Formula for figuring series resistor values for LEDs

The Model Railroad System includes a program, Resistor, that will do this computation (you can select the supply voltage, the LED voltage, and the LED current). It will also let you know what wattage resistor you need and will also find the nearest stocked value and display the color bands for such a resistor.

On 8/28/2008 11:13 AM Robert Heller spake thus:

wrote:

That's nice.

The little formula above requires only paper and pencil (or a calculator to those who prefer automation), and will work in a power outage without a UPS.

How are you going to light the LED when the power is out?

---john.

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These might help...

Resistors:

LEDs:

Bill Bill's Railroad Empire N Scale Model Railroad:

e:

me president, and I

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This calculator even shows you the colors on the resistor. Very neat.

snipped-for-privacy@panix.com (John Haskey) wrote in news:g96v0f$frv$ snipped-for-privacy@reader1.panix.com:

Well, I don't know about you, but my truck could easily provide enough power to keep my Digitrax system happy for MONTHs. If the system's got power, then my White LED headlights can light. :-)

The mains are out, and the residents of my model railroad are happy because they've still got electricity. Imagine that. lol

Puckdropper

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If one loses power during a thunderstorm, they could always send up kites to get the power they need for their model railroad.

Bill