This traditional flasher configuration with two transistors drives 5 LEDs with a supply that must be at least 12 V. For fewer LEDs, the supply can be made with lower voltage. The frequency is controlled by P1.

This traditional flasher configuration with two transistors drives 5 LEDs with a supply that must be at least 12 V. For fewer LEDs, the supply can be made with lower voltage. The frequency is controlled by P1.