A circuit for determining electrolytic capacitor polarity.

Thread Starter

mrmeval

Joined Jun 30, 2006
833
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.
 

SgtWookie

Joined Jul 17, 2007
22,210
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.
 

rwmoekoe

Joined Mar 1, 2007
172
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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