line follower doubt: pull up resistors

Discussion in 'The Projects Forum' started by hinduja.prasad, Mar 11, 2009.

  1. hinduja.prasad

    Thread Starter New Member

    Mar 11, 2009
    i am using a AT89S51 M.C i have heard of sumthing called pull up resistors......... wat exactly r these pull up resistors? wat r it's functions? how shld i connect them to the microcontroler???? and yes pls note that i am not using a H-BRIDGE. just d LM324 COMPARATOR AND L293D MOTOR DRIVER............
    PLSSSSSS reply soon..........:)
  2. SgtWookie


    Jul 17, 2007
    Pull-up resistors provide a source of current. They are normally used in open-drain and open-collector circuits.

    Why don't you post a schematic diagram of what you have designed thus far, so that we might be able to determine whether or not they may be necessary?

    The LM324 is not a comparator; it is an operational amplifier, also known as an "opamp" for short. Many comparators have open collector outputs; they require pull-up resistors.

    The L293D is a 4-channel push-pull driver.

    Before we can suggest a course of action, we need to see your schematic.