Simple low voltage LED flasher circuit diagram – 1
Designed by Andre de-guerin, this low voltage LED flasher circuit diagram is using two section of a 74HC04 hex inverter IC to create squarewave oscillator that establish the flash rate, while a third section is used as a buffer that charged the capacitor in series with 470ohm resistor while the buffer output is at +1.5V. When the buffer output switches to ground (zero volts) the charged capacitor is placed in series with the LED and the battery which supplies enough voltage to illuminate the LED. A high brightness LED is recommended because the LED current is approximately 3 mA. A 100uF capacitor also used to double the battery voltage to obtain 3 volts for LED.
source : bill bowden’s circuit collection