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[Build Log] Merlin (Water Cooled r-atx SM8 w/dual Pedestals / Z97X-UD5H) - Page 114

post #1131 of 2434
Quote:
Originally Posted by mandrix View Post

Whut?
Yeah they do but the fan controller was closer. tongue.gif

You got a 12v LED?
The single LED's I buy I solder a 470K resistor in line and hook up to either 12v or a fan controller.

Yes there 12 volt. got 10 extra sets. need to strip the sleeve so the fit int the bottom of the res. the have a molex connector at the end.
lightning is a new world to me as it coms to solder resistors in between. smile.gif
Edited by TATH - 5/12/13 at 2:57pm
post #1132 of 2434
Quote:
Originally Posted by mandrix View Post

Whut?
Yeah they do but the fan controller was closer. tongue.gif

You got a 12v LED?
The single LED's I buy I solder a 470K resistor in line and hook up to either 12v or a fan controller.


I'd bet anything that's a 470 Ohm, (yellow purple brown gold) not K ohm (yellow purple yellow gold) resistor.

LED's are unique devices, sort of like a check valve,. . . until you apply at least the rated forward voltage, no current flows.

Once you exceed the forward voltage spec, current rushes thru without any internal limiting and unless you can precisely control the voltage right at the Vf threshold, the LED fries.

Resistors are placed in series to limit the current thru the led to stay below a safe limit.

To figure how much resistor to use with an led, look up the forward voltage for the led, red are usually the lowest at about 1.7V, green and white are the highest at about
3.4V & 3.9V respectively, and subtract that from the maximum supply voltage . . . 12V if planning on using a fan controller.

Take that result, and divide it by the maximum specified current for that led . . . Usually between 20 and 30 milliamps . . . 0.020 to 0.030 amps.

That result is the minimum resistance you need . . . so choose the next highest standard value. In that general range, they run: 270, 330, 390, 470, 560, 680, 820 ohms.

Most 5mm size leds can normally work fine at 25ma as the max. . . though they don't seem to be much brighter than they do at 20ma


Example:

White led with a Vf of 3.9 and with 25ma of current as the target:

12 - 3.9 = 8.1V

8.1V / 0.025A = 324 ohms

The nearest, going higher, standard value is 330 ohms


For a red led, Vf = 1.7V target current 25ma:

12 - 1.7 = 10.3V

10.3V / .025A = 412 ohms

Next standard value is 470, so you'll have a bit less than the target of 25ma.


You can put leds in parallel, as long as they are the same make and color, using half the resistance for 2 leds as for one, 1/3 for 3 etc.

The problem is, that if you break a wire to one, the other gets all the current and fries.

If you put them in series, then you need the cumulative forward voltage of all of them before they come on at all.

You could get maybe 5 or 6 red ones in series with a small value resistor, but 4 green or white ones wouldn't even come on at 12V.


Best practice is to run one resistor with each led.


If you find 12V leds, they have a resistor built in, so its max brightness is whatever that resistor limits the current to.


Darlene
post #1133 of 2434
Thread Starter 
Jeez, yes, I meant 470 ohm resistors. I'm old dammit I forget things.

So Tath you meant you have led's with the resistor already soldered in place. When you said 12V led's that threw me off.

I buy the resistors and the led's and solder it all up myself, make the leads the lengths I want. Cheaper, too.

For the RGB's I didn't need resistors since the Aquaero has the resistance built in.
BTW the Aquaero RGB header is:
Pin 1 Red
Pin 2 Blue
Pin 3 Ground
Pin 4 Green


Back to the Jesse Stone movie marathon.
post #1134 of 2434
Quote:
Originally Posted by IT Diva View Post

I'd bet anything that's a 470 Ohm, (yellow purple brown gold) not K ohm (yellow purple yellow gold) resistor.

LED's are unique devices, sort of like a check valve,. . . until you apply at least the rated forward voltage, no current flows.

Once you exceed the forward voltage spec, current rushes thru without any internal limiting and unless you can precisely control the voltage right at the Vf threshold, the LED fries.

Resistors are placed in series to limit the current thru the led to stay below a safe limit.

To figure how much resistor to use with an led, look up the forward voltage for the led, red are usually the lowest at about 1.7V, green and white are the highest at about
3.4V & 3.9V respectively, and subtract that from the maximum supply voltage . . . 12V if planning on using a fan controller.

Take that result, and divide it by the maximum specified current for that led . . . Usually between 20 and 30 milliamps . . . 0.020 to 0.030 amps.

That result is the minimum resistance you need . . . so choose the next highest standard value. In that general range, they run: 270, 330, 390, 470, 560, 680, 820 ohms.

Most 5mm size leds can normally work fine at 25ma as the max. . . though they don't seem to be much brighter than they do at 20ma


Example:

White led with a Vf of 3.9 and with 25ma of current as the target:

12 - 3.9 = 8.1V

8.1V / 0.025A = 324 ohms

The nearest, going higher, standard value is 330 ohms


For a red led, Vf = 1.7V target current 25ma:

12 - 1.7 = 10.3V

10.3V / .025A = 412 ohms

Next standard value is 470, so you'll have a bit less than the target of 25ma.


You can put leds in parallel, as long as they are the same make and color, using half the resistance for 2 leds as for one, 1/3 for 3 etc.

The problem is, that if you break a wire to one, the other gets all the current and fries.

If you put them in series, then you need the cumulative forward voltage of all of them before they come on at all.

You could get maybe 5 or 6 red ones in series with a small value resistor, but 4 green or white ones wouldn't even come on at 12V.


Best practice is to run one resistor with each led.


If you find 12V leds, they have a resistor built in, so its max brightness is whatever that resistor limits the current to.


Darlene

Thanks so much good information!!!!
post #1135 of 2434
Thread Starter 
Quote:
Originally Posted by seross69 View Post

Thanks so much good information!!!!
Darlene is one of the resident electronics guru's, definitely a great source for info. thumb.gif
post #1136 of 2434
Quote:
Originally Posted by mandrix View Post

Darlene is one of the resident electronics guru's, definitely a great source for info. thumb.gif

Yes I have noticed this. She always has good information sometime a little to technical but just have to read slow and not be in hurry.
post #1137 of 2434
Thread Starter 
Just heard from Aqua Computer, the Aquaero Pro I mailed out over 3 weeks ago finally made it to them. Was getting worried.....!
When it gets repaired I'll put it back in Merlin with the other Pro and take the LT probably and put it in my Switch 810.

So I finally got all the 1/2" copper tubing in place, leak testing going on now. I'm debating if it was worth it all but it's done for now.
Pics later!

Still trying to decide how/where to mount the NZXT & other led's down in the pedestal under the case fan holes so the light shows up through the acrylic. Probably have to pull a rad to mount anything...pretty tight for space down there!
post #1138 of 2434
Always busy makng progess but I wonder if and when you ever get to use this computer???
post #1139 of 2434
Thread Starter 
Quote:
Originally Posted by seross69 View Post

Always busy makng progess but I wonder if and when you ever get to use this computer???
confused.gif Usually it's not down more than a few hours, but there are 4 computers in the house, two of which are within arm's reach. I just toggle the HDMI switch to feed my backup to the monitor or go sit in the living room and surf on the TV. thumb.gif

Snapped some pics with different res colors











post #1140 of 2434
That all looks so nice but is it the way you are holding the camera or is tube a little sideways. believe me I am not trying to criticize just maybe help?

All the colors look great. cant tell you what I like best..
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