Signal delivery through glass for lightening detector
bdb
Posts: 30
I'm trying to think out of the box here.
I have plans from a book for a homebrew lightening detector.· Antenna is basically some PVC pipes covering a copper pipe, attach a few NPN transistors and a coax cable.··· Interface antenna to optoisolator.····
*) As a Ham, I'm well used to leading a coax through a window - replace a window pane with plexiglass.· Either 1) put a small nick in the corner, the cable runs through the nick, and seal the nick around the calbe.· or 2) replace pane with plexiglass, but in the plexiglass put an SO-239 barrell connector - providing a cable attachment on each side.
However, the barrell connector idea adds 2 connections, each connection eats up·a couple of dB, and the signal itself is a rather weak signal.
*) I could connect the antenna to an outside radio transmitter.· But that would add to the cost, power consumption, etc.
*) I could go with a plan similar to the "through the glass antenna", using magnetic coupling to go through the glass.· But again, we're talking a really weak and erratic signal.
So I've started thinking, as I'm gonna use an optoisolator anyway, Does anyone make an optoisolator that goes through a glass pane ?· Admittely, the glass would scatter the light some.·
I have plans from a book for a homebrew lightening detector.· Antenna is basically some PVC pipes covering a copper pipe, attach a few NPN transistors and a coax cable.··· Interface antenna to optoisolator.····
*) As a Ham, I'm well used to leading a coax through a window - replace a window pane with plexiglass.· Either 1) put a small nick in the corner, the cable runs through the nick, and seal the nick around the calbe.· or 2) replace pane with plexiglass, but in the plexiglass put an SO-239 barrell connector - providing a cable attachment on each side.
However, the barrell connector idea adds 2 connections, each connection eats up·a couple of dB, and the signal itself is a rather weak signal.
*) I could connect the antenna to an outside radio transmitter.· But that would add to the cost, power consumption, etc.
*) I could go with a plan similar to the "through the glass antenna", using magnetic coupling to go through the glass.· But again, we're talking a really weak and erratic signal.
So I've started thinking, as I'm gonna use an optoisolator anyway, Does anyone make an optoisolator that goes through a glass pane ?· Admittely, the glass would scatter the light some.·
Comments
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- Stephen
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
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Mike2545
This message sent to you on 100% recycled electrons.
Do some research into this high voltage enterprise first.
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Better yet – post your book schematic and description of the whole setup.
You lightening· “source” ea antenna can under right condition generate more than few volts!
Some commercial receivers used to sport a neon bulb in the antenna input.
Relatively large antenna (140 feet long) would light up this neon during a local thunderstorm like a Christmas tree!
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The “ fire on ” voltage of these neon bulbs was in vicinity of 100V!
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If I would build a lightening detector I would not route the “antenna” into my shack – only the detected data. Just add to your project· “remote” lightening detector.
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And of course – be prepared to write your test setup off (and other possessions) as loss if you get a direct hit.
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By the way – my short ham radio antenna feed line (coax) is wrapped with few turns of wire -about 10 feet long -·and connected to the ground rod and I do not feel very comfortable when Texas thunderstorm rolls by!
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Just be careful and good luck.
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Cheers
Vaclav
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It's lightning, not "lightening".
Ever spent any time in a greenhouse? ·IR transmits through glass alright, UV does not.· IR transmits well enough·through glass fibre-optic cable, too, that's what hi-speed internet's all about.·
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Manetheren
·) that would protect your tower electronics from a direct hit.
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Manetheren
@Mike2545 and vaclav_sal
I think the detector in question her simply picks up the RF emitted from Lightning. It is as harmless as any other type of antenna.
There are a couple of safety items including that the antenna is a 12 " (just under 1/3 meter) piece of copper pipe and the mounting is at a low level (I'm looking at maybe 5 feet off the ground). The author doesn't call it such, but the circuit board next to the antenna uses a couple of NPNs, 2 small diodes, 2 resistors and 9V battery - so that board would fry pretty quickly but is only a couple of dollars and a few minutes work. I'd also thought of putting in another wall of something that would fry fast, just in case.
Then the end of the coax attaches through an optoisolator to the BS2.
Even with that, thanks so much for the idea of getting a fiber optic kit to play with. A lightening arrestor sounds like a good idea too - For my personal safety, all my radio equipment is disconnected except when I'm using it. But the problem with a lightning detector is that I'd want to run it specifically because there is bad weather.
Also hadn't thought about how much I'd loose if I just mounted the antenna inside.
So I think what I'll do is first make an indoor version. And also look into fiber optics as a way of putting it outside.
Again, thanks for all the help and ideas.
I'm going to have to look up the Bitson book. Was able to get a table of contents and it looks quite interesting.
To your question, I don't know for sure, but in the front of my book he has a thank you to the folks who had input to his projects, and one of the persons listed was Tim Bitson. So I'm suspicious that you're directly on the mark.
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Mike2545
This message sent to you on 100% recycled electrons.
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· -- Carl, nn5i@arrl.net
What you are building is a specialized radio receiver.· Design it with that understanding, and you'll see that most of·your fretting is needless.
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· -- Carl, nn5i@arrl.net
Post Edited (Carl Hayes) : 4/22/2009 10:48:56 PM GMT
Of course the IR from a hot object will have a wider spectrum than the narrowband IR from a remote control.· Some of that will be at frequencies that don't pass through some kinds of glass very well.· But most of it will get through without much trouble.· Don't believe it?· Feel your sunward windowpane on a sunny day.· If the glass were absorbing much IR it would get very hot, and burn your hand·-- compare it with a black iron pipe left out in the same sunlight.
Does your car have a black steering wheel?· Does it get painfully hot when you park facing the afternoon sun?· That heat is IR coming through glass.· Notice that the windshield glass didn't get nearly so hot.· That's because it isn't absorbing much IR.
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· -- Carl, nn5i@arrl.net
Post Edited (Carl Hayes) : 4/22/2009 10:56:48 PM GMT
So I think I have a do-able plan.
I'd still like to add a tad of protection, and was initially thinking of putting a light signal on one side of my window glass and receiver on the inside (basically an optoisolator with an inside and an outside part. Seeing the suggestions, I'd like to thank everyone. I'm kind of leaning to a Fiberoptic kit - both for the better isolation and the chance to get a little experience.
Again, Thanks so much for your help
My coax cables (seven of them) pass through long barrel connectors stuck through holes in a piece of wood cut to a length that just fits across the bottom of a window opening.· I opened the window (10 years ago), put the board with the barrels in the bottom of the opening, lowered the window down on the board, put screws in the sash to lock the window in place (foiling any really inept burglars), and stuffed plastic foam around the top of the sliding window to keep out the bugs.· Then I hooked up the antennas to the outside ends of the barrels, and hooked my antenna selector switch to the inside ends of the barrels.
It's been there ten years and is doing fine.
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· -- Carl, nn5i@arrl.net