Low current consumption lamp flasher

Posted on Aug 16, 2012

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 Cl 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.

Low current consumption lamp flasher
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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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