A solid state relay makes it possible to manipulate an electrical load without locomotion.
We already know that an electromechanical relay cannot work without a moving part. On the other hand, a solid state relay will function optimally without a spring, coil, or any other mechanical component. To carry out its operation, a solid state relay makes use of the peculiar electrical qualities of a semiconductor.
A solid state relay makes it possible to distinguish between input contact and output contact. A very common example is a switch. Furthermore, a solid state relay can provide control over an alternating current and a direct current. They do not make use of the conventional NO contacts found in electromechanical relays; instead they make use of a switching transistor.
Although the operating principle of a solid state relay is similar to that of an electromechanical relay, the electromechanical relay has several limitations. One of such limitations is the slow pace of switching between input and output voltage. The size and lifecycle of an electromechanical relay is also a problem. The solid state relay does not have any of these drawbacks.
A solid state relay is not subject to wear and tear due to the absence of a moving component. This means it is possible to switch between voltages at a much faster pace. Unlike an electromechanical relay, a solid state relay does not produce any sound.
Although solid state relays are readily available. They are quite expensive and this is the comparative advantage an electromechanical relay has over it. A solid state relay of any capacity, size, or calibration can be bought from a standard electrical store.
With a minute input voltage, a solid state relay can manipulate an output voltage with a high value.
Solid State Relay Input
A solid state relay has a component that makes it easy to distinguish between input voltage and output voltage. This component is known as an optocoupler or opto-isolator. The opto-isolator consists of a diode that constantly emits light and supplies illumination.
This diode is linked to the input drive section of the solid state relay such that when an electrical current flows through it, it lightens up. The opto-isolator is also used for transmitting signals whose frequency value is not high. It is also used for the transmission of direct currents.
The circuit structure of a solid state relay is such that the opto-isolar and a resistor are connected in series.
The minimum permissible voltage value of a solid state relay is 3V DC. Therefore, before it can be powered on an input current greater than this value must be passed through its input terminals. A logic gate and switch are good sources of direct current signals.
Solid State Relay DC Input Circuit
A direct current voltage is not the only way to switch on a solid state relay. We can also employ a sinusoidal waveform to achieve it.
The input voltage is only permitted to be equal to the solid state relay starting voltage on one condition and that condition is that the activating signal must come from a mechanical contact or relay contact.
Solid State Relay output
The measurement of the output of a solid state relay is similar to its input value. This means it can either be an alternating current or direct current. The configuration and circuit structure of a solid state relay output is such that only a form of switching operation can be executed. Power transistors are the most popular switching devices used for direct current solid state relays