24 hour countdown timer with 1 hour warning

Discussion in 'The Projects Forum' started by badboydano, Mar 6, 2011.

  1. badboydano

    Thread Starter New Member

    Mar 4, 2011
    I'm using a MX073 as a 24 hour count down timer.
    When there is 1 hour left, I want a warning signal to commence.
    At 59 minutes 59 seconds, digit 6 is blank and digit 5 is a zero.
    I have a logic cct that goes high when digit 6 is blank.
    I have a logic cct that goes high when digit 5 is a zero.
    Now I need a logic cct that goes high when both conditions are true.
    I think that the problem I face is this:
    These conditions do not exist at the same time.
    I think that digit 6 turns on then off and then digit 5 turns on then off.
    I think that I have to find a way of "slowing" digit 6 down so that it happens the same time as digit 5.
    I have attached cct diagrams to help explain.
    I think that I can use an RC cct to slow (delay) it.
    But I don't know how long to delay it for.
    I think that it is maybe 1 clock cycle.
    Does anyone know how long a clock cycle might be in an ATMEG8?
    I don't have access to an ohh-silly-scope.
    I don't know if it is using it's own internal clock cycle or "borrowing"
    one from it's DS1307 buddy.
    Any thoughts, anyone?
    Thanks, Badboydano