"Greg Mayman" bravely wrote to "Mike Ross" (02 Oct 03  08:25:00)
 --- on the heady topic of "VEHICLE LED'S"

 -=> Mike Ross said to Greg Mayman
 -=> about "VEHICLE LED'S" on 09-29-03  00:15.....

 GM> Let's look at the current and power versus voltage from your
 GM> table. I have added three extra columns that show the increase
 GM> in voltage (d-V), current (d-I) and power (d-P) from the previous
 GM> step.

 GM> % rated V  %Current  % Power     d-V       d-I     d-P
 GM> ----------------------------
 GM> 60         75        45
 GM> 70         81        57       +16.7%    +8.0%    +26%
 GM> 80         88        70       +14.3%    +8.6%    +22%
 GM> 90         94        85       +12.5%    +6.8%    +21%
 GM> 100        100       100       +11.1%    +6.3%    +18%
 GM> 110        106       117       +10.0%    +6.0%    +17%
 GM> 120        113       136       + 9.1%    +6.6%    +16%
 GM> 130        119       155       + 8.3%    +5.3%    +14%

 GM> It is obvious that the power change is about THREE TIMES the
 GM> current change.

 GM> The lamp is a lot closer to a constant current load with changing
 GM> voltage (as I said) than it is to a constant power load, which is
 GM> what you were claiming.

I made the comparison starting at the nominal power rating, between a
linear resistance and the lamp. Seems to me that to compare the lamp to
itself doesn't show how the current and power deviates from their linear
plots. I found current deviated slightly more than the power curve.
Remember the lamp's resistance increases with temperature so to change
the temperature a bit requires slightly more current change than power.

 Mike
 ****

... Archimedes found calculus 2300 years ago.
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