where can I get a "PCB spark gap" device?

Logicnibble schrieb:

I want to add PCB spark gaps to my project in order to protect against

ESD (also add varistors, etc).

 

I've seen an example on this site:

http://www.airborn.com.au/method/sparkgap.html

 

Have anyone used anything similar?

Are there any device in any library available for eagle?

If you really want to use such, simply draw them they way you like.

However, such "spark gaps" have been extensively discussed - and

opinions on them range from "better than nothing" to "pure nonsense".

The problems are:

- You need some minimum distance to avoid unwanted shorts during PCB

  production;

- The PCB production process always has some tolerances - taking these

  into account you finally get gap lengths that vary at about 1:3 or

  even 1:4.

- Given these large tolerances, you can never predict the sparking

  voltage by any means, or to a tolerable voltage.

- Additionally, since you need to leave the contacts uncovered from

  solder stop mask, you get environmental influence which further

  increases tolerances, regarding to spark ignition voltage.

- Finally, dirt, humidity and other residues will be collected on the

  blank surfaces and eventually raise more serious problems than they

  were intended to protect against.

My personal conclusion: They are not worth the time to draw them. If you

need spark gaps, get them as components.

Tilmann

Tilmann Reh wrote:

Logicnibble schrieb:

 

I want to add PCB spark gaps to my project in order to protect against

ESD (also add varistors, etc).

 

I've seen an example on this site:

http://www.airborn.com.au/method/sparkgap.html

 

Have anyone used anything similar?

Are there any device in any library available for eagle?

 

If you really want to use such, simply draw them they way you like.

 

However, such "spark gaps" have been extensively discussed - and

opinions on them range from "better than nothing" to "pure nonsense".

 

The problems are:

- You need some minimum distance to avoid unwanted shorts during PCB

  production;

- The PCB production process always has some tolerances - taking these

  into account you finally get gap lengths that vary at about 1:3 or

  even 1:4.

- Given these large tolerances, you can never predict the sparking

  voltage by any means, or to a tolerable voltage.

- Additionally, since you need to leave the contacts uncovered from

  solder stop mask, you get environmental influence which further

  increases tolerances, regarding to spark ignition voltage.

- Finally, dirt, humidity and other residues will be collected on the

  blank surfaces and eventually raise more serious problems than they

  were intended to protect against.

 

My personal conclusion: They are not worth the time to draw them. If you

need spark gaps, get them as components.

 

Tilmann

Thanks Tilmann!

I guess you're right, it's going to be a pain in the neck with so many

uncontrollable events...

When you speak about spark gaps as components, are you referring to the

GDT (gas discharge tube)?

Logicnibble schrieb:

When you speak about spark gaps as components, are you referring to the

GDT (gas discharge tube)?

Exactly.

However, since they are large, expensive and somewhat exotic, I prefer

other ways of protection whenever possible (until now, this means

"always" ).

Tilmann