"Home made" LED grow lights...

looks awesome, wicked huge heatsinks lol

Originally Posted by Rasser

But don't feel silly I'm educated in electronics although in the late eighties, when I got my lap psu I was scratching my head over it
until I got the dohh and that's properly why I'm writing all this.

17 years running PC's and never have I got a busted MB, harddisk, graphics card as a result from a defective power supply
so I would not hesitate running LED directly on the rails from th PC PSU if the voltage suited within a safety margin.
But I'm still planning to use a current sensing feedback loop if I put a serious amount of led on the line.

Edit: And sorry MajorCoco for walking all over you thread.

I'll default to your knowledge then. My formal education is in music so you'll be wasting time arguing with me unless you want to talk about Wagner I've built a couple grow lights with excellent results but they're nothing fancy--just LEDs wired in series. I'm more concerned with the thermal design and spectra than anything else.

I did have a PSU fail once, by plugging in a bad floppy drive. So it can happen.

This is a DIY thread so I think any design discussion is pertinent!

Originally Posted by Rasser

Have a link for that diagram ?

No problem. Here is what I found...

http://www.instructables.com/id/Circ...rent-Source-1/

By the way folks..I have no problem at all with DIY chat on this thread, so don't worry about that!

One day we may have to work on a White LED/DIY sticky of some sort to gather all this info together into one place, but for now I think we need more chat and more people to experiment with this sort of thing before we can do that, so all these threads are helping get us there....

Just a brief update on the grow itself....
Even though I was vaguely thinking about harvesting a while ago now, development of the buds has been very slow recently. It is now day 66 of 12/12 (day 55 of actual flowering), well past what the seed company estimated (45-55 days), and I'm still not sure I want to harvest yet based on trichs and the overall fullness of the buds.

That being said, I did find one person on the net who had grown this strain before who stated clearly that he had found that 55-65 days was required for flowering. As usual, he doesn't say if this is 60 days of 12/12, or 60 days of the plant showing flowers, but whatever happens I'm going to cut down the smallest, most done plant either today or tomorrow and start it drying. The other 2 will stay in flower at least another week, maybe even 2 if I think it's needed...just to be sure.

^^^^Good to hear about your actual grow in here major ha.............yeah they need their own thread, but it is still good info for diy'ers

Edit: hey rasser, bass, etc........ask the mods to sticky a diy led thread.........Id be the first to vote for that(sure many others would too/ its great info)..........

I've just looked at that chart at thought, that's a dramatic rise in current on such a small voltage deviation, not good.
But how is that visible when connecting LED in series.

Parallel: using 3V DC supply
2.9V = 450mA
3.0V = 700mA
3.1V = 1000mA

Serial: using 12V DC supply powering a 4 LED's
11.9 = 2.975V = 650mA
12.0 = 3.000V = 700mA
12.1 = 3.025V = 750mA

Serial: using 24V DC supply powering a 8 LED's
23.9 = 2.9875 = 690mA
24.0 = 3.000V = 700mA
24.1 = 3,0125 = 710mA

So by the time we get to 15-30 pcs in serial the voltage variation that is acceptable is very large.

That seems pretty convincing, thank you very much for the explanations
Can you wire up multiple rails from one single power supply in series ?

Originally Posted by patrikantonius

That seems pretty convincing, thank you very much for the explanations
Can you wire up multiple rails from one single power supply in series ?

Your welcome.
No unfortunately not, since they have common ground.

And even thou there is 7V between +12v and +5v with witch you can run a 12V fan slowed down on,
you can't draw any serious current that way, the power supply protect itself and shuts down.
I tested it 30 seconds ago on a 12V-0.25W fan and a 12V-60W water heater.
You have to have true "dual channels" typical two windings on a transformer.
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While we are at it. In case you wonder how to run a PC psu on the table with no mb
You short circuit the green PS_ON wire with any black wire with a paper clip or wire
and keep it during running operation.


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Thanks for the diagram MajorCoco, I did a fast calc on 3x3W LED's to see the waste in the resistor and it is:


There is some loss in the regulator all depending how close or far the voltage is to the needed by the led's.
I love the simplicity and it should be relative easy to scale up or mod.
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I have found a LED series/parallel array wizard witch uses a resistor as current limiter: http://led.linear1.org/led.wiz
It's good when you have a voltage match, but terrible with large differences, you quickly end up with spending half the power in the resistor.