I am working on trying to build a simple circuit that turns on and latches an Led when a lightning rod gets struck by lightning. This is what I have come up with so far. The idea with the circuit is that I will have a coil of wire around the lighting conductor, so that when there is a strike there will be an induced current in the coil that is clamped down to 5-6v by the tvs diode which then turns on the SCR and latches, turning the LED on. The circuit can then be reset by the normally closed push button. Does this look like a viable idea? Also the values are all temporary so please feel free to suggest different ones. Thanks

 

The coil will definitely need to be insulated from the rod.
Normally the coil would be on the down cable not directly on the rod from a brief research on the subject.

 

Add a small capacitor in parallel with D4 so the device is less sensitive to interference.
Remove NC switch SW1. Add NO switch in parallel to the SCR. A NO switch is much more reliable, especially at low supply voltages.

 

I don't know if this is important but lightning is DC.

 

The coil will definitely need to be insulated from the rod.
Normally the coil would be on the down cable not directly on the rod from a brief research on the subject.

That is what I meant to do. I guess I wasn't clear in how I said it.

 

Add a small capacitor in parallel with D4 so the device is less sensitive to interference.
Remove NC switch SW1. Add NO switch in parallel to the SCR. A NO switch is much more reliable, especially at low supply voltages.

Do you mean put the NO switch between the anode and the gate of the SCR?

 

Do you mean put the NO switch between the anode and the gate of the SCR?

Between anode and cathode

 

Which shunts the current off the SCR, turning it off.

 

Interesting subject. Some 40 years ago a company I was working for scrapped a project. Among the tossed stuff were digital counters. Also quite a few Photo Transistors, I think they were 2N2222 type. For some unknown reason I decided to connect the emitter and collector across the two points on the counter where normally a switch would have gone. I put one in the refrigerator to see how many times in a day the refrigerator door was opened. I don't remember the number but one evening one was sitting on the table when there was a flash of lightning. I looked at the counter and the number had greatly increased. So I hit the reset button on the counter and stuck it in the window. With the next flash of lightning it counted something like 35 pulses during that single flash event. Other flashes had far higher numbers. Of course this was done in the evening.

I share this because I'm wondering why the need to detect lightning. Back in my teenage years I worked at a church camp. We had the CB radio going for communication between the main lodge and where we were working on the property. With any AM radio you can hear lightning strikes some distance off. I can't tell you how far away from the receiver the lightning was but it was far enough that when you heard the static from the lightning you wouldn't hear the thunder.

 

Interesting subject. Some 40 years ago a company I was working for scrapped a project. Among the tossed stuff were digital counters. Also quite a few Photo Transistors, I think they were 2N2222 type. For some unknown reason I decided to connect the emitter and collector across the two points on the counter where normally a switch would have gone. I put one in the refrigerator to see how many times in a day the refrigerator door was opened. I don't remember the number but one evening one was sitting on the table when there was a flash of lightning. I looked at the counter and the number had greatly increased. So I hit the reset button on the counter and stuck it in the window. With the next flash of lightning it counted something like 35 pulses during that single flash event. Other flashes had far higher numbers. Of course this was done in the evening.

I share this because I'm wondering why the need to detect lightning. Back in my teenage years I worked at a church camp. We had the CB radio going for communication between the main lodge and where we were working on the property. With any AM radio you can hear lightning strikes some distance off. I can't tell you how far away from the receiver the lightning was but it was far enough that when you heard the static from the lightning you wouldn't hear the thunder.

The reason I am making this project is that I live off grid at the peak of a mountain and my house and land gets struck by lightning at least once a year. I have a radio tower with some antennas on it and a lightning rod at the top. I have been trying to ground everything and protect it from lightning damage and since grounding everything I have had several very close lightning strikes. The thing is I don't know if my tower was struck or if it was just somewhere nearby. If I know the tower was actually struck I can have a bit more confidence in the grounding I have already done

 

I've seen documentaries on lightning. What I saw was that cloud to ground lightning begins to excite the ions in the air and ground. Fingers reach up from the ground while downward traveling fingers reach toward the ground. When one of the fingers find a pathway to another finger the lightning strikes. Only one pathway gets completed. People who've been struck by lightning and lived have likely been involved in these fingers, the ones that didn't connect. Their injuries can be significant but they haven't been hit by the full force of the lightning. I suppose this would qualify as well to know if there was an event whereby grounding saved the day.

One afternoon during a lightning storm I was standing on the shipping dock, not out in the rain. I heard crackling sounds coming from the water cooling tower. I think it was those fingers causing that. However, lightning found a path to ground via a different route because about 1 or 2 seconds after the fizzling sound there was a flash of lightning. A few seconds later we heard the thunder. Lightning was less than a mile away but the thunder wasn't instantaneous.

 

The way to protect equipment from an actual lightning strike is to disconnect it. If your ground system has one ohm of resistance , then ay 100 amps you will have 100 volts across that resistance. BUT lightning current is much greater, AND the much faster rise time is affected by series impedance, as well. A LIGHTNING STRIKE, YEARS AGO, on my 18 pipe foot mast supporting my wire antenna, blistered the paint, and damaged a number of items inside the house.

An adequate antenna to detect a lightning strike nearby is a ten foot wire within a hundred feet of the strike.