Technical Article

Connectors Used in Industrial and Robotic Cable Termination

May 30, 2023 by Simon Mugo

Industrial and robotics cabling requires specialized termination strategies. This article introduces connectors involved in automation applications for cable-to-cable or cable-to-device termination.

Industries involving automation and robotics make use of many connectors for I/O signals, power, and data. Connectors find use in terminating cables to other cables, sensors, wireless communications, high-speed wired communication, motion, drone, robots, pneumatics, hydraulics, and electric industrial systems, just to name a few.

With the introduction of Industry 4.0, more sophisticated and advanced robots are being introduced in the area of automation with the aim of efficiently and economically performing the expected outcome. Drones, robots, and cobots are intertwined with IoT technology requiring more advanced and sophisticated types of connector solutions.

This article defines connectors, the various types that exist for industrial use, and how to select the best connector for your industrial purpose.


Defining Connectors and their Need in Industrial Automation

Connectors are industrial automation devices designed to ensure a smooth data and power flow throughout the system. The components should ideally provide a seamless connection that enables very reliable and efficient signal distribution within a given industrial system.

Connectors are accompanied by several important features that allow them to survive in industrial and robotic environments. Such features include being ruggedly built to ensure survivability in heavy-duty production lines. Also, connectors should have the ability to deliver in high moisture, temperature, and extreme vibration environments. All connectors should have very low resistance in order to increase transmission speed and minimize voltage losses and signal errors.


Industrial automation connectors

Figure 1. A small variety of industrial connectors. Image used courtesy of Adobe Stock


Industrial Automation Major Connector Types

There are many major connectors used in the area of industrial automation ranging from coaxial, D-sub, fiber optic, RJ45, USB, display, and SCSI connectors, and this article introduces many of the common applications


Coaxial Connectors

These are often recognized as RF and some older network connectors. They find use in the connection of network devices, transmission lines, and other components in RF and microwave frequencies. They provide RF connections in measurement, test, and communication fields. They are good for circuit assessment, interconnection, testing, and components packaging into a system.

A good coaxial connector is chosen based on operational frequency, impedance, reflection performance, insertion loss, size, environmental requirements, and cost. The source and the connector impedance should match for maximum power transfer achievement.


Coax connectors

Figure 2. Different types of coaxial (coax) connectors used in industrial automation. Image used courtesy of Adobe Stock


Fiber Optic Connectors

This type of industrial automation connector is used in light transmission instead of transmitting electric signals. Due to the application, its termination must be perfect. They are used to properly align the microscopic optical fibers to interconnect cables, media converters, or optical switches.

The connector is made up of three parts: the ferrule, the coupling mechanism, and the connector body. The ferrule is the part that holds the fiberglass with a firm grip on the cable fiber. The connector body is made up of metal or plastic to support the ferrule. Finally, the coupling mechanism is very useful when it holds the connector in position once attached to other peripheral devices.

The fiber optic connectors can be classified into ST, SC, FC, and LC types. ST is made up of a straight tip with a 2.5mm ferrule made of either metal or plastic, widely used in fiber optics. The SC-type ferrule is 2.5mm and is purposely used to hold together a single fiber. It has a push-on and pull-on mechanism that is used for connecting and disconnecting purposes. The FC-type is good in the area of the telecommunication industry. They have threaded coupling that offers a firm and durable connection. Finally, the LC type has a well-designed retaining tab held in a duplex with a polymer clip.


Fiber optic connectors

Figure 3. Types of fiber optic connectors. Image used courtesy of Adobe Stock


D-Sub Connectors

D-Sub stands for D subminiature. This type of connector has found historical use in many areas of industrial automation, especially in computers. They are used in circuits of low current and fairly low speed such as micro switches, trim motors, and data signals control and display units. We have both male and female D-Sub connectors ranging from 9 to 50 pins with a few standard variations.


D-sub connectors

Figure 4. D-Sub connector on a PC board. Image used courtesy of Adobe Stock


USB Connectors

USB stands for Universal Serial Bus, an important connector used to carry out digital communication that happens within a short distance. It can be connected to the USB port on devices to enable the transfer of digital signals through the USB cable. It is made up of pins ranging between 4 to 24, enabling the transfer of both data and power.

Different types of USB connectors are available for use in industrial automation and other applications such as USB 1.0, USB 2.0, USB 3.0, and USB 3.I, and rated for various speeds. They are also named according to the application: USB type A, type B, and type C illustrated in Figure 5 below.


USB Connectors

Figure 5. Types of USB connectors. Image used courtesy of Adobe Stock


RJ45 Connectors

The connector is an 8 conductor 8 position layout, significant in the area of data network, for example, Ethernet. RJ is an abbreviation for Registered Jack, and there are other variations besides the RJ45, although less common in modern industrial systems. They are used in connecting patch panels to system network switches, connecting a NIC of a computer to the data port, and attaching LAN cables to the computer in most cases.


RJ45 Connectors

Figure 6. RJ45 connectors and sockets in a network switch. Image used courtesy of Adobe Stock


Display Connectors

Industrial automation involves a lot of visual displays. Display connectors are used in such areas. Display connectors are used to transmit data that should be displayed on screens like computer monitors. They are used to carry audio, video, and other data forms. They exist in many types, including HDMI, DVI, and display port connectors.

Generally, connectors can be classified as board-to-board, cable-to-cable, wire-to-board, and panel feed-through connectors.


What to Consider Before Selecting the Right Connector

Before the user selects the connector, he or she must understand the demands of the application in order to select the following parameters.

Wire gauge: This is the size of the wire’s cross-sectional area which determines the weight, resistance, and amount of safe current that passes through the cable. The proper gauge wire should match your connector selection.

Environment: A proper connector selection should consider the environment to which it shall be subjected. For instance, you cannot pick a plastic connector to work in an extremely high-temperature environment or pick a connector made of iron and subject it to a corrosive environment.

Current rating: The current rating is the amount of current that the system will continuously carry within the safety limits. Some connectors can pass higher currents for brief durations.

IP rating: Ingress protection describes how much a connector is protected against liquids and solid objects intrusion. When you do a quick look at the IP, it has two digits; the first is the protection level protection against solid material, and the second number is a representation against liquid penetration.

Standard approval: Ensure that the connector you select has undergone tests to be compliant with the required industrial standards set by the local government authorities such as the NFPA and UL in North America.

Engagement force: Always consider the environment, location, and users of the connector to determine the right amount of force it should take to engage and disengage the device.


Connectors in Industrial Automation and Robotics

When industrial systems and robots are subjected to harsh operating environments, engineers are expected to select compact and reliable connectivity devices to achieve the best data and power transfer.

Most connectivity is made through the use of an M12/M8 connector system, heavy-duty connection, RJ45 connectors, circular plastic connectors, terminal blocks, and relays. Best connector selection implies the best outcome in system performance through better power and data transmission.