1.5 Volt LED flasher

              flash a led from a single cell             


Introduction

With this circuit it is possible to operate a LED from a single 1.5 Volt cell. The LED will flash
about every second.

Circuit description

R1, C1 and IC1B build a slow oscillator (about 1 Hz).
When the output of IC1B is low, the outputs of IC1A/D will become high and the outputs of IC1C/E will become low:
C2 is now charged to 1.5 Volt
When the output of IC1A becomes high, the outputs of IC1A/D will become low and IC1C/E will become high:
Charged capacitor C2 is now switched "in series with" the battery voltage: C2 is discharged through the LED until the voltage
of the battery and C2 together is lower than the LED forward voltage.

IC1A/D and IC1C/E are put in parallel to increase the peak current trough the LED.

Note: red LEDs have lower forward voltage and will therefore work best with this circuit; the best choice will be a high
efficiency red LED.

Led flasher schematic:

Picture of the assembled circuit:

Download specifications of key components at the  Component specs page

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