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Caddilac Deville LED brake/tail lights, how did they do it?

J

JazzMan

Jan 1, 1970
0
I was looking at the above this evening, all of the LEDs
were of equal brightness and the tail light portion did
not dim when the brake/turn portion flashed. There looked
to be probably more than a hundred LEDs per side, how do
they control and maintain brightness? Is each LED individually
trimmed and controlled current-wise?

The lights are a bit too expensive to just go buy one to
disassemble, and I doubt GM would email me the schematic
and design particulars, so I thought I'd pose the question
here where all the smart people seem to hang out. :)

JazzMan
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JazzMan said:
I was looking at the above this evening, all of the LEDs
were of equal brightness and the tail light portion did
not dim when the brake/turn portion flashed. There looked
to be probably more than a hundred LEDs per side, how do
they control and maintain brightness? Is each LED individually
trimmed and controlled current-wise?

The lights are a bit too expensive to just go buy one to
disassemble, and I doubt GM would email me the schematic
and design particulars, so I thought I'd pose the question
here where all the smart people seem to hang out. :)

JazzMan

The Cadillacs I've seen around LA sure don't have uniform brightness on
the LEDs. That instant turn on/off is creepy to look at IMHO. Couldn't
they add some capacitors to sloppy up the on/off time?

The only automotive LED assembly I saw was the center brake light on a
VW Jetta. It had 3 or 4 strings of LEDs (12 total LEDs) with a resistor
for each string and 1 series 1N400x for reverse polarity protection. It
ran a total of 280 mA and was blindingly bright on the bench. The
series diode had failed but still read a normal diode drop with a Fluke
8060 though the forward voltage drop was several volts under load.

GG
 
D

David L. Jones

Jan 1, 1970
0
JazzMan said:
I was looking at the above this evening, all of the LEDs
were of equal brightness and the tail light portion did
not dim when the brake/turn portion flashed. There looked
to be probably more than a hundred LEDs per side, how do
they control and maintain brightness? Is each LED individually
trimmed and controlled current-wise?

The lights are a bit too expensive to just go buy one to
disassemble, and I doubt GM would email me the schematic
and design particulars, so I thought I'd pose the question
here where all the smart people seem to hang out. :)

Probably just multiple constant current regulators driving a series
string of LEDs. Doubt it would be any fancier than that.
They might pay a bit more to get the primo LEDs that are more tightly
matched in brightness.

Dave :)
 
J

Jasen Betts

Jan 1, 1970
0
I was looking at the above this evening, all of the LEDs
were of equal brightness and the tail light portion did
not dim when the brake/turn portion flashed. There looked
to be probably more than a hundred LEDs per side, how do
they control and maintain brightness?
Is each LED individually trimmed and controlled current-wise?

There's a thing called Kirchoff's law that says that devices
connected in series will all experience the same current.
The lights are a bit too expensive to just go buy one to
disassemble, and I doubt GM would email me the schematic
and design particulars, so I thought I'd pose the question
here where all the smart people seem to hang out. :)

they could be powering all those LEDs in series using a voltage
booster or they could be doing it in series groups of 4 from 12V


Bye.
Jasen
 
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