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
    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!!!

  2. pwdixon


    Oct 11, 2012
    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
    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


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

    AAC Fanatic!

    Aug 7, 2008
    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
    That takes care of the 5 minutes.

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