It is summer and my air conditioner isn't perfect. It is frequently 30 degrees C. Also, the LED is going to be mounted in something that will block cooling air flow to it.Marks256 said:Yes, but isn't 25°C room tempurature?
Not if its ambient air is more than 25 degrees C.So then it should run at 100mA?
I would probably use 80mA max because the performance isn't much less but the reliability will be greatly improved.What would you suggest running it at? And why would you run it at that?
Marks256 said:For the last time, i am 100% sure that these are the ideal/normal/recomended characteristics. Yes, i know my math was off. I didn't quite know what 100mA equals in amps. I know now that it is .1.
Is this right? I just drew it quick. Thanks.
Marks256 said:So, what is power disipation? Is it how many watts of power the curcuit requires?
Marks256 said:I have another question; If i had a power supply that supplyed 2watts of power, and a curcuit that used only .25watts, would the powersupply force the two watts into the curcuit, or would it just give what the curcuit needed?
JimB said:LEDs (and ordinary diodes, transistors etc) do not obey Ohms Law.
JimB
RadioRon said:Ohm's Law only states that V=I*R. It does NOT state that if you calculate R at one current then that R will remain constant at other currents.
RadioRon said:This is simply the behavior of a resistor. Ohm's law holds true at any current through a diode, for example, where you can calculate what the resistance is, AT THAT PARTICULAR CURRENT. A diode is simply one of many electronic devices where the relationship of current to voltage is not a straight line. In other words, its resistance varies as current through it varies. Same with transistors.
RadioRon said:Off the top of my head, I can't recall any device that doesn't obey ohm's law. Can anyone suggest a device that doesn't and why?
eblc1388 said:Ohm's law only states that the "relationship" between current and voltage across certain material remains constant, so V=I*R is not ohm's law but a direct result of applying ohm's law as ohm's law implies that for centain material, the proportional constant is called R so one can work out either the current or the voltage if the other is known, or work out R if both voltage and current is known.
Ohm's Law only states that V=I*R. It does NOT state that if you calculate R at one current then that R will remain constant at other currents. This is simply the behavior of a resistor. Ohm's law holds true at any current through a diode, for example, where you can calculate what the resistance is, AT THAT PARTICULAR CURRENT.
RadioRon said:Please provide text references that support the above statement.
Uh...yeah...but at at the same time...no...that is the definition of Ohm's law. You can't say that [insert definition of Ohm's law] is not Ohm's law, but is instead [insert definition of Ohm's law].eblc1388 said:I cannot agree. Ohm's law only states that the "relationship" between current and voltage across certain material remains constant, so V=I*R is not ohm's law but a direct result of applying ohm's law as ohm's law implies that for centain material, the proportional constant is called R so one can work out either the current or the voltage if the other is known, or work out R if both voltage and current is known.
A common filament lamp bulb does not obey ohm's law between the range from zero to normal working current because its resistance has changed many times. But it will still obey ohm's law if it's element is immersed in liquid nitrogen and being kept at a constant temperature.
eblc1388 said:You first.
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