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# 10 LED string.

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Join Date: Apr 2011
Posts: 36

 02-22-2012, 12:05 AM
Ok, I am putting some super bright red LED's in my computer case for lighting. after playing around with different arrangements I came up with this, I just wanted to know if I missed any potential problems.

Data sheet is here:
What i can gather:
current is 70mA
Vf is 2.5V

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 02-22-2012, 02:30 AM
70mA seems an awful lot.

Do you have the specs on these LEDs? 20mA is probably closer to what I'd expect unless they're a high powered LED.

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Join Date: Feb 2012
Posts: 43

 02-22-2012, 02:47 AM
He did say super bright in his OP, but 70mA does seem excessive.

Quote:
 Solution 2: 2 x 5 array uses 10 LEDs exactly +12V + -|>|- -|>|- -/\/\/\- + R = 100 ohms + -|>|- -|>|- -/\/\/\- + R = 100 ohms + -|>|- -|>|- -/\/\/\- + R = 100 ohms + -|>|- -|>|- -/\/\/\- + R = 100 ohms + -|>|- -|>|- -/\/\/\- + R = 100 ohms The wizard says: In solution 2: each 100 ohm resistor dissipates 490 mW the wizard thinks 1W resistors are needed for your application Help together, all resistors dissipate 2450 mW together, the diodes dissipate 1750 mW total power dissipated by the array is 4200 mW the array draws current of 350 mA from the source.
from http://led.linear1.org/led.wiz

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Join Date: Apr 2011
Posts: 36

 02-22-2012, 03:00 AM
Guess I forgot the link for the Data sheet:
http://www.allelectronics.com/mas_as...ec/LED-912.pdf

Do you foresee this causing excessive load on the 12V rail of my PSU?

Edit, it already has A TON of fans (6x 120mm and 2x 140mm for ventilation alone)

Last edited by TbirdMan; 02-22-2012 at 03:04 AM..

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 02-22-2012, 03:14 AM
The LED wizard said it would dissipate 4.2W at 350mA, so depends on your power supply, I suppose.

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 02-22-2012, 03:34 AM
Quote:
 Originally Posted by TbirdMan Guess I forgot the link for the Data sheet:
Yep, so 70mA seems fine.

You may be able to get lower dissipation by placing three in each string, but given the environment, I'm not sure it would make that much difference.

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