Classic relays are an electro-mechanical component that allows a smaller current device to switch a higher current device or load on and off. In principle, they are just like the MOSFET or optocoupler we used previously. So, why have relays? Here are a few reasons:
- For high voltage and current loads, they tend to be much cheaper compared to an equivalent MOSFET.
- At high currents, they do not get untouchably hot like a MOSFET.
- Similar to an optocoupler, relays also provide electrical isolation between the input and output circuits.
- They are simply electrically controlled switches so they are easy to understand and use for non-electrical engineers.
- They have stood the test of time and proven to be a simple and robust way to control high loads (even though they eventually will wear out—the SRD-05VDC-SL-C datasheet lists its rated life expectancy to be 100,000 operations).
There is also a type of relay known as a Solid State Relay (SSR) that has no...