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

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

Got Designs?
Please eMail
if you want me to link to and/or post your original design
NOTE:  We make every effort to link to original material posted by the designer. 
Please contact us if our link is not to your site!  Thanks.

DiscoverCircuits.com -- Hobby Corner
Last Updated on: Tuesday, June 01, 2021 03:06 PM

Hobby Circuits List

The contents & graphics of Discovercircuits.com are copyright protected.
LINK to Dave's circuit, but DO NOT COPY any files to your WEB SITE server

More  AC Power Control Circuits


Most solid state relays require at least 5ma and often more input control current, to fully turn on the device.  But such current levels often force battery powered circuits to use excessively large batteries.  The relay hobby circuit shown below demands only 50uA of input current.  This about 100 times lower than that needed by a typical optically isolated solid state relays.  The circuit uses a combination of a high current TRIAC and a very sensitive low current SCR, to control up to 600 watts of power to a load, while providing full isolation and transient protection.

At the heart of the circuit is a Darlington type opto-isolator A1 from NEC.  This device needs only 50uA of current through the LED section to activate the Darlington side.  A bridge rectifier and a couple capacitors, strips off a bit of current from the 120vac line, through the load.  A zener diode limits the generated DC voltage to 8v.  When the opto-isolator is turned on, current is routed to the gate of a sensitive SCR.  When turned on, the SCR routes current pulses to the main control TRIAC, through a bridge rectifier.  A 15v zener delays the trigger point of the TRIAC slightly, so a minimum 30 volts peak to peak is always available to maintain current to the SCR circuit. 

Click on Circuit Below to view PDF of Schematic

More  AC Power Control Circuits

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

HOME Schematics Index Hobby Corner Dave's Circuits Contact Info
Imagineering Ezine Dave Johnson & Associates Faraday Touch Switches

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

Copyright  January, 1998 - June, 2021     David A. Johnson  All Rights reserved. 
 Linking is ALLOWED but COPYING any content or graphics to your web site is EXPRESSLY PROHIBITED.