Oscillator circuit of 2.7Mhz

Discussion in 'General Electronics Chat' started by sikafo, Jul 29, 2009.

  1. sikafo

    Thread Starter New Member

    Jul 29, 2009
    Hi everyone,

    I need help making an oscillator circuit of 2.7Mhz.
    Its used to make a piezo disc vibrate at its resonance frequency.
    The circuit i have currently gives out 1.6 Mhz,
    Does anyone know which values can i change to make this circuit give around 2.7Mhz?

    Thank you :)
  2. KL7AJ

    Senior Member

    Nov 4, 2008
    You will need a 2.7MHz crystal...it is what determines the frequency.
  3. davebee

    Well-Known Member

    Oct 22, 2008
    So what you want to do is have the piezo disc behave like a crystal?

    Where did you get the information that it's resonant frequency is 2.7 mHz?

    That seems very high; piezo discs I've seen are used in the audio range, more like 2.7 kHz, which would make more sense as a resonance value for a large, thick disc.
  4. sikafo

    Thread Starter New Member

    Jul 29, 2009
    I got the resonance frequency from the piezo datasheet.

    The piezo diameter is about 1.5 cm and height of 0.1cm which makes it small and i think that is why the resonance frequency is very high :)

    This circuit is used to make the piezo vibrate thus the need for the circuit which i have to give out 2.7Mhz :)

    The piezo is supposed to act as a pump to push out water from a small hole.
    In other words i want to make a small micro dispenser XD

    Thanks everyone for helping :)[​IMG]
    Last edited: Jul 31, 2009
  5. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    Where is the power input to the circuit - I'm guessing across the cap on the left?

    Other than the crystal, the tuning components appear to be the 68uH inductor and the two caps on the right, one being in series with the piezo so the effective value is unknown. It's a parallel tuned circuit as the cap on the left links them out at RF.

    Try reducing the values of the 47000 & 1800pf caps by about 30 - 50%?

    That should put the resonant frequency up somewhere near.
  6. 12189187

    New Member

    Jul 31, 2009
    Reduce the Cap value at left end of circuit or increase the turns on the coil.
    This may bend the crystal frequency up or not. Try it.
  7. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    The cap on the left appears to be power decoupling, it's massive compared to the others in the tuned area.

    To increase the frequency of a tuned circuit, you *decrease* the turns on the inductor (or reduce the values of the Tuning caps as I suggested above).