Solid State Relays- The Inner Secret

Solid State Relay as the name suggests is solid state in nature, that its construction is based on completely electronic parts. There are not any moving components as in their mechanical device counterpart. This relay is also controlled by a small amount of power and might control huge amount of power. However the main distinction is that the input & output is made of semiconductors like Optocouplers, Diode & Thyristors. This kind of construction has several benefits over the standard Electro-Mechanical Relays (EMR) that we are going to see later on.

Let us see what it's made of. Solid State relays or Relay Board is often broadly speaking classified into main 3 types. This classification is principally based on input circuit that's used in the design. This input circuit decides how isolation is obtained between input & output. 

1. Electrical device coupled SSRs 

2. Reed Relay Coupled SSRs

3. Photo coupled SSRs

Transformer coupled SSRs - this kind of SSRs consists of small transformer at the input aspect. This input power is supplied to a small transformer's primary aspect & the output of secondary aspect is employed to trigger a TRIAC or SCR, that successively management the output power. This way isolation is obtained through electrical device.

Reed Relay Coupled SSRs - this kind of SSRs encompass tiny reed switch at the input aspect. The input power is applied to a coil encompassing reed switch with or while not using an amplifier. The contacts of reed switch are accustomed trigger the output circuit having TRIAC or SCR or a power transistor. Therefore here the isolation is achieved through use of reed switch. This is how a smart home relay works.

Photo-coupled SSRs - this sort of SSRs use the sunshine supply to supply isolation between input & output. Input power is applied to visual or actinic ray supply like LED (Light Emitting Diode).