Reduce 14v DC to 12v DC

A

adc1947

New Member
Hello.... first time posting... and need some help....

I need to reduce 14v dc to 12v dc.

I have 48w LED that draws 4.5 amps at 12v. If powered at 14v, the amp draw increases to around 7 to 8 amps. LED is fine when powered with the 12v, but is greatly over heating at 14v.

In searching internet for solution to reducing the 14v to 12v, I came across similar issue where there was a need to reduce 15v to 12v and the suggested solution was the use of a 0.6R 25w resistor.

Will the above work or should the 0.6R resistor be a different value since I am working with 14v and not 15v....??

I have found 0.6R resistors with 50w and 100w ratings, but have not purchased to try them.

Any help and comments will be much appreciated.
 
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I've used the wire wound resistors, similar to the ones in your Amazon link, in several applications. Mouser, Newark and Digikey sell them up to higher ratings.

You seem to have rejected the 35 W resistor because it's rating it too large. That isn't the right thing to do, because the power rating of a resistor is the maximum it can be used at, with a really good heat sink, and you can use it for any power from zero to its maximum.

A common recommendation is to use resistors at less than half their power rating.

If the resistor generates 25 W of heat, use at least a 50 W rated resistor. It will run much cooler and be more tolerant of overloads. Even at 25 W, on a heat sink, a 50W resistor may be too hot to touch.

(I think others have mentioned as well, but the LEDs don't have to be run at their maximum rating. Less current means that the LED runs cooler and is slightly more efficient, but of course it also means less light output)
 
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Diver300 said:
If the resistor generates 25 W of heat, use at least a 50 W rated resistor. It will run much cooler and be more tolerant of overloads. Even at 25 W, on a heat sink, a 50W resistor may be too hot to touch.
Click to expand...
Received two off Amazon today... and as you point out, they are rated at 50w...
 
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adc1947 said:
Received two off Amazon today... and as you point out, they are rated at 50w...
Click to expand...
If it is the typical metal body 50W case , they are not rated for 50W unless mounted on a heatsink = 286 sq inch surface area, 0.060" thick. e.g. https://www.seielect.com/catalog/sei-kal.pdf But then as I indicated before, you shouldn't need 50W rating as you should be dropping ~2V/14V or 15W of power with the correct R value that does not exceed the rated current. The best solution is still the DCDC current limiter like the one shown before https://www.electro-tech-online.com/threads/reduce-14v-dc-to-12v-dc.166157/post-1451795
 
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