Topic: Directional Lightning Detector from 4 Raspi Lightning Detectors?

[mikejz]

I was thinking about wanting something more than a non-directional lightning detector but less expensive than a Boltek.  I had an idea:  Would it be possible to put four non-directional lightning directors in a square (like https://www.sparkfun.com/products/15441) and write some code to compare the time the strike is detected on each one and arrive at a direction and distance?

Just wanted to know if anyone tried this yet. 

[Aussie Susan]

I think there might be some fundamental issues with your approach.
The first is that light/radio travels at 3x10^8m/s Therefore you really need to be able to get the timing below the nanosecond range. While that is perfectly possible, it would require careful design of the electronics, taking close note of the lengths of wires etc as well as propagation delays within any components. The further apart you can space the detectors the better but I'm guessing that 10s of metres (or more) apart might be difficult in a domestic situation.
Also the device you link to would appear to have some processor in it (as it talks about programmable detection levels etc.). Also the communication protocol is SPI and the datasheet specifies a maximum frequency of 2MHz. The alternative is I2C but there the maximum speed is 400kHz. Therefore there will be timing issues when trying to combine the signals from 4  of these units that could throw of the direction calculation quite badly.
In theory, I guess you would only need 3 devices but that would not get around the issues I've mentioned above.
My initial thought is that you could use 3 (or 4) coils/antenna to detect the lighting strike and use the signals directly to generate a phase difference between them. Again the circuitry would need to operate very fast but such phase detection is a 'fairly well known' problem in the radio world.
Sorry to be a 'downer'....
Susan

[Tln7559]

Like Susan hints, if you use a setup with multiple, offset sensors, it requires very strictly timed read-out between the sensors.

In my mind the very legacy configuration for an RDF pops up as more practibly feasible:
2 loops or ferrite-bars perpendicularly oriented at 1 pole, with additional central pole-antenna possibly as global reference.
Simultaneous read-out of the signals by difference in amplitude should hint to angle toward lightning.
Minor detail that you have to find out whether lightning is in front or in the back.

Accuracy of such RDF-setup for radio transmissions is very reasonable, because stable mutual positions and transmission from point-source.
Accuracy for lightning-detection?
Probably not applicable, because lightning is electronically a very 'wild' event and also might spread over a wide area in the sky .....

[Cutty Sark Sailor]

1. Assuming you can determine the Discharge energy pk...
as from these two antennas, and assuming they are phased together:

2. you can 'assume' that illustration is ± North-NorthEast.
Distance is a whole different can of worms....but we seem to have a good discharge peak, so assume >±6-10km but <50km - 80km

[Tln7559]

😉 legacy solution for range calculation is 2 synchronised, sufficiently & accurately spaced ‘RDF’s:
then by triangulation the distance to the emitter can be calculated.

However, range accuracy is a function of the spacing between the ‘RDF’s relative to the angles and the mutual accuracy of the angular measurements: maths …..
OK if Lightning perpendicular to line connecting both ‘RDF’s, but really bad if Lightning along the connecting line.
In that perspective the setup with 4 sensors in a square might be more uniform.

Indeed can of worms …..