Safety Capacitor

[Yevgenip]

Hello...
I've seen a cap being put in parallel with a switch's connectors to insure that the spark resulting from the switch would not damage the delicate components. My question is: How do I know what capacitor to use? i.e. What Voltage and Capacitance?

Thanks.

 

[ante1]

Hi Yevgeni,

A cap paralleled with a switch is supposed to protect the switch contacts from arcing. 8)

 

[EnigmaOne]

This is an old (dates back to some time in the 1930's) technique of quenching switch contacts to protect them from arcing, pitting and poor service life.

Most generally, I've seen 0.1uF, ceramic disc capacitors used across the contacts of 120VAC power switches, with working voltage ratings from 250V to 1000V; which leads me to believe that anything over the peak voltage of the switched circuit will work just fine.

 

[ante1]

Hi Enigma,

So you are that old? Just kidding! To add to this, DC is always more harmful to the contact surfaces than AC and in some cases there are also

 

[EnigmaOne]

Definitely not that old!

Some of my favorite vintage equipment definitley dates back to the 30's and 40's; which gave me exposure to the engineering of that era.

...and I certainly forgot about DC switches arcing too.

 

[ante1]

Excuses, excuses! Vintage equipment, sure! ;D

 

[EnigmaOne]

I'd resort to the lame, "fine wine" remark, and beat you with my cane; but my momma taught me to always respect my elders. ::: fleeing because I still can :::

 

[ante1]

I can relate to the

 

[Yevgenip]

Thanks guys.

Now I know I don't even need that capacitor because my switch doesn't need protection - my circuit does.

Thanks.