I am not an electrical engineer so I’m just going to copy and paste one here from a Stack Exchange discussion about this idea:
“Please, stick to the NFPA 79 Standard, Table 13.5.1, which specify the allowable ampacities for conductors with smaller sections (30 AWG to 10 AWG) than the NEC ampacities (14 AWG to 2000 kcmil).
This standard rates 2A for 24 AWG, 90 deg., single conductor.
And considering 8 carrying conductors inside a same cable, we should apply a 70% derating factor, with an estimate of 1.4A for 24 AWG, 90 deg., 8 carrying conductors.
This consider could vary according specific manufacturer certifications. Also, this assumes a CAT6 Cable as 24 AWG”
That’s assuming a pure copper cable, I don’t know the derating factor for copper over aluminum core
that’s pretty cool and all but the link is broken. it looks like it’s saying that i need to limit the current to 1.4a per wire and use cat 6. i have several boxers of cat 6a and a couple of cat6. i need to check the wire size of the 6a but i think it’s also 23awg, same as cat6. i know the cat 5e is 24awg. that’s why the copy pasta confused me.
can you post a link to the place you found this? since i know for a fact that information i quoted is wrong i need to look at the rest of it. otherwise i’ll just move along with cat6a. that cable is too big to use almost anywhere else anyway.
this is why i posted here before doing anything. i figured there would be some folks who have an idea of what NOT to do. i have the gist of what to do from previous projects.
I’d be slightly concerned about running household AC on a network cable. CAT data cables are specified for ~50V maximum operating voltage to support POE. It’s the voltage, not the current that’s concerning.
Would it work? Probably be fine. I wouldn’t want it in my house though. I’d buy a 300V rated spool of hookup wire in your position.
I didn’t spend enough time looking at all the prior comments before I posted that. I thought there was still a plan to string many household type AC-bulbs together. I’m going to leave my earlier comment as-is because I do think 120VAC on CAT5/6 cables is ill-advised.
For running 12VDC and and amp or two, sure. Different story altogether.
For clarity, what is your current plan? Lot’s of T1-3/4 LEDs strung in series/parallel running from a PC power supply?
I just designed and built my own veg lights some of the info in these posts may be helpful:
yeah, straight up dc from computer power supplies to each led. i’ll work out all the details once they get here, 300 of these in three different colors that cover the spectrum pretty well. i may put an ac-dc converter in there for the whole room, but have to see how things work out. that would include me buying a converter whereas i have almost 50 power supplies lying around. thanx for the info, i can use all i can find to save me making the same mistakes.
The boards I designed would accommodate those LEDs and I have 4 empty ones. Happy to send you a couple but soldering them is a challenge…absolutely doable but you probably wouldn’t use a soldering iron. I’d do it on a skillet. Are you familiar with hot-plate reflow? If you are up to it and interested I’m happy to give them to you.
wow. if you don’t mind i could use one of them, maybe. my first thought was strip lights instead of a square. i was going to use a venetian blind i have that broke. one try with the concave side, one with the convex side, and one flat with the aid of a heat gun. i’m a glutton for punishment sometimes but i do love a challenge and was planning on hand soldering all 300 of them. i have done reflow before but if i recall correctly that would involve pcbs, and i want to stay away from those. that was another reason for using strips, and if the plastic didn’t work i have a backup plan with some air shears and a washing machine in the scrap pile. if you still have them after i fail at the strip lights i’ll hit you up. thanx a bunch!
gotta be parallel the way i’m thinking but i have to wait to start putting it together to see what works out best. if i use 3v leds and run 2.2v in them i should be good, just gotta do the math and see how many i can run with one power supply. i’m thinking 500w average, but some are server power supplies. thanx for confirming the reflow for me, thought i was missing something that could save a bunch of time. i’ve been trying to think all day of a way to set up the wires like i want them and reflow them but i got nothing.
So you want to run 300 LEDs in parallel from these power supplies?
Presumably the 3.3V output? How are you getting 2.2V from a server power supply? Can you draw a schematic of what you are thinking? Are you planning on current limiting resistors?
The issue with constant-voltage supplies for LEDs is several-fold. For one, brightness is directly, and almost linearly, proportional to current. The other, is that voltage is only somewhat reliably correlated to the current. More voltage, more current. Problem starts with the fact that each LED is slightly different. So if you apply a fixed voltage, let’s just say, 3V, some LEDs are going to draw a bit more current than some of the others. As that LED that draws more current, it gets hotter. The funny thing about what happens next is that the hotter the diode gets, the more current it draws. So it gets still hotter. Eventually that LED burns out, and the next LED gets in line for failure. This is one of the fundamental reasons most commercial lights are wired as multiple parallel strings of series diodes. Statistically some of those variations average out, as well as lower current and losses for a given power level. And they regulate current rather than voltage to maintain a constant brightness level, as well as ensuring dissipation doesn’t get out of control.
The other concern of import is the power dissipation. Let’s assume you max out your 500W supply into 300 LEDs. You are going to be putting 1.7W into each LED. A lot of that still gets dissipated as heat. It’s a significant amount. That’s why large aluminum PCBs are typically used.
You are going to have a few problems. Don’t take this the wrong way but I don’t think this is going to work the way you expect. I’m happy to help you sort it out, I do this for a living. A simple way to solve several of the potential issues would be to match compliance voltages to your power supply levels using series strings. This can also set your levels of dissipation to tractable levels, which is probably less than 0.5W per LED or so.
variable resistors are the way to do current limiting and voltage reduction. fixed resistors are the next option. it’s going to work exactly as i envision it. they’ll look like crap, probably take way too long to make, and then last for about two years. strip lights with little clusters of three diodes in each group. no way all of them will fit on one strip, i may end up with three strips per light. i got the 2.2v number from a 3v diode at ~70% to keep the heat down and make them last longer. the parallel/series option is an idea, probably what i’ll do with each cluster. i may end up with 6 or 9 in a cluster. almost like little cobs without the board.
hell, i’ve got a lot of problems solved already just by posting this thread. thanx for the info. if you think of anything else i need to look out for let me know. i may start them this weekend if they get here. i need to get these plants out there to the farm under something. i’ve got some shop lights for temporary lighting until i get these done or, failing that, buying one.
This is another reason to use current regulation of some kind. 3V ~300mA. 5% variation in voltage yields a current variation of almost 50%. I’ll also note that these LEDs in particular are very nice and forgiving units, the others I looked at were considerably more temperamental. So you’ve got that going for you.
I guess overall power dissipation isn’t too much a concern (you have multiple power supplies available), but be mindful of power dissipation in a variable resistor, in a fixed resistor same concern but unless you have lots of these they are going to be getting really hot. Variable resistors in particular get pretty expensive for higher power levels (usually called rheostats). A better approach for the thermal/cost reasons is typically a lot of distributed, inexpensive fixed resistors.
I’d investigate if you can make your power supply variable voltage. If you can control the output voltage you have an additional knob to turn. If that’s the case you could still get variable brightness with fixed current-limiting resistors in each LED circuit. Another thing to consider, perhaps, is purchasing a constant-current LED driver. Or making a solid-state current regulation circuit using transistors with a heatsink.
These are 0.2W-class LEDs. They are specified to much higher power levels which is nice but assumes proper thermal management. I’d design your current control mechanism to accomodate currents from 40mA (~2.65V) to maybe 300mA (~3V). These things are going to get hot, really fast at the high end of that.
Good luck! It is absolutely doable. I’m not trying to take the wind out of your sails, hope it doesn’t come off that way. Just trying to keep your venetian blinds from melting and your LEDs from being destroyed within seconds of first turning power on.
you’re not, and i have yet to actually look at the specs closely and figure out the math. all of the information you have given is great and very much noted and filed away. that is how i took it, as one og helping another. that’s what i love about this place and just about the only place on the internet i spend time. i’ll have to have a look around the scrap pile and see what type of resistors to use. i have almost 200lbs of circuit boards left over from the last scrap run and about 50 servers to scrap out. with all of the circuit boards in the pile, including more than 20 tvs, i should be able to cobble something together. i can’t wait to get started.
I realize this is a DIY thread for the most part, but ViparSpectra is offering a state of the art lensed LED for an amazing price. I just received one of these and the specs seem to be right on. It’s a small light, perfect for a 2x2 or single plant but with the discount (just click on the box) it’s under $90 with tax and shipping.
so much for getting started this weekend. just looked at the receipt real close to get the spec sheets to look at and they sent 200 of the same ones, not the 2 different colors i needed. no i’m missing the 480nm spectrum completely. also, they are two different brands and have different power needs so there’s another challenge. i thought about that when ordering and think i can overcome that by just running all of that brand off of one circuit and putting the others on another if that makes sense. i may draw it up this weekend just to see, maybe leave out a space for the other color and make them to see how it works. if i do i’ll make sure to put a thread on it as a tutorial, just in case it pans out.
actually this thread is to show mainly cheap effective market options as to me DIY lights unless for area specific applications one doesnt need to go down that route anymore due to the cost and availability of whats out there, plus there is the diy led strip thread i started years ago, but commercial options are on par or better performance wise and even cheaper now when sales pop up.
Like that XS1500 you posted, excellent light and if i had a space to use it id likely have it.
Hey Guys, not sure where else to post a growlight mini review, but I received the light above and it’s better than I’d hoped.
I have a few newly sprouted seedlings and they perked up and fluffed out in the first 12 hours under this small rectangle of sunshine. This is a breeding run so it’s 12/12 from seed, and delivering the right photon flood is a huge factor.
The “Lensed LEDs” tech really works. Not perfect and I don’t have the gear to do a detailed PPFD map, but the Lensed spread was impressive. The center was still hot, but the “Center” was a much bigger area than my older ViparSpectra XS1500, and the edges still got plenty of juice…
More interesting, to me at least, is the suggested height and %intensity program that ViparSpectra includes in the User’s Guide. They set a target height above the tops of 11" of your canopy – Throughout the grow, so you raise the light as the plants stretch, and set the Dimmer according to their chart.
So, I tried that on my seedlings. set at 11" above the little canopy @ 25% dimming… So I measured the PPFD with that setting and it averaged 280 PPFD, perfect for healthy seedlings. They loved it.
The kicker, is that ViparSpectra has also mapped the light over at typical 2x4 tent, using just two of these lights, with a spacing of 9.5" between them. I sort of believe them.
After reading this thread, I picked up this one for a 3x3 veg chamber. I was going to build a QB to replace a 315W CMH, but considering time and materials, and $65 price tag, this was great deal for me. The dimmer feature is very nice, solidly built, and it was up and running within 15 minutes of being dropped on the porch
I’m running two in a 3x4 at the moment for a lower-power option to my 500w panel in the 4x4 and the distribution is superb, I can definitely snug them right down to the canopy and run both at 75% no problem, got the right one set up remote so the left light’s dial controls both, first time doing that but it’s nice
