Rheostat

[Gandalf]

I am getting this Rheostat, and I was wondering if there was some way to change the way the LED is set up.

Right now it is always ON, even if there is no Fan attached.

But that's not my problem, my problem is that I want to be able to see the LED dim or brighten when I turn the RPM's of ym fans up or down......

Is there anyway I can do this?

Here is the Rheostat.

http://www.pcmods.com/details.asp?prodID=4

[Trieber]

http://www.bit-tech.net/article/52/

Read that article. It is some where in there, they mention it a few times, they have it set up pretty simple and they say the LED should dim at lower speeds etc and glow brighter at higher speeds. Good luck, and tell me how it goes, I'm gonna try this soon.

[Gandalf]

Originally posted by Trieber
http://www.bit-tech.net/article/52/

Read that article. It is some where in there, they mention it a few times, they have it set up pretty simple and they say the LED should dim at lower speeds etc and glow brighter at higher speeds. Good luck, and tell me how it goes, I'm gonna try this soon.

Thankyou!! :D

But this is how to make my own, nt how to change the one that I am getting.......anyone know how?

[Trieber]

I know some electrical stuff, what kind are you modding? If you post a pic I can probably take a look, and if I have no idea, ask my grandpa lol, he's an electrical engineer, also, some of the drawings in that article are pretty universal, I'm betting your fanbus or whatever might be similiar to that and modding it might only take adding a wire or two..

[GigaFrog]

I never used a rehostat. I am building myself a PWM for my main fan (like the electrobus).
Man, I can't believe you are paying $60 for 3 pots.

If you want to drive an LED in parallel to the fan, just connect the LED between the leads of the fan, with a biasing resistor. The longest lead of the LED is the +.
The biasing resistor will limit the current. You will have to adjust its value depending on how dim and how bright you want it. Try first with a 1K resistor. If it is too dim, reduce the resistor to increase current.


Hope this help.

[Gandalf]

Originally posted by GigaFrog
I never used a rehostat. I am building myself a PWM for my main fan (like the electrobus).
Man, I can't believe you are paying $60 for 3 pots.

If you want to drive an LED in parallel to the fan, just connect the LED between the leads of the fan, with a biasing resistor. The longest lead of the LED is the +.
The biasing resistor will limit the current. You will have to adjust its value depending on how dim and how bright you want it. Try first with a 1K resistor. If it is too dim, reduce the resistor to increase current.


Hope this help.

Will this let the LED brighten and dim when the fans are being slowed or sped up?

[Diggrr]

You could try it like this pic. I haven't done it, but it would seem to me that the same circuit that controls the fan would control an led with a resistor that adapts it to 12 volts. You'de have to do the math to find the correct resistor.

*edit* I know this isn't the way a reostat hooks up, just to illustrate puting the led circuit the same place the fan circuit hooks up.

[GigaFrog]

Will this let the LED brighten and dim when the fans are being slowed or sped up?

Yes it will.

Look at Trieber's link, the page about rheostat fanbus. The second picture on this page ("switched rheostat fanbus"), they have 3 fans, and each fan has its own LED+resistor, connected to his leads. When you turn the rheostat, it will modulate the voltage of both the fan and the LED, in the exact same proportions. They use 470 Ohms bias resistor on the LEDs, I was not far off!

Looks fun actually, I may install the same kind of LED on my PWM fan driver.

Good luck.