Want a fun way to observe the enormous electric fields generated by approaching thunderstorms? First published in Elektor in June 2003, this clever lightning intensity detector gives experimenters exactly that.
Want a safe way to observe the enormous electric fields generated by approaching thunderstorms? First published in Elektor in June 2003, this clever Lightning Intensity Detector gives experimenters exactly that. Rather than trying to detect lightning directly, the circuit senses changes in the surrounding atmospheric electric field, offering a fascinating glimpse into one of nature's most powerful phenomena.
The Circuit
B. Oehlerking’s detector works by measuring the strength of the local electric field, which rises dramatically as a thunderstorm approaches. A simple telescopic whip or one-meter wire serves as the sensing antenna, picking up tiny electrical potentials induced by the atmosphere. Because these voltages can be surprisingly high, the input signal is first heavily attenuated by resistor divider networks before being fed into a pair of CMOS 4093 Schmitt-trigger ICs.
The circuit compares the incoming signal against two preset thresholds. When the electric field exceeds approximately 1.3 kV/m, the first LED illuminates, indicating elevated atmospheric activity. If the field continues to rise beyond roughly 13 kV/m, a second LED lights to warn of much stronger electrical conditions. Thanks to the Schmitt-trigger inputs, the detector has built-in hysteresis, preventing the LEDs from flickering as the measured field hovers around the switching points.
Powered from a 9-V battery, the finished project is compact, portable, and consumes very little current. It is intended as an educational instrument for observing the changing electrical environment before and during thunderstorms. Of course, it is not meant to be a lightning predictor or safety device. Used responsibly from a sheltered location, it provides an intriguing way to witness invisible atmospheric processes in real time.
Hands-On Experimentation
Although inexpensive weather sensors and internet-based lightning maps are now widely available, this 2003 project remains a rewarding hands-on experiment because it measures a physical phenomenon directly rather than relying on remote data. Building the detector provides valuable insight into high-impedance analog design, electric-field sensing, threshold detection, and the practical use of Schmitt triggers in measurement circuits.
The Lightning Intensity Detector Project
The original article, “Lightning Intensity Detector,” appeared in Elektor June 2003. Check out the article.
Editor's Note: The article first appeared in a 2003 edition of Elektor. Some of the parts and components might not be available; nevertheless, we think you will find the article informative.
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