lighting leds

Posted on Feb 6, 2014

For longest life, we recommend you run them at 20-25 milliamps (ma). HOWEVER, in our LED flashlight conversions (and many commercial LED flashlights), the LEDs are run at 50-60ma, twice the rated current. One of our test LEDs ran at 98ma for over 200 hours without damage or appreciable light loss. So go ahead and experiment with running them at over rated current

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if you are willing to take the risk of a shorter life. In my opinion, a flashlight bulb that lasts 100 hours is a huge improvement and cost saver over the incandescent alternative which gives only 15-20 hours before it dies. You must use some method of limiting current to your strings of LEDs. The easiest is simply using the right number of LEDs for your supply voltage. Each white LED gives a voltage drop of 3. 6 volts. So, for a 115 volt DC light, you could use 32 white LEDs in series (115 / 3. 6 = 32 +/-) with NO current limiting (they will limit themselves by their inherent voltage drop). In reality, though, there are many other circuit design issues you need to look at to build a reliable 115VAC home LED lighting fixture! We link to a few resources farther down on this page, and you can always Google up `LED lighting circuits` for more information. Reverse polarity will not damage an LED unless the voltage is very high-it simply will not work, and will not pass current through. However, be sure to check the manufacturer`s rating for the specific LEDs you are using-there are some out there, particularly the latest models, that can be damaged by relatively low reverse voltages. The diagram below shows how the LED package is marked for polarity. The next easiest is a simple resistor. The resistor does consume power, though, but is usually needed since an `ideal` 3. 6 volt source is rarely available. Use Ohms law...

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