555 or op amp design?

Discussion in 'The Projects Forum' started by idmiller, Jul 4, 2014.

  1. idmiller

    Thread Starter New Member

    Jun 16, 2013
    I am wondering which is more effective. The circuit would use 1 pot to change a pulse from 1hz to (60-120hz). The circuits I have built require a large range to be able to do this. An example is it takes 1/2 turn of the pot to go from 1hz to 1.5hz then 1/4 of the turn to go from 1.5hz to 20hz and the remainder from 20 to 60 quite rapidly. Outside of using a pic to register the pot and change the value accordingly can this be done?
  2. wayneh


    Sep 9, 2010
    A standard 555 circuit is the way to go. You may want to tailor your pot is it's not giving you the control you want. See the links here.
  3. k7elp60

    Distinguished Member

    Nov 4, 2008
    Have you tried using a multiturn pot?
    Last edited: Jul 6, 2014
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
    It sounds like you are using a linear pot. You should use a log taper (audio taper) pot. Your control of rotation vs. frequency will be much smoother.
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    But he wants a log freq effect?

    A linear pot on a 555 gives linear period change, which is log freq change. A standard 555 circuit and linear pot should get pretty close to his desired spec.
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    Are you saying that is a disadvantage of circuits you have tried, or is it the response you actually want? Do you want a linear frequency response to pot variation, i.e 1/4 rotation gives 30Hz, 1/2 gives 60Hz, .... ?