Programming pic voltages

Discussion in 'Embedded Systems and Microcontrollers' started by FFtravism, Mar 31, 2009.

  1. FFtravism

    Thread Starter Active Member

    Aug 21, 2008
    I a building a flashing led circuit. I have a PIC16F88 that drives a set of leds. I am working on the resistors to use. Using with 5.5v source. 2.2v forward led with 20ma it says 1x 56ohm resistor for each 2 LEDS. That means for a led light bar with say 100 leds atleast 50 resistors. If I could use a higher voltage say 10v or 12v I could use 4 LEDs with a 180ohm resistor. But I am limited by the PIC. I am using the Kit 149bc pic programer. Is there a pic I can use that will support higher voltages or and I stuck using the PIC16f88?
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    To save a lot of time and frustration, I'd suggest a PicKit 2, $35 from Microchip, $49 with the dev board.

    Not only is it a very speedy USB programmer, but it doubles as a logic analyzer (with windows software, adjustable triggers), and a USART diagnostic tool!
  3. SgtWookie


    Jul 17, 2007
    I suggest that you don't attempt to drive a large number of LEDs directly by the PIC.

    Instead, use driver IC's like a ULN2003 or ULN2803. Respectively, they have seven or eight Darlington pairs internally, can handle up to 50v on the collectors, up to 500mA current per output, have internal 2.7k base current limiting resistors, and have internal diodes to protect against reverse EMF.

    One ULN2803 will handle an entire port, RA thru RD. ULN2003's are a good bit less expensive right now though, so if you don't mind doing a bit of extra routing on the PCB layout, you'll be penny wise. These peripheral IC's are really easy to use. They can only sink current though, they can't source it - so if you were thinking of Charlieplexing, they won't work for that.
  4. russ_hensel

    Well-Known Member

    Jan 11, 2009
    ULN2003 or ULN2803 are "low side switches" for row column drive or charlie also consider UDN2981A thru UDN2984A which are "high side switches"