Quote Originally Posted by argentic
I'm a complete dummy in electronics.

Hew uses very bright LED's. Is it possible to make individual LED's change light emission intensity (kind of rheostat)? With two pontiometers you would be in business.

But maybe I'm talking bullsh...
'fraid so. My understanding is that the dimming is strictly by varying duty cycle in a pulsed constant current source. That's how Huw's circuit works as I recall. The spec sheets for the Luxeons seem to require a constant current somewhere between 750ma and 1000ma for operation. I'm left wondering if his inability to get a harder contrast than 4.5 comes from some sort of intermittency effect. Would raising the frequency help. I have an old book by Zakia suggesting that intermittency effects go away as the pulse frequency goes above a certain point. Is low MHz sufficient? Any phys chem dudes out there?