15 minute timer latching

Discussion in 'The Projects Forum' started by Planetping, Feb 8, 2016.

  1. Planetping

    Thread Starter New Member

    Feb 1, 2016
    3
    0
    Hi!

    I need to build a timer circuit that allows a powered microphone to go live for 15 minutes when a momentary switch is pushed. An led indicator is also required to light for the 15 minute duration.

    I am thinking a 555 monostable design connnected to the positive side of the mic/led power. Tried a few configurations but could do with a working prototype ASAP!!

    Thanks in advance

    PP
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,979
    744
    Last edited: Feb 8, 2016
    Johann likes this.
  3. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,282
    1,236
    What voltage goes to the microphone?
     
  4. Planetping

    Thread Starter New Member

    Feb 1, 2016
    3
    0
    12v . It's being fitted to a vehicle.
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,528
    1,248
    Lotsa timer modules on ebay, some with digital setpoints and a display. What is the microphone current draw at 12 V? Also, do you really need to switch power to the mic, or just enable/disable its output?

    ak
     
  6. Planetping

    Thread Starter New Member

    Feb 1, 2016
    3
    0
    switching the output is and option as long as an indicator led can also be switched. Looking like I may need 100's of these so the easier to make the better!
     
  7. dannyf

    Well-Known Member

    Sep 13, 2015
    1,780
    360
    Putting the input signal isuch easier. A cmos 555 can do it easily. A mcu is cheaper and has a lower part count.
     
  8. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,979
    744
    Switching the output is easy, mosfet or relay, you haven't said which timer you're using, if its for mass production then a pic or other tiny microcontroller is best, forget the 555 timer its useless.
     
    Johann likes this.
  9. Picbuster

    Member

    Dec 2, 2013
    374
    50
    Dodydave, you speak pic the best language in electronics. Second to none.
    the 555 timer is..... well you said this lately.
     
    Dodgydave likes this.
  10. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,528
    1,248
    IF the OP has a PIC programmer
    AND IF he is fluent in PIC assembler OR PIC Basic OR C++
    THEN the cost of clean regulated power for the PIC still has to be figured into the budget.

    While this application might be beyond the reach of a 555, there are other timer solutions. I think a dedicated 4060 + 4093 design could compete even without the PIC's programming overhead.

    Here is the original form:

    I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail.
    - Abraham Maslow, The Psychology of Science: A Reconnaissance (1966), Ch. 2, p. 15.

    ak
     
    Johann likes this.
Loading...