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AC Power Control Circuits
Last Updated on: Friday, October 03, 2014 10:36 AM

Circuits Designed by Dave Johnson, P.E. :
  • 50ua Drive Current for Solid State Relay Requirement - 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  … [Hobby Corner Circuit by Dave Johnson]  Added October 2005
  •  AC Line Under/Over Voltage Alarm
    Power lines, which deviate much beyond normal voltages can damage expensive electronic equipment.  The 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.… [Hobby Corner Circuit by Dave Johnson]  Added May 2005

  • AC Power Line Hi/Lo Voltage Tester
    If you wish to test a line-powered device under both a 15% high and a 15% low voltage condition, you can use the circuit below.  The circuit uses an 18v transformer with a 3 amp rating.  A double pole, double throw toggle switch then switches in the trans … [Designed by David A. Johnson]  Added May 2005
     
  • Active AC Power Line Indicator
    The circuit below is designed to detect when a power cable is active (hot). When the flat sensor end of the device is held near an active AC line, the bright green LED on the top of the housing will glow.  It is powered by a 3v CR2032 lithium coin cell.  I … [Designed by David A. Johnson]  Added November 2010
     
  • Bi-Directional Charge Coupled Powers MOSFET Relay
    The circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply. Since the coupling capacitor values used to drive the FETs are small, the leakage current from the power line in … [Hobby Corner Circuit by Dave Johnson]  Added October 2005
     
  • CHARGE COUPLED BI-DIRECTIONAL POWER MOSFET RELAY
    The circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply. Since the coupling capacitor values used to drive the FETs are small, the leakage current from the power line in … [Designed by David A. Johnson]  Added October 2005  Published in Electronic Design, Nov. 8, 1990.

     
  • High/Low Voltage Tester on AC Power Line
    If you wish to test a line-powered device under both a 15% high and a 15% low voltage condition, you can use the circuit below.  The circuit uses an 18v transformer with a 3 amp rating.  A double pole, double throw toggle switch then switches in the trans … [Hobby Corner Circuit by Dave Johnson]  Added May 2005

     
  • Hot AC Power Line Indicator
    The circuit below is designed to detect when a power cable is active (hot). When the flat sensor end of the device is held near an active AC line, the bright green LED on the top of the housing will glow.  It is powered by a 3v CR2032 lithium coin cell.  I … [Hobby Corner Circuit by Dave Johnson]  Added May 2005
     
  • Line Powered White LED Array
    There has been a lot of excitement lately in the lighting industry.  Some companies are beginning to manufacture general lighting fixtures, which replace incandescent and fluorescent lamps, using LED lights.  When proper heat management is designed into t … [Designed by David A. Johnson]  Added February 2010
     
  • SOLID STATE RELAY REQUIRES ONLY 50uA DRIVE CURRENT
    This circuit demands a control current that is 100 times smaller than that needed by a typical optically isolated solid state relays. It is ideal for battery-powered systems. Using a combination of a high current TRIAC and a very sensitive low current SCR … [Designed by David A. Johnson]  Added October 2005

 

 
Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

50ua Drive Current for Solid State Relay Requirment- 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 … [Hobby Corner Circuit by Dave Johnson]

AC Line Powered LED Strings- This shows 4 different ways to string white LEDs that are powered by a 120vac or 240vac power line.  The circuit was designed by Ken Schultz. … [Hobby Corner Circuit by Dave Johnson]

Bi-Directional Charge Coupled Powers MOSFET Relay- The circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply. Since the coupling capacitor values used to drive the FETs are small, the leakage current from the power line in… [Hobby Corner Circuit by Dave Johnson]

Charge Coupled Bi-Directional Power MOSFET Relay- The circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply. Since the coupling capacitor values used to drive the FETs are small, the leakage current from the power line in… [Designed by David A. Johnson]

Circuit Level-Shifts AC Signals- 10-Jul-03 Issue of EDN  AC signals can emanate from many sources, and many of these sources are incompatible with the most popular interface voltages, such as TTL. A temptation always exists to capacitively couple the ac signals because capacitive couplin… [Design Idea by Ron Mancini, Texas Instruments, Bushnell, FL]

Line Input for Zoom H2- NOTE: Must register on this site… [Published in Elecktor July/Augu, 2010]

Solid State Relay Requires Only 50ua Drive Current- This circuit demands a control current that is 100 times smaller than that needed by a typical optically isolated solid state relays. It is ideal for battery-powered systems. Using a combination of a high current TRIAC and a very sensitive low current SCR… [Designed by David A. Johnson]

Why Limit Your Power Supply's Input Range?- 20-Mar-03 Issue of EDN  Multilayer capacitor doubles as varactor-Taking only a cursory look at the input-voltage ratings of your power-supply IC can limit the usable input-voltage range. With careful examination of an IC's operating specifications and cir… [Design Idea by Michael Day, Texas Instruments, Dallas, TX]

AC Power Control Circuits


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