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

DiscoverCircuits.com has links to 45,000+ electronic circuits, cross-referenced
into 500+ categories.    We have searched the web to help you find quick design ideas.

HOME Schematics Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches
Welcome to DiscoverCircuits.com - online since 2002

See Media Kit for
Advertising Opportunities

Attention Designers:  Please alert us by eMail if we have linked to sites
where your original material has been copied without your permission.
We will change to the LINK to your site.  
Thank you.

 

DiscoverCircuits.com -- Hobby Corner
Last Updated on: Tuesday, October 24, 2017 02:54 PM

Hobby Circuits 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  Safety Circuits

12v Battery Load Cutout Circuit -- August 23, 2009

 

Lead-acid batteries should not be discharged below a certain point if they are to last.  Also, you donít want certain 12v powered devices, which might be plugged into a carís cigarette lighter outlet, to drain the car battery down to a point where the carís engine will not start.  To prevent battery damage or a dead battery, the circuit below disconnects a load from the battery when the voltage dips below a fixed but adjustable voltage and will not reconnect the load until a reset button is pressed.  To keep the whole circuit efficient and compact, a medium current rated p-channel FET forms the power switch. 

A 8.2v zener diode forms the voltage reference while a second 15v zener diode acts as a transient voltage protector.

This hobby circuit uses one half of a popular LM393 dual voltage comparator to monitor the battery voltage and the adjustable reference voltage.  If the battery voltage drops below the adjusted level, the comparator changes state.  One half of a popular CD4013 dual flip/flop latches the on/off condition.  A reset button must be pressed to reestablish power to the external load.

A rather long 5 second time constant filter is used in the voltage comparator circuit.  This allows the circuit to ride out the dip in battery voltage, which always takes place when the carís engine is started.

Click on Drawing Below to view PDF version of Schematic

12V Battery Voltage Monitor Circuit

More  Safety Circuits

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

 


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


Discovercircuits.com endeavors to credit original designers.   Please alert us by eMail so we can
delete links to material that have been copied without your permission
.   Thank you.


© Copyright of all original material on this website is the property
of David A. Johnson, P.E. (Dave Johnson & Associates ) unless otherwise noted.  

Linking is ALLOWED but COPYING any content or graphics to your web site is EXPRESSLY PROHIBITED.
All material is provided "as is" without guarantees or warranty of any kind, either expressed or implied.