Economical multi LED Chip Projects for Growing

This is a cabinet rig that runs off 12 volts and uses four 30w Bridgelux design chips (1WW 3000K & 3CW 5000K) and four 30 watt 12 volt drivers that limit current to 1 A. The rig draws 160 watts off the DC power supply (an old ATX PC power supply) at a whopping 15A! I had to use thick wire from the lamp to the power supply to avoid overheating and power loss. This is a very inefficient design from an electrical perspective, each chip/driver uses 40 watts of power. I haven't measured the power consumption of the chips but I'd be surprised if it was over 28 watts each.

Since the driver input voltage is 12 volts and the output voltage is in the 30-36 volt range the boost converter in the driver has to work harder to bump up the voltage 3 times over input, this is costly in terms of energy. So if each chip uses only about 28 watts of power where does the rest go? Well, the fans use .5Ax12V=1.2W, but each driver (really a current limiting dc-dc boost converter) uses 12 watts.


I wouldn't recommend this design to anybody and the only reason I built it was because I had the parts laying around. A better, simpler and cheaper design would be to use two 50w 120 VDC drivers and run pairs of chips in parallel off them, that way you can switch them on or off in pairs. Always place the switch for LED drivers on the supply side, meaning if your using an AC driver place the switch between the plug and the driver

Parts List:

• Fans -- http://www.ebay.ca/itm/181130219481?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

• 12VDC 30W drivers -- http://www.ebay.ca/itm/10w-20w-30w-50w-Constant-Current-LED-Driver-DC12V-to-DC30-38V-For-high-power-led-/321461904029?pt=US_Light_Bulbs&var=&hash=item4ad89f629d

• 30W LEDs -- http://www.ebay.ca/itm/30W-warm-white-High-Power-LED-bead-Light-Lamp-Chip-3000k-3500K-3400-3500lm-45mil-/131391524293?pt=LH_DefaultDomain_0&hash=item1e978b8dc5

• A 2"x12"x1/4" piece of aluminum plate, three heat sinks, a couple of switches, screws, connectors etc.

To power the cabinet rig above I converted an old ATX power supply. It has two 12volt rails, one is 10 A and the one I'm drawing power from is 15A. I'm gonna hook a 12v fan up to the power supply and put it on the hole behind the power supply (see photo) for cabinet ventilation.

It seems there is something wrong with this board, when trying to attach photos I lose text like above. There was a paragraph of description above " I wouldn't recommend..." that evaporated, this is the second time it happend

The lamps shown in this post were made using simple hand tools and an electric drill. A set of good sheet metal cutters and a hand nibbler tool make all the difference when working with sheet metal boxes like power supplies. Most of the work in making these lamps is sheet metal and mounting the hardware. I bought a 12" x 8' long 1/4" sheet of aluminum plate at the local scrap dealer for a buck a pound and I've picked up small pieces of aluminum angle there too. I can easily cut the 1/4" aluminum plate into sections (like for heat spreaders) using a skill-saw with a carbide tipped blade (most come with one). Wear goggles and/or safety glasses when cutting aluminum as pieces fly everywhere and make a mess.

I got a half dozen old PC heat sink/fans and power supplies from the local recyclers and lot's of heat sinks fans and power supply's from computer/electronics repair shops. From an old tower type PC you can harvest screws, heat sinks, fans, metal power supply boxes and sheet metal. Old audio amplifiers usually contain great heat sinks for LED builds and you might even use the metal amplifier box to house a project as well as screws and other useful things like power cords.

I'd like to build a lamp using an old 4'x4' or 4'x3'x4"H recessed fluorescent light fixture box. I'd strip out all the old ballasts etc and replace the translucent plastic panel at the bottom with 1/4" aluminum sheets and cover the bottom side with LEDs and the top side with junk heats sinks. The metal box would contain the drivers switches and fans, as well as, direct air flow and serve as suspension points, just one power cord required for a 1000 watts of top light.

Did you play with the full spectrum ones at all on their own? I'm curious how they perform, especially with the pricing being about as high a buying a Cree COB. How do you think they perform vs there cool/warm counterparts?

nomofatum said:

Did you play with the full spectrum ones at all on their own? I'm curious how they perform, especially with the pricing being about as high a buying a Cree COB. How do you think they perform vs there cool/warm counterparts?

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My garden is a work in progress and I'm building a proper tent now. The clones from the two girls shown ( from fem seeds) are coming along nicely and when I have some clones to compare and some more lights built, I'm planning a test. I started these plants and vegged them under 6 x 42w CFL s in a cabinet until they were about 10" high. It was a bit of a race with the slow boat from China for a while, as I started with 1 single canister light then built the second as the parts arrived. I managed to keep pace with the growing plants, but I used 2 grow chips (100 &120w) and warm white chips to veg for 30 days and that caused a bit of stretch. I gave 2 plants to a friend to grow out with his LED rig and kept 2, that way I can see what the final 4 plant setup will yield and give each plant a good test in the kind of grow it will inhabit. Next I'll have to pick a clone(s) and grow them in something like plastic milk cartons or laundry baskets lined with geo textile cloth to make 1 cuft air pruning pots (Google or YouTube air pruning). You can see an example of my dollar store air pruning pots in one of the fan light pictures above. Here is another picture of an air pruning pot I made from a small plastic basket and some geo textile ($10. for 3'x30'). and it sits in a dollar store wash basin.

DIY-HP-LED said:

It seems there is something wrong with this board, when trying to attach photos I lose text like above. There was a paragraph of description above " I wouldn't recommend..." that evaporated, this is the second time it happend

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Had that issue too, add pics first then press up arrow a few time to get back to the top, then add text. Goofy bug.

DIY-HP-LED said:

I used 2 grow chips (100 &120w) and warm white chips to veg for 30 days and that caused a bit of stretch. ]

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Do you mean lanky type stretch (like HPS vegging)? The cool white ones so far have resulted in dense bushes for veg for me. I think they are doing best when I run 2/3 cool 1/3 warm for veg, but just cool is pretty close to the same.

nomofatum said:

Do you mean lanky type stretch (like HPS vegging)? The cool white ones so far have resulted in dense bushes for veg for me. I think they are doing best when I run 2/3 cool 1/3 warm for veg, but just cool is pretty close to the same.

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3:1 CW : WW is what I'm planning for my veg light, probably 3 pairs of 2 chips in an old Colman camping stove with a large 1/4" aluminum plate place in a large hole cut in the bottom of the stove. I might try to run this off of a 350 watt 36 volt regulated power supply with no drivers, I can tweak the voltage of the power supply a bit and if I balance the load correctly it should work fine and drive about a half dozen of those cheap Chinese 100 watt chips

When the plants were under 6 X 42w 5000K CFLs (1 -2" away) they were very compact with short inter nodes, when I placed them under the LED's I noticed rapid growth and upward stretching of the lower tips especially, right up along side the main stem. When I started using angled lamps in the corners (2 ea of 2x canister lights at around 45 degrees) and the fan light, I tied out the bottom branches to the edge of the pots and the next tier of branches to the one under. I didn't top the plants or trim any fan leaves, since I want to get an idea of what these plants look like and yield with out too much playing around. I have noticed that the fans on the lower and mid plant tend to hang vertically and out of the way since I added the angled corner and fan lamps. I think they are responding to the side lighting by growing at right angles to the light, but they tend to be a bit limp at this stage anyway. I'll start chopping the fans soon starting at the bottom with the beat up yellowing leaves and gradually working my way up as the large old ones yellow. Right now there are no shadows in the garden and the fans are still producing and storing goodies for the plant and getting plenty of light.

Some interesting things for those inclined to DIY LED grow builds:

• Aluminum conducts heat about 5 times better than steel and copper conducts heat 2 times better than aluminum.

• A typical desktop PC heat sink and fan can dissipate about 100 watts of heat, CPUs have to run cooler than LEDs

• Most CPUs run at about 80 watts and 100 watt LED chips run at between 55 and 80 watts. Unlike CPUs though, LEDs get rid of at least 20% of that energy in the form of visible light (it's more but I'm being conservative), so if you put 100 watts of power into a pair of 100 watt LEDs they will only create 80 watts of heat at the most.

• If your heat sink is too hot to touch your running things a too hot and will need to increase the heat sink mass and or fan airflow.

• For every 10 degrees C cooler the LED junctions run, light output per watt doubles down to -20 C. If you want efficiency, then liquid cool your LED chips with circulated super cooled antifreeze/water and build using PC gamer liquid cooled computer parts!

DIY-HP-LED said:

• For every 10 degrees C cooler the LED junctions run, light output per watt doubles down to -20 C. If you want efficiency, then liquid cool your LED chips with circulated super cooled antifreeze/water and build using PC gamer liquid cooled computer parts!

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I was planning my liquid cooling setup for if I did summer, but this is a good point, with temps well below freezing outside I may just have to push that up. It would be very easy to install a radiator outside and a small pump to push through copper line and solder it to my rack.

edit: maybe thermal adhesive, how hot can I get them if I were to solder without destroying the chip?

Also that sounds too good to be true. If you were running at 50c dropping to -20c would result in 64 times as much light?

I can actually potentially cool them to -20c (-4f) on a cool day it will be a fair bit colder than that outside.

nomofatum said:

I was planning my liquid cooling setup for if I did summer, but this is a good point, with temps well below freezing outside I may just have to push that up. It would be very easy to install a radiator outside and a small pump to push through copper line and solder it to my rack.

edit: maybe thermal adhesive, how hot can I get them if I were to solder without destroying the chip?

Also that sounds too good to be true. If you were running at 50c dropping to -20c would result in 64 times as much light?

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Probably not, looking at the Vero datasheet the other night, a voltage drop of less than 10v's from test [2.1amps?] when Ta is -20C, when "test" Ta is normal ambient 25C.

Can't speak for diodes with unknown specs....educated guess says less... if ran at a lower effiicency for instance.

Abiqua said:

Probably not, looking at the Vero datasheet the other night, a voltage drop of less than 10v's from test [2.1amps?] when Ta is -20C, when "test" Ta is normal ambient 25C.

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I'm confused you mention voltage drop but I see no mention of light level. So it used less energy, 10v would be 20-35% depending on what vero they were testing. But did the light level stay static or go up or go down?

nomofatum said:

I was planning my liquid cooling setup for if I did summer, but this is a good point, with temps well below freezing outside I may just have to push that up. It would be very easy to install a radiator outside and a small pump to push through copper line and solder it to my rack.

edit: maybe thermal adhesive, how hot can I get them if I were to solder without destroying the chip?

Also that sounds too good to be true. If you were running at 50c dropping to -20c would result in 64 times as much light?

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I saw the 10 degree thing on a short YouTube training video by a quality LED manufacturer Philips or OSRAM I think, should be easy enough to verify with Google though. Even if you cooled the backs of the chips to -30 C the junctions can only dissipate heat so fast through the back plate of the chip and better chips have thicker copper backs. All I can say is verify the facts before committing to an expensive and challenging project.

Most chip manufacturers suggest 3 sec touch on the terminals with a soldering iron, so soldering chips on is a no no. Screws and thermal epoxy adhesive like Arctic Silver work best, also adhesive CPU thermal pads or tape might work for adhering LEDs to heat sinks. If I were to build a refrigerated lamp it would be a big one with all the hoses and wires contained in on 2'x4' or 3'x4' box with wires and hoses kept to a minimum. But I think it would be easier and cheaper to just add more air cooled LED lamps or one big air cooled one. If you want a challenge and some fun go for it, I might play around with it myself one day, just for fun.

DIY-HP-LED said:

I saw the 10 degree thing on a short YouTube training video by a quality LED manufacturer Philips or OSRAM I think, should be easy enough to verify with Google though. Even if you cooled the backs of the chips to -30 C the junctions can only dissipate heat so fast through the back plate of the chip and better chips have thicker copper backs. All I can say is verify the facts before committing to an expensive and challenging project.

Most chip manufacturers suggest 3 sec touch on the terminals with a soldering iron, so soldering chips on is a no no. Screws and thermal epoxy adhesive like Arctic Silver work best, also adhesive CPU thermal pads or tape might work for adhering LEDs to heat sinks. If I were to build a refrigerated lamp it would be a big one with all the hoses and wires contained in on 2'x4' or 3'x4' box with wires and hoses kept to a minimum. But I think it would be easier and cheaper to just add more air cooled LED lamps or one big air cooled one. If you want a challenge and some fun go for it, I might play around with it myself one day, just for fun.

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Liquid cooling would be pretty easy in my case. I'm already using my air pump in my garage (below freezing for the majority of winter). If I were going to do water cooling I would drill 2 more holes and run the 2 pipes. If I wanted to go for full outdoor cold there is a window in the garage I can open. If I had the parts I think I could make the modifications in a few hours.

I was talking about soldering a copper water line to the heatsink/angle-aluminum/channel in my case not soldering the chip on. It's a question of could I solder without the heatsink working too well in reverse and overheating the chip through the heatsink and thermal adhesive. In any event I can order a big thing of thermal adhesive from china or make my own thermal epoxy if needed. I just need my scrapper buddy to come through with a nice motorcycle radiator for free/almost free.

nomofatum said:

Liquid cooling would be pretty easy in my case. I'm already using my air pump in my garage (below freezing for the majority of winter). If I were going to do water cooling I would drill 2 more holes and run the 2 pipes. If I wanted to go for full outdoor cold there is a window in the garage I can open. If I had the parts I think I could make the modifications in a few hours.

I was talking about soldering a copper water line to the heat sink/angle-aluminum/channel in my case not soldering the chip on. It's a question of could I solder without the heatsink working too well in reverse and overheating the chip through the heatsink and thermal adhesive. In any event I can order a big thing of thermal adhesive from china or make my own thermal epoxy if needed. I just need my scrapper buddy to come through with a nice motorcycle radiator for free/almost free.

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I don't believe you can solder copper to aluminum, you can solder aluminum to aluminum though, with a blow torch and aluminum soldering rods. If you try and solder on the heat sink, use a wet cloth around the chip to try and keep it cool.

A cheap light meter and a small single chip test rig using a liquid CPU cooler block (on ebay) would be my first move, after some internet research. You should be able to see if this idea works in the real world, if it's worth it and what problems you'll encounter. I believe I've seen these cooler blocks for around $20.

An old heater core from a car can do the same job and should be cheaper and easier to get. The liquid radiators for PC cooling are surprisingly cheap too.

I believe you can solder copper to aluminum, the hard part is getting rid of the aluminum oxide with a suitable flux.

ballist said:

I believe you can solder copper to aluminum, the hard part is getting rid of the aluminum oxide with a suitable flux.

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I stand corrected and second this, it can be done, but it ain't easy.

You might try sandwiching the copper tubing between two pieces of angle or channel aluminum, screws and nuts can pull it together pretty tight, and of course slather on lots of thermal paste. Also, if you could pull the tubing through two rollers or somehow flatten it a bit ( a vice or even car jack), you can increase the contact surface greatly. I believe a flattened copper tubing sandwich with two pieces of aluminum angle or channel as the bread and heat sink paste for a dressing might be the best approach. All held tightly together with bolts, nuts and washers.

More detail on the prototype Fan Lamp
Here is another photo of the Fan Lamp with the lights off so more detail can be seen. You don't need a particularly heavy heat sink for this application, since even on the low setting this fan has lots of air flow. In fact it could easily cool a half dozen or more cheap 100W chips. When I build the final Fan lamp it will have four chips and two 100W 3A 36V current limiting drivers running pairs of cheap 100W warm white LED chips in parallel. I'm gonna connect the LED heat sink to the fan cage with a hinge instead of "L" brackets so I can change the angle of the light in relation to the fan with an adjusting screw of some kind.

If you want to build one of these fan lights, the easy way would be to attach 2 of these enclosed 120v LED drivers to the back of the fan cage. Screw 4 cheap 100W warm white LEDs onto a heat sink with M3 screws. You can just drill holes and drive the screws right into the aluminum heat sink with a little heat sink paste for lubrication, no taping is required. Go slow and careful and back up the screw frequently and you'll drive it tight, if you screw up and drill the hole too big or strip the hole, just use a strand of copper wire along side the screw to tighten it in the hole and nip off the excess. Also you can buy a pre-drilled & tapped heat sink on ebay. Because of the large amount of airflow you can get away light on the heat sink for this one. Solder wires to the LEDs and put connector plugs rated for at least 3 A on the ends to connect to the driver wires, this will make cleaning the fan and building it much easier. Also tape down the fan switch to prevent it from being turned off accidentally!

More detail on the double chipped canister lamps
Here is a better picture that shows how I converted the lamp to two chips using a 1/4" piece of aluminum plate. Because I wanted to keep the distance between the chips close, I couldn't use the lens retaining rings. I used brass wire instead until I can come up with a better solution, works fine so far, it looks like crap, but it grows plants! I overlapped the two positive terminals on the LEDs and soldered them to a common red wire, the negatives are connected together as well. I bent the LED contacts up a bit to increase the clearance to the aluminum and in some cases, put pieces of super 33 (hi temp) electrical tape under the contacts. If you wanted you could encapsulate the wire ends and contacts in silicone rubber caulking for added safety.