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the right resistor? Answered


Hey guys got a question. I want to add an ultra bright LED from my mini mag light to my atx benchtop power supply. The LED ran off 3v (2 AA’s.) The line I want to use is the 3.3v (14 amp) from the atx to power it. What size/power rating resistor should I use?

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guyfrom7up

8 years ago

Is the led stand alone or a module with built in resistor? if it has a built in resistor it should be fine, otherwis (assuming 3 volt drop)

3.3 volts-3 volts=0.3 volts
0.3 volts= current x resistance

assuming 20mA (aka 0.02 amps) of current,

resistance=0.3/0.02= 15 ohms

so you want 15 ohms or some similar value, but 15 ohms should be a standard value