AVR-Chat

I need to generate a 0-10V signal to control some dimmable LED drivers.  I know I could do it with a DAC, but I think I might be able to save a part by generating a PWM signal and smoothing it out with a capacitor to make a voltage out of it.  My problem is, I don't know how to properly size the capacitor to get a reasonably smooth signal.  The output would change slowly.  A full 0-100 or 100-0 transition would take at least a minute and usually many minutes.

Can someone provide some guidance about how to size the capacitor and what type of capacitor is best suited for this type of thing?

Thank you.