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,
Lighning protection
Started by ●January 27, 2016
Reply by ●January 29, 20162016-01-29
Reply by ●January 29, 20162016-01-29
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.
Reply by ●January 29, 20162016-01-29
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
Reply by ●January 29, 20162016-01-29
>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
Reply by ●January 31, 20162016-01-31
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
Reply by ●January 31, 20162016-01-31
>I'm guessing the sensor conditioning/detectionthreshold 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