LEDs? what voltage?

jman1310 · 02-18-2005, 04:00 AM

i recently wc my pc. afterwards i connected all my fans to the antec fan lead which runs the fans at a little over 5 volts. the only thing i hear now is the pump

The problem: all the LEDs in all my fans are off due to the low voltages or very dim

The Question: can i run the LEDs in the fans off a seperate wire harness? there are at least 15 LEDs (3 fans of 4 and 1 fan of 3) and if i did this i would probally add a few more elsewhere

i have heard that LEDs like 3 volts can i get this from the power supply or is that a really bad idea? (i'm thinking about the 3.3volt line that powers the CPU) i just cheched and it's rated for 28amps

i have also heard that if you run them in series or parrallel (can't remember which) the voltage to each LED will be determined by #LEDs / volts
so 4 LEDs on a 12 volt circuit would each get 3 volts
this makes sense mathmatically but doesn't sound logical to me

how difficult will it be to wire LEDs in fans to a seperate circuit? is this somthing that it may be easy to buy a bulk pack of LEDs and just replace all the LEDs?

jman1310 · 02-18-2005, 04:49 PM

nothing? sheesh, I need help here

redleader · 02-18-2005, 08:21 PM

Voltage makes no difference, so long as its above a specific value for the LED. Everything is determined by the resistor used in series with the LED. You're not giving the resistor enough voltage, so its not giving the LED enough current.

Either switch out the resistor for a smaller one, or give it the rated voltage for the resistance built into the fan. I've never seen an LED fan, so I don't know how easy it would be to get at the leds. Ideally you could just disconnect the resistor-diode circuit from the fan and plug it into a 12v source. Otherwise you could buy proper resistors, desolder the included ones, and then solder in the new ones. Of course if you did this and plugged the fan back into a 12v line, you could burn out the LEDs.

If you wire LEDs without a resistor (put 4 in series across the 12v line) they'll probably pop in a second or so. Internally each LED has ~0 resistance once its biased, so a resistor is required to keep them from pulling a few amps and melting.

iroc409 · 02-21-2005, 12:15 PM

i found out the hard way a long time ago that 12v straight to a not-12v led will make them EXPLODE - sparks and all. LOL.

redleader · 02-21-2005, 03:48 PM

Its not the voltage that matters, its the current. You could hook up any sized LED to 12v, and its either going to explode or not light up at all. Actually you can use any voltage drop LED you like, and any voltage, it makes no difference.

jman1310 · 02-25-2005, 10:58 AM

this is what I was looking for

link

thanks for your help

02-18-2005, 04:00 AM	#1
jman1310 Cooling Savant Join Date: Oct 2004 Location: Sunny Florida Posts: 246	LEDs? what voltage? i recently wc my pc. afterwards i connected all my fans to the antec fan lead which runs the fans at a little over 5 volts. the only thing i hear now is the pump The problem: all the LEDs in all my fans are off due to the low voltages or very dim The Question: can i run the LEDs in the fans off a seperate wire harness? there are at least 15 LEDs (3 fans of 4 and 1 fan of 3) and if i did this i would probally add a few more elsewhere i have heard that LEDs like 3 volts can i get this from the power supply or is that a really bad idea? (i'm thinking about the 3.3volt line that powers the CPU) i just cheched and it's rated for 28amps i have also heard that if you run them in series or parrallel (can't remember which) the voltage to each LED will be determined by #LEDs / volts so 4 LEDs on a 12 volt circuit would each get 3 volts this makes sense mathmatically but doesn't sound logical to me how difficult will it be to wire LEDs in fans to a seperate circuit? is this somthing that it may be easy to buy a bulk pack of LEDs and just replace all the LEDs? Last edited by jman1310; 02-18-2005 at 04:35 PM.

02-21-2005, 12:15 PM	#4
iroc409 Cooling Savant Join Date: Oct 2002 Location: midwest side, yo Posts: 596	i found out the hard way a long time ago that 12v straight to a not-12v led will make them EXPLODE - sparks and all. LOL. __________________ :shrug:

02-18-2005, 04:49 PM	#2
jman1310 Cooling Savant Join Date: Oct 2004 Location: Sunny Florida Posts: 246	nothing? sheesh, I need help here

02-18-2005, 08:21 PM	#3
redleader Thermophile Join Date: Jun 2001 Location: The deserts of Tucson, Az Posts: 1,264	Voltage makes no difference, so long as its above a specific value for the LED. Everything is determined by the resistor used in series with the LED. You're not giving the resistor enough voltage, so its not giving the LED enough current. Either switch out the resistor for a smaller one, or give it the rated voltage for the resistance built into the fan. I've never seen an LED fan, so I don't know how easy it would be to get at the leds. Ideally you could just disconnect the resistor-diode circuit from the fan and plug it into a 12v source. Otherwise you could buy proper resistors, desolder the included ones, and then solder in the new ones. Of course if you did this and plugged the fan back into a 12v line, you could burn out the LEDs. If you wire LEDs without a resistor (put 4 in series across the 12v line) they'll probably pop in a second or so. Internally each LED has ~0 resistance once its biased, so a resistor is required to keep them from pulling a few amps and melting.

02-21-2005, 03:48 PM	#5
redleader Thermophile Join Date: Jun 2001 Location: The deserts of Tucson, Az Posts: 1,264	Its not the voltage that matters, its the current. You could hook up any sized LED to 12v, and its either going to explode or not light up at all. Actually you can use any voltage drop LED you like, and any voltage, it makes no difference.

02-25-2005, 10:58 AM	#6
jman1310 Cooling Savant Join Date: Oct 2004 Location: Sunny Florida Posts: 246	this is what I was looking for link thanks for your help

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