A circuit for determining electrolytic capacitor polarity.

Discussion in 'General Electronics Chat' started by mrmeval, Feb 25, 2008.

  1. mrmeval

    Thread Starter Distinguished Member

    Jun 30, 2006
    833
    2
    I have a problem at work where the polarity on capacitors is mismarked. I'd like to find a way to test if the polarity is wrong non-destructively. This would be out of circuit.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Check out this PDF document that Sencor put out regarding testing non-polarized electrolytics using their Z-meter:
    www.sencore.com/custsup/pdf/TT139.pdf
    The equivalent representation of polarized vs nonpolarized electrolytics is illuminating.

    Have a read here for a "quick and dirty" test:
    http://www.piclist.com/techref/caps.htm

    If you don't have an NE566/SE566 handy (they're getting scarce, Electronic Goldmine has run out), you might try using a single CMOS 4093 NAND gate as an oscillator. You could use the remaining three gates to drive a small speaker or the like.
     
  3. rwmoekoe

    Active Member

    Mar 1, 2007
    172
    0
    fill the cap with a small voltage, say 1 volt or so, test the voltage drop in 10 seconds or so. test it in both polarity. the least voltage drop is the right polarity.
     
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