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: Monday, October 09, 2017 03:35 PM

Hobby Circuits' Circuit 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  AC Power Line Circuits    Alarms     Voltage Sensors

AC Line Under/Over Voltage Alarm     (March 29, 2009)

Power lines, which deviate much beyond normal voltages can damage expensive electronic equipment.  This hobby circuit below sounds an alarm whenever the line voltage is higher or lower than normal.  I set the alarm limits at about +-15% from standard levels.  This hobby circuit rectifies and filters the power line signal.  I set the resistor values, so the DC voltage produced is close to 1% of the RMS value of the line.  Thus, a 120vac line would yield about 1.2v DC.  That voltage is fed to a pair of voltage comparators. 

The outputs of the comparators decide if the sampled voltage is above, below or acceptable.  Three LEDs indicate the voltage range.  A green LED is lit if the voltage is OK.   If the voltage is outside normal levels, the circuit sounds an alarm using a small magnet or piezoelectric beeper.  I have shown recommended resistor values for both 120vac and 240vac power lines.

Click on Drawing Below to view PDF version of Schematic

AC Line Under/Over Voltage Alarm Circuit

More  AC Power Line Circuits    Alarms     Voltage Sensors

Hobby Circuits' Circuit 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.