Turn-off delay

Discussion in 'General Electronics Chat' started by Dritech, Mar 21, 2012.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Hi all,

    I want to delay the supply to the PIC and LCD be approx 5 seconds when the turn off switch is pressed. Is this possible to do when you have the turn off switch connected directly to the mains ? can this be done by using a capacitor? if yes what value to use and how to connect it?

    Thanks in advance.
     
  2. jimkeith

    Active Member

    Oct 26, 2011
    539
    99
    Yes, this is feasible--I have done things like this.
    The recommended location of the capacitor is at the output of the rectifier for linear regulators, or at the line voltage rectifier for switching regulators.
    The value may be calculated if enough information is known about load current and regulator head voltage etc. --otherwise it may be easily determined via experimentation.
     
    Dritech likes this.
  3. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Hi, thanks for the reply.
     
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