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  • Author Author: tariq.ahmad
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Driving LEDs to Create a Flux Capacitor -- DC to Daylight 08

In this episode we make a PWM LED driver using transistors and an Arduino Nano, which provide dimming and sequencing functionality for a Flux Capacitor. While not an exact replica, it does make a good demonstration of pulse width modulation and how to drive LEDs with a current sink/source

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  • Hello all! If you have suggestions on how to improve this project, especially related to software let me know here. One of the things I'd like to do is to "power up" three LEDs at the same time so the pulsing looks more natural... meaning three of the LEDs are actively ramping through the PWM values out of phase. I think this would require three nested loops and maybe a state machine. Ideas?

  • in reply to Derek (DCtoDaylight)

    One loop should do:

    Let's say as example that when LED A is 0, then B is 85, 3 = 130 (each 1/3 offset of each other).

    #define A_OFFSET 0
    #define B_OFFSET 85

    #define C_OFFSET 130

    uint8_t counter = 0;



    // helper method

    void setLed(uint8_t pin, uint8_t value, uint8_t offset {

      uint8_t intensity = ((uint32_t)(value + offset)) > 255 ? 255 : (value + offset);

      analogWrite(pin, intensity);

    }




    // where you want to make them glow:

    for (counter = 0; counter <= 255; counter++) {

      setLed(A, counter, A_OFFSET);

      setLed(B, counter, B_OFFSET);

      setLed(C, counter, C_OFFSET);

    }
  • in reply to Jan Cumps

    ... but that will make led 2 and 3 flip directly to their offset value, and that's not what you want he?

    Changing the helper function should fix that. Thinking ...

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  • in reply to Jan Cumps 
    #define A_OFFSET 0
    #define B_OFFSET 85
    #define C_OFFSET 130
    #define MAX_OFFSET C_OFFSET

    // helper method

    void setLed(uint8_t pin, uint32_t value, uint8_t offset) {
      uint8_t intensity = 0;
      if (value > offset) {
        intensity = (value - offset) > 255 ? 255 : (value - offset);
      }
      analogWrite(pin, intensity);
    }

    // ...
    for (uint32_t counter = 0; counter <= 255 + MAX_OFFSET; counter++) {
      setLed(A, counter, A_OFFSET);
      setLed(B, counter, B_OFFSET);
      setLed(C, counter, C_OFFSET);
    }