Moved post!

[The_Entertainer]

Hi, all

I am new to this place so plz forgive me for stealing the thread.
I need help with my first electronics project.
I am building a simple DC fan controller for my computer. I already bought rheostats and tested them. My problem is that I want to implement a set of lights that will indicate the power going to the fans (well sord of). I decided to use 5 LED's for this but as you know the voltage varies between 5v-12v DC. So I was thinking to create something like a sub channel for every LED so that it lights up at the needed voltage and goes out at the unneeded voltage. I can control it when it turns on by simply using a different kind of voltage regulator. The problem is that if I increase the voltage 2 much, LED's will blow. So I am looking for something that will act as an over voltage protector as well. For example LED # 1 will start at 5V and will have a maximum voltage coming in of 6V, just so it doesn't blow on me. My question is: What can I use to control the maximum voltage???

P.S. I tried some zenner Diodes but that didn't work...

Thanks, for your time! Any suggestions would be great!!!!

 

[audioguru]

An LM3914 IC has 10 LED drivers and 10 voltage comparators driving them. It also has a ladder of 10 resistors that you can set to turn on the comparators from your fan's 5V to 12V.
The LM3914 has a pin to select a bar of lighted LEDs or just a moving dot of a single lighted LED. Look for its datasheet in Google.