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Lightning Detector (VLF Receiver)   |   Original Design
Lightning Detector (VLF Receiver)
07/09/2009
This project was one that just kind of jumped out at me one day while browsing through the internet,  I happened to find a link to Charles Wenzel's site (www.techlib.com) while I was looking for schematics for the Radio Shack Weather Station. His site was full of weather related circuits and more.

I do not have much of a use for it for what it is designed for, but, I do like the fact that you can make it into a conversational piece when there are thunderstorms, so I figured what the heck, I'm going to make one..... So I browsed through his differrent versions and decided on building his 5 volt version first, some people at other forums building the same project were having trouble finding the inductors, which by chance I had the same exact values needed in my "parts pile"!
Lightning flashes generate a broad spectrum of radio frequencies with especially intense emissions in the VLF band. This receiver is designed to pick up a band near 300kHz which is fairly empty except for lightning static. This device is basically a VLF (Very Low Frequency) Radio that is tuned to pick up the static discharge from lightning, instead of listening to crackles on a speaker, it displays it with a light. (Other versions of this circuit can be made with a speaker out put if you would really like to listen to the static! Others have incorporated meters to see the intensity of the strike and to determine the distance of the lightning.)

I decided to start with the basic circuit and the lamp driver option for it.

Other people who have made these have housed them in different enclosures and such, I tried to find a suitable one for mine but I really couldn't settle on which one, from an old transistor radio enclosure, to a plain plastic box!.... This small plastic enclosure for a clock and a couple of reflective dishes from a PIR sensor array kept cathing my attention in my "pile" of parts, maybe I can use these to make it look like it came out of an old science fiction movie!

But that's later on for now, on to making a PCB for the Detector circuit!!!
So I drew up the circuit in Eagle Lite, created the pcb, ran the pcb_gcode.ulp, and imported the file into my CNC and whalla! I have a Lightning Detector PCB!!
Although I can produce the PCB's, I have not yet found a cheap and easy way to make a good solder mask and screenprinting, so I hand wrote everything with a fine tip marker, doesn't look very professional, but the components will cover most of it up anyway. This atleast aids in parts placement ;)~
This is the completed PCB with the components mounted and soldered into place, I even hot glued the inductors in place so they won't get knocked off or something.... you never know! I also temporarily soldered the maglite bulb in place that I am using as the lamp for testing....
Here it is during testing attached to a 2' telescoping antenna via the coiled copper wire and connected to 4 AA batteries..... I used the trusty "lightning simulator" (AKA, charcoal grill lighter) to test it, everytime you click the lighter within a few inches of the antenna, you can see the lamp flash. Now I just have to wait for an actual lightning storm to see if it really works!!! (waiting sucks!!!!)
While waiting for the lightning to arrive..... I started playing around with the clock frame and the reflectors..... I had seen one design on Charles site where they had used some coiled up copper wire to the finished design, which really looked cool to me, it was like something out of a science fiction movie or something....
I decided to use this wire scheme to connect the lamp to the PCB, I coiled up one conductor, and just ran a straight piece down the center of it for the other conductor, I then hot glued the wires in place inside the clock base. I ended up using this same wire coils to dress up the posts on each side of it, I then attached one of the reflective plastic pieces I had onto the posts....
Bottom view of the old clock base, where I hot glued the lamp "leads" to the inside of it. I then just soldered some short pieces of wire onto them and soldered the other ends onto the PCB.
Fuzzy shot (everything else looks in focus except for what I was aiming at! Dang auto focus and highly reflective surfaces!!!) showing the lamp "leads" coming through the top before the lamp was soldered onto them....
Picture of the base with lamp soldered into place, I was going to make a lamp socket to make it easier to replace the lamp in case it burned out, but I had seen some dark clouds coming our way and wanted to get everything re-connected together to test it just in case there was some lightning.
Here is the LD PCB, neatly tucked away inside the old clock base.... as you can see there is plenty of room in case I decided to add the other options later on.... I was thinking of using one of my LM3916 VU Meter IC's to make an LED meter to visually show the frequency of the strikes... that will be later on once the main detector circuit is tested to be properly functioning... still waiting for that storm with lightning! (Nature has a funny way of playing with you when you least expect it, I had to wait for the wind for days when I worked on the windmill generator project!) We have had a couple since I started this project, but none with lightning activity....
This is it with the clear dome on, (which I got from one of those cheap zip-zap remote controlled cars...) I attached the parabolic reflector onto it with a nylon machine screw and nut. Now when the lamp flashes it casts a bright flash out around it.. I am still not content with the way it looks! It is just missing something! Everytime I look at it I keep thinking "Danger! Will Robinson, Danger!" .....;(
I ended up discarding the parabolic dish reflector and clear dome for now, (atleast for this project, back to the pile they go for another project perhaps.)
I replaced the parabolic dish reflector for this cone shaped one to be able to cast the light a little better, the dome shaped parabolic dish blocked some of the light and narrowed it a bit, this ought to cast it a little wider... I salvaged the cone out of a solar landscape LED light fixture that I had taken apart for the solar panel that I had used for another project in the past. I attached it to the bottom reflector with some 14 AWG solid conductor wire that I had stripped the insulation off of, I twisted the middle of the wire and "screwed" it into the cone, I then fashioned 2 "legs" from each end of the wire, ran and wrapped those around some mounting holes that were already on the bottom reflector (seen better in the pic below).
Atleast I am not hearing that "Danger! Will Robinson, Danger!"  in my head anymore! lol...
I have the main reflective piece temporarily hot glued in place, I will eventually attach it with some copper mounts to make it permanent... hot glue works in a pinch every time!
There was some small lightning flashes late one nite, but off to a distance... I could still see the lamp flash along with the lightning.... now I really can not wait for a lightning storm to hit to see this thing really put on a show!

Imagine that, watching lightning in the safety of your home!

Now it sits and waits for lightning..... I will eventually get some kind of clear dome to put over it, the original one I was going to use is not deep enough to accommodate for the new top reflector, I wish the glass dome that was originally on the clock did not get broken (thats how I ended up with the clock base to begin with, someone elses junk can be someone elses spare parts;)~ ) I might also add in the LED activity meter , and whatever else I come up with to connect to the output of this detector, once I get to see it in full action!


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