30 second - 5 minute pulse generator

Discussion in 'The Projects Forum' started by zumdar, Feb 2, 2014.

  1. zumdar

    Thread Starter New Member

    Feb 2, 2014
    1
    0
    Hello! I am new to the forums so greetings and thank you for reading this and any help you can provide!

    So, I am trying to build a pulse generator to send half second, ~6V pulses to a small fan that blows into windchimes, creating a pleasant chime every so often.

    I would like to make it variable by potentiometer to blow at minimum once every 30 seconds and at most around once every 5 minutes. I have been looking into using a 555 in monostable mode, but all my calculations end up with me having a R1 value of around negative 50k ohms:confused:. I am pretty new to this so bare with me.. Is it even possible for the 555 to oscillate at rates this low? Thank you for any help you can provide!!!

    -William
     
  2. pwdixon

    Member

    Oct 11, 2012
    488
    56
    I haven't used a 555 for years but I would think that this is possible using a CMOS 555.
     
  3. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    Yes you can use 555 to generate such time periods but it won't be tht accurate.

    Try to build one and use a LED to monitor the ouput. You are gonna need a fairly large capacitor to time 5 minutes
     
  4. ScottWang

    Moderator

    Aug 23, 2012
    4,854
    767
    google "555 cmos timer 30 minute".
     
  5. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    397
    R-C time, 1 meg & 200 uF, discharge , pin 6 to pin 7, 150 K. Fan VCC to pin 3.
     
  6. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    That takes care of the 5 minutes.

    What are you planning for an output relay or 1/2sec delay off?
     
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