Industrial facilities are an increasingly complex web of wiring, including networking for Internet of Things (IoT) nodes alongside digital electronics interconnect. While digital networking is standardized using wired protocols like Ethernet and BACnet, and wireless networking protocols like Wi-Fi and Bluetooth, the digital interconnect between control computers such as single board computers (SBCs) or programmable logic controllers (PLCs), and peripherals such as sensors or actuators, can vary widely.
Confusing things further, the interconnects can use a variety of cables, connectors, and pinouts that look very similar, but are totally incompatible.
The onus is upon system designers to reduce these incompatibilities and ensure interoperability, while also lowering costs, accelerating system assembly, and improving reliability, despite the harsh conditions of the industrial environment. One way to accomplish this is to standardize on an IP67 or IP68 rated USB-C cable assembly. This can make life a whole lot easier for technicians by improving cable assembly compatibility across a range of equipment.
This article describes the problems of digital interconnect in industrial applications and how standardizing on USB-C cables and connectors for simple digital interconnect can resolve many of these issues. It then introduces a variety of USB-C connectors and cable assemblies with unique characteristics, including IP67 compliance, from PEI-Genesis, Amphenol LTW, and Bulgin, before discussing how they can provide ubiquitous, reliable, and robust connectivity for computer-to-sensor/actuator applications.
Digital interconnect in industrial automation
Industrial equipment is managed by control computers, which can be an SBC, a PLC, or a nearby laptop. The control computer often connects to nearby devices needed by the equipment, which can be broadly defined as sensors. These include switches, optical and environmental sensors; and actuators such as motors, solenoids, or lights. For most heavy industrial equipment, the designers at the equipment manufacturer select the connector type used for the cable ends and select the electrical protocol used. For a custom industrial control, the engineers and technicians select and install the computer, actuators, sensors, connectors, and cables. Once the connector type and electrical protocol are selected, it cannot be later changed without a long and expensive refit process. As such, when planning the industrial operation, it is important to decide on what type of digital interconnect to use for sensors and actuators very early in the design process. As with any system that makes extensive use of interconnected digital systems, the larger the operation, the more time and money can be saved by standardizing on equipment, including cables.
When setting up or reconfiguring equipment, technicians must have the proper cabling readily available with compatible connector terminations. At first glance, two electrically incompatible cable assemblies can look the same and can even have similar connectors that look like they might almost fit, but don’t. This non-obvious compatibility can frustrate technicians and delay system deployment. Even when using proper cables, it may take several attempts to properly orient a non-reversible keyed connector on the cable to the equipment to ensure a solid connection. In a low-light environment or where speed of deployment is of the essence, standardizing on one cable assembly reduces frustration while also ensuring interoperability between machines. This not only saves time but also saves cost as the cable assembly can be purchased in bulk.
Advantages of USB-C for digital interconnect
To address the problem of ubiquitous digital interconnect, USB-C cable assemblies are suitable for most applications between industrial equipment. USB-C plugs and receptacles are keyless, double-sided blade connectors that are rotationally symmetrical. This ensures a solid connection on the first insertion, saving time and frustration so technicians no longer have to fumble to properly orient a keyed connector. USB-C cables can also provide power to the sensor or actuator, an added advantage.
An industrial facility can standardize on USB-C cabling and connectors for most digital interconnect between control computers and the sensors and actuators, simplifying cable assembly inventory and connector interoperability. Industrial IP67 USB-C cables and connectors are heavy-duty and can withstand heat, solvents, and liquids commonly found in harsh industrial facilities. USB-C industrial cables are also built to minimize power and signal loss and are more tolerant of the abuses of bending and twisting forces.
USB-C connectors can support USB 2.0 and USB 3.1. The USB-C standard requires that USB 3.1 ports and cable assemblies be backwards compatible with USB 2.0 speeds of 480 megabits per second (Mbits/s). This prevents compatibility issues by allowing USB 2.0 ports to use the same cable assemblies as USB 3.1. However, USB 3.1 allows for much higher speeds. USB 3.1 Gen 1 cable assemblies support up to 5 gigabits per sec (Gbits/s), while USB Gen 2 cable assemblies support up to 10 Gbits/s. To identify the transmission speed, cable assemblies with USB-C connectors on each end are required by the USB specification to have an e-marker chip embedded in the connector housing that identifies the cable assembly’s maximum power and data transmission speed. The data in the e-marker chip is read by the USB host on first insertion and informs the USB host as to the cable’s maximum transmission speed, ensuring that the USB host sends data appropriately. USB-C cable assemblies that only support USB 2.0 speeds are not required to have an e-marker chip, so if no chip data is sent, the USB host will send data at 480 Mbits/s.
The USB-C standard allows for a maximum power delivery of 3 amperes (A) at 5 volts DC for a total of 15 watts of power. This is the standard for common USB cable assemblies. However, the specification for USB 3.1 Gen 1 and later allows for 5 A at 20 volts for 100 watts of power. USB-C cable assemblies designed for USB 3.1 power delivery must contain an e-marker chip that identifies the power delivery capacity or the USB host will default to 15 watts. This improves safety by preventing power overload conditions that could destroy the cable.
While the focus here is on standardization of USB-C cable assemblies for digital interconnect, it’s important to be aware that there are three cable assembly capacities:
- USB 2.0 mode: no e-marker, can supply 15 watts power and 480 Mbits/s data
- USB 3.1 Gen 1: e-marker, provides 100 watts power and 5 Gbits/s data
- USB 3.1 Gen 2: e-marker, provides 100 watts power and 10 Gbits/s data
If a lower capacity USB-C cable is used with properly configured higher capacity USB-C hosts and devices, the USB host will throttle the power and data to the lower capacity. This increases safety by preventing a power overload on the cable while improving reliability by ensuring compatible data rates. A facility can simplify this further by only using the standard that provides the maximum required power and data delivery. Unless an industrial automation facility is performing high data operations such as streaming live video, standardizing on USB 3.1 Gen 1 cable assemblies can be a safe choice. Typically, 5 Gbit/s USB 3.1 Gen 1 cables are specified for a maximum of 2 meters (m), which is sufficient for control computers to connect to nearby sensors and actuators. If there is a need to reliably send 10 Gbit/s data, USB 3.1 Gen 2 cables are specified for a maximum 1 m, as sending 10 Gbits/s through longer cables can cause data loss along the cable length due to signal reflection or attenuation.
USB-C cable assemblies
For designers expecting to send high-speed data in a harsh environment, there are a number of rugged and reliable solutions. For example, PEI-Genesis supplies the IPUSB-31WPCPC-1M Sure Seal IP67 USB 3.1 Gen 2 cable assembly (Figure 1). The cable is 1 m long and is rated for operation over -20°C to +85°C, appropriate for most harsh industrial environments. The cable jacket is made of polyvinylchloride (PVC) resin which has excellent water resistance and ultraviolet (UV) ray tolerance. Commercial jackets can crack or discolor under prolonged exposure to sunlight.
industrial-fig1.jpg?la=en&ts=14f9e032-a4f8-406d-aee7-da6b06b7ab23″ title=”Sure Seal IPUSB-31WPCPC-1M is a 1 m USB-C cable assembly” alt=”How to Use Industrial USB-C Cables to Ensure Interoperability, Lower Costs, and Improve Reliability”>Figure 1: The Sure Seal IPUSB-31WPCPC-1M is a 1 m USB-C cable assembly made for industrial applications. The connector with the lock nut gasket provides a secure IP67 waterproof connection to a sensor or actuator. Dimensions shown are in millimeters. (Image source: PEI-Genesis)
The IPUSB-31WPCPC-1M has a standard USB-C plug connector on one end made of molded PVC resin with a stainless steel USB-C plug. This end connects to a USB host connector on the SBC or PLC. The other end has a sealed molded plug with a nylon lock nut and a rubber gasket. This provides a solid and secure IP67 seal to the sensor or actuator.
The Sure Seal IPUSB-31WPCPC-1M contains an embedded e-marker chip identifying its capacity to the connected equipment. The e-marker chip operates over the full -20°C to +85°C range of the cable assembly. This ensures that the cable can be properly identified even when the equipment is turned on in either temperature extreme.
USB-C connectivity in extreme environments
For extremely harsh environments, Amphenol LTW offers the UC30FL-NCML-SC01 USB-C one-meter cable assembly (Figure 2). The entire cable length is surrounded by a polypropylene plastic (PP) conduit that provides additional protection from shock, cutting forces, and strain from bending around corners. The conduit also provides protection for the enclosed cable when under extreme vibration. The conduit is glued to each end of the cable and cannot be removed.
industrial-fig2.jpg?la=en&ts=724bccdc-a196-4815-944b-29ef3c7fe714″ title=”Amphenol UC30FL-NCML-SC01 USB-C cable assembly” alt=”How to Use Industrial USB-C Cables to Ensure Interoperability, Lower Costs, and Improve Reliability”>Figure 2: The UC30FL-NCML-SC01 USB-C cable assembly is enclosed in a PP conduit that protects the enclosed cable from shock and harsh vibrations. Dimensions are in millimeters. (Image source: Amphenol LTW)
The cable assembly has a common USB-C host connector on one end that plugs into the USB host. The other end has a heavy-duty circular connector with a reinforced strain relief. It has a sealed molded plug with a silicone gasket secured by a nylon lock nut. This provides a waterproof, airtight seal that is resistant to most chemicals. The cable and circular connector are IP67 rated, both mated and unmated, protecting the circular USB-C plug from the environment even when it is not connected.
The UC30FL-NCML-SC01 is fire resistant to UL94V-0, meaning the PP cable can withstand up to 10 seconds of flame. The PP cable is also resistant to oil, gasoline, and most solvents. Each plug can operate over -40°C to +85°C, while the nylon lock nut and the PP conduit can withstand higher temperatures, from -40°C to +115°C. This makes this cable assembly particularly appropriate for connecting to sensors and actuators in industrial gasoline engines and generators.
The embedded e-marker chip identifies the cable as supporting 5 Gbit/s data transfers, appropriate for high-speed gasoline generators that need to constantly monitor engine operation to maximize efficiency.
USB sensors in marine applications
In some cases, the control computer for the equipment has a USB-A connector but needs to connect to a USB-C connector. This requires a cable such as Bulgin’s PXP4040/C/A/2M00 USB-A to USB-C cable assembly (Figure 3). This cable has a USB-A plug on one end and a circular USB-C plug on the other and operates over -40°C to +80°C. The USB-C connector and cable can operate when submerged under 10 m of water for two weeks. It is also resistant to salt water, making it appropriate for marine equipment, including industrial machinery aboard tankers and cargo ships. The cable assembly is rated to IP68, except for the USB-A connector, which is rated to IP66.
industrial-fig3.jpg?la=en&ts=d1a1585e-00bf-4bad-b1e7-53c2a1e07d9e” title=”Bulgin PXP4040/C/A/2M00 has a USB-A plug on one end and a USB-C plug on the other” alt=”How to Use Industrial USB-C Cables to Ensure Interoperability, Lower Costs, and Improve Reliability”>Figure 3: The PXP4040/C/A/2M00 has a USB-A plug on one end and a USB-C plug on the other. It is resistant to salt water and the USB-C plug can withstand being immersed in 10 m of water for up to two weeks. (Image source: Bulgin)
The Bulgin PXP4040/C/A/2M00 also has a flammability rating of UL94V-0. The cable jacket is made of PVC resin, making it suitable for marine deck applications.
The USB-C cable shell is made of polycarbonate-polybutylene terephthalate (PC/PBT), a high-strength material often used for car bumpers. The PC/PBT connector housing has high resistance to chemicals and has enough flexibility to tolerate high impacts in cold temperatures down to -40°C. Even when struck with high force, the connector will resist fracturing and will crack gracefully. This provides tamper resistance for USB security sensors, including freeze attacks where a connector is fast-frozen and then struck with a hammer.
The USB-C specification does not allow for an e-marker chip to be embedded in a cable that has a USB-A plug on one end. This cable assembly is specified to provide up to 5 A and support a data rate of up to 5 Gbit/s over its 2 m length, although some USB-C peripherals may note the absence of an e-marker chip and default to 480 Mbits/s.
Standardizing on USB-C cable assemblies for digital interconnect in an industrial environment simplifies cable inventory, and provides fast and easy connectivity due to the rotationally symmetrical design of the plug and receptacle. USB-C cables can identify their power and data transfer capacity to the host control computer to prevent data loss and dangerous power overload conditions. The proper selection and use of an appropriate USB-C cable assembly in industrial systems can also improve reliability, reduce maintenance, and lower overall cost.