I need HELP with Custom LED

wiki said:

Chlorophyll a is the most common of the six, present in every plant that performs photosynthesis. The reason that there are so many pigments is that each absorbs light more efficiently in a different part of the electromagnetic spectrum. Chlorophyll a absorbs well at a wavelength of about 400-450 nm and at 650-700 nm; chlorophyll b at 450-500 nm and at 600-650 nm. Xanthophyll absorbs well at 400-530 nm. However, none of the pigments absorbs well in the green-yellow region, which is responsible for the abundant green we see in nature.

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mogie said:

Bulbs in the range of 2700 to 6500 on a kelvin scale is ideal for growing

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If this is indeed true then it would be wise to use mostly 450nm and 650nm? I can't find those where I buy LEDs http://www.superbrightleds.com
So I would go with
5mm White LED

5400k peaks at 450nm

If I want to power it with 5v DC 1.5A what kind of resistors do I need?
(yellow violet black) to keep it below max or (orange white black) to max it out?
With (yellow violet black) I can run 60 LEDs?
With (orange white black) I can run 50 LEDs?
This should only be 7.5 watts?

Can I use just one resistor on the ground?

I guess I should calcutate the watts used from the input which would be 120v x 0.2a = 24 watts

24 watts for 60 LEDs sounds better but I don't think I understand this all correctly

I need 39 Ohms is (orange white black) that is what the supplier I use has they don't have the 47 Ohms I wanted.

$40 for 50 LEDs and 50 resistors if I decide to buy


x10

+----|>|---/\/\/----+ R = 39 ohms
+----|>|---/\/\/----+ R = 39 ohms
+----|>|---/\/\/----+ R = 39 ohms
+----|>|---/\/\/----+ R = 39 ohms
+----|>|---/\/\/----+ R = 39 ohms

before I buy anything I would like to know if this is correct or really screwed up

You dont need to use resistors in your LED design. You need Constant Current drivers.

Read the stickies!

do a reality check http://led.linear1.org/led.wiz i use this calculator

SnotBoogie said:

You dont need to use resistors in your LED design. You need Constant Current drivers.

Read the stickies!

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are you talking about these?
https://www.rollitup.org/led-other-lighting/633304-if-you-new-led-want.html
https://www.rollitup.org/led-other-lighting/240615-led-users-unite.html
https://www.rollitup.org/led-other-lighting/486179-led-companies-w-links.html

I'd say these are runners up for most horrible sticky on RIU.

mmmmbrownies said:

do a reality check http://led.linear1.org/led.wiz i use this calculator

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thats where I got the ASCII

Your judgement is bad, and it shows...


If you had read any number of threads here you wouldnt still be thinking in the way you are, so judging by your posts you havent read anything yet

I don't want a constant current driver or a DynaOhm... all 50 of the resistors needed only cost $6.50 and the LEDs are priced a bit high at $38.50 for 50.

You have the right idea, DIY LED is where its at. But if you use resistors and 5mm LEDs, the lamp's efficiency will barely outperform incandescent (5-10%). If you use constant current drivers and top bin SMD LEDs, your lamp can be as high as 45%-50% efficient. You could build it as small as 10 dissipation watts but the bigger you go the less the shipping cost will factor in.

Small constant current drivers are normally very inefficient (50% or less) but I came across one the other day that is 80% efficient, 2-8 watts, $5 so they are out there.