature stabilizes somewhere below that.

Most of my works will keep the heatsink feel like 80F:twothumbs but uses alot of material:shrug: and generally underperforms due to stress for longevity

 

[photonwave]

Can you flip it over so we can see the heatsink side?

Thermal issues are limiting all my current high power designs. I'd like the see the heat-sink side to see how it deals with the issue.

I wish I could but I can't disassemble these tubes. I can tell you about it.

The thermal design is pretty simple, actually - internally, there is a short "I-beam" that acts as the heat path between LEDs and the entire aluminum housing. The trick is to provide enough surface area for heat dissipation, which is where the outside groove design comes into play. The tubes, running constantly after 12 hours, are barely warmer than my hand.

I learned much about thermal dissipation cutting custom heatsinks for old toasters of computers (old P4, even older Pentium Pros, etc.) during my overclocking days.

 

[photonwave]

When working with LEDs for fixed lighting. Its good to keep in mind that proper heatsinking is the extent to which a fixture, on for any duration of time, can safely be handed by your hand without incurring a first degree burn, which the heatsink should not, under any nominal ambient temperature exceed 120F. This is important for fixtures mounted were you can reach or touch under normal activities.

LED junctions will fry at 150C, or about 302F, so even if it feels too hot to touch, theres plenty of space between the "idea" and "thermal runaway." Care has to be given that the temperature stabilizes somewhere below that.

Most of my works will keep the heatsink feel like 80F:twothumbs but uses alot of material:shrug: and generally underperforms due to stress for longevity

I can help you with your thermal design and cut out your required materials. Just tell me what materials you have access to and we'll work from there!

 

[blasterman]

The linear heatsink you are using sounds like it has about the same thermal resistance as 2" alu bar we typically use. Except, your's looks a lot prettier

The problem is that you can't get a whole lot of intensity without resorting to much bigger sinks, or active cooling. Active cooling means a more compact heat sink, and then you have to raise it a lot to get the same coverage.

 

[photonwave]

The linear heatsink you are using sounds like it has about the same thermal resistance as 2" alu bar we typically use. Except, your's looks a lot prettier

The problem is that you can't get a whole lot of intensity without resorting to much bigger sinks, or active cooling. Active cooling means a more compact heat sink, and then you have to raise it a lot to get the same coverage.

The basic idea inside the bar is a skeletal frame inside connecting to the heat junctions. Also, the end caps have a tiny hole knocked into them to allow for pressure generated by heat to allow air to flow from one direction to the other and escape. This helps create a passive vacuum that helps keep the internal part of the heatsink cooled. From there, thinner pieces work better than thicker pieces in heat release, and the external fin design increases surface area for cooling.

Also, with some of the fans we have now days (I have some barely 15mm in thickness that fit between hard drives) active cooling doesn't necessarily mean needing a slightly larger space to accommodate, you just have to rethink the thermal design slightly.

 

[blasterman]

with some of the fans we have now days (I have some barely 15mm in thickness that fit between hard drives)

Small mm fans are noisy, unreliable, and you'd need one over each LED area to work. It's less of a problem with brick type heat sinks because you can use low rpm 120mm fans that are pretty inaudible. However, that means your LEDs have to be more centralized and thus have to be raised considerably.

At 1watt red LEDs are pretty easy to handle the heat. At 2watt things start getting really warm and at 3watt you need some massive sinks.

Problem is, if you wan't to compete in the commercial market you need to be working at 2-3watt levels.