Connecting pulse output to piezo alarm

Discussion in 'The Projects Forum' started by ahfa, Jun 24, 2014.

  1. ahfa

    Thread Starter New Member

    Jun 24, 2014
    Dear all,

    I am mechanical engineer with no background to circuitry and electronics. I am trying to connect a flow switch ( using hall effect ,12 dc input) and I want it to trigger a piezo alarm (12V dc) when water flow stops.

    There are three wires from the flow switch, two for power and one for signal out. the signal out is pulse signal based on the flow. I need to know how to connect this pulse signal to piezo alarm so that alarm goes off when there is no flow.

    Any help would be much appreciated.

  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    i would use a pulses rectifier and op amp comparator like this.The op amp will go low on no pulses received, set the preset to the desired trigger level.
  3. wmodavis

    Well-Known Member

    Oct 23, 2010
    Or you could use a retriggerable monostable that would change output state when the output pulses from the flow meter stopped retriggering it.
  4. ahfa

    Thread Starter New Member

    Jun 24, 2014