Re: [CAD_CAM_EDM_DRO] What size capacitor should I use?

Simon Arthur wrote:

>I was told this by my high school electronics teacher. I believe it was
>due to the fact that larger caps can't charge or discharge as quickly.
>So there's a break even point between too little capacitance and too much.
>
>Simon
>

Well - this is somewhat true, but you have to look at filter frequency
response to see the truth of the matter.

A capacitor is effectively an open circuit to low frequencies (DC), and
is a dead short for high frequencies. That's why you use a bypass cap
across sensitive electronics. The DC voltage sees an open circuit, and
higher frequency AC signals (noise) see a dead short to ground, so they
don't reach your sensitive electronics.

The capacitance determines what frequencies qualify as "high" or "low".
The higher the C value, the lower the frequency that sees an open
circuit, so a larger value cap will pass more high frequency noise than
a lower value. This isn't really "ripple" though - that's low
frequency, and will therefore be reduced by larger capacitors.

- Steve