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I have a small DC motor acting as a generator, spinning at 500RPM. From it, I get 1V with ½V ripple, which a 1000uF electrolytic capacitor smooths nicely.

I may wish to drive the motor in reverse, getting -1V.

To do smoothing in either situation I'd need a 1000uF unpolarised capacitor, which as far as I know you can't get.

Is there another way?

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    \$\begingroup\$ Is rectifying the output current an option? \$\endgroup\$
    – Marcus Müller
    Commented Apr 22 at 12:22
  • \$\begingroup\$ you could use the non-polarised connection of two 2000uF in antiseries \$\endgroup\$
    – Neil_UK
    Commented Apr 22 at 12:43
  • \$\begingroup\$ 1000 uF non-polarized capacitors DO exist, just Google it. They may be pricey, but they are available. @Neil_UK's suggestion will also work, as would rectifying output (though with only 1 V to work with that might not be desirable.) \$\endgroup\$
    – John D
    Commented Apr 22 at 16:01
  • \$\begingroup\$ Thanks. I will look for unpolarised caps. Also, I'll try +- -+ electrolytics - will that definitely be ok? Won't one of them always be under reverse polarity? I won't do rectification, though - I want the positive and negative! \$\endgroup\$
    – GrahamRounce
    Commented Apr 22 at 17:26
  • \$\begingroup\$ The +--+ electrolytics, shunt each capacitor with a schottky diode. That will limit the reverse voltage across each to -0.3 V, probably safe. They will rectify the AC to bias the centre terminal. If you have a bias supply available, or a small battery to hand, bias the middle terminal through a high value resistor to guarantee that each cap only sees the correct polarity. \$\endgroup\$
    – Neil_UK
    Commented Apr 22 at 19:56

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