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Where can I learn more about capacitors?

One of the things that still baffle me today is when to use and how to select the correct capacitor.

I've read through this chapter about capacitors: http://www.allaboutcircuits.com/vol_1/chpt_13/index.html

Afterwards I feel I undestand how they work, but still don't have the two most basic questions answered: 

  • When do you need to add use a capacitor? (signal smoothing, power storage)
  • How do you select the correct capacitor? (how many Farads should it be for my application?)

Can somebody point me to a good explanation or resource online?  Maybe somebody could write a blog entry or walkthrough about this.

 Thanks!
 

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GroG's picture

Wikipedia always has something - they have decoupling or bypass too.

Now in a humbly simplistic way, I like to think of capacitors as little fast acting batteries. For example, if all your current goes away suddenly - the cap will try to compensate by releasing its current too.

Or, preferrably I think of them as little pools of water... when all your water goes down the drain, the little pools drain out too, and will try and compensate....

One common use of caps are filtering and tank circuits .. going along with the previous analogy, if you ever poke a slow moving stream you'll notice little waves, if you connect it to a pool of water and poke some more you'll notice changes in the frequency.

So in a nutshell caps are often used to supress or enhance certain frequency.
Large electric motors sometime use them to start.
Big caps you have to be careful with - you may have turned off all the power or uplugged the device - but a cap will hold onto its charge until something (possibly you) discharge it (youch).
I've used them to build a tesla coil (high frequency) and attached a french horn player, this was for sadistic fun :)

oh - for the values - i never remember and have to look them up each time ... or i don't care and try something convienent

jka's picture
This page: http://www.uoguelph.ca/~antoon/gadgets/caps/caps.html has a lot of info on capacitors. I havn't read it all but it looks like it's got all the info you will ever need on caps.
jgillick's picture
Thanks, that was a really good read.  Does anyboy have other resources as well?  I'm trying to learn all I can one topic at a time.
BaseOverApex's picture
Have you found out what "decoupling" means yet? It's something that's been hounding me for a while!
jgillick's picture
I haven't yet.  I still feel like I know very little about capacitors and when/how to choose the correct one.