Franzis Verlag is known for its electronics kits. After the bat detector already impressed me, the lightning detector is now up, which is currently available for 16.95 € instead of 34.95 euros directly from Franzis .
The device is already largely complete, which is also a good decision given the SMD components. Only some soldering experience is needed to complete an additional IC, piezo speaker, a pin header and other peripheral components, which only takes a few minutes.
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The finished lightning detector can then be installed in the cardboard box. The speaker is glued to the cardboard with a strip of adhesive tape, which simultaneously serves as a membrane. Once two AA batteries are inserted, the circuit begins calibration, which is indicated by the flashing of the first green LED and is completed after 2 seconds. This also indicates the correct function of the device.
A green LED briefly lights up when lightning is within range and the speaker emits a beep. Three more LEDs show the approximate distance of the lightning strike: green approx. 50 km, yellow approx. 30 km and red 10 km or less.
With the jumper in position 2 and a connection wire of the speaker over the coil, lightning can be simulated. Much more interesting, of course, is real use during a thunderstorm, and as luck would have it, various thunderstorm cells build up around us shortly after completion. With the jumper on position 1, you activate the sensitive mode, which detects lightning at over 100 km distance. With another jumper on position 3, you can activate the memory mode. This allows you to record the proximity of the last thunderstorm, even if it has already passed.
Zap! It works amazingly well!
I positioned the Franzis lightning detector away from power supplies, PCs and other sources of interference and simultaneously tracked the lightning activity on Lightningmaps.org . The lightning detector beeps and indeed the events can be clearly assigned on Lightningmaps. The thunderstorm is located a good 50 km away to the north. Other thunderstorm cells are located to the east near Prague, which is about 180 km away as the crow flies from us. These lightning strikes are not detected.
If jumper 1 is plugged in during operation, individual lightning pulses are also evaluated. If it is already plugged in when the batteries are inserted, the sensitivity also increases. When the strikes come closer, this is acknowledged with the corresponding LEDs. Here too, I was able to confirm the plausibility using lightningmaps.org.
How it works
The lightning detector was developed by Burkhard Kainka , who has been known for decades for hundreds of circuits in various electronics magazines, books and also for Kosmos electronics kits. He uses an IC of type TA7642, which is actually a medium wave receiver. Since lightning emits electromagnetic pulses and thus radio waves, this can be received via an antenna, in this case a small ferrite coil and the TA7642.
A microcontroller adjusts the sensitivity of the receiver so that the background noise from other sources just doesn’t trigger an event. As soon as lightning strikes, the signal rises above this threshold and the microcontroller counts a pulse. If at least two pulses per second are detected, this is counted as lightning, the speaker beeps and the green LED briefly lights up.
Conclusion
For 16.95 euros, the Franzis lightning detector is not only fun, it also works amazingly well. The build is simple and only requires basic soldering skills.
Thunderstorm photographers are informed when a thunderstorm is nearby, as the lightning detector is said to run for more than half a year on one set of batteries. This means you can activate the detector during the season and be warned even without a thunderstorm app.
More info and ordering: Franzis Shop
Tinkering idea: Lightning detector for the smart home
I’ve already tried and built various lightning detectors. One of them with a special AS3935 module from AMS (instructions from Heise are HERE ). Unfortunately, it was quite unreliable, although the module is not exactly cheap. Other DIY builds worked quite well, but were always quite susceptible to interference from pulses that had nothing to do with thunderstorms.
The Franzis lightning detector, on the other hand, is very reliable and insensitive to interference. It therefore also lends itself as a lightning detector for the smart home. I will connect the LED outputs with an ESP8266/NodeMCU and via ESP-Easy to my Symcon hub and thus add the lightning detector to my weather station.
Hi! I'm Markus – the Fricklr. ⚡ Electrical engineer, 🎵 musician (bass, guitar, keys) and professionally 'something with the internet' 🌐 for over 30 years – nowadays with AI too 🤖 – a 55-year-old generalist from Bavaria, Germany.
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