Saturday, Luray Martin and I sided the previously open sided woodshed with slabwood from his brother’s sawmill, and lit it up with LED’s wired to our home’s battery bank. We wired sets of four 20ma 3.6 volt 120k mcd LED’s in series, giving enough light for getting wood, starting the emergency generator, or otherwise navigating in the dark.
Based on the calculator at http://led.linear1.org/led.wiz, we used a single 1 ohm resistor in series with the 4 LED’s. Our LED’s see 14.4 volts while the battery bank is charging, have a diode forward voltage of 3.6 volts, and a diode forward current of 20ma.
The wizard says:
- each 1 ohm resistor dissipates 0.4 mW
- the wizard says the color code for 1 is brown black gold
- the wizard thinks 1/4W resistors are fine for your application
- together, all resistors dissipate 0.4 mW
- together, the diodes dissipate 288 mW
- total power dissipated by the array is 288.4 mW
- the array draws current of 20 mA from the source.
More LED info.