This circuit diagram show a simple low voltage LED flasher with a single 1.5 DC volts battery, the popular LM3909 LED flasher IC, and a few components. The capacitor uses as a time generator for the LED sequence, variable depend on its values. Many functions and applications of this circuit diagram. Very easy to build, cheap but have a high performance.

source : bill bowden’s circuit collection
low-voltage-led-flasher-2