Solid State Relay Electronic Circuits


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Solid State Relay Circuits
Last Updated on: Wednesday, May 14, 2008 03:17 PM

Circuits Designed by Dave Johnson, P.E. :

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 into the control circuit is a tiny 4uA. Only about 1.5mA of DC is needed to turn on and off 400 watts of AC or DC power to a load.

Solid State Relay 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. 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.

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, the circuit can control about 600 watts of power to load while providing full isolation and transient protection.

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

120 VAC Lamp Chaser using Solid State Relays: (Circuit / schematic design added 6/06)

120 Volt AC Lamp Chaser using Solid State Relays: This circuit is similar to the LED clock using12 neon indicator lamps instead of LEDs. It operates from2 high capacity ni-cad cells (2.5 volts) which keep it going for a couple weeks. High voltage (70 volts) for the neon lamps is obtained from a small switching power supply using a 74HC14 Schmitt trigger Squarewave oscillator, high voltage switching transistor, and10 mH high Q inductor. Most any small PNP transistors can be used that have a C/E voltage rating of 80 or more. (Circuit / schematic design added 6/06)

2 Lead Solid State Breaker Resets Itself: 03/30/95 EDN-Design Ideas / (added 03/03) - Simple dc circuit breaker can protect a power supply from the ever-present screwdriver or even isolate a satellites dual power system from a short circuit in one subsystem

AC Switching with TRIAC from TTL: (Electronic Schematic / circuit added 4/02)

AN-252: Using the AD2S80 Series Resolver to Digital Converters with Synchro's; Solid State Scott-T Circuit.: AN-252 - Analog Devices Application Notes (Circuit / schematic design added 6/06)

AN762: AN762 Applications of the TC62X Solid-state Temperature Sensors: Microchip Application Note - Published 23-Jun-04 (Circuit / schematic design added 6/06)

Application Circuits of the TC620/TC621 Solid-State Temperature Sensors: Microchip Application Note - Published 16-Aug-04 (Circuit / schematic design added 6/06)

Applications of the TC62X Solid-state Temperature Sensors: Microchip Application Note - Published 23-Jun-04 (Circuit / schematic design added 6/06)

Electromagnetic Emissions Test Report on Solid State Energy Meter: Electro - Analog Devices Application Notes (Circuit / schematic design added 6/06) This report describes electromagnetic immunity testing performed on September 9, 1999 through September 10, 1999 on the Solid State Energy Meter. Testing was performed pursuant to IEC 1036:1996, a standard for alternating static watt-hour meters for active energy.

Electronic Circuit Breaker: This circuit uses the on-resistance of the MOSFET as the current sensor. Reset it by removing the input power or the load. The circuit draws no current unless tripped. Designed by Andrew R. Morris (added 09/05)

SCR phase control yields solid state switch: 03/15/01 EDN-Design Ideas / (added 11/05) SCRs (silicon-controlled rectifiers) / PDF contains multiple circuits - scroll to find the one of interest, or thyristors, have higher current and voltage ratings, lower conduction losses, and more robustness than triacs. For these reasons, SCRs are better suited to high-power applications. This is high power dimmer circuit for115V AC.

SCR Tester: This simple SCR tester can be made with only a couple components. It will provide a visual 'go' or 'no-go' indication--it is simply a voltage source, a lamp, and a resistor through which gate current is supplied. (added 2/06)

Semiconductor Relays: general info and many example circuits (Electronic circuit added 5/02)

Simple Electronic Circuit Breaker: This circuit uses the on-resistance of the MOSFET as the current sensor. Reset it by removing the input power or the load. The circuit draws no current unless tripped. Designed by Andrew R. Morris (added 09/05)

Solid state blinker for automotive applications: AN454 that limits the output current slew rate (di / dt) during the switching edges.... (Circuit / schematic design added 6/06)

Solid State Relay Saves Battery's Life: 09/01/94 EDN-Design Ideas / (added 2/05) The circuit in Fig 1 uses a low-resistance p-channel FET, Q4, to disconnect a load from the battery when the battery's voltage drops below a certain value. After you disconnect the circuit, it remains off until you remove and replace the battery.

Solid State Relay: (Circuit added 9/04)

Solid state relays simplify monitoring electric car Battery Voltage: 02/19/04 EDN Design Ideas / (added 1/05) Figure 1 shows the propulsion system of an electric vehicle. It includes an electric motor, drive electronics, a mechanical transmission, vehicle control/power management, a charging system, and a battery. The long-term performance of the electric vehicle depends on ensuring the electrical health of the battery and its charging system....

Solid State Switch for DC Operated Gadgets: (Electronic Circuit / Schematic added 10/04)

Solid-state relay saves Battery's life: 09/01/94 EDN-Design Ideas / (added 2/05) The circuit in Fig 1 uses a low-resistance p-channel FET, Q4, to disconnect a load from the battery when the battery's voltage drops below a certain value. After you disconnect the circuit, it remains off until you remove and replace the battery.

Solidstate Remote Control Switch: (Electronic circuit design added 02/05)

Solid-State Tesla Coil, #1: (added 2/06)

Solid-State Tesla Coil, #2: (added 2/06)

Square Tesla Coil: (added 2/06)

Switch Intelligently Controls Current: 03/30/00 EDN-Design Ideas / (Electronic circuit added 5/02) - This circuit can intelligently control ac or dc current when connected in series with a load

Transformer Driver ControlsBiDirectional Switch: 07/17/97 EDN-Design Ideas / (Electronic Circuit diagram added 03/03) -- You can use a transformer-driver IC to simply control a MOSFET on/off switch

Two Lead Solid State Breaker Resets itself: 03/30/95 EDN-Design Ideas / (added 03/03) - Simple dc circuit breaker can protect a power supply from the ever-present screwdriver or even isolate a satellites dual power system from a short circuit in one subsystem

Using the AD2S80 Series Resolver to Digital Converters with Synchro's; Solid State Scott-T Circuit.: AN-252 - Analog Devices Application Notes (Circuit / schematic design added 6/06)