Matt, As far as I know, the effect you mention cannot produce a higher voltage than the capacitor was charged to recently. Sean On Mon, Oct 22, 2018, 7:20 AM Matthew Miller wrote: > You're seeing an effect called "bounce back". This commonly occurs > with high voltage caps. > Putting a 1M resistor across the cap will help with the safety here. > Lots of info in the answers to the stackexchange question: > > https://electronics.stackexchange.com/questions/282972/capacitor-gaining-= voltage-over-time > > Take care. > On Sun, Oct 21, 2018 at 6:04 AM Manu Abraham > wrote: > > > > Hi, > > > > I did not forget to put the sq brackets this time, Bob . :-) > > > > Not a query, but tripped on this one, wondered for a while, later on > > alone realization dawned. > > Thought about sharing this one on the list. > > > > Have a 230V/12-0-12 CT transformer, of which 0 &12 connected to a > > Bridge rectifier, the output of which is smoothed out by a 680uF/200V > > capacitor, providing about 16VDC (12 x 1.4142). The power supply > > worked well and good enough. > > > > The transformer was left connected to the mains for a while, in absent > > minded mode of operation. A few days later, just before wanting to > > test a small board measured the voltage on the power supply, saw it > > was about 80V. > > > > Sat in thoughts for about an hour what was wrong, thought maybe the > > transformer windings had sprung a leak. Thought about it for a moment, > > then thought probably the capacitor was getting charged due to no > > load. > > > > Discharged the capacitor with a huge spark. Things pretty much settled > down. > > > > At least thoughts burned up a few hours, where that 80Vdc was coming > from. > > After that, sat back and laughed at myself. > > > > Cheers, > > Manu > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .