LM555 as variable frequency oscillator

Discussion in 'General Electronics Chat' started by xyz9915, Jun 16, 2009.

  1. xyz9915

    Thread Starter Member

    Feb 24, 2008
    23
    0
    Hello!
    I need a circuit in which the frequency of LM555 astable multivibrator can be controlled externally I mean by the help of transistor etc. So, please guide what modification may be done in the attached circuit
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    Pin 5 of the 555 os called CV (control voltage).
    When you put a resistor of 1K to that pin and give a voltage to the other side of the resistor, you can influence the triggerpoints of the 555.
    This will result in a frequency change controlled by tha applied voltage.

    Greetings,
    Bertus
     
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