fan header voltages

[_SNOWMAN_]

Im looking at using CPU fan header for LEDs..... I wanted to have a set of LEDs change brightness with temperature. Low temps they will have little to no glow. I figured fan speed control would be best since it changes with temps and only have CPU header available. Hard to explain I guess but I need to know what pin does what.   4 pin CPU header is

1. GND  

2. 12V / Speed control

3. Sense

4. Speed Control

 

I have a converter made up to reduce from 12v to 5v but need a pin that delivers variable voltage..... Im guessing it would be #4 for 0-12v power and #1 for ground but not sure.   Only need power and ground

 

 

Dont have a multi meter in the house atm

[Queek]

Im looking at using CPU fan header for LEDs..... I wanted to have a set of LEDs change brightness with temperature. Low temps they will have little to no glow. I figured fan speed control would be best since it changes with temps and only have CPU header available. Hard to explain I guess but I need to know what pin does what.   4 pin CPU header is

1. GND  

2. 12V / Speed control

3. Sense

4. Speed Control

 

I have a converter made up to reduce from 12v to 5v but need a pin that delivers variable voltage..... Im guessing it would be #4 for 0-12v power and #1 for ground but not sure.   Only need power and ground

 

 

Dont have a multi meter in the house atm

I'm not sure that this will work.  CPU fan headers are usually monitored by the motherboard to ensure that the fan attached to the header is spinning.  If the fan isn't spinning, usually they won't let you boot.  

You might be able to get it to work on other fan headers if you can control the voltage of them.  Otherwise I think you're looking at a dimmer module.  

 

To people who understand the electronics of LEDs: can you just dim LEDs by lowering voltage or do you need to control duty cycle or some such?

[_SNOWMAN_]

Dug up an old Sears multi meter. Measured about 3 volts from #4..... LEDs wont power on that low.  #4 doesnt seem to get any higher than 3v even under a load.   <_<     Ill try to find some more info.   My idea was, Green LEDs (or any color)stay on contant and red LEDs to glow brighter as temps went up

[W-L]

-SNIP-

 

Theoretically yes this can be done as long as your motherboard has the proper sensors and software to create a custom fan curve. There are even LED strips you can get with 3 pin fan headers that are class for this type of use., I suggest using LED strips since it would be a bit less work.

https://www.dazmode.com/store/category/12in-30cm-led-connect/

 

As for your situation though you will need to ensure that header you use for the LED strip is set only on voltage control, you can then vary the voltage in the software provided by the motherboard to set the fan curve usually dictated by a percent. You would want to set the lowest setting of the fan curve to be just above the cutoff voltage where the LED strip turns off most are 6-7V and will go up to a max of 12V which is the same as your fans., the best is to set it on manual control and give it some trial an error until you can get those LED to the proper brightness levels that you'd like.