Forums

Lighning protection

Started by Phil Hobbs January 27, 2016
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