1. #1
    Lee Roberts's Avatar
    Lives in Wigan, United Kingdom. Current Activity: Viewing Admin Control Panel Has been a member for 7-8 years. Has a total post count of 2,380. Received thanks 117 times, giving thanks to others 579 times. Made a monetary donation to the upkeep of the community. Referred 9 members to the community.
    As it says on the "Tin":


  2. #2
    Quote Originally Posted by Lee Roberts View Post
    As it says on the "Tin":

    Just be careful, that equation assumes the LED requires 20 milli Amps of current, the proper equation is (Vsupply - Vled) = IR, or R = (Vsupply - Vled) / I in this case. V is in Volts, I is in Amps, and R in Ohms.

    20 mA = 0.020 Amps.

    Some minature LEDs go pop on less than 20mA :)

    Technically speaking LEDs require a certain current, not a certain voltage, so it is possible to run a LED from a higher voltage supply without a current limiting resistor, as long as the supply is switched so that the average current is at or below the LEDs forward current.
    Last edited by ZeroCount; 16-03-2009 at 11:58 PM. Reason: Additional information
    The more I learn about this hobby, the brighter the light of knowledge grows, the deeper is the pit of ignorance revealed...

  3. #3
    I'm using this online calculator - you will also get the power requirements for the resistor - it calculates the Wattage of the resistor - depending of the voltage of the circuit


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