555 Timer help

Discussion in 'General Electronics Chat' started by Danno., Jul 28, 2015.

  1. Danno.

    Thread Starter Member

    Apr 6, 2015
    39
    1
    Hi,

    I am trying to work out exactly what this timer is functioning as, it is part of a CPU reset circuit. Pin 7 is not connected so I cannot work out how the C1 discharges, in normal operation when power is applied 5v is present and 12Vdc is present on terminal H3 which operates the relay. The function of terminal F15 is unkown.

    Could somebody shed some light onto what's going on please, is it monostable, astable or other?

    Thanks
    Dan
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,795
    951
    It looks to me it is functioning as a 5 volt watchdog reset.
     
  3. Danno.

    Thread Starter Member

    Apr 6, 2015
    39
    1
    Could you elaborate more please?
     
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