Designing an 8x8 RGB Led array + controller

Discussion in 'General Electronics Chat' started by melillo, Oct 4, 2016.

  1. melillo

    Thread Starter New Member

    Nov 15, 2010
    2
    0
    Hi everybody,

    I want to design an 8x8 RGB Led array and it's corresponding controller. I did this schematic, but because the Leds and some components are surface mount, I cannot test it easily before sending it to a PCB manufacturer. My question is: do you see any errors or flaws in this circuit? To simplify, the schematic I show you is for a 4x4 array. As you can see, there is one PCA9634 per color (R, G, B), and each PCA9634 feed a row of four Leds simultaneously. The intensity of each Leds is controlled by PWM inside the PCA9634. The rows are activated one after the other by the CD4051 at a rate defined by the PIC18F4550 microcontroller.

    If you have any comments or questions, I will gladly answer!
    Thank you in advance and have a nice day,
    Marc
     
  2. Sensacell

    Well-Known Member

    Jun 19, 2012
    1,128
    266
    The CD4051 is not suitable for the high-side driver, it cannot handle much current.

    At Vdd 5v Ron is 470 ohms typical- it's not a power switching device, it's for low power signals.
     
  3. melillo

    Thread Starter New Member

    Nov 15, 2010
    2
    0
    Thnak you very much Sensacell, I overlooked that parameter. A search a bit and came up with this new design, where I replaced the CD4051 by a 74HC138 and some PNP transistors. Does it make more sense?

    Thanks a lot and have a nice day!
    Marc
     
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