oscillator help

Discussion in 'The Projects Forum' started by mohit204, Nov 7, 2009.

  1. mohit204

    Thread Starter New Member

    Nov 7, 2009
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    hey,
    i am planning to do a witricity exp.I have designed a Colpitts oscillator using a normal BC107 transistor.I am getting my desired frequency(about 1 Mhz,allowed upto 15Mhz ,so frequency lying within the RF realm is not a problem),but the problem is that the output voltage and wattage of the oscillator are very very low.
    Is there any means by which i can increase the voltage and wattage of the oscillator without compromising on the frequency.
    Will replacing the normall colpitts by a crystal oscillator or a colpitts crystal oscillator be a wise idea,in terms of frequency stability as well as output voltage and wattage
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    I realise there has been a previous and particularly relevant comment about your intentions. If operating in the USA at an educational institution you apparently have to comply with these emission rules

    http://en.wikipedia.org/wiki/Part_15_(FCC_rules)

    I guess you can also work in the ISM band but I'm not sure of the restrictions that apply in that case.

    It's a big jump to transmit 60W starting from a small transistor oscillator - you'll need a substantial RF amplifier - probably not something you'll build without a good deal of experience behind you. Over what gap do you do you want to send this energy - mm's , cm's or meters ???? Is this part of formal coursework you are undertaking?
     
  3. mohit204

    Thread Starter New Member

    Nov 7, 2009
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    hey,
    I am allowed to work upto 15MHz.So the frequency isnt a problem.
    I am planning to amplify the signal that i get from the oscillator using a power amplifier of class C.the distance to be transmitted is a few cm's
     
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    I think it's worth pressing this point - by who's authority are you allowed? Spectrum regulators have the final authority and they will expect strict compliance within the rules laid down regarding RF emissions in a particular country.

    I'm also not sure what particular advantage there is to be gained in illuminating a 60W lamp. Why not start out small? - if you can illuminate a small incandescent torch globe over this range using the same principle, then you've demonstrated competency. I can remember doing this sort of thing many years ago using a vacuum tube based RF oscillator.

    Your Colpitts oscillator approach should work fine - you should be able to obtain reasonable short term frequency stability with attention to careful circuit layout and good shielding / housing.
     
  5. mohit204

    Thread Starter New Member

    Nov 7, 2009
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    hey,
    I am a student from India.I have already demonstrated witricity by lighting a LED.In the first experiment,i used a function generator to obtain a frequency of 169Khz.The LED lit at a maximum distance of 35cms.however,this time i plan to light a bulb using an oscillating circuit,followed by amplifying the signal from the oscillator.

    You mentioned using vaccum tubes in your model.I was wondering if using vaccum tubes in my oscillator,instead of using the normal transistor,would provide a better power output.Since,here not only are we concerned with the frequency ,but only obtaining sufficient power to transfer also seems to be a concern.
     
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