Homebrew PCBs

Hi all,

I have been looking at some board from some other stuff, laser jets 
I've pulled apart and alarm panels and stuff, and I have seen more 
than a few sections near terminal connections that look like 
triangles in a row, and a mirror image so the very tips of the 
triangles seem to touch.

any idea why ?
and is one does them (for the reason in the response) is there a real 
need for them ?

Dave

Dave,
     When a building is struck by lightning, long runs of wires in 
the building like Alarms and Computer networks, receive an induced 
high voltage. Some circuits use a spark gap.  The gap can be a simple 
gap to ground or a solid state device. The old devices looked like 
tubes. My guess is the are spark gaps....then again they could be 
test points.
                                                  John  



--- In Homebrew_PCBs@yahoogroups.com, "Dave Mucha" <dave_mucha@y...> 
wrote:
> Hi all,
> 
> I have been looking at some board from some other stuff, laser jets 
> I've pulled apart and alarm panels and stuff, and I have seen more 
> than a few sections near terminal connections that look like 
> triangles in a row, and a mirror image so the very tips of the 
> triangles seem to touch.
> 
> any idea why ?
> and is one does them (for the reason in the response) is there a 
real 

> need for them ?
> 
> Dave

--- In Homebrew_PCBs@yahoogroups.com, "crankorgan" <john@k...> wrote:
> Dave,
>      When a building is struck by lightning, long runs of wires in 
> the building like Alarms and Computer networks, receive an induced 
> high voltage. Some circuits use a spark gap.  The gap can be a 
simple 
> gap to ground or a solid state device. The old devices looked like 
> tubes. My guess is the are spark gaps....then again they could be 
> test points.
>                                                   John  


I'd go for the spark gaps.  there are pleanty of individual posts 
lableled TP3 and such.

but it seems a strike would wipe out the whole board, even with some 
drain.

Dave

--- In Homebrew_PCBs@yahoogroups.com, "Dave Mucha" <dave_mucha@y...> 
wrote:

> I'd go for the spark gaps.  there are pleanty of individual posts 
> lableled TP3 and such.
> but it seems a strike would wipe out the whole board, even with 
some 
> drain.

It isn't to save the board, it is to reduce the chance for fire. And 
lightning may hit many miles away, you could be looking at the sun 
outside and bam! Your fax machine bites the dust from a lightning hit 
far away. Those points mean the majority of the energy dumps there 
rather than in the components.

The physics of an arc are such that once it forms, relatively little 
voltage is dropped across the arc. Relatively little may still mean a 
hundred volts.

Just like fuses in an amplifier are not there to save the amp, they 
are there to prevent the amp from catching fire. I'm not talking 
about the speaker fuses.

Steve Greenfield

We used them as spark gaps during CE surge testing. The problem is that once they fire, you may get carbon tracks, but they are cheaper than gas tubes. One key thing is to not use solder mask over them, as when it vaporizes carbon tracks are assured.

We also used them as cut to select options when using one pcb assembly for multiple products.Its a lot easier to cut through a party hat with a xacto knife, than any other trace.
Ron

  ----- Original Message ----- 
  From: Dave Mucha 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Tuesday, September 09, 2003 8:58 PM
  Subject: [Homebrew_PCBs] Re: makeing party hat traces


  --- In Homebrew_PCBs@yahoogroups.com, "crankorgan" <john@k...> wrote:
  > Dave,
  >      When a building is struck by lightning, long runs of wires in 
  > the building like Alarms and Computer networks, receive an induced 
  > high voltage. Some circuits use a spark gap.  The gap can be a 
  simple 
  > gap to ground or a solid state device. The old devices looked like 
  > tubes. My guess is the are spark gaps....then again they could be 
  > test points.
  >                                                   John  


  I'd go for the spark gaps.  there are pleanty of individual posts 
  lableled TP3 and such.

  but it seems a strike would wipe out the whole board, even with some 
  drain.

  Dave




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