Smooth LED fading via PWM

[HankMcSpank]

For this specifically LED it might work and as long as the voltage is absolutely stable.

But I insist on using a current source. You will be able to control the brightness for a really 0 to 100%.

Even for a test it is interesting.

I have a client that for more than a year is refering to his power (chinese) LEDs as 24Volts... And I reply with the current of your LEDs is....

Ioannis

If my calculations are right, when sinking current, my 16f1828 is working out at about 52 Ohms of series resistance per pin - now whether the resistance comes by way of a resistor, or the resistive properties of the silicon inside the PIC IO driving circuitry...resistance is resistance?

V Supply = 3.268V
V drop measured across blue LED = 2.931V
remianing V drop across PIC pin = 3.268V-2.931V = 0.337V
Current through LED (inferred by measuring current into whole circuit - 11 LEDS - then taking a little off (3mA for the PIC) & dividing by 11 = 6.4mA

Resistance of PIC pin R = V/I =....or 0.337V/0.0064A = 52.65 Ohms.

So why not simply treat the PIC's pin as a series 52 ohm resistor for the purposes of LED current calculations? (ie what am I missing?)