What is a solid state relay?

A solid state relay (SSR) is a relay that does not have a moving contact. SSRs operate similarly to mechanical relays that have moving contacts, however they employ semiconductor switching elements such as thyristors, triacs, diodes, and transistors.

Solid state relays vs. electromechanical relays

Electromechanical relays use a physical moving part, generated by using electromagnetic forces, to connect contacts within the output component of the relay.


Solid state relays don’t have moving parts - instead they use a low power electrical signal to generate an optical semiconductor signal, typically with an octocoupler, that transmits and energises the output signal. When activated, the input optical signal acts as the “switch” that allows a high voltage signal to pass through the SSR’s output component.


Typical application of OMRON Solid State Relays

OMRON has a range of relays for heater control such as the G3PJ, G3PH and G3PF series. These relays enable high-precision, high-frequency temperature control for reflow ovens, moulding machines and sintering ovens. Models are available with fault detection and cyclic control.


For three-phase motors we offer solid-state contactors such as the G3J series, which provide smooth starting and stopping functions to suppress sudden motor operation and thus reduce mechanical stress. They are ideal for conveyor belts and other applications requiring smooth movement.


Socket/plug-in type solid-state relays like OMRON’s G3RV-SR, G3B and G3F series have the same shape as our general relays and are suitable for high-frequency switching, signal exchange with controllers and other I/O applications.


Where to find solid state relays in Australia

OMRON’s diverse solid state relay offering features cost-effective, slim sized models and a wide variety of compatibility options. For example, panel-mounted solid state relays integrated with heat sinks or with separate heat sinks.


Separate installation of heat sinks allows you to match heatsinks to housings of your devices. These relays are mainly built into the devices, like on the G3NA and G3NE series.


Some relays have the same shape as plug-in relays, allowing you to use the same socket. They are usually built into control panels and used for I/O applications for programmable controllers and other devices. OMRON offers the G3F(D), G3H(D), G3R-I/O, G3RZ, and G3TA series.


PCB mounted SSRs have a terminal structure for mounting to PCBs. The product lineup also includes MOS FET relays, which are mainly used for signal switching and connections. Some that See our G3M, G3S, and G3DZ series.


OMRON has a wide range of solid state relays and latching relays, plus latching relay switches and DC switching relays.