LED Blowing (regulator needed)

Hi All,

My mind gone blank for the moment on how best to solve a friends problem, hoping you could help.

He has a small boat and has fitted an aftermarket 12V LED 'light' to the top of his mast. It periodically blows.

On having a look around his boat I'm pretty sure he's running the module straight from the normal 12V battery - I'm thinking the alternator charging the battery (13.2-14V) is possible over stretching the unit or evan a PIV issue is occuring

OK presuming I'm right on either or both, obviously a reverse biased diode woill solve the PIV issue but what about a simple voltage regulator to supply the LEDS.

A 78x12 is the a simple solution but I'm unsure on the headroom voltage needed to get a nice 12V output.

Another thought is a Zener (could you help on the design values e.g. power disipation, current limiting resistors etc)

Lastly, I thought an inductor in series to smooth out any ripples the advantage being the power handling abilities(again design formulae would be great)

Any other suggestions would be greatly appreciated

Thanks in advnce
Dotnet

You need to find out WHY it keeps blowing, for a start drawing the circuit out and posting it here would help - then we could perhaps make suggestions?.

The LED lamp may be (most likley is) poorly designed. A series diode should take care of transient problems and a shunt capacitor would help in transient over voltage. The 13.8 volts during battery charging should not be a problem, but the engine starter can produce 60+ volts transient.

Just thought I'd point out that the 7812 regulator needs a voltage input of about 13.5 to 14volts (minimum) to operate properly. I dont know if the 13.5ish volts from the alternator would be enough.

Thanks for the replies

Dotnet

I currently incountered almost the same problem when I installed some LED indicator lights on a go-cart. It wound up being real simple for me. I just added a 10 Ohm 15 watt resistor on the positive wire to the LED. I cant say as if this will work for you but you might keep it in mind.