PIC Powering LEDs

Discussion in 'The Projects Forum' started by qZanity, Feb 4, 2014.

  1. qZanity

    Thread Starter New Member

    Feb 2, 2014
    Okay I have 2 projects that I need to complete.

    In my first project I have 10 super
    Bright LEDs, all I need to do is make a chaser which means only 1 LED is powered on at any single time. Using Charlieplexing. Is it okay to drive the leds directly from the pic chip?

    Now in the other project I must power around 10 LEDs, but they will all be on at the same time, I'm using the pic to make them flash etc. so what's the best way to drive a large number of LEDs from a pic?
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Check the data sheet for the current in/out of a pin, it's typically 25mA per pin, and 200-250 total per device. Personally, I try to limit it to no more then 10 mA per pin to limit the voltage drop (rise).

    No way to say can you do this as I don't know what your LED needs but sounds like you need buffers, and hefty bi directional buffers to do charliplexing; I have no source for those.

    There's some nice drivers that work well, look up numbers in this series: UNL2003 UNL2004 UNL2008.
  3. t06afre

    AAC Fanatic!

    May 11, 2009
    It will depend on LED. What is your typical LED current?
  4. qZanity

    Thread Starter New Member

    Feb 2, 2014
    The max forward current rating on the LED's are 30mA
  5. BobTPH

    Active Member

    Jun 5, 2013
    I made a pin / ornament in the shape of a star using a 44-pin PIC. It has 31 superbright LEDs which I drove directly from a PIC pin each. At 1mA they were plenty bright and well below the limits for the PIC.

    qZanity likes this.