> Would, for testing purposes, two or three of the same capacitance in series do? nope; put two of three of what you've got in there already in, in parallel, t

> Would, for testing purposes, two or three of the same capacitance in series do? nope; put two of three of what you've got in there already in, in parallel, that's how you sum capacitance. (internally they're huge plates held apart from each just the tiniest little bit, with capacitance =~ surface area. more caps in parallel makes more surface area, so more capacitance). if we were using ideal capacitors, nicwilson's suggestion would be be fine. non-ideal caps have ESR, though, which will burn up some of the power we want to feed into the microcontroller if/when it tries to draw too much. paralleling caps lowers the effective ESR of the lump of capacitors capacitor. > I'll see if I can find another motherboard with a PS/2 port. there are also actual ps/2 to usb converters available as well. (not the little dongles that came with keyboards; those were just for keyboards that knew both protocols and needed physical conversion.) something like https://www.amazon.com/TRENDnet-Converter-Universal-10-4-10-9-TU-PS2/dp/B0007T27HI/ https://www.amazon.com/TRENDnet-Converter-Universal-10-4-10-... is probably just smart enough to perform the conversion, but not smart enough to limit the power going to the keyboard, so i bet you can pull 500mA through it, a fair bit more than the 275mA guaranteed to ps/2 keyboards.