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reading capacitor value from code printed on it?

Discussion in 'Electronic Basics' started by Bill Christens-Barry, Aug 19, 2004.

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  1. I have a circuit board with a capacitor that needs replacing (it got
    burned when an adjacent triac went out). The capacitor is a small "bead"
    shape, and has the code:

    1C4
    ME5

    printed on it.

    I can't find anything on the web about this particular code format - can
    anyone help me figure out what its value and max voltage is?

    The circuit has another one of these capacitors, and I thought about
    pulling it and trying to test its value. My idea is to charge it up to a
    known voltage, and time how long it takes to discharge through a known
    resistor. My problem is that I don't know what the impedance of the DVM
    voltmeter is, and this will influence the discharge rate due to its
    parallel resistance. Any ideas on how to approach this? I guess I could
    do this experiment twice, using two different known resistor, and back
    out the meter resistance. Any better ideas? I don't have easy access to
    any good electronics bench equipment, so am looking for simple approach.

    BTW, I could post a digital closeup photo of the capacitor if that would
    help.

    Thanks.

    Bill Christens-Barry
     
  2. Any chance that it is actually 104 rather than 1C4 - if so, it may be
    an 0.1 uF capacitor - very common value for power supply bypass
    capacitors.




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  3. Best sugestion:
    Go buy a capacitance meter.

    Second best suggestion:
    Build an oscillator that make use of _one_ capacitor. It's important that
    you are able to calculate the oscillation frequens for that particular
    oscillator. You have an formula f = (r, c). Turn this into
    c = (f, r).
    Example: http://www.national.com/an/AN/AN-31.pdf page 8. The formula should
    be like this:
    T = 2 * R1 * C1 * ln( 1 + ( 2*R2/R3 ) ) ( T = 1/f )
    Turning the formula to calculate C:
    C1 = T / ( 2 * R1 * ln( 1 + ( 2*R2/R3 ) ) )

    Hope this helps : )


    Geir
     
  4. Yes, that turned out to be the answer! Careful inspection
    showed that some of the paint had chipped off.

    Thanks.
     
  5. Best sugestion:
    Go buy a capacitance meter.

    Second best suggestion:
    Build an oscillator that make use of _one_ capacitor. It's important that
    you are able to calculate the oscillation frequens for that particular
    oscillator. You have an formula f = (r, c). Turn this into
    c = (f, r).
    Example: http://www.national.com/an/AN/AN-31.pdf page 8. The formula should
    be like this:
    T = 2 * R1 * C1 * ln( 1 + ( 2*R2/R3 ) ) ( T = 1/f )
    Turning the formula to calculate C:
    C1 = T / ( 2 * R1 * ln( 1 + ( 2*R2/R3 ) ) )

    Hope this helps : )


    Geir

    Btw: This is second time i post this message. It doesn't show up in the
    news-group after the first time I posted it.
     
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