e-licktronic Forum

So I've just started my build tonight and have run into some confusing issues. I've started the power supply and the online instructions call for a 680uf 35v electrolytic capacitor but the one in the mouser BOM is a 680 25v. Does this make a difference? Also when moving to the main board part of the power supply build it calls for 100uf 10v Electrolytic capacitors in the online manual but the mouser BOM has them at 100uf 6.3v...This has my novice ass very confused. Why would you put together a mouser BOM that contains different parts then what you have stated in your online build instructions?

The voltage part of the spec is just how much voltage the capacitor can withstand. Capacitor aging for electrolytic types is also determined by voltage and temperature.

As long as it's the same capacitance, the rest is less important in general. As long as the part fits physically it could be 63V, 100V whatever. If we suppose +12V in, there's still a very good margin even with the substitute part. Without checking the schematic, the low voltage one could be in a +5V circuit, or even be exposed to lower voltages.

Other things to look at for capacitors are ESR - equivalent series resistance, which you generally want to be as low as possible, and the tolerance which should be as tight as possible where it's critical - ie VCF circuits. In most cases such as power filtering and IC decoupling the tolerance is not that critical at all.

Check Wikipedia, as well as other DIY pages about capacitors, when to use which type etc. In this case the change shouldn't be a problem.