T&T: Soft start on Nav lights ( was: Converting my Running/Anchor Light to LED

[Candy Chapman and Gary Bell]

Arild, Lee, et al.:

As you probably already know, soft start protection is useful wherever 
tungsten filaments are used because of 'inrush current.'  When a 
tungsten filament is first turned on it is cold, and it's resistance is 
very low.  It initially draws many times it's normal current while it 
heats up to it's working temperature(a matter of milliseconds), where 
it's normal ratings are seen.  The nominal ratings for a filament light 
bulb are based on the resistance of the tungsten filament at it's 
nominal power setting, which has a far higher resistance than when it is 
cold.  That is why your porch light always dies by going flash when you 
turn it on one dark cold morning, -- inrush current.  BTW, halogen/xenon 
bulbs are also filament bulbs, they have the same behavior. 

LED's are little lasers, they don't have the resistive behavior 
(negative thermal coefficient of resistance) found in fillament light 
bulbs.  No inrush current issues at all.  They also have lifetimes that 
suggest that they will outlast us all.  By all means, replace all your 
navigation lights with LED units, and never have to fuss with them again. 

Mr. Science, aka Gary Bell


>> -----Original Message-----
>> From: LA Licata
>  
>

>> I think that what killed my running and stern light twice over 3
>> years was the turning them on and off so frequently.
>  
>


REPLY
Back in the early days of television when TV had vacuum tubes, we had a
special resistor that gradually turned on the heater filaments to prevent
exactly that kind of damage to the tubes. Sounds like its time to
reintroduce this filament protector for use on light circuits. To use modern
parlance its called a "soft" start up.

Arild