Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

AC frequency

  1. Jul 12, 2007 #1
    Hi, I'm technically a biologist so talk slowly!

    Can anyone tell me, or point me in the right direction of a resource, that explains how you can change the frequency of an input AC source? e.g. in a "lab-pack" power supply.

    Thanks very much,

  2. jcsd
  3. Jul 12, 2007 #2
    Can you be a bit more specific?

    Are you talking about a lab signal generator? If so do you want to know how it works or how to operate one? And what is the frequency range of your AC source?
  4. Jul 12, 2007 #3

    Yeah like a lab signal generator or anything similar. I'm just thinking conceptually how it works really. Presumably it must take a mains frequency e.g. 50 Hz, but has the ability to adjust the frequency eitherway (also presumably at the expense of the potential difference). I was just wondering what type of circuitry in a basic sense it uses to do that. Its probably a semi-conductor in modern units, but is there a "classical" way to do it?

  5. Jul 12, 2007 #4
    Just like any electronic device, take the AC 50/60 Hz power from the wall outlet and converts it to DC voltage.

    So now you have a DC voltage converted from wall's AC and now can do the fancy stuff.

    There is thousands of different oscillator designs frankly, but the principle is the same.

    Need to have a resonator element. That's something that will actually oscillate when excited with an electric current, but will die down really quick.

    Then you need an amplifier that will amplify the resonator and feed some of its output back to the resonator in phase, such that the resonator will oscillate indefinitely.

    To change the frequency, you would have to adjust the resonator. There is thousands of different resonator concepts out there. The most basic one is an LC tank. Composed of capacitor and inductor. By changing its values the tank will oscillator at different frequencies.

    The amplifier is now made of transistors. The "classic" were the vacuum tubes amplifiers, big and expensive.

  6. Jul 12, 2007 #5
    Perfect, exactly what I wanted! Thank you!:smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook