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Author Topic: ESD protection ... what rating for capacitors? [solved]  (Read 798 times)
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Following on from this thread: http://arduino.cc/forum/index.php?topic=112404

I followed the link to:  http://www.sparkfun.com/products/10628

And then: http://www.sparkfun.com/datasheets/Widgets/MP3Trigger/vs10XXan_output.pdf

In that document it mentions putting in a 10 ohm resistor in series with a 10 nF capacitor, from left/right signals to ground, to suppress ESD.

What it doesn't mention is, what rating capacitors would you use there? Since you are trying to handle 8 KV ESD, I presume you don't try to find 8 KV capacitors. Would 50V do? Or am I missing something?
« Last Edit: June 30, 2012, 10:16:13 pm by Nick Gammon » Logged

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Following on from this thread: http://arduino.cc/forum/index.php?topic=112404

I followed the link to:  http://www.sparkfun.com/products/10628

And then: http://www.sparkfun.com/datasheets/Widgets/MP3Trigger/vs10XXan_output.pdf

In that document it mentions putting in a 10 ohm resistor in series with a 10 nF capacitor, from left/right signals to ground, to suppress ESD.

What it doesn't mention is, what rating capacitors would you use there? Since you are trying to handle 8 KV ESD, I presume you don't try to find 8 KV capacitors. Would 50V do? Or am I missing something?

Good question.

This led me to my own research, and this: http://www.ce-mag.com/archive/01/Spring/Lee.html and this: http://www.tdk.com/pdf/esdmodel.pdf and this: http://www.resistor.in/?q=ESD

I'm still chewing on this.

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You have to think in "charge" instead of "voltage".
A high voltage spike will be suppressed because it's charge will flow into the capacitor.
The voltage of the capacitor will probably not rise above 5V.
So a normal 10nF of 50V is okay.

I used a resistor and capacitor in series many times as spark-suppressors to prevent spark with relay contacts or with bells like these: http://www.gcsescience.com/pme6.htm. For the bells I used 47 ohm and 100nF.
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Would 50V do?
Yes, but even lower would work as well.

If you think about it, if it were a problem, capacitors would be subject to static handling damage like semiconductors and they are not are they.
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Thanks for the answers.

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... if it were a problem, capacitors would be subject to static handling damage like semiconductors ...

Good point.
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