Directional Lightning Detection  feasibility?  - Page 1
Forum section: electronics / projects

author: kuhny1
author_rank: Newbie
timestamp: July 05, 2016, 01:23:32 am
content: Hi all,So I have always wanted to build a long range lightning detection system and I think this may work. I have made a portable one using the AS3935, but obviously it only gives distance and not position (like north, south, east, west, etc.).Please excuse my ignorance if this in the wrong topic, I was going to put this in the RF section but it has more to do with the project than the RF part.Anyway, So last year we have bought a state lease camp in PA and there happen to be a directTV dish left behind in the tool shed. So the first thing that came to my mind was, why don't I build a short range weather radar. Unfortunately, there are two bottle necks with that idea (and possibly many more). One, making a stepper motor rig would be a nightmare, and two i don't think that the FCC (or the FAA for that matter) would be very happy about me making a high power RF transmitter (many watts or possibly kWs of power) and receiver.So after a bit of thinking and weighing out the risks, and I eventually figured I would just wait for that project until i could get a license for high power transmitters. So then I came up with the idea of using the dish as a lightning detector. This would eliminate the need to have a elevation axis motor and I wouldn't risk bringing planes down, or getting a unpleasant knock on my doorstep.So the plan is1. Hack into the dishe's LNB and just tap off the feedhorn. (done)2. Bring the tap to the coax line out port. (done)3a. Make a very high gain amp hopefully with a gain of 1000 or more, and since I don't care about signal quality, just power level, I think I can just use a standard OP AMP (I'll just use a LM324 because I have one laying around)3b. Use the LNB's amplifier which normally has a gain of 1000. I would do this, but I dont know how I can create the phantom power it requires4. Do some tests on a small scale with a negative ion generator or better yet a storm if one happens to roll through.5. Make the bracket for rotation with a reasonably beefy stepper.6. Put the amplified signal into an ATMega328's or an ATTINY85 analog pin and hope it doesnt destroy it because of Over Voltage (not sure how that could happen but my luck)...7. Put the analog value through a distance calculation (made by observations of the storm's distance and analog in readings, this could take time)8. Send the rotation position, and distance to my computer and display the strike on a map that has my location and hopefully a radar image. (this could take time also because I'm planning to make this in processing)So I guess the main questions are:1. (Most important)Does my whole plan sound feasible?2. Would the dish's feed horn even pick up on a lightning strike or should I make my own pick up? Im asking this because Im not entirely sure what frequency a lighting strike emits. I know they do a massive burst of EMFs at varying frequencies. But I don't know if they ever emit into the microwave region. I have read however (link below to this), that they emit from 0Hz to Gamma in one strike though, which means they will certainly emit microwaves. I have found out that TV satellite dishes are listening for microwave signals (+5GHz).3. Would a negative ion generator be similar enough to an actual strike to test at close ranges? I'm pretty sure that a ESD is the same thing as a lightning strike but just on a EXTREMELY smaller scale, right?Thanks for reading!!Where I got the lightning emission frequencies:https://www.physicsforums.com/threads/rf-emitted-from-lightning-strikes.153295/

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 05, 2016, 04:12:52 am
content: Hmm, in the GHz you'll probably just get thermal energy from the plasma. It's pretty hot, so it's much noisier than the background, but only a hundred times or so, ballpark -- not a strong return. Though that's 40dB, which isn't bad at all for a noise source!That first reply is just making a crazy guess -- it's not based on the physics of the event. The lightning strike itself takes some microseconds (about light speed from cloud bottoms to ground) to 'ignite', and tens or hundreds to reach full intensity (and perhaps seconds more as different parts of the cloud finally discharge in a large one!).The "ignition" part will be the most radiative, with a cutoff characteristic of the length dimension. So, presumably, in the MF range (~km wavelength). -20dB/dec is a reasonable cutoff rate, at a guess; which matches the figures from the last post, so that's cool (with ref, no less: STANAG 4236!). The secondary cutoff might have to do with the diameter of the lightning bolt itself, dunno.In any case, there's a lot more energy at low frequencies, so it would be more effective (at least, to track at greater range) to use low frequencies. With the obvious downside that you need a much larger antenna array...A long baseline array would probably be good, as you can harness the impulsive nature of the signal. Track spikes on each of three (more or less equilaterally arranged) antennas, and do a little math on the relative delays.Anyway, back to the dish -- the downside is, you have strong directivity (not usually a downside!), which means you'll really only get a return by luck, if you're pointed at a strike. But maybe if you're tracking distant storms, this is okay. On the other hand, at enough of a distance, everything looks like a blob again, so you have poor directivity in a relative sense! You can't really discriminate anything without an array, you need those degrees of freedom to tell what's going on.As for other cool things you could do: if you can get a nice wideband spectrum analysis, of the burst, you might observe some interesting quirks in the noise at those frequencies, like electron cyclotron resonance. These frequency peaks will depend upon where in the plasma the charges come from, and what the magnetic field is at that location. The magnetic field varies during the strike, which means the frequencies should be sweeping up and down all over the place.Since the plasma itself is pretty dense and hot, it may be too indistinct -- not like, say, planetary cyclotron signals that are strong enough, and distinct enough, to see from space! You also might not notice it with a narrowband receiver, because the sweep rate is probably quite fast (kHz+?); it would simply look like noise to such a receiver. With a wideband (some GHz wide, perhaps) receiver, and Fourier analysis of the burst (which, mind, is some Gbits now, so I seem to be suggesting quite an undertaking of hardware here...), you should be able to see the correlation of peaks sweeping over microseconds to milliseconds.A receiver of 1MHz or lower bandwidth probably wouldn't be interesting enough to really observe much of this sort of thing, so you should have some freedom even within the hardware you've got.Tim

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 05, 2016, 04:27:26 am
content: Does it need to work during the day as well as at night? If it's night only, it would probably be easier to detect the direction of the flash, with the electromagnetic detector only to prevent false positives from artificial light sources.

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 05, 2016, 04:32:59 am
content: I remember from back in the 1960s an article in Scientific American magazine in the monthly column "The Amateur Scientist". It was a lightning detector which had a pair of diople antennas crossed at 90 degrees, and some sort of analog circuit to do the strike and direction detection. Of course that was back long before the days of any kind of computer processing for that sort of thing was available outside a research lab.

author: djacobow
author_rank: Super Contributor
timestamp: July 05, 2016, 04:54:23 am
content: Why not two or three AS3935's, connected to antennas that are orthogonal or 120 degrees apart. I believe in 3935 reference implementation the antenna is just an inductor (the one in their ref design is just a wire on ferrite SMD, put into a ckt tuned for 500kHz, IIRC), so this seems easy. The processor can use the distance or power readings and make some sense of that.You can get hobby boards for low $, so you could buy two and arrange them orthogonally and see what you can see, as they say.One weird thing about these devices is that they do not generate an interrupt until they are done "processing" the strike and have determined that it is indeed lightening according to their algorithm. The result is a delay between strike and notification that I suspect would be unacceptable where strikes are coming fast and it really matters, like in an aviation sferics application.

author: Jeroen3
author_rank: Super Contributor
timestamp: July 05, 2016, 05:42:24 am
content: The current technology of lightning "radar" uses triangulation with multiple antenna locations. It's not a "radar".Instead of directional detector. Place multiple synchronized detectors.Here you have a site that also shows triggered detectors.http://en.blitzortung.org/live_lightning_maps.php

author: Kleinstein
author_rank: Super Contributor
timestamp: July 05, 2016, 08:46:57 am
content: The more useful radio signal is at lower frequencies, more like 100 kHz to 1 MHz. The idea with two orthogonal dipoles is also good to get a direction. Magnetic antennas don't need to be that large.The only difficulty is to get the distance - this might work if you can hear the thunder. The more normal way would be several antennas at larger distance (e.g. > 100 km) apart, so nothing to do locally.For many regions there is wether radar available vie internet.

author: kuhny1
author_rank: Newbie
timestamp: July 05, 2016, 11:28:05 am
content: Quote from: Jeroen3 on July 05, 2016, 05:42:24 amThanks Jeroen3I forgot about the AS3935's giving the power level of the strikeand inductive antennas are directional right?but the only problem is that they are directional in both horizontal ways <----->so i would have to find a way of shielding the one end of the inductor (not sure how to do this because they listen for 500kHz) so that only one end receives RF. then i would just judge direction based off of which sensor got more power received and compare that to the rest of themQuote from: T3sl4co1l on July 05, 2016, 04:12:52 amThanks Tim!!Ok so I understand from your post that listening for microwave pulses would be impracticable and not likely. So what I guess what I can try is to make my own pickup with some copper wire (sounds a bit sloppy). Also I should mention that i do want the directional aspect of the antenna so I can plot out their position by rotating the dish slowly; about a full revolution every minute. And I should also say that I dont care about how many strikes, i just care about their distance and position. And I might make it so that the dish stays pointed at the source for a while and then continue rotating.

author: chris_leyson
author_rank: Super Contributor
timestamp: July 05, 2016, 11:47:17 am
content: QuoteI think it was maybe the CEGB, central electricity generating board, built an array of magnetic detectors back in the 70's. I seem to remember that the base lines were quite long, think the article appeared in "Wireless World".

author: Kilrah
author_rank: Unknown
timestamp: July 05, 2016, 12:27:58 pm
content: Quote from: kuhny1 on July 05, 2016, 11:28:05 amBut that won't work, since a strike is a very short pulse. Either when it strikes it's within the coverage of your antenna and you can detect it or it isn't and you''ll never know about it, and in neither case can you determine where it was.The only potential way would be to have the antenna rotate VERY fast e.g. so that it makes at least more than one turn during the strike so that you can "map" the intensity over 360° and figure out where it was the strongest. But that would likely not even be enough given that as mentioned earlier the intensity of the strike also varies over time... so you'd then needseveralfull turns during the strike and hopefully an average of the angles of max intensity discovered on each turn could give you something... but then you get a dish rotating at thousands of RPM, not very practical. And that still doesn't give you distance, only angle. Would need another source of data e.g. sound to find out distance.As mentioned the only practical way to get a precise location is triangulation over a wide area.

author: LaserSteve
author_rank: Super Contributor
timestamp: July 05, 2016, 02:06:50 pm
content: Lightning detection in the academic world is done using two MF loops at 90 degrees to each other, as well as TDOA in more modern systems.Tune two magnetic loops to a locally un-used frequency between 100 KHz and 500 KHz and use a sound card to demodulate the signals after downconversion to audio.Use four ferrite rods as a "Adcock" antennaThen there is TDOA, but unless your cabin has high speed internet, or unless you can locate a remote site someplace else on the mountain, TDOA is difficult.This is commonly done for aircraft lightning warning systems, as well. AKA "Stormscope".Theory:http://www.atmo.arizona.edu/students/courselinks/spring13/atmo589/lecture_notes/apr18/apr18.htmlFascinationhttp://en.blitzortung.org/live_lightning_maps.php(also sells hardware kit!)Hardware:http://www.stormwise.com/index.htmlhttp://salsburg.com/Lightning-Detector.pdfhttp://www.ijaiem.org/ITechCON-2014/EXTC-02.pdfhttp://www.lightningradar.net/(Join forum to gain hardware access..That sucks, but I understand why they do it!)http://www.blitzortung.org/Documents/TOA_Blitzortung_RED.pdfMy favorite sound card vectorscope..http://www.satsignal.eu/software/audio.htmlYou may find a "Wenzel Cloud Charge Monitor" or Field Mill to be interesting Mountain Cabin projects..Enjoy,Steve

author: kuhny1
author_rank: Newbie
timestamp: July 06, 2016, 11:45:37 am
content: Quote from: LaserSteve on July 05, 2016, 02:06:50 pm

author: SL4P
author_rank: Super Contributor
timestamp: July 08, 2016, 06:24:04 am
content: I know bugger all about this field, but my starting point withotu any budget - would be a combination of visual, aural and other sensing technologies - scoring the aggregate based on discovery and research.I'm not sure a satellite dish would factor in as much as a simple optical sensors (phototransistors) within a prism, and some tiny HF horns feeding tiny piezo transducers (microphones)... followed by some DSP algorithms to filter and score the environmental events.But as I said - I know bugger all about this field!

author: Don Hills
author_rank: Regular Contributor
timestamp: July 08, 2016, 10:44:06 am
content: The way it's done in Australia is to have widely spaced receivers, clock synchronised by GPS, then triangulation. Look at gpats.com.au for one such network.

author: bench_knob
author_rank: Regular Contributor
timestamp: July 11, 2016, 06:20:42 pm
content: How about this, been around for a long time (saw his website back around 1996); offers both hardware & software design files gratis:http://lightningradar.net/I notice others have also cited the above URL. Lightening-RADAR, does exactly what you desire. It determines location, direction and power. It does so without any moving components and, it is very reliable.bench knobedt: added additional content for clarity.