Relays were first employed in long-distance telegraph circuits as amplifiers back in the 1800s. They repeated the signal coming in on one circuit and re-transmitted it on another circuit. They were also commonly used in telephone exchanges and early forms of computers to carry out logical operations. Nowadays, relays are predominantly used to switch starting coils, heating elements, pilot lights, and even audible alarms. The fundamental objective of a relay is similar to that of a valve. While one regulates the flow of liquid, gas, and air, the other directs the flow of electricity. In electromechanical relays, contacts are opened and closed with the help of a magnetic force. Solid-state relays have no contacts and the switching is done electrically.
What is a Solid-State-Relay?
Solid-state relays, or SSRs, can be compared to the modern, 21st-century version of the EMR. These relays consist of a sensor, an electronic switching device, along with a coupling mechanism. With the help of a semiconductor, the relay switches on and off when a small external voltage is applied in its control terminals. It has three circuits: an input circuit, a control circuit, and an output circuit. The input circuit performs the same function as the coil on an electromechanical relay. The circuit is stimulated when a voltage higher than the pickup voltage is applied to the circuit and deactivated when the voltage falls below the minimum drop-out voltage of the relay. The control circuit estimates when the output component is energized or de-energized.
Why Should You Pick a Solid-State Relay?
Fast & Energy Saving - The primary difference between solid-state relays (SSRs) and electromechanical relays (EMRs) is that SSRs are devoid of any movable parts. This feature creates an array of great advantages of using this type of relay. As the relay does not have to energize a coil and manually open and close contacts, it actually utilizes 75% less power than EMRs. This also results in the fact that the relay switches at a much faster rate.
Lifespan - An SSR will outlive an EMR by many, many years. Again, attributing to that fact that without the presence of movable contacts, there is no part that can be worn out and damaged. An EMR has an average lifespan of around one million cycles, while on the other hand, an SSR has a lifespan of approximately 100 times that.
Silent, Compact & Powerful - Lacing movable parts, SSRs are totally silent electrical devices. Solid-state relays do not have bulky, clunky electromagnets attached to them, and therefore present themselves as a small and compact alternative. Their small size also saves precious installation space. Being small, however, does not hinder their power to function. In fact, since optical coupling completely isolates the circuits of the relay, there’s no need to worry about the relay being adversely affected by too much voltage.
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