Relays: Electromechanical vs Solid State

Electromechanical Relays: https://www.rspsupply.com/c-3683-electromechanical-relays.aspx

First let’s start with electromechanical relays, or EMR. The first thing you should know about EMR’s is that they use physical moving parts within the relay to achieve the desired functionality. These moving parts include the contacts that switch between that normally open and normally closed stationary contacts in the relay. This movement is made possible by and electromagnet. When power is applied to this magnet, it will act on the movable contact causing the relay to switch. In an EMR, it is common to here the switching sound that is represented as a “clicking” noise. This audible noise can be helpful when determining the functionality of the relay.

Solid State Relays: https://www.rspsupply.com/c-3685-solid-state-relays.aspx

Now let’s talk about solid-state relays and some of the characteristics that make them up. A solid-state relay will use a low power electrical signal to generate an optical semiconductor signal, this then will transmit and energize an output signal. So, when this is activated, the input optical signal will act as the switch, then allowing a higher voltage signal to pass through the relays output components. The internal circuitry of a solid-state relay is far more complex than an EMR, but the one main take way you should remember is that, in a solid-state relay, there are no physical moving parts.

Now that we have a better understanding of what makes up each of these two types of relays, let’s now talk about some of the advantages and disadvantages of each. Hopefully this comparison can help you better determine which type of relay will be better suited for you specific application. First looking at EMR’s: because of their more simplistic design and functionality, they are often less intimidating to installers and operators. Also, because of this simple design, the cost of an EMR is quite a bit less than that of a solid-state relay. Another benefit of using a EMR is that fact that in many cases testing is easier because of the audile “clicking” noise that they make, and also, in many cases you can manually switch the contact depending on the relay, which can also offer a lot of convenience depending on the situation. Lastly, EMR’s are much more common, which makes finding replacement parts much easier. Some disadvantages to using an EMR would be that they can generate a significant amount of signal noise depending on the application. Also, the typically consume much more power then a solid-state relay, which over time can lead to more cost. Another point to consider is, they do not switch as fast as a solid-state relay, so in situations where switching speed is important, an EMR may not be the best option. Lastly, EMR’s an create potential arcing situations, so they are not suitable for areas that may have a high potential for combustion, such a class 1 div 11 environment.

Now let’s look at solid-state relays: some of the advantages in using this type of relay would include the fact that they generate very little “noise” during operation which can be very beneficial depending on the application. They also consume very littler power in comparison to EMR’s, which over time can save a lot of money. They are very shock and vibration resistant which can offer a level of reliability not seen in EMR’s. Also, there is no danger of generating a spark, so using them in more volatile environments is acceptable. Lastly, they have the ability to switch at a very rapid rate, must faster than an EMR. Some disadvantages of using this style of relay would include the fact that they are quite a bit more expensive then EMR’s. Because of the higher level of complexity and cost, they are not as common as EMR’s, therefor they are harder to find replacements for. Testing functionality is also not a simple as with an EMR because of the lack of ability to manually switch this type of relay, and also because there is no audible “clicking” noise when the relay switches, like you would see with an EMR.

In conclusion, depending the application and a variety of other factors… will larger dictate which relay is best for your specific needs. There are definitely no right or wrong answers as to which is best. They each offer advantages and disadvantages that will factor into which relay will work best for your scenario.

Other videos on relays: https://www.youtube.com/watch?v=nTx9n8BNhgQ&list=PL08lhrRW3Ce6bkHDvm4rwDlKjFQ074Wqu

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