When the circuit is in operation the (dis)charging of C1 determines the maximum current. The electrolytic has a minimum voltage remaining which is equal to the LED voltage, causing the pulses to be smaller than the very ﬁrst pulse: (5 – 2 × 1.6) / 470 = 3.8 mA peak. If one LED is sufficient then you can replace either D1 or D2 with a Schottky diode; the pulse through the remaining LED then becomes slightly larger. The use of two LEDs has the advantage that the discharge current of C3 is also used by the indicator, which makes the circuit more efficient. The oscillator can of course be replaced by a different type, for example the classic Schmitt-trigger/inverter type using a 74HC14 and RC network.
LED Flasher Circuit Diagram
The version used here has the advantage of offering a better stability. C1 makes IC1f switch faster. The resistors have been made as large as possible, so the adjustment of the ﬂash frequency is best done by varying the value of C2. The period with the component values given is about 6 seconds, so a LED will ﬂash every 3 seconds. The current consumption is determined mainly by IC1f, since this is almost working as a linear ampliﬁer. The circuit doesn’t draw more than about 1.3 mA in total. The LEDs used should preferably be red ‘low-current’ or ‘high-efficiency’ types. The current pulses will then be slightly larger and the efficiency of red LEDs is still better than that of green or yellow ones.