There is an ingenious lightning detector circuit presented at techlib.com web site that works amazingly well. It consists of a micropower AM radio receiver and a very cunning spike detector. With the wire antenna 1m long, the original circuit is able to detect incomming thunderstorms approximately from 5 to 10 km away.

What might be annoying, though, is that the circuit is so sensitive that it reacts not only to lightning strikes but also to all kinds of electrical disturbances often produced at home and around it. In order to leviate users from being disturbed every now and then by meaningless ticks and cracks produced by the detector, we designed a signal post-processing subcircuit which filters out almost all signals not originating in lightning strikes. As the subcircuit utilises a pair of CMOS ICs, adding it to the original detector rises the overall battery power consumption only for a tiny fraction.

* * * * *

Misteriously and in absolute accordance with the Murphy's law stating that it will not rain if one takes an umbrella to the picnic, since the day that we built the prototype circuit a month and a half ago, there haven't been even the smallest thunderstorms occuring around our city. As there is not much use of presenting untested devices online, posting of these pages will have to be delayed for a few more days...