Seeking Help - Building Custom-Designed DIY LED Grow Lights using CREE CXA3070 COBs

SupraSPL said:

My experience with PC power supplies is that they have a relatively low efficiency (or very low depending on the load) and a large standby power consumption. I did those tests before I had very accurate equipment to measure with and I am sure not all power supplies are created equal.

The AC DC conversion is a major factor in the total system efficiency of our lamps and since digital ballasts are so efficient ~90% I figure that should be our mark (for our drivers and fan power supplies). So in the case of driving PC fans, if we use wall worts we probably get 50-70% efficient with a very poor power factor. Maybe the drivers with built in 12V output can do a better job. Looking forward to your testing caretak3r.

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all i have is a crappy, tiny, half-broken multimeter. Oh, i do have a watt-saver as well. What all would be helpful, and what do I need to measure it?

My crap rat-shack multimeter can measure current, you just have to wire the meter in series with the load. Measure the voltage (in parallel) and current (in series) on each side of the driver to get the power (amps X volts) going in and out. Output power divided by the input power gives you the efficiency.

ok, first impressions from prelim testing of the 50-70w round driver from satisled (LD-TB50T70WP). I haven't even tried the 12V out yet because I've got to solder wires to the board (there is no white plug like pictured). I wired up a Vero18 3500K (29.5V as shown on specs) and fired it up. The dimming/adjustments are controlled by a Bonens 3296 potentiometer. The vero18 won't fire up (initially) unless I have the trimpot set so that it's getting 42W (as displayed by my KillAWatt). Once it's running, I can trim down to the point where the Killawatt shows 26W. On the top end, I can get 93W reading on my Killawatt.

Mellodrama said:

How do you know they're top bin? I followed your link, and DigiKey is probably a great choice, but I don't see anything about binning. Probably missing something really obvious...

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You can tell they are top bin from the part number. You can reference the bin codes in the spec sheet.

For example: the "Z2" and "Z4" in the parts I ordered indicate the bin code. These were the best available anywhere at the time I ordered them.

SupraSPL said:

My experience with PC power supplies is that they have a relatively low efficiency (or very low depending on the load) and a large standby power consumption. I did those tests before I had very accurate equipment to measure with and I am sure not all power supplies are created equal.

The AC DC conversion is a major factor in the total system efficiency of our lamps and since digital ballasts are so efficient ~90% I figure that should be our mark (for our drivers and fan power supplies). So in the case of driving PC fans, if we use wall worts we probably get 50-70% efficient with a very poor power factor. Maybe the drivers with built in 12V output can do a better job. Looking forward to your testing caretak3r.

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I'm curious to look into this, because I was under the impression that modern PC power supplies were actually pretty good at conserving power. I believe they already convert AC into DC power. A standard molex from a PC power supply runs at +12V.

By using a PC power supply, it seems like a ton less work from my perspective. It already provides several 12V Molex outputs which I can plug the cooling fans directly into without any modifications. A simple fan speed controller should allow me to dim 6 different 45watt channels. Throw all of this in a mini itx case and call it a day.

The main motivation here is to show just how easy it can be to build your own badass DIY panels. If I can easily plug-n-play my panels using everyday PC components and not lose a ton of money in electricity upkeep, then I'm all for it. Imagine just soldering on a few molex adapters and being done with it! If it's really that easy, a lot of us could forget the often-shady LED manufacturers and just build our own kick-ass panels in minutes.


I have a kill-a-watt and a few different PSUs I can do some tests with. I'm curious what the PC PSU cost (per/month) would be compared to dedicated drivers like the ones you bought. Perhaps I can grab some numbers and plug them into that sweet spreadsheet?


Also, would something like this work? If it only pushes out 2 amps total, then it probably won't power all 3 panels. If it's 2 amps per 3-pin output, maybe it'd work though. Maybe use one(or 3) of these instead of a PC PSU? Or each panel with its own unit and thermal sensor? Could look pretty cool, and you'd have constant monitoring of chip temps!

All that said... ...if using dimmable drivers is a far better solution electricity-wise, then I'll probably just order the ones you got and build a custom enclosure for them.

Observe & Report said:

My crap rat-shack multimeter can measure current, you just have to wire the meter in series with the load. Measure the voltage (in parallel) and current (in series) on each side of the driver to get the power (amps X volts) going in and out. Output power divided by the input power gives you the efficiency.

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thanks for the detailed instructions - will see what I can get

my craptasic radioshack mini-multimeter says it can only handle 200ma of current, so I suppose i should stick to using it for voltage measurement for now until I can get a better one.

I'll try and get to the store today, but in the meantime, I can also add that the 12v out reads 10.4V when the killawatt is showing 45W pull, and 10.7V when the killawatt shows 75W pull

caretak3r said:

my craptasic radioshack mini-multimeter says it can only handle 200ma of current, so I suppose i should stick to using it for voltage measurement for now until I can get a better one.

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My ratshack meter has three terminals: common/ground in the center, and V/A on the right with a limit of 400mA. However, the third terminal on the left is only for measuring current and can handle 10A but is unfused. Maybe yours is similar.

Ya not all power supplies are created equal thats for sure. My 2006 Vaio desktop is a serious power hog and so is my PS3 even in standby. But my laptops and mac mini power supplies are very efficient. Here is a cheapo that might be efficient. If there are any power supplies that are 88% efficient I would be pleasantly surprised. On the other hand the actual difference in power saved if you are just running some fans on it should only be a buck or two.

Observe & Report said:

My ratshack meter has three terminals: common/ground in the center, and V/A on the right with a limit of 400mA. However, the third terminal on the left is only for measuring current and can handle 10A but is unfused. Maybe yours is similar.

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ya, mine is truly crappier than yours it only has 2 leads/terminals. I'll pick up a better one soon, maybe tonight.

Hey caretakr,

I bought some 3070 chips today and undecided on how I want to drive them?
Would love to hear how that 50-70 w driver throttles them? thanks for input.

edit: what was lead time on order from satisled?

caretak3r said:

my satisled order arrived and I happened to have picked up one of the round 50-70W drivers (12v out as well) in addition to the driver I pointed out to you in your thread. I can report on it within the next few days. I still need to lap my heatsinks and get the COBs clamped down for testing.

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mtnstream said:

Hey caretakr,

I bought some 3070 chips today and undecided on how I want to drive them?
Would love to hear how that 50-70 w driver throttles them? thanks for input.

edit: what was lead time on order from satisled?

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i don't have a 3070 though I may order one just for fun and to compare. took just over 2 weeks to get the drivers.

I might pioneer those dimmers. Thanks

caretak3r said:

i don't have a 3070 though I may order one just for fun and to compare. took just over 2 weeks to get the drivers.

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I'm ordering a new HTPC which will use the same corsair PSU I linked earlier. Before I put the box together I'll run the PSU through my kill-a-watt. Then I'll mess around with adding fans/LEDs on a fan speed controller to get some numbers and report back.

Thanks gaius very helpful test.

If you're willing to spend the dough you can find PC PSU's that are awful close to 90% efficiency.. There's only one problem with that. From the tests I've read on Anandtech and other websites these PSU's reach maximum efficiency when they're supplying power to a load that's drawing roughly 70 to 80% of the PSU's upper capacity. In other words, a good quality 80+ 400W PSU would be most efficient somewhere above 300W output.

got a new multimeter just for you guys

so, the 12V out only puts out 80ma. I connected a 120mm fan to it, and it read 9.6V @ 80ma. I connected a big strand of strip LED lights and voltage dropped, but it maintained 80ma. I dialed down the trimpot to the minimum needed to fire the COB up - Killawatt read 43W at the plug @ 120V, .36A. On the DC side I was at 29.1V, 1.27A so 36.9W. I guess that means that at this setting, the driver is 37/43 = 86% efficient. When I connected the fan, I saw no increase in power pulled from the killawatt, in fact the wattage would drop by a tenth or two. So I tested the LED DC with / without the fan connected. With the fan connected, the current dropped to 1.23A, a difference of 40ma.

Mellodrama said:

If you're willing to spend the dough you can find PC PSU's that are awful close to 90% efficiency.. There's only one problem with that. From the tests I've read on Anandtech and other websites these PSU's reach maximum efficiency when they're supplying power to a load that's drawing roughly 70 to 80% of the PSU's upper capacity. In other words, a good quality 80+ 400W PSU would be most efficient somewhere above 300W output.

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Mello,
I believe what you are referring to is the ROI on going with the more efficient PSUs. They found that PC users needed to run them high all the time in order make up for the extra $$$ spent on 80+ certification. Since I'm running a constant current, this doesn't apply to me so much.


Check out these other AWESOME write-ups on PC PSUs:

• How to pick the best PC power supply
• Is it worth investing in a high-efficiency power supply?
• Analyzing Power Use: 80 Plus Bronze vs. Platinum

So anyhow after reading all of that I ended up ordering a badass 760 watt 80+ Platinum power supply, and added in a heavy-duty 6-port (45-watt per channel) fan speed controller. I went with the big PSU to ensure I have at least double wattage I plan to run at, because a 50% load is supposed to be ideal for reaching ~92% effeciency. This one power supply should be able to handle up 3-5 complete panels, while also staying cool and super efficient. The modular design makes it even easier to manage the cable rig too.

[HR][/HR]
Got my COB chips in yesterday! I should probably order my heatsinks now.

Excited to start testing all this sheeit!

gaius, I re-read all of your posts trying to make sure I've got a handle on you plan. It SOUNDS like you intend to run fans and leds from a PC power supply, but you havn't mentioned which dc step-up bucks you intend to use. What is the plan there?

caretak3r said:

gaius, I re-read all of your posts trying to make sure I've got a handle on you plan. It SOUNDS like you intend to run fans and leds from a PC power supply, but you havn't mentioned which dc step-up bucks you intend to use. What is the plan there?

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Not sure I'm following you. The PSU provides DC12v. Should be the same as hooking the LEDs up to a car battery (like Supra did). The fan speed controller will provide 0-45 watt of DC power to each LED chip.

Am I missing something here?

Gaius said:

Not sure I'm following you. The PSU provides DC12v. Should be the same as hooking the LEDs up to a car battery (like Supra did). The fan speed controller will provide 0-45 watt of DC power to each LED chip.

Am I missing something here?

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yep, i think so. Supra used a DC-DC converter - here

specs:

a PC power supply is constant voltage, not constant current. You're missing some components if you want to use PC power supply as LED driver.