Bill Turner wrote:

How interesting. I wonder if they are pulse width modulated to
compensate for day/night? What other reason could there be?


That might be it. It would be a convenient and efficient way of
adjusting brightness. They also might be compensating for voltage and
temperature by changing the pulse width.

Roy Lewallen, W7EL

That might be it. It would be a convenient and efficient way of
adjusting brightness. They also might be compensating for voltage and
temperature by changing the pulse width.

Hi Roy, You can do all the above with a regular light bulb. I think the
reason they use multiple LED's is to reduce the mean time between failures. If
a regular bulb fails, you are dark. If half of the LED's fail you still have
light. They generally have 20 plus LED's. in the stuff I have seen. Also,
LED's tend to last than bulbs (I think)
73 Gary N4AST

On 07 Jan 2005 01:00:31 GMT, (JGBOYLES) wrote:

LED's tend to last than bulbs (I think)
Only if the bulbs are in American cars.

Hi Gary,

The filament lightbulb lifetime increases at the inverse 12th power of
its reduction from the "suggested" operating voltage. This curve
actually holds only for about the first 5 to 10% of voltage depression
(otherwise they would last forever at half power). This is one reason
to buy industrial bulbs (rated at 130V).

The benefit of LEDs is lowered current consumption for the same
brightness (which I will warn is another one of those tricks of the
brain). This is also a deficit for turn signals because it has a
tendency to change the tempo of the flashing which can be mistaken as
multiplexing. :-) The suggested fix is placing a resistor in
parallel to return the circuit current demand to the original level.

73's
Richard Clark, KB7QHC