Adjusting LED color temp?

[lynkynpark86]

I want to make a light that has 4 white LEDs, a red LED, and a blue LED. I want to have a know that controls the blue-red ratio. Is this possible with only a variable resistor (highest resistance = red at capacity, blue off; lowest resistance = red off, blue at capacity)?

 

[XmodAlloy]

That is certainly possible! You simply need a pulse width modulator and an output inverter. Run the blue off the PWM output and the red LED off the inverter.
I personally like this: http://www.robotroom.com/PWM.html PWM schematic, very easy to build on a single layer board.
Good luck!

 

[KJ6EAD]

What are you using for power; batteries, regulated supply or unregulated supply?