LOW_CURRENT_CONSUMPTION_LAMP_FLASHER

Published:2009/6/30 23:04:00 Author:May | From:SeekIC

The circuit is economical in components, and will work with virtually any transistors and is reliably self-starting. The voltage Vb can be taken from a divider, as shown at the right. If taken from a fixed source, flashing becomes slower as battery voltage falls.The lowest drive current into the base of Tr3 is about (Vb-0.6 V)/(R2 + R4). Resistor R4 limits the initial current from C1 and, as shown, R2 and R4 can be roughly equal when a divider is used for Vb. Resistor R2 equals R6R7/(R6+ R7). With the voltages shown, and with R2 = R4, the on-time is about 1.1 C1R2 and the off-time about 0.28 C1R1. Using the component values shown the period is about 0.55 sec. with a duty cycle of about 7% and a mean battery current including the Vb divider, about 1.5 mA.



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