For as mysterious, fascinating, and beautiful as lightning is at a distance, it’s not exactly a peaceful phenomenon up close. Not many things are built to withstand millions of volts and tens to hundreds of thousands of amps. Unsurprisingly, there’s a huge amount of effort put into lightning protection systems for equipment and resources that need to be outside where thunderstorms sometimes happen. Although most of us won’t be building personal substations, church steeples, or city-scale water towers in our backyards, we might have a few radio antennas up in the air, so it’s a good idea to have some lightning protection and possibly an alert system like [Joe] built.
The start of this project came about when [Joe] noticed static on his crystal radio’s headset when there was a storm in the distance. When disconnecting the antenna in this situation, he also noticed sparks, and then thought that placing a neon lamp in the circuit would essentially allow those sparks to form in the lamp itself. The sparks only cause the neon to glow dimly, so a capacitor was added to allow the voltage to increase, making the sparks of light in the lamp more visible. These sparks are still quite dim, though, so two LEDs were added in series with opposite polarity, allowing one to detect negative charge and the other to detect positive.
With the LEDs installed in the circuit, it’s much more apparent when there are charged clouds around, and with the addition of an RF choke, [Joe] can use this circuit at the same time as his radio while also getting alerts about potential thunderstorm activity. This isn’t the only way to detect lightning strikes, though. There are plenty of other ways to get this job done, and we’ve even seen lightning detectors so sensitive that they can detect socks-on-carpet static discharges as well.
Thanks to [Charles] for the tip!
Very nice project! I wonder how to make it just like a charged cloud detector without increasing the danger of lightning.
I remember when I was younger, tuning to dead medium wave frequencies on the radio as I could hear clouds charging up before a lightning strike. You could possibly use an SDR and some clever software to start listening out for these events.
I wonder if it would be possible to do that, but with three SDRs spaced apart, and triangulate where the lightening is charging up.
I once used a “long” wire of 30 feet connected to a pair of FETs each with an LED powered by a 9v battery and an in series resistor. Almost any cumulus cloud would make one LED glow continuously. Clear air would sometimes do the same.
This is excitation in an H field antenna, a magnetic antenna. Definitely want a a lightning diverter upstream of your crystal set, to give the lightning an opportunity to find ground instead of coming into your house on the channel of copper plasma that used to be your antenna wire.
There’s awesome stuff happening in the electric field, as well, which might also be in play with the neon detector. Franklin’s bells is the prettiest demonstration I’ve seen of it:
https://www.youtube.com/watch?v=rR7rH9McYEw
The most important thing I learned from this project is that Angelfire still exists. XD
Time to check my Geocities account.
People have been doing this with neon bulbs for longer than I’ve been alive, and I’m old.
What I think might be more interesting would be to make it audible … like maybe a low impedance speaker in series with a couple of back-to-back diodes and probably a current limiting resistor across the feedline.
By the way, I almost always put a short across my coax during the lightning season, but a few years ago I had left the end of the coax from an 80m Inverted-V just laying on the floor … disconnected from the rig of course. There was an incoming storm that was still several miles away, but we already had clouds building over head. I had one hand on the floor and as I bent down to put a short across the coax with my other hand and I drew a thick blue arc about two inches long. The current ran through both arms (and obviously also through my chest) and both of my biceps were sore for about three days afterward. Supposedly the voltage required to jump two inches in reasonably dry air is on the order of 150,000 volts … possibly a bit less in this case since the end of the coax had a PL-259 with a sharp tip. This was all without any nearby lightning strike.
Now you are going to make me have to go look it up to heck my ‘calibration’…
My internal voice says it’s ~10kv/0.25inch @ 50% humidity.
But who knows what it actually is?
Remember kids, just because you remember something, doesn’t mean it’s correct…
Well, I absolutely remember the heavy blue 2″ long arc, and I am very good at estimating dimensions. The humidity was probably more like 30% (I live in southern Arizona), but who knows what it actually was. But yes, I’ve seen figures over almost a 3:1 range for the voltage required to jump that distance. 150 KV was the middle ground.
I want to know what coax you were using, and especially the connector, that can withstand 150 kV, even briefly. I’ve used plain old RG-59 with no problem at 3500 V with MHV connectors, but I’ve also seen N connectors on RG-214 break down at 2 kV (though I’m sure the cable itself is good for better than 10 kV). I’ve never tested it, but I would guess a PL-259 would not be better.
You didn’t understand what I wrote, then. I never said that the voltage was differential on the coax … I said it jumped from the coax to ground, which made it common mode and not relevant to the breakdown voltage of the dielectric inside the coax.
funny little spring-loaded contacts for wire attachment. Looks very old-school. I guess the author had some drawers full of those ?
What are those contacts exactly ? Still manufactured ? They are new to me.