Solid State Relays

A solid state relay (SSR) is a type of switch that controls the flow of electricity using semiconductor components. Similar to a mechanical relay, it is intended to turn on and turn off in response to an electrical signal. But this is more dependable and long-lasting than a mechanical relay.

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Solid State Relay


What is a solid state relay?

A solid state relay (SSR) is a type of electronic switch used to control electrical circuits. SSRs are often used in industrial applications as they have high efficiency, higher reliability and lower power consumption than other types of switches, such as thyristors or semiconductor devices.

Solid state relays are made of assembly-line technology and have very low power consumption and require minimal maintenance. 

They are designed to handle continuous duty cycles and are perfect for applications where high-speed switching is required like motor start/stop controls or lighting control systems.


Solid State Relay Working:


The working principle of a solid state relay can be explained as follows.
When a voltage is applied to the input of a solid state relay, the relay is triggered by an optocoupler or an electronic device such as a diode, LED, resistor, or transistor. In the output circuit an electrical signal is sent to the trigger circuit. The switching element of the output circuit is turned on. When the switching element turns on, the load current flows and the device connected to the output can be controlled. Removing the input voltage disables the control circuit and turns off the solid state switch.


Solid State Relay Circuit Diagram:

Solid State Relay Price On Robocraze:

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Buy solid state relay at the best price on Robocraze!



1. Where can I find a solid-state relay online?

Solid state relays can be obtained in online stores such as Robocraze.

2. Where can I find a solid-state relay nearby at a physical store?

Solid State relays are found in many electronic stores at your local city market. Since the availability of the solid state relays are not guaranteed at such local shops, it is recommended to confirm availability before visiting the store.

3. What is the price of a solid-state relay?

Solid state relays vary from a few hundred rupees to sometimes much higher depending on the size, rating, voltage load, current load, safety features etc.

4. How to wire a solid-state relay?

A solid state relay has four terminals, two to control the relay and the other two to open and close connections in between depending on the input terminal voltage. The input terminals must be connected to the the VCC and GND of the controlling device (ie microcontroller or sensor) while the other two terminals act like two ends of a switch, establishing connection when the input voltage goes above threshold and disconnection when the input voltage goes below threshold


5. How to use a solid-state relay?

When the input voltage goes above the designed threshold, the relay establishes connection between the two output terminals and disconnects the terminals when the input voltage goes below the threshold voltage.


6. How to test a solid-state relay?

You can test the solid state relay using continuity mode on the multimeter. Place the multimeter probes across the two output terminals and turn it on in continuity mode. If the input voltage goes above threshold, the multimeter should emit a sound indicating that the circuit is complete, and it should not emit a sound when the input voltage is below threshold


7. How much current does a solid-state relay draw?

This varies between different models of solid state relay. Typically a Solid state relay will consume far less current than an electromechanical relay - about 10-20 mA. But current consumption of different solid state relays depends on exact models so refer to the particulate relay datasheet for accurate numbers.


8. What is the difference between a relay and a solid-state relay?

A relay generally refers to an electromechanical mechanism, where there is a physical movement of components inside the relay due to the supplied controlling current, causing the switch to close. A solid state relay has no moving parts and is controlled by transistors in switch mode and optocouplers for circuit isolation


9. Do solid-state relays click?

No. Since Solid state relays have no moving parts, it does not have any clicking sound and is also much faster than typical relays used.

10.Why is a solid-state relay better than a switch?

Solid state relay offers the same advantages of having a relay in place instead of switch. While a switch will always be dependent on an external human operator, relays can be controlled electronically thereby giving the user much more flexibility in its implementation.

11. How long do solid-state relays last?

Solid state relays are very reliable devices and will almost always outlast an electromechanical based relay due to the fact that it doesn’t have any moving parts. While a typical EMR lasts about one million cycles, a SSR is designed to last at least 100 times that. The most likely way a SSR gets damaged is if the supplied voltage is greater than the specified in the datasheet


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