In this video, we’re going
to learn about IO-Link. What is IO-Link I hear you say? Well, listen closely, and you’ll find out! At RealPars, we love helping you learn, so if you enjoy this video as
much as we enjoyed making it, click the ‘Like’ button. Subscribe and click the ‘Bell’ and you’ll receive notifications
of new RealPars videos, so you’ll never miss another one! IO-Link is a communications
protocol that works point-to-point. A point-to-point communication connection is a communications connection between
two separate endpoints or nodes. IO-Link is bi-directional
meaning it works two ways, and works over a short distance. It is primarily used to communicate
with sensors and actuators in plant or factory
automation processes. Sensors and actuators are usually
connected via Fieldbus connections, allowing them to be in remote locations. With IO-Link, the field devices, such as actuators or sensors, connect to a ‘Master’ device which
communicates to a controller, usually a PLC, or Programmable
Logic Controller. The connection between the IO-Link
Master and the field device is established via an
unscreened 3 wire cable, no more than 20 meters long. The IO-Link master is capable of processing
digital signals and analog values. Its versatility means it is capable
of integrating into existing systems and can communicate using the
industry-recognized Profinet, Profibus, or Modbus, to name a few. The IO-Link master establishes the
connection between the IO-Link devices and the automation system. As a component of an I/O system, the IO-Link master is installed
either in the control cabinet or as remote I/O, directly in the field. An IO-Link master can have several
IO-Link ports or channels. An IO-Link device can be
connected to each port, meaning IO-Link is a point to point
communication and not a Fieldbus. The IO-Link protocol allows an IO-Link port to be operated in one of four
different operating modes. The first mode is the IO-Link mode. This means that the port is
used for IO-Link communication. The second mode is the DI mode. This means that the port acts in the
same way as a digital input device. The third mode is the DQ mode. This means that the port acts in the
same way as a digital output device. The fourth mode is Deactivated. This means that the port is not
assigned to any other modes and is reserved for when the port is unused. IO-Link is a very robust communication
system That operates using 24 volts. Transmission errors can occur
for a number of reasons, in general a cable fault or a power surge can
temporarily interfere with transmissions. If an error is detected, the message attempts transmission
up to an additional two times. Only after the transmission
has failed for a third time does the IO-Link master recognize
a communication failure. Upon recognizing this, the IO-Link master will signal
the communications failure to the higher-level controller. This can then alert operators or
maintenance staff of the issue, so they can physically attend
to and rectify the problem. An IO-Link device has 4
types of transmission. “Process Data”, “Value Status”,
“Device Data”, and “Events”. The Process Data is considered as the
latest state of the sensor or actuator, such as speed. Process Data is transmitted cyclically, which means automatically, at
regular defined intervals. Up to 32 bytes of process
data can be processed, and it’s defined by the
high-level controller. The Value Status indicates whether
the Process Data is valid or invalid and is transmitted along with
the Process Data cyclically. The Device Data holds detailed
information about a device. Basic information such as the
serial number or version number and more advanced information such as parameters or diagnostic information are able to be retrieved
from each IO-Link device. Device Data is transmitted acyclically, at the request of the IO-Link master. This means that it is not
automatically transmitted but will be transmitted after a
request from the IO-Link Master. Device Data can be read from the
device, but also written to. A device is able to
trigger an Event, which in turn signals the presence
of an Event to the IO-Link Master. An example of an event is an
error or warning message, for example a short circuit, or
a device that is overheating. This information can be used to display
indicators or messages on HMI devices, such as error messages
signalling a wire break or a communication failure, once the IO-Link Master has processed the
message to the High-Level controller. The transmission of device
parameters and events occurs independently from the cyclic
transmission of Process Data. This means that they do
not impact each other, so critical messages do not have to queue, until already buffered messages are sent. So, let's try and summarise
what we’ve learned today. IO-Link is a simple communications protocol. It is used primarily for communications
to simple 3 wire sensors and actuators. An IO-Link Master has slave devices, such as an actuator or
sensor, attached to it. The IO-Link Master can then communicate
over a Fieldbus connection to the higher-level controller, most likely in our case, a PLC,
or Programmable Logic Controller. The IO-Link ports can
serve different purposes, from signaling that it is unused, to signal that it is in Input mode, Output mode or for IO-Link communication. An IO-Link device transmits Process Data and Value Status periodically, at a regular defined interval. This is called cyclic transmission. Device Data, such as diagnostics and Events are transmitted when they are needed. This is called acyclic transmission. That’s it for this video! I hope you
have enjoyed learning about IO-Link. It is a very simple communications protocol that can be quite complex to learn about! Getting the set up of the
IO-Link configuration correct is heavily dependant on the device
that is being communicated with, so checking the field devices instructions is a necessity to be able
to communicate correctly. Don’t worry though, once it is set up, they are very easy to maintain, and often work seamlessly with
no additional work required. Want to learn PLC programming
in an easy to understand format and take your career
to the next level? Head on over to realpars.com
