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Old 04-23-2012, 07:14 AM   #32
rwidman
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City: North Charleston, SC
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Quote:
Originally Posted by Duvie View Post
As mentioned previously heat is the killer of LEDs .
The real killer of LEDs is too much current and too much current is caused by too much voltage, even for a split second.

The cheap way to control current through an LED is with a series resistor, but there are problems with that approach. For one thing, it is inefficient because power is dissipated in the resistor.

The real problem is, that on a boat, wired to the boat's 12 volt (nominal) electrical system, there can be variations in the actual voltage from under 12 volts to possibly 14 volts or more and short duration spikes of much more than that. If a dropping resistor is calculated for 14 volts, the light output will be less at 12 volts. If it is calculated for 12 volts, the LEDs will have a much shorter life.

A better way is with a voltage regulating circuit, but the best way is with a constant current "driver" circuit. This assures the optimum current flowing through the LEDs regardless of variations in the incoming voltage.

When you see in the specifications that a particular product is suitable 9 -30 volts or similar, you are buying a product with a constant current driver. These are the ones you want.

One more "tidbit" - These driver circuits will sometimes produce RF interferance that may or may not be a problem. I installed two LED replacement lamps in my berth area and was watching TV. I turned one of the lamps on and the TV signal froze. Turned the lamp off and the signal came back. Only on channel seven.

I had to install RF filters in the lamps to get my channel 7 TV back. It didn't bother the other channels.
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