please let me know if there is a better place to post this
ok is there a difference between 500mA at 12V Vs. 500mA at say 4 or 6 or 8 V
is it the same power ? does the led show a difference in brightness
let me lump another one thats been avoiding me if you want to go for the bonus prize
can anyone link me to a chart of a measurement of heat outputted by an XML at say 100mA to 3A or so ....
for example at 300mA it makes X amount of heat and need X amount of heatsinking at room temp of X , anythign general to pretty involved would help alot
thank you in advance , sorry this has just been eluding me
Ok, i'm not an expert but i'll try to give you an answer..
You can use this law to calculate "power"
Where p=power (watt), v=voltage (volt) and i=current (A). So you can have different watt with same current if you use a higher voltage.
I hope i didn't say something stupid.. this are all school memories.
In this post you can find a spreadsheet to calculate the led temp. i don't think you can have a perfect equation to calculate the temperature at any current. There are too many variables
XM-L's should be powered from a 3.3v source, this is referred to at it's forward voltage or Vf.
Our batteries generally have a higher voltage than that, but battery voltages sag significantly under load so with that factored in we generally are pretty close to the recommended VF.
Generally for testing purposes you would only want to power them from a power supply you can set the voltage and current on. For long term use you are probably better using a driver circuit.