HFU HF Underground
Technical Topics => Equipment => Topic started by: Rob. on July 27, 2019, 1828 UTC
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I've been looking for an inexpensive lightning detector for a little while now. I decided to try this one out mainly because the price was low enough to take the risk:
https://www.amazon.com/gp/product/B00EO1H3X8/
I set it up a couple of days ago and placed it on the windowsill next to my NOAA WX alert radio and literally forgot about it. Today I was working in a room on the other side of the house and heard this strange beeping. I searched the house and found that the new lightning detector was going off. Since there was no expectation of storms forecasted and it was a beautiful sunny day I felt that I just wasted $30 on a piece of junk. I looked at https://www.lightningmaps.org/ to confirm my immediate condemnation of the device, and lo and behold, there were t-storms all over the place. Most were 15-30+ miles away but this little pocket detector was picking up most (95%) of the lightning strikes I saw on lightningmaps.org. IMPRESSIVE!
I wouldn't call this a life saving device but it will be good enough to warn me to disconnect my coax.
(https://www.acurite.com/media/wysiwyg/blog_images/02020-alt-800x800_1_camping.jpg)
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Neat! An hf rig is almost always tuned to an 11MHz freq here, if it starts popping with tstorm noise you can be sure it's close.
Once had a zepp antenna fed by ladder line and a AEA AT300 antenna tuner, one day noticed a pop and then a static sound coming from the tuner. Went over and watched as the dual swr needles started to rise in unison and peak, hold, and then pop! and they dropped back down to start all over again. A tstorm around 100 miles away was putting enough static on the zepp it could arck the tuner.
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I had a very low expecation of this little device but was very pleased with it. Consistantly detecting t-storms over 20 miles away. I'm going to keep one (bought two more at $25 each) out near the swimming pool as well. Looking to interface it with some other devices to alert me when I am out and about.
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It'd be interesting to see the inners, what it uses for an antenna.
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(https://i.ibb.co/wNrGysL/accurite-internals.png) (https://imgbb.com/)
The innards as requested. Antenna is top left, small diameter coil with lots of turns. Crystal wasn't marked.
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Neat and thanks!
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I was able to get a short video of the device detecting while showing the lightningmaps.org page:
https://gofile.io/?c=jjMoEE
I am noticing that detection to my north and east is less reliable than to my south and west. This corresponds identically to my RF line of sight. I would think that since the electromagnetic disturbance is at a high altitude that this should not be the case and terrain would be somewhat irrelevant.
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So, I received two additional detectors in the mail today and am doing simultaneous testing. There are sweet spots in the house that detect better than other locations. Put all three in the same spot and they detect identically. Had two sitting on windowsills in the same room and were not detecting as well as the one in the sweet spot.
Oddly, the sweet spot is on top of a wine refrigerator next to the NOAA weather radio and the bad spot was far away from any electronics or motors. The sweet spot didn't seem to have any directionality issues as mentioned in previous post.
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I wondered if there'd be directionality as I presume the antenna is a ferrite bar and you know how those are.
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The link below is for a lightning detection chip and it includes some discussion of how the detection algorithm works. I don’t know if it is the particular one in your device, but the algorithm is probably similar.
https://cdn.sparkfun.com/assets/4/0/5/3/7/AS3935_Datasheet_EN_v2.pdf
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HEY!!!! I've used something like this for decades. it's called a portable AM radio receiver. And, it can detect daytime lightning from +50 miles, or more. plus, it hears 100% of lightning strikes. At night, at full sensitivity, it can detect lightning from 1/2 the country. And also at night, I switch over to the optical lightning detector, my own two eyes. They can even more accurately detect what precise direction the lightning is coming from over 80 miles away! Wow...... Just sayin'... Hmmmmmmmm, can ya fool that Lightning device by flipping ON a switch of something high current? Does it go off near bug zappers, electric fences, and noisy spark plug cables? Yeah, I don't believe that I need to buy this.
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Neat package and display. Maybe worth $25 if you're not handy.
Except for the audio alert, you can do the same thing for a few pennies: Take a small neon lamp, attach an antenna to one wire and a Ground to the other and *voila* watch it flash.
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Good point on the directionality of the ferrite. I'll have to test that during the next storm. Placing them next to each other at right angles should show a difference if true.
This is more of a lightning alert, not just a simple detector, I have to say it has already given me significant advanced warning of three fairly severe storms headed my way... and prior to any NOAA WX alert for my area. Since I rarely have the inclination or time to spend watching a neon lamp flash* or monitoring vacant AM radio frequencies 24/7 I appreciate the alert/detector's ability to warn me to get my kids out of the pool and to disconnect the antennas on my expensive radio gear. The loss of either of those significantly outweighs the $25 purchase. :)
Something else I noticed is that they do not false (algorithm in the detection chip). I tried several household methods and nothing would make them go off. The three I have also detect identically when placed together so that helps to build some confidence that when they beep it is a genuine strike. Mileage may vary if you are in a more urban environment as I am pretty rural here.
I enjoy coming across an inexpensive device that exceeds original expectations and ends up being very useful. One of these devices will be sacrificed for additional experimentation. I thought it was worth sharing my experience since we all need to disconnect those antennas when lightning is near.
* I will admit to spending a few minutes watching Chris' riveting neon lamp flashing on his live Youtube feed the other day. :)
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I suspect the algorithm is what makes this stand out from an untuned AM radio. When I was researching roll-your-own loopstick antennas, one of the most informative posts I found was at a WX forum with a bunch of guys building lightning detectors. I read through a bit and it looks like these things are more complex than simple static detection in low bands.
I was a lifeguard at my county waterpark years back, and they had one that certainly cost more than $25. The art isn't detecting lightning somewhere on your half of the country, as mentioned here, but rather to detect when lightning is close enough to be dangerous. The park lost revenue if there weren't bodies in the pool, so precision was worth the premium.
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Yes, those places have warning devices that range up to several thousand dollars. Saw one in Florida a while back. They will also text an alert as well as have a voice notification over two way radio option. Totally different league.
There is a Raspberry Pi shield out there, too. Might take some time to look at that someday.
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I bought a couple of these too. I was thinking about how I might use one of them to automatically ground the antenna input on my KiwiSDR receiver...
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A nice circuit description of the chip inside the detector:
https://www.digikey.com/en/articles/techzone/2013/mar/incoming-storm-a-lightning-detector-from-ams
Some interesting discussions, including antenna directionality:
https://www.wxforum.net/index.php?topic=30627.0
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You can watch for it coming on a vintage TV switched to channel two or three. If the power goes out you can look out the window as the Dood suggested.
I've seen more "heat lightning" this year than I have in forty years. That stuff can be a couple of hundred miles away, generated by storm fronts you'll never see locally.
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I remember it being a rare thing when it got so dark in the middle of the day that the street lights turned on. Seems like it's happening once or twice a week this summer.
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"The AS3935 chip only contains an omnidirectional antenna, so no triangulation. It also bears mentioning that the AS3935 was *not* intended to be used as a scientific instrument, but rather as a personal safety add-on in smart phones and stuff to alert the owner to the threat of an approaching storm. It also seems to be extremely sensitive to antenna orientation, so just using it as a personal safety device is sketchy. "
lolwut
Also, that chip is pretty neat, I want one. Shame the weather stations for home use don't have this built in.
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Some weather stations have a lightning detector add on. Not sure how well that works.
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Pretty good. They're usually late 60's/early 70's black and white GE portable TV's tuned to Channel 2 or 3.
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Good old General Electric. Compactrons and nuclear power on the cheap! :D