Power cut-off delay after release.

Discussion in 'The Projects Forum' started by Slava Thereshin, May 16, 2016.

  1. Slava Thereshin

    Thread Starter New Member

    May 16, 2016
    Good day.

    After spending some time in the search section I didn't find any leads, so I ask for your help.

    I have a simple circuit with lipo battery, motor and a microswitch.
    I want to design a second, monostable circuit that will detect current in the main circuit and activate a 5v motor, and after the main circuit cuts off, run the 5v motor for 4 more seconds.
    If the main circuit re-engeges during the 4 second period, the 5v motor should continue to run until main circuit disengages again, and again run for 4 more seconds.
    The second circuit is powered by a 9v battery and a 7805 voltage regulator.
    The main circuit has a very large inrush current, around 90A+, with variable voltage of between 11v and 15v.

    I tried to make a one-shot 555 circuit with no luck, and have no idea how to tap into high current circuit.

    So I ask for your advice, can anyone assist?
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    Start by posting a circuit diagram of what you have, what inrush current supply is it, to detect current you need a series resistor with op amp sensor, or transistor or current transformer.
  3. dl324

    AAC Fanatic!

    Mar 30, 2015
    Do you require electrical isolation between the two circuits? Does the first motor have a switch that's accessible as a trigger for the second motor?