capacitor informtion

Experience....Text books, also some of the decent catalogues give info as to typical applications, e.g Farnell, RS.

A couple of examples
Typically Electrolytics for smoothing in power supplies and decoupling audio signals say 100s to 1000s of uF. Ceramics for decoupling higher frequencies in 5v supplies typically 0.1uF 0.01uF. Polyester for other stuff timing caps...?

Often circuit values aren't too critical except for say a few components which set gains, frequencies or timings. Electrolytics are often +/-20% many other caps are =/-10%. Take care with voltage ratings on electrolytics go at least 50% over what you 'need'. Also any capacitors going on mains voltages must be specially rated (X or Y rated...the catalogues explain this).
Hope this helps...Ask something more specific if you want more help.

Del

...one other consideration: polarized and non-polarized, ie:

polarized = DC-voltage, with specifically marked "+" and "-" terminals, as used in uni-polar applications: filtering, intergrating, etc..

non-polarized = AC-voltage, with no specific "+/-" terminals, as used in bi-polar applications: coupling, differentiation, etc..

Hello Bill 500

You ask a question which would require the equivalent of many pages of a textbook to respond properly.

If you advise the "certain situation" you intend, then it may be possible to assist you.

Because "situations" vary in their specifics, there are many variables.

Reply here, with

Kind Regards....

Thank you for the reply. I rebuild old Lucas motorcycle magnetos. Because they have a rotating armature the capacitor must fit inside the armature housing. I didn't explain any details on my initial visit because I wasn't sure what expect. I have tried to gain information from the major magneto manufactures, but get very little help. And maybe I agree with them, I may be reluctant to give away information that took many years aquire too... With that said maybe I'm still out in the cold? I've been rebuilding these magnetos for approx. 7 years now. I have the armatures re-wound and I do the rest. I capacitors I use have been recommended by other rebuilders, but they are sometimes hard to get and the prices are rediculous! Even with the recommended capacitors I still experience failures, that's why I would like to have a little better knowldege of what I really need. I've been lucky they have failed on my test bench and not after I've shipped them off. I have used several types of capacitors; but I'm not familiar enough to know the exact difference. The values are 630v .22UF. I guess my question would be what "Type" of capacitor would be correct for a magneto application and how do I determine if this value is correct? Thanks for all your help! One other quick question, what is the difference in UF or a PF micro farad rating?

Bill

Hello Bill 500

The value of 630v 0.22μF for the early Lucas magnetos is correct.

These were normally paper insulated inside a metal can type.

I had an early BSA motorcycle, which had this capacitor fitted, and repaired others which used the same capacitor (We called them "condensers" in those days).

Equivalents: 1 Farad = 1,000,000μF (microfarad) = 1000000000000pF(picofarad)

A useful weblink for equivalents is here: http://online.unitconverterpro.com/unit-conversion/convert-alpha/convert.php?cat=capacitance

Note: the above weblink places you directly on the "Capacitance" page.

Hope that assists you.

Kind Regards....

Thank you, I will check the web page. Also appreciate the definition of the Farad!

Thank you for the reply! I have used polyester film type and mylar metalized film type. Both have given fair results, but both have failed. Unfortunately the only paper-in-oil can type are to big to fit the space. When the magneto starts to fail, the points will start to increase arcing and then skip fire. This is done on my test bench firing spark plugs under pressure. Thanks again for your help