A bolt from the blue

The phrase “A bolt from the blue” is sometimes used to refer to a sudden, brilliant idea. Just such a thing happened when ams (formerly know as Austria Microsystems; URL: www.ams.com) came up with the AS3935 sensor IC. It was created so that people could be protected from litteral bolts from the blue: lightning strikes.

A programmable lightning sensor, the AS3935 detects when potentially hazardous lightning activity is approaching and in the vicinity. It detects cloud-to-cloud and cloud-to-ground flashes, so users or automated machinery can evaluate the risk presented by approaching storms and take appropriate action.

Since light travels at 299,792, 458 m/s while sound only travels at 343.2 m/s, the time between seeing a bolt of lighting and hearing its thunder is a good measure of the distance between the lightning and the person hearing the thunder. So when a lightning flash is seen and the thunder is heard less than 30 seconds later, the storm is about 10 km away. In such cases, the US National Weather Bureau recommends that you should head immediately for a safe shelter and stay there until 30 minutes after you hear the last clap of thunder a practice referred to as the 30/30 rule.

However, since thunderstorms can travel at ground speeds up to 113 km/hr, that doesn’t give you a lot of time to find safe shelter. The AS3935 can give you better warning; it can detect lightning activity up to 40 km away, which provides you four times as long to prepare. And the sensor is reliable: it avoids false readings by rejecting interference signals from such common man-made sources as fluorescent lighting, motors, microwave oven, switches, and other RF emitters.

The beauty of this device is that it can be incorporated into many types of portable devices key-chain fobs, watches, ATVs and golf carts, fishing rods, GPSs as well as into stationary emergency systems such as back-up power supplies, allowing them to prepare for possible outages. It’s probably the most useful and beneficial lightning-related product since Ben Franklin’s lightning rod.