What is it?

This circuit uses a CR1225 coin cell battery to flash an LED (very brightly) at a rate of about once every 1.5 seconds. The flasher can run for up to a year continuously on a single battery.

Why did you make it?

I originally made this circuit to serve as a long term weather proof beacon for geocaching. The flashing LED served as a subtle indicator for geocachers as to the location of the cache. I have since used the circuit as a faux aftermarket car alarm on the dashboard of my car. The flashing light is meant to mimic the flashing LED on the aftermarket car security systems to deter break-ins.

What makes it special?

Although it has few practical applications, this circuit is somewhat unique in terms of its extremely small size/weight, and its very low power requirements. Many other LED flasher circuits are significantly bulkier and powered by significantly larger batteries.