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05-05-2023, 06:38 PM
Hi Guys
What you see there is one of the effects of the imperfections of capacitors, especially of electrolytics which are pretty far from ideal as you get while still having a "decent" capacitor.
People think that a capacitor will hold a charge forever once the power is removed and there is no load. This is not the case. Maybe it should be, but real world assemblies are imperfect. Charge gets "trapped" in electrolytic dielectrics and redistributes itself after power is removed exhibiting the roller coaster voltages you saw.
"Super caps" with around a Farad of capacitance have optimised imperfection allowing them to be used as an alternative to a backup battery for digital circuit. Typically the drain is at the microamp level when in standby, so the device, say a VCR, will "remember" the setting used last time.
What you see there is one of the effects of the imperfections of capacitors, especially of electrolytics which are pretty far from ideal as you get while still having a "decent" capacitor.
People think that a capacitor will hold a charge forever once the power is removed and there is no load. This is not the case. Maybe it should be, but real world assemblies are imperfect. Charge gets "trapped" in electrolytic dielectrics and redistributes itself after power is removed exhibiting the roller coaster voltages you saw.
"Super caps" with around a Farad of capacitance have optimised imperfection allowing them to be used as an alternative to a backup battery for digital circuit. Typically the drain is at the microamp level when in standby, so the device, say a VCR, will "remember" the setting used last time.
