This isn't the normal resistor question, and I'm familiar with the theory and Which is better: using a resistor with an LED, or "precisely" matching the Vs to the given LED's Vf rating?
I have one of these impressive LEDs. I'm intending to build a lamp out of it. The max forward current is listed at 720ma. The Vf is given as a broad range of 12-14V, which is fairly useless. On briefly applying a 12.0V supply to it through a multimeter I observe it consuming about 850ma. Clearly I need a small resistor in there, but is there a sensible way to work out the value required other than stacking increasing numbers of 0.1 Ohm resistors in series with it and plotting my own Vf/If graph?
(The device seems to be 12x strings of 4 individual dies wirebonded to a thin PCB on an aluminium bar, where the dies are covered in translucent material to act as protection and diffuser.)
Is a Vf/If graph likely to be stable as the device heats up?
I have an IR noncontact thermometer. Is this likely to give sensible readings when pointed at an LED, or will it over-read?