The AS3935 Franklin lightning sensor IC, capable of detecting lightning up to 40 km away, has been developed by austriamicrosystems. The IC utilizes a RF receiver that detects the electrical emissions from lightning activity. An algorithm then converts the RF signal into an estimation of the distance to the head of the storm. Drawing on extensive meteorological survey data, the algorithm produces an estimated distance-to-storm calculation from 40 km down to 1 km, while rejecting disturbances from man-made signals such as motors and microwave ovens. With multiple low-power modes, a listening mode current consumption of 60µA and housing in a 4mm x 4mm 16-pin MLPQ package, the AS3935 can be integrated into a variety of portable/outdoor devices, as well as uninterrupted power supplies, power conditioners, and smart grids needing early detection for surge damage prevention. Typical applications require a microcontroller with SPI or I2C interface and seven other passive components, allowing all to fit in a space the size of a keychain remote. The AS3935 Franklin lightning sensor IC is available today for sampling.