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AC Power Control Circuits
Last Updated on: Monday, December 25, 2017 01:43 PM
 

Circuits Designed by Dave Johnson, P.E. :
50ua Current Drives Solid State Relay Requires Only -  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 . . . Hobby Circuit designed by Dave Johnson P.E.-June 3, 2000

AC Line Powered LED Strings -  This shows 4 different ways to string white LEDs that are powered by a 120vac or 240vac power line.    This hobby circuit was designed by Ken Schultz. __ Designed by Ken Schultz-December 7, 2008

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 Circuit designed by Dave Johnson P.E.-March 29, 2009

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 . . . Hobby Circuit designed by Dave Johnson P.E.-June 3, 2000

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. . . Circuit by Dave Johnson P.E.-June 3, 2000

Detects Low Voltage 120VAC Power Line    -  This hobby circuit will turn on a beeper when the line voltage drops below 100 volt AC . . . Hobby Circuit designed by Dave Johnson P.E.-July 09, 2006

Low Voltage 120vAC Power Line Alarm   -  This circuit will turn on a beeper when the line voltage drops below 100 volt AC.   . . . Circuit by David Johnson P.E.-July 09, 2006

Power Line Alarm   -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac.   . . . Circuit by David A. Johnson P.E.-July 09, 2006

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 . . . Circuit by David A. Johnson P.E.-June 03, 2000

SSR Requires Ultra Low Control Current   -  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 . . . Hobby Circuit designed by David Johnson P.E.-June 03, 2000

Under/Over Voltage Alarm on AC Line   -  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 . . . Circuit by David Johnson P.E.-March 29, 2009


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

120 VAC Low Voltage Alarm -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac.. . . Circuit by David Johnson P.E.-July, 2006

5.8 watt audio power Amplifier -  A simple and very cheap audio power amplifier

50ua Current Drives Solid State Relay Requires Only -  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 . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

AC Line Powered LED Flasher -  Some of the latest LEDs are amazing.  They can produce a surprising amount of light with very little current.  In the light flasher application shown below I take advantage of a nice surface mounted LED from King Bright.  This flasher circuit draws only about 3ua of average current from the AC power line to flash this green LED.  This flasher might be used as a power indicator light . . . Hobby Circuit designed by Dave Johnson P.E.-December, 2008

AC Line Powered LED Strings -  This shows 4 different ways to string white LEDs that are powered by a 120vac or 240vac power line.    This hobby circuit was designed by Ken Schultz. __ Designed by Ken Schultz-December, 2004

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 Circuit designed by Dave Johnson P.E.-March, 2009

AC Power Line High/Low 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. . . Circuit by David A. Johnson P.E.-March, 2010

AC Power Loss Alarm -  Iíve been having a problem with my instant hot water system lately.  This system circulates electrically heated water throughout my house using a small pump.  The pump is wired into a ground fault interrupter   (GFI) module.  Every now and then, the GFI trips, leaving me without hot water. . . Circuit by David A. Johnson P.E.-March, 2009

AC power supply -  I have done a lot of work with valves in recent years.  For me valves have many advantages, least of all the price; since they are now "obsolete" it is quite easy to get hold of them for next to nothing at rally's and junk sales.  I recently purchased a couple of hundred battery valves for less than SEK1   (GBú0.10 US$0.15) each. __ Designed by Harry Lythall-SM0VPO

AC-power your without a transformer -  07/17/13  EDN-Design Ideas Editor's Note: Here's another take on the transformerless AC line power supply, which finds use in some well-insulated, low-power devices.  Our technical reviewer pointed out that Cac should be an X-rated safety type, and I think we'd both feel better if the ground symbol wasn't there!  SMPS circuits offer an efficient way to reduce AC from a mains source to any desired level for powering low-voltage circuits, though this comes at the cost of components such as control ICs, switching transistors, inductors, etc.  Figure 1 shows a simple way you can use more common components to step-down and regulate the AC mains to the desired low DC voltage. __ Circuit Design by Raju Baddi

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 . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

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. . . Circuit by Dave Johnson P.E.-June, 2000

Circuit Level-Shifts AC Signals -  10-Jul-03 EDN-Design Ideas 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 __ Circuit Design by Ron Mancini, Texas Instruments, Bushnell, FL

Detects Low Voltage 120VAC Power Line  -  This hobby circuit will turn on a beeper when the line voltage drops below 100 volt AC . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

LED Strings powered by AC Line -  This shows 4 different ways to string white LEDs that are powered by a 120vac or 240vac power line. __ Designed by Ken Schultz, drawn Dave Johnson 12.18.2004-December, 2004

Level-Shifts AC Signals -  10-Jul-03 EDN-Design Ideas 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 __ Circuit Design by Ron Mancini, Texas Instruments, Bushnell, FL

Line Input for Zoom H2 -  NOTE : Must register on this site __ Designed by Published in Elecktor July/Aug, 2010

Low Voltage 120vAC Power Line Alarm -  This circuit will turn on a beeper when the line voltage drops below 100 volt AC.. . . Circuit by David Johnson P.E.-July, 2006

Power Amp-Single Polarity Power Supply-Using Model 423  -  No description, just schematicOpAmps Lab Inc is the manufactor ofAmplifiers (Video / Audio / Distribution / Microphone / Equalization / Line / VCA / Power), Switchers (Routing / Assign / Matrix), Mult (Press) (Network-Feed) Boxes, Audio Transformers, Oscillators, Power-Supplies, Custom Sub-Systems. __ Application OpAmps Lab Inc.

Power Line Alarm -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac.. . . Circuit by David A. Johnson P.E.-July, 2006

Servo-Constant-Current Drive Amplifier-Using Model 440C  -  No description, just schematicOpAmps Lab Inc is the manufactor ofAmplifiers (Video / Audio / Distribution / Microphone / Equalization / Line / VCA / Power), Switchers (Routing / Assign / Matrix), Mult (Press) (Network-Feed) Boxes, Audio Transformers, Oscillators, Power-Supplies, Custom Sub-Systems. __ Application OpAmps Lab Inc.

Servo-Position-Using Model 423  -  No description, just schematicOpAmps Lab Inc is the manufactor ofAmplifiers (Video / Audio / Distribution / Microphone / Equalization / Line / VCA / Power), Switchers (Routing / Assign / Matrix), Mult (Press) (Network-Feed) Boxes, Audio Transformers, Oscillators, Power-Supplies, Custom Sub-Systems. __ Application OpAmps Lab Inc.

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. . . Circuit by David A. Johnson P.E.-June, 2000

SSR Requires Ultra Low Control Current -  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 . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

Under/Over Voltage Alarm on AC Line -  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. . . Circuit by David Johnson P.E.-March, 2009

Use an Integrator Instead of Coupling Capacitors -  02/16/12  EDN-Design Ideas Level-shift a signal with an unknown dc offset to a known offset without ac coupling.  An ultrasonic sensor circuit requiring self-adjustment to the level of an ac-input signal also must accommodate the signalís unknown and variable dc-bias voltage.  The circuit cannot use an ac coupling capacitor, and the resulting output must be level-shifted to a known dc offset.  The design uses a dc-offset compensator (Figure 1). __ Circuit Design by Vladimir Rentyuk, Modul-98 Ltd, Zaporozhye, Ukraine

Why Limit Your Power Supply's Input Range? -  20-Mar-03 EDN-Design Ideas 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 circuit topology, you may be able to work around that input-voltage limitation.  For instance, The data sheet for TI's (www.ti.com) TPS61042 shows that it has all the functions necessary for providing a constant-current drive to a white-LED circuit; however, the input voltage of the IC does not meet the input-voltage requirements of this Design Idea.  The dual lithium-ion input voltage varies from 6 to 8.4V, but the TPS61042 input-voltage range is 1.8 to 6V. __ Circuit Design by Michael Day, Texas Instruments, Dallas, TX


AC Power Control Circuits


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