looks awesome, wicked huge heatsinks lol
The current limiting function has allays been in use when you mounted a 5mm LED to 12 volt via a resistor.
On this page there is a calculator for finding the ohm value to limit the voltage to operational levels -Great if you want to use a small led in a car.
Using 500mA and 2.2V(1.1W) connecting that to 12V requirer a resistor in series with a value of 22 ohm and capable of absorbing 5.5W of heat.
Not very piratical firing 5.5W of in a resistor to drive a 1.1W LED - It works better with micro amps and 2.5mm indicator led's
The resistor is a passive current limiting device - if the LED suddenly starts to draw more amps then the voltage over the resistor increase and decrease over the LED and the current goes down.
Thank you !
looks awesome, wicked huge heatsinks lol
Last edited by Damnecro; 06-15-2012 at 11:23 PM. Reason: bakws
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!
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)..........
Last edited by PSUAGRO.; 06-14-2012 at 08:38 AM. Reason: check edit
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.
Last edited by Rasser; 06-14-2012 at 10:13 AM.
That seems pretty convincing, thank you very much for the explanations
Can you wire up multiple rails from one single power supply in series ?
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.
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.
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.
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.
Last edited by Rasser; 06-15-2012 at 06:59 AM.
Ok...I got a little impatient this evening. These plants are definitely finishing slower than I'm used to seeing under an HPS (although I'm used to using a 400W HPS, which is much more than I've got here, so that is probably part of it) so I decided to take the main cola from the small one. It doesn't really look too bad, but the trichomes really aren't looking like she's ready. I'll have another close look at the cola tomorrow, and decide then whether to chop the rest of that plant or not. It's a tiny plant, and the cola only weighed in at 14g fresh....so probably only 3 or 4g dry....so it may be better to chop it now and give the other two plants the light.
I wasn't expecting a good yield off this plant anyway, but I hope it's good smoke!!
The other 2 plants will be going for at least 7 days more yet...I took a tiny bit of popcorn and will test this tomorrow after a 24hr dry..