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Led in parallel and switched NPN transistors

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  • Led in parallel and switched NPN transistors

    I have the following circuit designed to drive 3 PWM pins off a 3v3 Arduino Pro Mini -- one pin for each of R, G, B in this set of 5 RGB LEDs.
    Click image for larger version

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    At first ,my questions are:

    Is this a reasonable design?

    How do I determine the resistor settings for both the base transistor resistors (2N3904), and the LED resistors?

    Is there a way to simplify/minimise on power wastage, resistor usage, etc?

    Then I looked into some books and websites and I figured out some ideas.But I'm not sure if I'm right.So please give me some suggestions.Thanks a lot.
    Electronics For You ( EFY / E4U ) is the world's #1 source for news on electronics, interviews, electronics projects, videos, tool reviews and more!
    Last edited by jayke; February 8th, 2017, 02:44 PM.

  • #2
    Here's the datasheet of 2N3904 for your reference : http://www.kynix.com/uploadfiles/pdf8798/2N3904.pdf

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    • #3
      Originally posted by jayke View Post
      I have the following circuit designed to drive 3 PWM pins off a 3v3 Arduino Pro Mini -- one pin for each of R, G, B in this set of 5 RGB LEDs. Attachment


      At first ,my questions are:

      Is this a reasonable design?

      How do I determine the resistor settings for both the base transistor resistors (2N3904), and the LED resistors?

      Is there a way to simplify/minimise on power wastage, resistor usage, etc?

      Then I looked into some books and websites and I figured out some ideas.But I'm not sure if I'm right.So please give me some suggestions.Thanks a lot.
      Please share a large size image of the circuit.

      Comment

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