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Thread: 3.7v or 4.2v for calculating resistors?

  1. #1

    Default 3.7v or 4.2v for calculating resistors?

    Hey all,
    Going to start a Tri-Cree RGB hilt using one of my many 3.7v 18650's as the power source. I know how to calculate resistor values needed, but not sure if I should calculate input voltage as 3.7 or 4.2 (fully charged pack). Or, should I calculate both and average them out?
    Thanks!

  2. #2

    Default

    Use the 3.7V value.
    TCSS MODERATOR
    All n00bs READ these first (PLEASE)!!!:
    1. Forum Guidelines
    2. FJK’s “Down and Dirty” guide to Ohm’s Law

    "Yeah, yeah, I've heard it all before... you want blindingly bright, super loud, running 1138 blinkies off of the cheapest sound card you can find AND you want all of it to run on a battery the size of a dime, and run for a very, VERY long time. That one cracks me up every time..."
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  3. #3

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    Thank you FJK! I'll calculate the 3.7v value.

  4. #4

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    I would also check out Erv's video on how to calculate actual vF for individual LEDs, as the datasheets can sometimes be inaccurate. It requires a benchtop PSU.

    https://www.youtube.com/watch?v=S5IICsTwTYE
    For Wisdom, look backward. For Hope, look forward. For Victory, look inward.

  5. #5

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    Quote Originally Posted by BlessedWrath View Post
    I would also check out Erv's video on how to calculate actual vF for individual LEDs, as the datasheets can sometimes be inaccurate. It requires a benchtop PSU.

    https://www.youtube.com/watch?v=S5IICsTwTYE
    A tenth of a volt here or there won’t really matter. The resistors are usually rounded up anyway, which covers inaccuracies in voltages.
    TCSS MODERATOR
    All n00bs READ these first (PLEASE)!!!:
    1. Forum Guidelines
    2. FJK’s “Down and Dirty” guide to Ohm’s Law

    "Yeah, yeah, I've heard it all before... you want blindingly bright, super loud, running 1138 blinkies off of the cheapest sound card you can find AND you want all of it to run on a battery the size of a dime, and run for a very, VERY long time. That one cracks me up every time..."
    My email: fjk_tcss@yahoo.com

  6. #6

    Default

    Rounded up on the TCSS calculator and ordered the proper ones. Thanks for the help & input!

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