Electronic Circuits and electronic circuits, electronic schematics plus an extensive resource for hobbyists, inventors and engineers

DiscoverCircuits.com, has 40,000+ electronic circuits, cross-referenced
into 500+ categories.    We have searched the web to help you find quick design ideas.
We make every effort to link to original material posted by the designer. 
Please let us if you would like us to link to or post your design.

HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches

DiscoverCircuits.com -- Hobby Corner
Last Updated on: Thursday, June 25, 2015 06:22 AM

Hobby Circuits' Category List

The contents & graphics of Discovercircuits.com are copyright protected.
LINKING to Dave's circuits is permitted but DO NOT COPY any files to your WEB SITE server

More  Indicator Circuits 
Micropower Circuits     Light Flashers

3v Low Battery Voltage Flasher Circuit
designed by David Johnson, P.E.

Many battery powered devices use two AA alkaline cells.  Often you will not know when it is time to replace the batteries until the device powered by them actually stops operating.  The hobby circuit below can be connected to a 3v battery, to give you some warning when the battery is nearing its end of life. 
It will flash a LED when the battery voltage drops to about 2.4 volts.  The electronic circuit draws only 1ua of current in standby mode and jumps to only 20ua when flashing, so it can safely be included without depleting the battery energy.  A voltage detector IC from Panasonic (Microchip also makes similar devices) is used to monitor the battery voltage.  The device’s open drain output swings low, when the battery voltage is below 2.4 to 2.5 volts.  This action turns on the two transistor oscillator circuit, which drives the LED with short current pulses lasting only 2ms.  I published this Flasher circuit in the January 2 issue of EDN magazine in 1997.

 

Click on Drawing Below to view PDF version of Schematic

Circuit Circuit Under Voltage LED Flasher Circuit designed by David Johnson, P.E. (Dec 24, 1998)


More  Indicator Circuits     Micropower Circuits     Light Flashers

Hobby Circuits' Category List
eMail David A. Johnson, P.E. about this circuit


HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches


 About Us   |  Advertise on DiscoverCircuits.com   |   Report Broken Links  |    Link to DiscoverCircuits.com  |    Privacy Policy

Copyright  2002 - 2015 David A. Johnson & Associates.  All Rights reserved. 
 Linking is ALLOWED but COPYING any content or graphics to your web site is EXPRESSLY PROHIBITED.