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555 timer pin 5

Harry
Expert 2920 points

I am trying to use one 555 timer to have a circuit that can change the duty cycle with no effect on the frequency using a Variable resister and also be able to change the frequency by a different variable resister which will have no effect on the duty cycle set. 

Would this  work?

I also  want t to know about the PIN 5 that not many uses.

Will i be able to fix another variable resister to give a variable voltage at the PIN 5 )control pin and expect the frequency to change with no effect on the Duty cycle already set by it?

  • 0
    TI__Guru**** 153916 points

    Isuru,

    The Duty cycle POT will not affect the output frequency but the Duty Cycle is affected by frequency setting. Also the minimum duty cycle is limited.
    Pin 5 voltage sets the threshold voltage on pin 6. The trigger threshold on pin 2 is always 1/2 of pin 6.

    To get independent frequency and duty cycle is best done in two stages. This circuit does this.

     

  • 0 in reply to Ron Michallick
    Expert 2920 points

    thank you. 

    smart thinking out of the box. Totally forgetting the o/p of the 555. and using the parasitical to trigger  something else. nice logic!