|
posted to rec.boats.cruising
|
|
external usenet poster
|
|
First recorded activity by BoatBanter: Nov 2008
Posts: 111
|
|
LEDs
Larry wrote:
Bruce In Bangkok wrote in
:
On Fri, 26 Dec 2008 23:55:48 +0100, "Steve Lusardi"
wrote:
I'm proud of you! I hope you used a voltage regulator for the LEDs? If
you didn't, you will seriously kill the expected life span.
Steve
Nope, the LED's he is talking about are designed to operate in a 12
VDC system, i.e., with system voltages as high as, probably, 15 VDC. I
initially built voltage regulators into the light fixtures I built
using the same 30 LED tubes. Bad! Dim lights. Then I had a closer look
at the "tubes". The LED's are wired in series parallel with resisters
for each series section to limit current Flow. You just plug them in..
Cheers,
Bruce
(bruceinbangkokatgmaildotcom)
Have you guys ever noticed how they "dim" LEDs for tail lights that
brighten to full power when you apply the brake lights?
The dim mode they feed a 50% duty cycle pulse at a kilohertz or so, not
important just too fast for human eyes to respond. Move your eyes fast
back and forth as you follow them and you can see they are pulsed on and
off very rapidly. Then, when the brake switch closes, the same LEDs
brighten up with pure DC applied for maximum brightness. It would be a
simple matter to build an LED dimmer for them out of a 555 timer IC as a
variable pulse width pulse generator driving a power transistor to
handle the load of the string......
http://www.rmcybernetics.com/project..._pulse_control
ler.htm
The heatsink is WAY overkill as the transistor is either off or
saturated. It will hardly get warm, even at 10A.
404 Larry!
|