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Solid State Relay Selection: How to Buy Solid State Relay

New AC solid state relay
New AC solid state relay
Resource: https://youtu.be/JNeG85uH-_o

Solid state relay technology offers many benefits, but also many variables to consider or to know about. For those looking to buy solid state relay devices, the following five selection points will help you choose the best module for your needs, whether you want it for an industrial application or general-purpose use.

What are solid State Relays?

Before the relay selection process, it’s good to first understand what these devices are. Essentially, solid state relays are semiconductor switches that can be used in place of electromechanical relays for various purposes, offering many benefits over their older counterparts.

The main solid state relay benefits include a much longer lifespan, faster switching speeds, and increased reliability. However, it is also important to consider some of the key factors that will affect your decision when looking at different types of SSR modules, as discussed below.

Different solid-state relay types
Different solid-state relay types
Resource: https://www.youtube.com/watch?v=QIhGGh0MUZE

How to Buy Solid State Relay

Solid state relay buyers will want the device for different reasons; it could be an electrician looking for a reliable switching device for home automation or an industrial engineer looking for a module to use in a machine tool.

No matter the application, there are certain factors that should be considered when making your purchase. Here, now, is how to buy solid state relay devices.

1. SSR Type

Different types of solid state relays are built to fit different electrical systems. The main types include DC to AC relays, AC to DC rays, and DC to DC types. There are also single-phase and three-phase solid state relays, and so on.

Buy solid state relay types that are compatible with your system. For example, if you are looking for an SSR to use in an AC circuit, then you will want a device that is rated for AC voltage and current.

2. SSR Isolation Method

One of the most important factors to consider when selecting SSR relays is the type of isolation used. The two main types of solid state relay isolation methods are optical and magnetic.

Optical isolators use light to create an electrical barrier between the input and output, while magnetic isolators use transformer action. Each type of isolation has its own advantages and disadvantages.

  • Optical isolators are faster and better electrical separation than magnetic isolators. However, they are also more expensive.
  • Magnetic isolators, on the other hand, are more common and less expensive than optical isolators. They also have a lower maximum voltage rating.

When choosing an SSR isolation method, consider the needs of your application. For most uses, optoisolators will provide the best results.

For some industrial applications where the higher load capacity of a magnetic isolator is needed, you may want to go for hybrid solid state relays. These combine the benefits of both methods by using an optical isolator for the control input and a magnetic isolator for the load current path.

3. SSR Output Voltage

Another important factor to consider by anyone intending to buy solid state relay products is the load type and voltage. The two main types of SSR loads are AC and DC.

AC loads are more common in household appliances such as air conditioners and washing machines. They are also found in office equipment such as printers and industrial machinery.

DC loads, on the other hand, are used with relays that are specified for direct current systems. Depending on the application when using a solid state relay, DC loads can be constant or resistive current types.

4. SSR Input Voltage

What input signal will be used? Solid state relays can be triggered by AC or DC signals. Some types of solid state relays allow both types of signals, while others are designed for only one type. Here is how to go about this selection point when looking to buy a solid state relay.

  • If you’re unsure of what type of input signal you will be using, choose a solid state relay with a universal input. This will allow you to use either an AC or DC signal.
  • While still on the topic of the solid state relay input signals, it’s important to consider the switching time. This is the amount of time it takes for the SSR to turn on or off.
  • For most applications, a few milliseconds will suffice. However, for industrial applications where speed is critical, you may want to choose a higher solid state relay speed.

5. SSR Mounting Method

Solid state relays come in different shapes and sizes. They can also be mounted in several ways, including surface mount, through-hole, or DIN-rail.

For anyone looking to buy solid state relay devices, therefore, it’s important to ensure you’re picking the right type in terms of installation requirements.

A panel mount solid state relay is one of the smallest and easiest to install. Through-hole solid state relays are larger and require more space for installation, but they offer better heat dissipation.

A DIN rail solid state relay is often large and more robust, making it ideal for industrial applications. Overall your choice of mounting method must match your application in terms of size, weight, and thermal considerations.

6. SSR Price

Price is always an important consideration when buying any product. The SSR price will often depend on the brand, features, load capacity etc., and range from $10 going up. When looking at the solid state relay price, it’s important to remember that you get what you pay for.

The more expensive models likely offer better features and performance. However, they may also be overkill for some applications. So it helps to consider the needs of your application before making a decision.

That being said, we would advise against going for the cheapest model on the market. Instead, choose a relay that offers good value for money. These are often the mid-range models.


The process to buy solid state relay devices can be a bit overwhelming, especially for anyone not familiar with the product. However, by keeping these five factors in mind, you can a good SSR for your needs.

You only need to identify the specific application you need it for and understand the various inputs, outputs, ratings, and prices. With the right SSR, you’ll be able to improve the performance of your application while also saving money.


I am William, Electrical Engineering Author. Dedicated to writing technical articles on Timer Relay, Monitoring Relay, Surge Protection Device and other electrical devices. With 7 years of writing experience, I am committed to providing accurate and in-depth expertise to my readers.

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