I figured. I really like your idea, and I was researching making led strings dim. Due to design, they really don't like dimming the same way incandescent bulbs do. A pwm dimmer essentially turns them on and off really quick to give the appearance of being dimmed.
I found these and put a set on order. I have a few strings for other projects, and your dash light idea is perfect. I'll put one of the dimmers and see how it works. 2A LED PWM Dimmer with Bypass (pair)
I figure for $20 it's really not cost effective to try and make my own. This design won't allow dimming on the fly, but it will get brightness to a comfortable use level.
