Lighning protection

On a sunny day (Thu, 28 Jan 2016 10:34:32 -0500) it happened Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote in
<n8dc91$rhm$1@dont-email.me>:

>I wish.  The design requirement is "It has to work through repeated 
>thunderstorms in an old wood/steel/cinderblock/mud/thatch/whatever 
>building in the hills of Bangladesh, with 200 metres of rusty steel 
>ductwork that may be carrying mains current, and very few grounds."


I have seen that situation,
and we decided to go optical fiber.
that worked, and had not speed limit due to capacitance,

On a sunny day (Thu, 28 Jan 2016 20:26:49 +0200) it happened
upsidedown@downunder.com wrote in
<ramkabdu0bgusob4p4lnllpf3bep8ig61j@4ax.com>:

>
>1.) you can use non-isolated RS-232 for equipments in the same room
>2.) use galvanic isolation (2 kV) RS-422/485 in the same building
>3.) use fibres between buildings
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
Exactly.

On Thu, 28 Jan 2016 09:32:29 -0800
Joerg <news@analogconsultants.com> wrote:

> On 2016-01-28 08:37, Joe Hey wrote:
> > On Thu, 28 Jan 2016 10:35:40 -0500
> > Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
> >
> >> On 01/28/2016 10:15 AM, Joe Hey wrote:
> >>> On Thu, 28 Jan 2016 10:03:51 -0500
> >>> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
> >>>
> >>> }snip{
> >>>
> >>>> Roight.  I'll probably use another of those 150 uF coupled
> >>>> inductors
> >>>                                                      ^
> >>>                              Shouldn't that be 'micrometer'? ;-)
> >>
> >> Nah, these ones are about 10 feet tall.  10000H, 150 uF.  ;)
> >
> > Hah :)
> >
> 
> With capacitance or Leyden flasks, shouldn't it be liters?
> 
> Oh wait, litres, of course.
> 

You got it. :)


joe

>I don't suppose the ducts are willing to be straight, to give you a 
>long view.

I need timing information so we can make sure the diverter door opens at the right time. A glass multimode fibre bundle of at least a millimetre might work, but that's no longer so cheap, and needs more than a wrench and screwdriver to install. 

Cheers

Phil Hobbs

John Larkin wrote:


> I wonder what burning cotton "sounds" like, namely converting the
> light to audio.
> 
> 
Ok, here's a crazy idea or two.  Have the sensor and detection logic on the 
machines.  Power from whatever source is available.  When fire is detected, 
sound a sonalert.  The sonalert fires into plastic water pipes, and the 
sound is detected at the other end in the control room.

Somewhat more down to earth, a scheme I thought up for a remote rain gauge 
that would be lightning-resistant, would be your sensor/detector flashes a 
laser into a fiber that is detected at the control room.  By sending a LOGIC 
signal on the fiber instead of the raw sensor input, you can't possibly not 
have enough signal.  I'm guessing the sensor conditioning/detection 
threshold stuff isn't really complex.

If you want to make sure the sensors don't lose power, you could have the 
logic signal be laser on = OK, and maybe laser off = failure and laser 
flashing = fire detected.

Jon

>I'm guessing the sensor conditioning/detection 
threshold stuff isn't really complex. 

It's a picoamp linear/log TIA and a couple of LM358s.  The photon budget and low cost are the most interesting parts. 

>If you want to make sure the sensors don't lose power, you could have the 
>logic signal be laser on = OK, and maybe laser off = failure and laser 
>flashing = fire detected.

Not that simple. It isn't just a fire alarm, it finds the first signs of fire (a spark) and kicks open a solenoid-powered divertor door to dump the burning material someplace safe. The panel will poll each concentrator box periodically.   Fibre isn't a good solution here because its installation and maintenance requires a level of cleanliness and skill that's unlikely to be available on site. It's also expensive, at least if you get the armoured kind, which we'd certainly need. 

Cheers

Phil Hobbs