Monday, April 1, 2013

1 5 volt dual LED flasher

This 1.5 volt led fasher runs more than a year on a single d" cell and alternately flashes 2 LEDs at about a 1 second rate. The circuit employs a 74HC14 CMOS hex inverter that will operate at very low voltages (less than 1 volt). One section is used as a squarewave oscillator (pins 1 and 2), while the others are wired to produce a short 10mS pulse on alternate edges of the square wave so the LEDs will alternate back and forth. The output sections each use a capacitor charge pump to increase the voltage for the LEDs. The circuit draws an average current of 800uA from the D battery and the LED peak current is about 40mA with a fresh battery and drops to about 10mA as the battery voltage falls to 1.1 volts. The capacity of a alkaline D cell is about 12 amp hours with a cutoff voltage of 1.1 so the circuit should run about 12/.0008 = 15000 hours or maybe 625 days, but I havent verified that yet. The idea for this circuit came from a single 1.5 volt LED flasher by Dave Johnson that can viewed at






Author : Bill Bowden 

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