Power Source

Discussion in 'The Projects Forum' started by robotkid249, Jul 31, 2009.

  1. robotkid249

    Thread Starter Member

    Mar 18, 2009
    24
    0
    Hello, I have a circuit to power "stuff" at about 12VDC, but it fluctuates at 150 kHz, and won't really power much because it is oscialtting. So, my question is: How do I turn the 150 kHz to 0, so I can power my projects.
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Post the circuit and more information about the output signal.
     
  3. yourownfree

    Active Member

    Jul 16, 2008
    89
    0
    you must have a switching power supply, the reason for the frequency.
    Probably just not big enough to power your project.If you stop it from working "zero" you will have nothing "zero". The only other way I can think of is to hook up a big electrolytic capacitor to it or hook up a voltage regulator then an electrolytic capacitor to smooth it out so there is no hum. It wold be nice as stated to see your diagram or block diagram to see what you are up to.
     
  4. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    Add a big cap or a rechargable battery after a diode. The battery need not be working , but will act as a capacitor..
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You really do need to post a schematic of your supply.

    I suggest that you need a relatively small amount of capacitance at the output of the regulator. A 0.1uF ceramic or poly cap and a 10uF electrolytic cap in parallel should take care of most (if not all) of that 150kHz noise. Both capacitors should have a rating of at least twice your supply voltage, or 2*12 = 24v. Using a really large cap on the output isn't a good idea, as a sudden transient in the circuit being powered will drain the cap, and may result in the power supply being "folded back", or shut down temporarily (reduced current) until the output capacitor is charged back up.

    Regulators such as the LM317 and 7812 really do need a small amount of capacitance at the output for good stability. While many regulators may not oscillate, some will under certain conditions.

    Lengths of wires does make a difference. If the input wires to your regulator are more than a few inches long, you'll need to add a cap to the regulator across the input to ground, somewhere between 0.1uF and 10uF.
     
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