Re: Cheap LEDs for automotive dashboard application

Randy MacKenna wrote:

I own a vehicle, whose designers had the wisdom (not!) to require that
half the dashboard be removed in order to change the instrument light
bulbs. Needless to say, I've gone many months with half my
speedometer lit, and the clock completely dark.

I have never seen a car where the panel needed to be disassembled to
replace the lamps. Sometimes its a bit of a chore getting your hand
behind the panel, but the lamps are typically held in bases that can be
removed with a quarter turn.

I'm about to undertake the repair, but before I plug incandescent
bulbs back in, I believe I may be able to Rube Goldberg small white
LEDs in place of the bulbs. I was thinking of these:

http://snurl.com/1pv3p

Question: Am I kidding myself here, and just substituting one problem
for another? Or, in an automotive application will these LEDs
actually be more robust than the incandescent bulbs?

I guess I'm worried that one >14VDC spike out of the voltage reg on
the car's alternator, and these LEDs will fry. Maybe if I add a
simple 12V regulator in front of them, that would do it (?)

Also, will these dim okay with the car's dimmer control...or will it
end up being an either "on" or "off" control?

Many vehicles use a simple rheostat in series with the panel
illumination circuit for dimming. With this arrangement, the LEDs will
not dim properly. They will remain at near full brightness until some
point is reached and then dim quite rapidly.

Some cars use a PWM dimmer. You could build one of these yourself and
replace the dimmer rheostat, incorporating some protection against
overvoltage.


Thanks,
Randy

--
Paul Hovnanian mailto:Paul@xxxxxxxxxxxxx
------------------------------------------------------------------
Have gnu, will travel.
.

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