1 Cell battery LED flasher circuits

Posted on Feb 13, 2013

The LED flasher circuits below operate on a single 1.5 volt battery. The circuit on the upper right uses the popular LM3909 LED flasher IC and requires only a timing capacitor and LED. The top left circuit, designed by Andre De-Guerin illustrates using a 100uF capacitor to double the battery voltage to obtain 3 volts for the LED. Two sections of a 74HC04 hex inverter are used as a squarewave oscillator that establishes the flash rate while a third section is used as a buffer that charges the capacitor in series with a 470 ohm resistor while the buffer output is at +1.5 volts. When the buffer output switches to ground (zero volts) the charged capacitor is placed in series with the LED and the battery which supplies enough voltage to illuminate the LED.

1 Cell battery LED flasher circuits
Click here to download the full size of the above Circuit.

The LED current is approximately 3 mA, so a high brightness LED is recommended. In the other two circuits, the same voltage doubling principle is used with the addition of a transistor to allow the capacitor to discharge faster and supply a greater current (about 40 mA peak). A larger capacitor (1000uF) in series with a 33 ohm resistor would increase the flash duration to about 50mS. The discrete 3 transistor circuit at the lower right would need a resistor (about 5K) in series with the 1uF capacitor to widen the pulse width.

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    Reverse RIAA Equaliser
    41-72MHz micro-receiver ( MC3362 )
    Telephone Line optical and sound Ring
    Musical telephone ringer
    Photo-Event Timer
    Digital Clock
    op amp summer as a digital to analog converter dac
    Square Wave Generator
    0-20V 3A bench PSU
    The ATL-3 Loop Antenna
    A dark detecting circuit for your jack lantern
    4 Channel Tranceiver