Touche'. Primarily ran them long term just to make sure it wouldn't burn up in case they got stuck on or something. Surely not the best way to run them. I fooled with some current limiting resistors on my 1W versions (1W 47ohm/350ma) but they so dang big. The 700ma equivalent is 1W 22ohm based on the online calculators. Eddie, what's your taking on going about them this way?

mmmm, not sure I would trust that online calculator if that's the numbers your getting but I no idea of the base assumptions.

Here's what I get based on the following

LED Vf varies from 3.2v to 3.6v, so lets use an average of 3.4v

3w LED with 700mA current

For a 12V supply the resistor of 12.28 Ohms drops 8.6v and dissipates 6.02W of power and limits current to 700mA

For LED Vf of 3.2v the same resistor would allow 720mA

for LEd Vf of 3.6 the same resistor would allow 680mA

This variance is not a big issue and well inside resistor tolerance values anyway.

Now if Vdd is 5V this gets worse as the resistor values are significantly lower (around 2 Ohms) with current varying from 610ma to 790mA at each end of the LED Vf specification.

However the Power dissipated in the resistor is less than 1.5W Max in all cases.

Cheers

Phil