Wednesday 8 February 2012

555 Timer Voltage Controlled Oscillator Circuit

555 Timer Voltage Controlled Oscillator Circuit

This is a circuit of a voltage-controlled oscillator (VCO) that uses the 555 timer IC as the main component. As expected, the 555 timer is configured as an astable multi vibrator to be able to serve as an oscillator. An astable multi vibrator is just a timing circuit whose output oscillates between 'low' and 'high' continuously, in effect generating a train of pulses. This is the figure of the circuit;


The difference of this circuit with the basic 555 astable circuit is that its 555's pin 5 is tied to an external voltage source.  Pin 5 is the 555's control voltage pin, which allows the user to directly adjust the threshold voltages to which the pin 2/pin 6 input voltages are compared by the 555's internal comparators.  Since the outputs of these comparators control the internal flip-flop that toggles the output of the 555, adjusting the pin 5 control voltage also adjusts the frequency at which the 555 toggles its output. Increasing the input voltage at pin 5 decreases the output oscillation frequency while decreasing the input voltage increases the output oscillation frequency.

11 comments:

  1. Whats Taking place i am new to this, I stumbled upon this I have found It absolutely helpful and it has helped me out loads. I am hoping to give a contribution & assist different customers like its helped me. Great job.
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    Replies
    1. Dear sir

      could you pl send a automatic water level control circuits with ic 555.2 transisters.level up-down controll.
      by
      yours truly
      mallesh.e mail : mallesh1977@gmail.com

      Delete
  2. hai my name is aseem here i find an error here the output is square wave pulse that means the output is varing 0 to 1 so the output is dc.the loud speaker does not gives real sound .here the ls gives only the huming so use a coupling capacitor series to the ls .if you need any thing in electronics visit and follow my blog www.freecircuits4u.blogspot.com

    ReplyDelete
    Replies
    1. Dear sir

      could you pl send a automatic water level control circuits with ic 555.2 transisters.level up-down controll.
      by
      yours truly
      mallesh.e mail : mallesh1977@gmail.com

      Delete
  3. hello all

    can i use 555timer as a VCO for frequency range (925MHz to 970MHz) and (1785 to 1900MHz)
    i need it in GSM jammer. other VCO'S are expensive so i want to use 555timer as vco.
    please help me out i will be very thankfull to you.
    thanks alot


    ghandal.khan@gmail.com

    ReplyDelete
    Replies
    1. Dear sir

      could you pl send a automatic water level control circuits with ic 555.2 transisters.level up-down controll.
      by
      yours truly
      mallesh.e mail : mallesh1977@gmail.com

      Delete
  4. The 555 timer will work to 100KHz. It will not work much above certainly at mobile phone frequencies as a jammer.

    ReplyDelete
    Replies
    1. Dear sir

      could you pl send a automatic water level control circuits with ic 555.2 transisters.level up-down controll.
      by
      yours truly
      mallesh.e mail : mallesh1977@gmail.com

      Delete
  5. is there any formula to adjust frequency between 11khz to 58khz in 555 as vco?

    ReplyDelete
  6. Dear sir

    could you pl send a automatic water level control circuits with ic 555.2 transisters.level up-down controll.
    by
    yours truly
    mallesh.e mail : mallesh1977@gmail.com

    ReplyDelete
  7. how does it work??

    ReplyDelete