While fieldbus solutions utilize sensors and devices with networking ability, they come with limitations. IO-Link provides one standard device level communication that is smart in nature and network independent. That enables interoperability throughout the controls pyramid, making it the most suitable choice for smart manufacturing.
IO-Link offers a cost effective solution to the problems. Here is how:
IO-Link uses data communication rather than signal communication. That means the communication is digital with 24V signal with high resistance to the electrical noise signals.
IO-Link offers three different communication modes: Process communication, Diagnostic communication (also known as configuration or parameter communication), and Events.
Process communication offers the measurement data for which the device or sensor is primarily selected. This communication is cyclical and continuous in nature similar to discrete I/O or analog communication.
Diagnostic communication is a messaging (acyclic) communication that is used to set up configuration parameters, receive error codes and diagnostic messages.
Event communication is also acyclic in nature and is how the device informs the controller about some significant event that the sensor or that device experienced.
IO-Link is point-to-point communication, so the devices communicate to the IO-Link master module, which acts as a gateway to the fieldbus or network systems or even standard TCP/IP communication system. So, depending on the field-bus/network used, the IO-Link master may change but all the IO-Link devices enjoy the freedom from the choice of network. Power is part of the IO-Link communication, so it does not require separate power port/drop on the devices.
Every open IO-Link master port offers expansion possibilities for future integration. For example, you could host an IO-Link RFID device or a barcode reader for machine access control as a part of a traceability improvement program.
As technology advances at a faster pace and the world becomes flatter, manufacturing operations are generally focused on efficient production to maximize profitability for the organization. In the new era of industrial automation and smart manufacturing, organizations are turning to data generated on their plant floors to make sound decisions about production and process improvements.
Smart manufacturing improvements can be divided roughly into six different segments: Predictive Analytics, Track and Trace, Error Proofing, Predictive Maintenance, Ease of Troubleshooting, and Remote Monitoring.To implement any or all of these improvements requires interoperable systems that can communicate effectively and sensors and devices with the ability to provide the data required to achieve the manufacturer’s goals. For example, if the goal is to have error free change-overs between production cycles, then feedback systems that include identification of change parts, measurements for machine alignment changes, or even point of use indication for operators may be required. Similarly, to implement predictive maintenance, systems require devices that provide alerts or information about their health or overall system health.
Traditional control system integration methods that rely heavily on discrete or analog (or both) modes of communication are limited to specific operations. For example, a 4-20mA measurement device would only communicate a signal between 4-20mA. When it goes beyond those limits there is a failure in communication, in the device or in the system. Identifying that failure requires manual intervention for debugging the problem and wastes precious time on the manufacturing floor.
The question then becomes, why not utilize only sensors and devices with networking ability such as a fieldbus node? This could solve the data and interoperability problems, but it isn’t an ideal solution:
Most fieldbuses do not integrate power and hence require devices to have separate power drops making the devices bulkier.
Multiple fieldbuses in the plant on different machines requires the devices to support multiple fieldbus/network protocols. This can be cost prohibitive, otherwise the manufacturer will need to stock all varieties of the same sensor.
Several of the commonly used fieldbuses have limitations on the number nodes you can add — in general 256 nodes is capacity for a subnet. Additional nodes requires new expensive switches and other hardware.
IO-Link provides one standard device level communication that is smart in nature and network independent, thus it enables interoperability throughout the controls pyramid making it the most suitable choice for smart manufacturing.
We will go over more specific details on why IO-Link is the best suited technology for smart manufacturing in next week’s blog.
Is it possible to safely switch off cylinders while simultaneously transmitting field data and set up the system in accordance with standards? Yes!
In order to rule out a safety-critical fault between adjacent printed circuit board tracks/contact points (short circuit) according to DIN EN ISO 13849, clearance and creepage distances must be considered. One way to eliminate faults is to provide galvanic isolation by not interconnecting safety-relevant circuits/segments. This means charge carriers from one segment cannot switch over to the other, and the separation makes it possible to connect the safety world with automation — with IO-Link. Safely switching off actuators and simultaneously collecting sensor signals reliably via IO-Link is possible with just one module. To further benefit from IO-Link and ensure safety at the same time, Balluff’s I/O module is galvanically isolated with a sensor and an actuator segment. The two circuits of the segments are not interconnected, and the actuator segment can be safely switched off without affecting the sensors. Important sensor data can still be monitoring and communicated.
The topological structure and the application of this safety function is shown in this figure as an example:
A PLC is connected to an IO-Link master module via a fieldbus system.
The IO-Link master is the interface to all I/O modules (IO-Link sensor/actuator hubs) or other devices, such as IO-Link sensors. The IO-Link communication takes place via a standardized M12 connector.
Binary switching elements can be connected to the galvanically isolated sensor/actuator hub (BNI IOL-355). The four connection ports on the left correspond to the sensor segment and the four ports on the right correspond to the actuator segment. Communication of the states is done via IO-Link.
The power supply for both segments takes place via a 7/8″ connection, whereby attention must be paid to potential separated routing of the sensor and actuator circuits. Both the power supply unit itself and the wiring to the IO-Link device with the two segments must also ensure external galvanic isolation. This is made possible by separating the lines with a splitter.
An external safety device is required to safely interrupt the supply voltage of the actuator segment (four ports simultaneously). Thus, the module can implement safety functions up to SIL2 according to EN62061/PLd and ISO 13849. For example, this can happen through the use of a safety relay, whereby the power supply is safely disconnected after actuation of peripheral safety devices (such as emergency stops and door switches). At the same time, the sensor segment remains active and can provide important information from the field devices.
The module can handle up to eight digital inputs and outputs. If the IO-Link connection is interrupted, the outputs assume predefined states that are retained until the IO-Link connection is restored. Once the connection is restored, this unique state of the machine can be used to continue production directly without a reference run.
An application example for the interaction of sensors and actuators in a safety environment is the pneumatic clamping device of a workpiece holder. The position feedback of the cylinders is collected by the sensor segment, while at the same time the actuator segment can be switched off safely via its separately switchable safety circuit. If the sensor side is not required for application-related reasons, galvanically isolated IO-Link modules are also available with only actuator segments (BNI IOL 252/256). An isolated shutdown can protect up to two safety areas separately.
There are typically three or more communication levels in the modern factory which consist of:
Enterprise level (Ethernet)
Control level (Ethernet based industrial protocol)
Device/sensor level (various technologies)
The widespread use of control and device level communications for standard (non-safety) industrial applications led to a desire for similar communications for safety. We now have safety versions of the most popular industrial control level protocols, these make it possible to have safety and standard communications on the same physical media (with the appropriate safety hardware implemented for connectivity and control). In a similar manner, device level safety protocols are emerging to allow standard and safety communications over the same media. Safety Over IO-Link and AS-i Safety At Work are two examples.
This table lists the most common safety control level protocols with their Ethernet-based industrial “parent” protocols and the governing organizations:
And this table lists some of the emerging, more well-known, safety device level protocols with their related standard protocols and the governing or leading organizations:
Ethernet-based safety protocols are capable of high speed and high data transmission, they are ideal for exchanging data between higher level devices such as safety PLCs, drives, CNCs, HMIs, motion controllers, remote safety I/O and advanced safety devices. Device level protocol connections are physically smaller, much less expensive and do not use up IP addresses, but they also carry less data and cover shorter distances than Ethernet based protocols. They are ideal for connecting small, low cost devices such as E-stops, safety switches and simple safety light curtains.
As with standard protocols, neither a control level safety protocol, nor a device level safety protocol can meet all needs, therefore cost/performance considerations drive a “multi-level” communications approach for safety. This means a combined solution may be the best fit for many safety and standard communications applications.
A multi-level approach has many advantages for customers seeking a cost-effective, comprehensive safety and standard control and device solution which can also support their IIoT needs. Users can optimize their safety communications solutions, balancing cost, data and speed requirements.
The development and design of a machine is followed by the assembly and commissioning phase. Commissioning is especially time consuming, but the replacement of components or devices can be so as well.
This often raises the question of how to simplify commissioning and optimize component replacement.
The answer is provided by the IO-Link communication interface. IO-Link is the first globally standardized IO technology (IEC 61131-9) that communicates from the controller down to the lowest level.
But how exactly does this help with commissioning and component replacement? This is very simple and will be explained now. Let’s start first with the assembly, installation and commissioning phase.
During installation, the individual components must be electrically connected to each other. While fieldbus use has simplified the installation process, generally speaking, fieldbus cables have a low signal level, are susceptible to interference, have little flexibility, and are expensive due to their shielding. This is where IO-Link comes into play. Because the weaknesses of a fieldbus protocol are negligible with IO-Link.
Included in an IO-Link system are an IO-Link master and one or several IO-Link devices such as sensors or actuators. The IO-Link master is the interface to the controller (PLC) and takes over communication with connected IO-Link devices. The interface uses unshielded, three- or four-conductor standard industrial cables. Therefore the standard communication interface can be integrated into the fieldbus world without effort. Even complex components can be easily connected in this way. In addition, the standard industrial cables are highly flexible and suitable for many bending cycles. Three wires are the standard for the communication between the devices and the IO-Link master and for the power supply voltage. These are easy to connect, extremely cost-effective and their connection is standardized with M5, M8 or M12 connectors.
The commissioning will also be supported by IO-Link. The devices can be parameterized quickly and easily through parameter maintenance or duplication. Annoying manual adjustment of the sensors and actuators is no longer necessary. This saves money and avoids errors. The parameters of the individual devices are stored in the PLC or directly in the IO-Link master and can, therefore, be written directly to the sensor.
Now that we have clarified the advantages of IO-Link during commissioning, we will take a look at the replacement of components.
Save device replacement during operation
A sensor replacement directly leads to machine downtime. IO-Link enables quick and error-free replacement of sensors. The parameters of a replaced IO-Link sensor are automatically written from the IO-Link master or the PLC to the new sensor. The accessibility of the sensor does not play a major role anymore. In addition, IO-Link devices cannot be mixed up, since they are automatically identifiable via IO-Link.
Efficient format and recipe changes
IO-Link offers ideal properties that are predestined for format adjustment: sufficient speed, full access to all parameters, automatic configuration, and absolute transmission of the measured values. This eliminates the need for time-consuming reference runs. Since the machine control remains permanently traceable, the effort required for error-prone written paper documentation is also saved. Format changes and recipe changes can be carried out centrally via the function blocks of the PLC.
Using high-durability cables in application environments with high temperatures, weld spatter, or washdown areas improves manufacturing machine up-time.
It is important to choose a cable that matches your specific application requirements.
When a food and beverage customer needs to wash down their equipment after a production shift, a standard cable is likely to become a point of failure. A washdown-specific cable with an IP68/IP69 rating is designed to withstand high-pressure cleaning. It’s special components, such as an internal O-ring and stainless-steel connection nut, keep water and cleaners from leaking.
Welding environments require application-specific cables to deal with elevated temperatures, tight bend radiuses and weld spatter. Cables with a full silicone jacket prevent the build-up of debris, which can cause shorts and failures over time.
High Temperature cables
Applications with high temperatures require sensors that can operate reliably in their environment. The same goes for the cables. High temperature cables include added features such as a high temperature jacket and insulation materials specifically designed to perform in these applications.
Selecting the correct cable for a specific application area is not difficult when you know the requirements the application environment demands and incorporate those demands into your choice. It’s no different than selecting the best sensor for the job. The phrase to remember is “application specificity.”
For more information on standard and high-durability cables, please visit www.balluff.com.
In the last post about the Basics of Automation, we learned how distances, travel, angles and pressures can be measured contactlessly, whether linear or rotary. In this blog, let’s take a closer look at IO-Link technology.
Throughout the history of manufacturing, as the level of automation increased, the demand for intelligent field devices grew. A variety of interfaces with different mechanical and electrical characteristics were created, and the need for standardization grew. The cooperative work of several companies developed the viable solution. Like USB in the PC world, IO-Link in automation leads to a considerable simplification of installation with simultaneously extended diagnostics and parameterization capability.
It’s a worldwide standardized I/O technology according to IEC 61131-9, in order to communicate from the control to the lowest level of automation. The universal interface is a fieldbus independent point-to-point connection that works with an unshielded industrial cable. The IO-Link Community founded in 2006, consisting of leading automation manufacturers, promotes IO-Link with the acronym “”USE””:
Universal – IO-Link is an international standard (IEC 61131-9)
Smart – IO-Link enables diagnostics and parameter-setting of devices
Easy – IO-Link provides great simplification and cost reduction
Also mentioned as the heart of the IO-Link installation, it communicates with the controller via the respective fieldbus as well as downward using IO-Link to the sensor/actuator level.
Sensors and Actuators The IO-Link capable intelligent sensors and actuators are connected directly to the IO-Link master via IO-Link. This enables the simplest installation, the best signal quality, parameterization and diagnostics.
Hubs The sensor/actuator hub exchanges signals with the binary and/or analog sensors and actuators and communicates with the IO-Link master.
IO-Link is well-suited for use in measurement applications that have traditionally used analog (0…10V or 4…20mA) signals. This is thanks in large part to the implementation of IO-Link v1.1, which provides faster data transmission and increased bandwidth compared to v1.0. Here are three areas where IO-Link v1.1 excels in comparison to analog.
Fewer data errors, at lower cost
By nature, analog signals are susceptible to interference caused by other electronics in and around the equipment, including motors, pumps, relays, and drives. Because of this, it’s almost always necessary to use high-quality, shielded cables to transmit the signals back to the controller. Shielded cables are expensive and can be difficult to work with. And even with them in place, signal interference is a common issue that is difficult to troubleshoot and resolve.
With IO-Link, measurements are converted into digital values at the sensor, before transmission. Compared to analog signals, these digital signals are far less susceptible to interference, even when using unshielded 4-wire cables which cost about half as much as equivalent shielded cables. The sensor and network master block (Ethernet/IP, for example) can be up to 20 meters apart. Using industry-standard connectors, the possibility for wiring errors is virtually eliminated.
Less sensor programming required
An analog position sensor expresses a change in position by changing its analog voltage or current output. However, a change of voltage or current does not directly represent a unit of measurement. Additional programming is required to apply a scaling factor to convert the change in voltage or current to a meaningful engineering unit like millimeters or feet.
It is often necessary to configure analog sensors when they are being installed, changing the default characteristics to suit the application. This is typically performed at the sensor itself and can be fairly cumbersome. When a sensor needs to be replaced, the custom configuration needs to be repeated for the replacement unit, which can prolong expensive machine downtime.
IO-Link sensors can also be custom configured. Like analog sensors, this can be done at the sensor, but configuration and parameterization can also be performed remotely, through the network. After configuration, these custom parameters are stored in the network master block and/or offline. When an IO-Link sensor is replaced, the custom parameter data can be automatically downloaded to the replacement sensor, maximizing machine uptime.
Diagnostic data included
A major limitation of traditional analog signals is that they provide process data (position, distance, pressure, etc.) without much detail about the device, the revision, the manufacturer, or fault codes. In fact, a reading of 0 volts in a 0-10VDC interface could mean zero position, or it could mean that the sensor has ceased to function. If a sensor has in fact failed, finding the source of the problem can be difficult.
With IO-Link, diagnostic information is available that can help resolve issues quickly. As an example, the following diagnostics are available in an IO-Link magnetostrictive linear position sensor: process variable range overrun, measurement range overrun, process variable range underrun, magnet number change, temperature (min and max), and more.
This sensor level diagnostic information is automatically transmitted and available to the network, allowing immediate identification of sensor faults without the need for time-consuming troubleshooting to identify the source of the problem.
In the first part of this series “Demystifying Class A and Class B Type IO-Link Ports” we discussed the two different types of IO-Link master ports and pointed out how they differ in operation and applications. The point of that blog was to ensure that when we choose one over the other, what is the opportunity cost of that decision.
In my recent blog, part #2 in this series, “Not all IO-Link Masters are Born Equal!“, we explored that even when multiple vendors provide or call out their IO-Link master, they are different in the implementation of features and functions they offer. IO-Link is IO-Link! It is a standard for communication but other features that accompany the communication differentiates how they behave; for example- sensor only master, hybrid master, and architecture backbone master.
In this blog, we will focus on various implementations of Port Type A (or Class A) and how they add varying degrees of value to your applications.
Implementation #1: Figure 1 below depicts the guts (electrical connections) of one of the three implementations of the IO-Link Class A master port. Two key things to notice here:
The power coming into the IO-Link master port is only device power. There is no output power with this implementation. The reason that it is designed like this is to only integrate sensor inputs.
Pin 1 and Pin 3 provide the device power and ground (common) to the IO-Link device, pin 4 is IO-Link communication. Pin 2 works as an input only for digital sensors like photo-eyes or prox switches. Basically, this port can be split to use one IO-Link sensor (pins 1, 3 and 4) and one standard ON/OFF sensor (pins 1,3, and 2).
Another alternate of this implementation is that some vendors may have another IO-Link connection on Pin 2. So, it serves to add 2 IO-Link devices off the same port. Unfortunately, I am not an expert to say whether this is according to the specification or not.
The Pros: Low power consumption and simplifies integrating smart sensors.
The Cons: By definition, a control system has both inputs and outputs – controlling “something” based on sensory inputs and logic. This implementation provides semi-standard implementation to the controls architecture. IO-Link promises unified communication across the plant floor not half of the plant floor. Characteristics of this type of master port would be max output current of about 250-300mA per port and about 2A per module (rated for up to 4A, if its carries UL).
Implementation #2: This implementation is a slight variation of the sensor only port (Implementation #1 above). It is achieved by adding an output capability for pin 2 on each port- shown in figure 2 below. It is important to note that although each port has output capability on pin 2, the output power is shared with the device power for the port. It implies that, in case of E-stop situations, where shutting off power to the valves/solenoids connected to pin 2 or an IO-Link device that requires an output power, the entire device power will be shut-off. Basically, the state of the device connected to pin 2 and state of IO-Link devices connected on pin 4 will be lost or requires more elaborate approach (programming, testing and validation) in the controls side to handling these types of safety situations.
This type of implementation is commonly found on hybrid IO-Link master’s Class A (type A) port implementation.
The Pros: Flexibility to use pin 2 for input or output – standardized approach to all devices.
The Cons: Lack of ability to control the output power separate from the device power – causing variety of controls approaches (lots of precautions) when incorporating machine safety.
Implementation #3: This implementation offers the most flexibility in designing the controls architecture that utilizes IO-Link. Figure 3 depicts the implementation below. In this case, the device power, as prior approaches, comes from pin 1 and pin 3 but pin 2 uses a separate power for output. The pin 2 on each of these ports can be used for input, output or to provide separate output power to the IO-Link devices. It is important to note that although pin 2 offers output power separate from the device power, the common/ground for this power is still tied to pin 3. The output power is separate but not isolated, like in the Class B port implementation discussed in the blog “Demystifying Class A and Class B Type IO-Link Ports“.
The two key advantages with this approach are: 1) High amperage output can be used from pin 2 to control valves or solenoids by splitting the port, and 2) IO-Link devices such as valve terminals or configurable I/O hubs that require output power can be connected with standard 4 pole cables without needing additional power cables or connectors.
This does appear very similar to implementation 2 where output power can be provided as well. The key difference is that since the output power comes from a different power line, it is not shared with the device power — as you know, amperage reduces when you have parallel circuits, so implementation 2 is subject to that principle whereas implementation #3 is not.
Another benefit with this approach is that a safety relay can be placed on the power going to pin 2 because the output power for the entire module is separate. That means in case of E-stop situations, the output power can be shut off without harming the device power. This eliminates the need for elaborated controls planning as the device state is maintained throughout the operation. After recovering from an E-stop, the valves and all other outputs go back to their original state. This significantly simplifies your controls architecture, offers standardized approach to cabling and provides unified interface for all devices.
To learn more about Balluff’s implementation of IO-Link masters please visit www.balluff.com.
Users of IO-Link have long been in search of a solution for implementing the demands for functional safety using IO-Link. As a first step, the only possibility was to turn the actuators off using a separate power supply (Port class “B”, Pins 2, 5), which powers down the entire module. Today there is a better answer: Safety hub with IO-Link!
This integrated safety concept is the logical continuation of the IO-Link philosophy. It is the only globally available technology to build on the proven IO-Link standards and profisafe. This means it uses the essential IO-Link benefits such as simple data transport and information exchange, high flexibility and universal applicability for safety signals as well. Safety over IO-Link combines automation and safety and represents efficient safety concepts in one system. Best of all, the functionality of the overall system remains unchanged. Safety is provided nearly as an add-on.
In the center of this safety concept is the new safety hub, which is connected to an available port on an IO-Link master. The safety components are connected to it using M12 standard cable. The safety profisafe signals are then tunneled to the controller through an IO-Link master. This has the advantage of allowing existing infrastructure to still be used without any changes. Parameters are configured centrally through the user interface of the controller.
The safety hub has four 2-channel safe inputs for collecting safety signals, two safe outputs for turning off safety actuators, and two multi-channel ports for connecting things like safety interlocks which require both input and output signals to be processed simultaneously. The system is TÜV- and PNO-certified and can be used up to PLe/SIL 3. Safety components from all manufacturers can be connected to the safe I/O module.
Like IO-Link in general, Safety over IO-Link is characterized by simple system construction, time-and cost-saving wiring using M12 connectors, reduction in control cabinet volume and leaner system concepts. Virtually any network topology can be simply scaled with Safety over IO-Link, whereby the relative share of automation and safety can be varied as desired. Safety over IO-Link also means unlimited flexibility. Thanks to varying port configuration and simple configuration systems, it can be changed even at the last minute. All of this helps reduce costs. Additional savings come from the simple duplication of (PLC-) projects, prewiring of machine segments and short downtimes made possible by ease of component replacement.