Date   : Mon, 06 Aug 2007 22:44:28 +0200 (BST)
From   : johan@... (Johan Heuseveldt)
Subject: Suppressor (Econet)

Hi,

On Mon 06 Aug, Pete Turnbull wrote:
> On 06/08/2007 14:02, Johan Heuseveldt wrote:
> 
> >>> If and when I would extend my Econet network, I would like to fit
> >>> Suppressors for safety reasons. If the cable is mounted along
> >>> floors/walls, it is more prone to things like mains power or lighting.
> 
> >> If it is entirely in one or two rooms in a single house, then transient
> >> suppressors are not really necessary.
> > 
> > It's just that /if/ something is going wrong, it can terribly going
> > wrong. Horror can be found@...<http://www.heyrick.co.uk> (Richard Murray)
> 
> I don't know exactly what happened there, but I suspect suppressors of 
> the sort that are used to try to prevent damage by lighning-induced 
> spikes are not going to be much help.  They almost certainly won't 
> prevent damage from shorts to low-voltage high-current devices like a 
> faulty PSU and probably not from a short circuit to a mains supply. 
> Experience here suggests they will prevent damage from spikes induced by 
> a nearby lightning strike, but possibly not from a very close strike.  I 
> lost a PC, a monitor, a modem, a cordless phone, a TV, a satellite box 
> (which melted), and the mains filter unit in a PDP-11 when a neighbour 
> had a direct hit, but the network was OK.

Lucky you then!
With lightning you'll never know where it flows to.

The suppressors have a kind of clamping diodes built in:

Clamping diodes can be used e.g. at the input of Analogues to Digital
Converter. Input will be clamped to both voltage rails, so input
voltage will stay within these limits.

The suppresors are able to protect against mains power on the network.
That's what I've learned so far, but I could be wrong though. The diodes
used are of the type Schottky, which are extremely fast; faster then
anything they protects! Also, their physical size is large, as they
need to be able to conduct 100's of amps during some time.

Question for me is: at which are these diodes clamped to? Does that
requires a good ground/earth connection/terminal?
How is the protection kept after it has kicked in? Is something
destroyed during the process, and needs replacing afterwards?

Indeed I think suppressors for lightning etc. are of a different type.
So both are perhaps mutually exclusive?

Thanks for your input. I'm still searching for details, and try to
determine whether or not I will need them. I'm certainly not in a hurry!


Greetings,
Johan

-- 
Johan Heuseveldt <johan@...              >
  aka  waarland

  The best place is a Riscy place
 
A puppy is not just for Christmas.
With careful carving it'll last well into the New Year.